Search

We appreciate Chang JS.'s interest in the article: "Benefit of respiratory gating in the Danish Breast Cancer Group partial breast irradiation trial". The author's response corroborates the statements and comments of Chang JS. [ABSTRACT FROM AUTHOR]

• For respiratory-gated radiotherapy near end-exhalation and irradiation fields involving the liver dome, components of geometric uncertainties originate from temporospatial diaphragm segment movements. • The displacements in a caudal direction of the diaphragm in dorsal/medial segments are significantly larger than those in ventral/right segments. • Personalized irradiating strategies, including inhalation phases of irradiation and beam angles of incidence, are required to reduce the temporospatial geometric uncertainties. The technique of gating near end-exhalation is commonly adopted to reduce respiration-associated geometric uncertainties for particle beam therapy. However, for irradiation fields involving the liver dome, how diaphragm movements generating liver–lung interface change, alongside geometric uncertainties, remain unspecified. Patients receiving respiratory-gated computed tomography (RGCT) with four-dimensional computed tomography (4DCT) scans during simulation were retrospectively reviewed. Differences (Δ) between RGCT and 4DCT images, including diaphragm displacements and liver–lung interface changes, were investigated to specify geometric uncertainties during early inhalation phases. Craniocaudal displacements (Δy, in sagittal/coronal planes) of diaphragm segments (dorsal/ventral/right lateral/medial), liver area changes (ΔA, in axial planes), and liver extent changes in specific directions of incidence (Δr, in axial planes) were analyzed. Altogether, 162 patients received simulating RGCT and 4DCT scans. In 22 of them, both images involved the liver dome. For most cases during early inhalation phases, the Δy values in the dorsal diaphragm were significantly greater than those in the ventral diaphragm (p < 0.05), the ΔA values were significantly enlarged with inhalation progressing (p < 0.05), and the Δr values in the dorsal direction were significantly larger than those in the ventral direction (p < 0.05). These results suggested that the dorsal diaphragm moves earlier and more in a caudal direction than the ventral diaphragm during early inhalation phases. For respiratory-gated radiotherapy near end-exhalation and irradiation fields involving the liver dome, components of geometric uncertainties are temporospatial, including diaphragm segment movements, inhalation phases of irradiation, and beam angles of incidence. [ABSTRACT FROM AUTHOR]

Herein are presented the recommendations from the Société française de radiothérapie oncologique regarding indications and modalities of lung cancer radiotherapy. The recommendations for delineation of the target volumes and organs at risk are detailed. [ABSTRACT FROM AUTHOR]

We present the commissioning and quality assurance of our clinical protocol for respiratory gating in pencil beam scanning proton therapy for cancer patients with moving targets. In a novel approach, optical tracking has been integrated in the therapy workflow and used to monitor respiratory motion from multiple surrogates, applied on the patients' chest. The gating system was tested under a variety of experimental conditions, specific to proton therapy, to evaluate reaction time and reproducibility of dose delivery control. The system proved to be precise in the application of beam gating and allowed the mitigation of dose distortions even for large (1.4 cm) motion amplitudes, provided that adequate treatment windows were selected. The total delivered dose was not affected by the use of gating, with measured integral error within 0.15 cGy. Analysing high-resolution images of proton transmission, we observed negligible discrepancies in the geometric location of the dose as a function of the treatment window, with gamma pass rate greater than 95% (2%/2 mm) compared to stationary conditions. Similarly, pass rate for the latter metric at the 3%/3 mm level was observed above 97% for clinical treatment fields, limiting residual movement to 3 mm at end-exhale. These results were confirmed in realistic clinical conditions using an anthropomorphic breathing phantom, reporting a similarly high 3%/3 mm pass rate, above 98% and 94%, for regular and irregular breathing, respectively. Finally, early results from periodic QA tests of the optical tracker have shown a reliable system, with small variance observed in static and dynamic measurements. [ABSTRACT FROM AUTHOR]

• Tumor movements smaller than 5 mm do not require motion mitigation. • Volumetric rescanning improve CTV dose coverage for intermediate tumor motions (5–10 mm) using a dense spot grid, whilst being more time efficient than respiratory gating. • Respiratory gating does not necessarily reduce dose to normal tissues for intermediate tumor motions. • Respiratory gating combined with volumetric rescanning improve CTV dose coverage for tumor motions larger than 10 mm using a dense or sparse spot grid. • A denser spot grid gives better CTV dose coverage. • Combined rescanning and gating treatments of moving tumors with proton pencil beam can be used effectively and efficiently. Respiratory motion during proton therapy can severely degrade dose distributions, particularly due to interplay effects when using pencil beam scanning. Combined rescanning and gating treatments for moving tumors mitigates dose degradation, but at the cost of increased treatment delivery time. The objective of this study was to identify the time efficiency of these dose degradation-motion mitigation strategies for different range of motions. Seventeen patients with thoracic or abdominal tumors were studied. Tumor motion amplitudes ranged from 2–30 mm. Deliveries using different combinations of rescanning and gating were simulated with a dense dose spot grid (4 × 4 × 2.5 mm3) for all patients and a sparse dose spot grid (8 × 8 × 5 mm3) for six patients with larger tumor movements (> 8 mm). The resulting plans were evaluated in terms of CTV coverage and time efficiency. Based on the studied patient cohort, it has been shown that for amplitudes up to 5 mm, no motion mitigation is required with a dense spot grid. For amplitudes between 5 and 10 mm, volumetric rescanning should be applied while maintaining a 100% duty cycle when using a dense spot grid. Although gating could be envisaged to reduce the target volume for intermediate motion, it has been shown that the dose to normal tissues would only be reduced marginally. Moreover, the treatment time would increase. Finally, for larger motion amplitudes, both volumetric rescanning and respiratory gating should be applied with both spot grids. In addition, it has been shown that a dense spot grid delivers better CTV dose coverage than a sparse dose grid. Volumetric rescanning and/or respiratory gating can be used in order to effectively and efficiently mitigate dose degradation due to tumor movement. [ABSTRACT FROM AUTHOR]

During radiotherapy treatment, there is always considerable risk that the timing of the treatment delivery and the volume movement results in degradation or undesired heterogeneities in the dose distribution. As there may be a simultaneous movement of the tumour, patient, and treatment machine, it is essential to minimize the uncertainties owing to motion in a clinical setting. Despite all clinical settings, tumour movement due to respiration is most important, because moving tumours can follow complex trajectories, that may affect patient treatment results, and cause difficulties in dose assessment. In this study, the effect of vertical movement on dose distribution was investigated. To overcome motion-related dosimetry challenges radiation-sensitive normoxic Methacrylic acid gels (nMAG) were used for dose evaluation. The selection of the gel dosimetry method was based on nMAG gel's ability to record corresponding target volume expansion via polymerized gel volume obtained during performed irradiation with simulated movement. Three identical sample batches of nMAG gels have been produced at once. Corresponding samples from each batch were irradiated to the same doses from the dose range up to 36 Gy and experimental results were averaged. A 6 MV FFF photon beam collimated to 1.0 cm2 was used for irradiation. X-ray CT and NMR imaging procedures were used for the dose profile and dose sensitivity evaluation by applying a gamma passing rate criteria of 3 %/3 mm. The movement of the gel was responsible for the reduction of the peak maximum dose by approximately 13.6 %. The shape and uniformity of the dose profiles were changing when applying different irradiation scenarios. Dose sensitivity evaluated in dynamic mode using MRI-R2 technique was 0.025 s- 1Gy- 1. This study has shown that polymer gels are sensitive enough to detect distorted dose distributions and evaluate the doses, obtained due to the movement of the irradiated target. [ABSTRACT FROM AUTHOR]

Heavy Ion Medical Machine (HIMM) at Wuwei Heavy Ion Therapy Center has been officially approved. The aim of this study was to demonstrate the dosimetric stability and safety of HIMM prior to subsequent clinical trials. Dosimetric verification of treatment plans was conducted using anthropomorphic phantoms in a uniformly scanned beam delivery mode. Both head-and-neck and thoracoabdominal regions of anthropomorphic phantoms dedicatedly inserted with a Farmer-type ionization chamber were scanned under a 64-slice CT scanner. Planning target volumes (PTV) were delineated according to the two sets of acquired CT images. The sensitive volume of the chamber was located in the center, rising edge, plateau and falling edge of PTV, respectively. Then treatment plans were designed for the target volumes using a carbon-ion radiotherapy planning system. Dose measurements were conducted following the IAEA guidelines. Virtual respiratory signals were generated to simulate respiratory conditions, and gating irradiation was conducted on the thoracoabdominal phantom. Dose measurements were performed three times at each point. For the dosimetric verification of both the head-and-neck and thoracoabdominal phantoms, the deviations between planned and measured doses were confirmed to be within acceptable limits. For respiratory gating irradiation, the deviation was 0.32% in the center of PTV. The irradiation time was increased approximately twofold as compared to the non-gated situation. Intraclass correlation coefficient (ICC) value of the measured dose was 1.000. The results met the requirements. The passive beam delivery mode of HIMM demonstrated satisfactory dosimetric performance, making it suitable for the upcoming clinical trials. • The aim of this study was to demonstrate the dosimetric stability and safety of HIMM. • Dosimetric verification was conducted using anthropomorphic phantoms. • Gating irradiation was conducted on the thoracoabdominal phantom. • This study is the first to publish QC results for domestic heavy ion therapy in China. • The passive beam delivery mode of HIMM demonstrated satisfactory performance. [ABSTRACT FROM AUTHOR]

Background: Respiratory patient motion causes blurring of the PET images that may impact accurate quantification of perfusion and infarction extents in PET myocardial viability studies. In this study, we investigate the feasibility of correcting for respiratory motion directly in the PET-listmode data prior to image reconstruction using a data-driven, projection-based, respiratory motion compensation (DPR-MoCo) technique. Methods: The DPR-MoCo method was validated using simulations of a XCAT phantom (Biograph mMR PET/MR) as well as experimental phantom acquisitions (Biograph mCT PET/CT). Seven patient studies following a dual-tracer (18F-FDG/13N-NH3) imaging-protocol using a PET/MR-system were also evaluated. The performance of the DPR-MoCo method was compared against reconstructions of the acquired data (No-MoCo), a reference gate method (gated) and an image-based MoCo method using the standard reconstruction-transform-average (RTA-MoCo) approach. The target-to-background ratio (TBRLV) in the myocardium and the noise in the liver (CoVliver) were evaluated for all acquisitions. For all patients, the clinical effect of the DPR-MoCo was assessed based on the end-systolic (ESV), the end-diastolic volumes (EDV) and the left ventricular ejection fraction (EF) which were compared to functional values obtained from the cardiac MR. Results: The DPR-MoCo and the No-MoCo images presented with similar noise-properties (CoV) (P =.12), while the RTA-MoCo and reference-gate images showed increased noise levels (P =.05). TBRLV values increased for the motion limited reconstructions when compared to the No-MoCo reconstructions (P >.05). DPR-MoCo results showed higher correlation with the functional values obtained from the cardiac MR than the No-MoCo results, though non-significant (P >.05). Conclusion: The projection-based DPR-MoCo method helps to improve PET image quality of the myocardium without the need for external devices for motion tracking. [ABSTRACT FROM AUTHOR]

Background: Respiratory gating reduces motion blurring in cardiac SPECT. Here we aim to evaluate the performance of three respiratory gating strategies using a population of digital phantoms with known truth and clinical data.Methods: We analytically simulated 60 projections for 10 XCAT phantoms with 99mTc-sestamibi distributions using three gating schemes: equal amplitude gating (AG), equal count gating (CG), and equal time gating (TG). Clinical list-mode data for 10 patients who underwent 99mTc-sestamibi scans were also processed using the 3 gating schemes. Reconstructed images in each gate were registered to a reference gate, averaged and reoriented to generate the polar plots. For simulations, image noise, relative difference (RD) of averaged count for each of the 17 segment, and relative defect size difference (RSD) were analyzed. For clinical data, image intensity profile and FWHM were measured across the left ventricle wall.Results: For simulations, AG and CG methods showed significantly lower RD and RSD compared to TG, while noise variation was more non-uniform through different gates for AG. In the clinical study, AG and CG had smaller FWHM than TG.Conclusions: AG and CG methods show better performance for motion reduction and are recommended for clinical respiratory gating SPECT implementation. [ABSTRACT FROM AUTHOR]

Proton therapy has shown potential for reducing doses to normal tissues in breast cancer radiotherapy. However data on the impact of protons when including internal mammary nodes (IMN) in the target for breast radiotherapy is comparatively scarce. This study aimed to evaluate normal tissue doses when including the IMN in regional RT with scanned proton beams, with and without respiratory gating. The study cohort was composed of ten left-sided breast patients CT-scanned during enhanced inspiration gating (EIG) and free-breathing (FB). Proton plans were designed for the target including or excluding the IMN. Targets and organs-at-risk were delineated according to RTOG guidelines. Comparison was performed between dosimetric parameters characterizing target coverage and OAR radiation burden. Statistical significance of differences was tested using a paired, two-tailed Student’s t -test. Inclusion of the IMN in the target volume led to a small increase of the cardiopulmonary burden. The largest differences were seen for the ipsilateral lung where the mean dose increased from 6.1 to 6.6 Gy (RBE) (P < 0.0001) in FB plans and from 6.9 to 7.4 Gy (RBE) (P = 0.003) in EIG plans. Target coverage parameters were very little affected by the inclusion of IMN into the treatment target. Radiotherapy with scanned proton beams has the potential of maintaining low cardiovascular burden when including the IMN into the target, irrespective of whether respiratory gating is used or not. [ABSTRACT FROM AUTHOR]

Background: We previously reported the clinical feasibility and positive impact on image characteristics of a data-driven cardiac respiratory motion (RM) correction method (REGAT) applicable to CZT SPECT myocardial perfusion imaging (MPI). Here, we evaluate its impact on the extent and severity of myocardial perfusion defects (MPD).Methods: We included 25 patients having a 1-day 99mTc-Tetrofosmin stress/rest MPI acquired with multi-pinhole CZT SPECT. Acquisitions were processed with REGAT to generate mean RM gated SPECT. These were summed either after (R-SPECT) or without realignment (NR-SPECT). We noted the maximal cardiac RM shift in the 3 axes of the left ventricle (LV). Both visual and semi-quantitative analyses of myocardial tracer uptake were realized. Studies were classified as having an impact on the extent/severity of MPD with REGAT if ≥1 segment presented a severity score changing by ≥1 level between NR-SPECT and R-SPECT. An impact on the extent of MPD was considered present if at least 1 segment shifted from normal (score = 0) to abnormal (score different from 0) or inversely.Results: Cardiac RM was >10 mm in 55% of studies. With visual and semi-quantitative analyses, an impact on the extent/severity MPD was observed in 14% of all studies (7/49) and 60% of studies with cardiac RM >15 mm. An impact on the extent of MPD was observed in 5 of the 7 upper listed studies. All studies presenting an impact on MPD had RM in the anterior to inferior LV axis >10 mm.Conclusions: A substantial number of MPI studies presented significant cardiac RM. Cardiac RM compensation showed a frequent impact on the extent/severity of MPD. [ABSTRACT FROM AUTHOR]

Purpose To combine the technique of respiratory gating and compressed sensing (CS) with the objective of accelerating mouse abdominal magnetic resonance imaging (MRI). Materials and methods To obtain the maximum acceleration, phase-encoding data from a phantom and mouse were obtained on a 4.7 Tesla scanner using the respiratory gating technique. The fully sampled data (FSD) were used to construct reference images and to provide samples to simulate retrospective undersampled data (UD) acquisition using respiratory gating. The UD and 95% of the UD on acceleration 2–5 rates were acquired and used for image reconstruction by CS. Quantitative assessment of reconstructed images was performed by structural similarity index (SSIM), peak signal-to-noise ratio (PSNR) and root mean square error (RMSE). Results The proposed method can accelerate phantom and mouse abdominal MRI acquisition between 2 and 4 rates by reducing the amount of FSD. For phantom UD acquisition, the mean time was reduced in 45.9% and for the acquisition of 95% of UD in 67.8%. For mouse abdominal image UD acquisition, the mean time was reduced in 44.6% and for the acquisition of 95% of UD in 62.5%. The metrics results show that the reconstructed image from UD and 95% of UD by using CS maintains an optimal agreement with their reference images (similarity above 0.88 for phantom and 0.93 for mouse). Conclusion This study presents a novel approach to accelerate mouse abdominal MRI combining respiratory gating technique and CS without the use of expensive hardware and capable of achieving up to 4 acceleration rate without image degradation. [ABSTRACT FROM AUTHOR]

Aims A systematic review of the literature evaluating the clinical use of respiratory-gated (four-dimensional; 4D) fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) compared with non-gated (three-dimensional; 3D) PET/CT for radiotherapy planning in lung cancer. Materials and methods A search of MEDLINE, Cochrane, Web of Science, SCOPUS and clinicaltrials.gov databases was undertaken for articles comparing 3D and 4D PET/CT tumour volume or 4D PET/CT for radiotherapy planning. PRISMA guidelines were followed. Results Thirteen studies compared tumour volumes at 3D and 4D PET/CT; eight reported significantly smaller volumes (6.9–44.5%), three reported significantly larger volumes at 4D PET/CT (16–50%), one reported no significant difference and one reported mixed findings. Six studies, including two that reported differences in tumour volumes, compared target volumes or studied geographic misses. 4D PET/CT target volumes were significantly larger (19–40%) when compared with 3D PET/CT in all but one study, where they were smaller (3.8%). One study reported no significance in 4D PET/CT target volumes when compared with 4D CT, whereas another study reported significantly larger volumes (38.7%). Conclusion The use of 4D PET/CT leads to differences in target volume delineation compared with 3D PET/CT. These differences vary depending upon technique and the clinical impact currently remains uncertain. Correlation of pretreatment target volumes generated at 3D and 4D PET/CT with postsurgical histology would be ideal but technically challenging. Evaluation of patient outcomes based on 3D versus 4D PET/CT derived treatment volumes warrants further investigation. [ABSTRACT FROM AUTHOR]

Purpose: To assess the ability of parameters derived from computed tomography (CT) histograms and the maximum standardized uptake value (SUVmax) of 18F-fludeoxyglucose-positron emission tomography/CT (FDG-PET/CT) images to distinguish solid lung adenocarcinomas from squamous cell carcinomas and to determine if these parameters are correlated.Methods: This study comprised 43 consecutive patients with solid lung cancer (<3 cm in diameter), who underwent both plain chest CT and FDG-PET/CT (adenocarcinoma, n = 25; squamous cell carcinoma, n = 18). Density histograms of targeted lung cancers were created from chest CT images, and kurtosis and skewness were calculated. On FDG-PET/CT, the SUVmax without/with respiratory gating (RG) were calculated for each lesion. The values for the 4 parameters determined for patients in each diagnostic group were compared by the Mann-Whitney test. The diagnostic characteristics of the parameters were assessed by receiver operating characteristic (ROC) curve analysis. Differences between these parameters were assessed by the chi-square test. SUVmax with RG, kurtosis, and skewness were combined for binary logistic regression analysis, and the differences between the combined parameters and SUVmax with RG were also assessed. Spearman rank correlation analysis was used to determine the correlations for kurtosis or for skewness with SUVmax without/with RG.Results: The differences in kurtosis and SUVmax without/with RG between the diagnostic groups were significant (kurtosis, P < 0.004; SUVmax without/with RG both P < 0.0001). ROC curve analysis indicated that each parameter (kurtosis value, skewness value, SUVmax, without/with RG) provided low-high ability to differentiate between 2 groups (area under the curve [AUC]: 0.760, 0.593, 0.900, 0.931, respectively). The ROC of the combined parameters provided the highest ability (AUC: 0.949). Both kurtosis and skewness were significantly correlated with SUVmax without/with RG. Kurtosis and SUVmax with RG were most strongly correlated (ρ = 0.618).Conclusion: Quantitative CT histogram values and SUV assessment can differentiate solid lung adenocarcinomas from squamous cell carcinomas. Kurtosis and SUVmax values were strongly correlated. The addition of RG and further combination of the parameters improved the results. [ABSTRACT FROM AUTHOR]

Background: Respiratory motion due to breathing during cardiac positron emission tomography (PET) results in spatial blurring and erroneous tracer quantification. Respiratory gating might represent a solution by dividing the PET coincidence dataset into smaller respiratory phase subsets. The aim of our study was to compare the resulting imaging quality by the use of a time-based respiratory gating system in two groups administered either adenosine or dipyridamole as the pharmacological stress agent.Methods and Results: Forty-eight patients were randomized to adenosine or dipyridamole cardiac stress 82RB-PET. Respiratory rates and depths were measured by a respiratory gating system in addition to registering actual respiratory rates. Patients undergoing adenosine stress showed a decrease in measured respiratory rate from initial to later scan phase measurements [12.4 (±5.7) vs 5.6 (±4.7) min-1, P < .001] and tended to have a lower frequency of successful respiratory gating compared to dipyridamole (47% vs 71%, P = .12). As a result, imaging quality was superior in the dipyridamole group compared to adenosine.Conclusions: If respiratory gating is considered for use in cardiac PET, a dipyridamole stress protocol is recommended as it, compared to adenosine, causes a more uniform respiration and results in a higher frequency of successful respiratory gating and thereby superior imaging quality. [ABSTRACT FROM AUTHOR]

Background: We developed a data-driven respiratory motion (RM) correction method (REGAT program) for multiple-pinhole detector CZT SPECT. We verified its clinical feasibility with myocardial perfusion imaging (MPI) and studied its impact on image characteristics.Methods: This retrospective study included 18 patients having stress/rest 99mTc-Tetrofosmin MPI SPECT. List mode was acquired on CZT SPECT and processed with REGAT. REGAT generates reconstructed RM-gated volumes that are summed either without realignment (NR-SPECT) or after realignment (R-SPECT). For both stress and rest, we calculated the maximal RM in the 3 axis, and image characteristics of both R-SPECT and NR-SPECT: minimum left ventricular (LV) cavity counts (LV-Min), maximum LV myocardial counts (LV-Max), LV contrast, and FWHM of both anterior (FWHM-ant) and inferior (FWHM-inf) LV myocardial walls.Results: At both stress and rest, cranio-caudal motion was the dominant axial movement and REGAT had a positive impact on image characteristics as reflected by variations between R-SPECT and NR-SPECT in LV-Min, LV-Max, FWHM-ant, FWHM-inf, and contrast. These latter were well correlated to the amplitude of cranio-caudal motion at both stress and rest.Conclusions: Data-driven RM correction of MPI acquired with CZT SPECT is clinically feasible and easily applicable. It presents interesting impact on image characteristics. [ABSTRACT FROM AUTHOR]

Background and purpose Ablative radiation therapy can be beneficial for pancreatic cancer, and motion mitigation helps to reduce dose to nearby organs-at-risk. Here, we compared two competing methods of motion mitigation—abdominal compression and respiratory gating. Materials and methods CBCT scans of 19 pancreatic cancer patients receiving stereotactic body radiation therapy were acquired with and without abdominal compression, and 3D target motion was reconstructed from CBCT projection images. Daily target motion without mitigation was compared against motion with compression and with simulated respiratory gating. Gating was free-breathing and based on an external surrogate. Target coverage was also evaluated for each scenario by simulating reduced target margins. Results Without mitigation, average daily target motion in LR/AP/SI directions was 5.3, 7.3, and 13.9 mm, respectively. With abdominal compression, these values were 5.2, 5.3, and 8.5 mm, and with respiratory gating they were 3.2, 3.9, and 5.5 mm, respectively. Reductions with compression were significant in AP/SI directions, while reductions with gating were significant in all directions. Respiratory gating also demonstrated better coverage in the reduced margins scenario. Conclusion Respiratory gating is the most effective strategy for reducing motion in pancreatic SBRT, and may allow for dose escalation through a reduction in target margin. [ABSTRACT FROM AUTHOR]

Purpose The aim of this work was the commissioning of delivery procedures for the treatment of moving targets in scanning pencil beam hadrontherapy. Methods EBT3 films fixed to the Anzai Respiratory Phantom were exposed to carbon ion scanned homogeneous fields (E = 332 MeV/u). To evaluate the interplay effect, field size and flatness for 3 different scenarios were compared to static condition: gated irradiation or repainting alone and combination of both. Respiratory signal was provided by Anzai pressure sensor or optical tracking system (OTS). End-exhale phase and 1 s gating window were chosen (2.5 mm residual motion). Dose measurements were performed using a PinPoint ionization chamber inserted into the Brainlab ET Gating Phantom. A sub-set of tests was also performed using proton beams. Results The combination of gating technique and repainting (N = 5) showed excellent results (6.1% vs 4.3% flatness, identical field size and dose deviation within 1.3%). Treatment delivery time was acceptable. Dose homogeneity for gated irradiation alone was poor. Both Anzai sensor and OTS appeared suitable for providing respiratory signal. Comparisons between protons and carbon ions showed that larger beam spot sizes represent more favorable condition for minimizing motion effect. Conclusion Results of measurements performed on different phantoms showed that the combination of gating and layered repainting is suitable to treat moving targets using scanning ion beams. Abdominal compression using thermoplastic masks, together with multi-field planning approach and multi-fractionation, have also been assessed as additional strategies to mitigate the effect of patient respiration in the clinical practice. [ABSTRACT FROM AUTHOR]

Background: Radiotherapy is based on the premise of accurate dose delivery to target volumes within a patient, while minimizing dose to surrounding tissues. Recent developments in the treatment of breast cancer have focused on “gating” the delivery of the treatment beams to minimize the effect of patient motion during treatment, and increasing separation between the target volume and organs at risk (OAR), such as lung, heart and left anterior descending coronary artery. The basic principle involves rapidly switching the treatment beam on or off depending on the patient breathing cycle. It is therefore important to know the characteristics of gated treatments such as latency. Methods: In this work an electrical PIN diode circuit (EPDC) was designed for quality assurance (QA) purposes to examine beam latency timing properties. Evaluation of the EPDC was performed on a TrueBeam™ (Varian, Palo Alto) linear accelerator and its internal gating system. The EPDC was coupled to a moving stage to simulate a binary pattern with fast beam triggering within predefined limits, the so called “gating window”. Pulses of radiation were measured with the PIN diode and the results were compared to measurements of current produced across the linac target. Processing of the beam pulses and calculation of the latency timings was performed by an Atmega328P microcontroller. Results: For beam-on latencies, 2.11 ms (6 MV) and 2.12 ms (10 MV) were measured using the PIN diode, compared to 2.13 ms (6 MV) and 2.15 ms (10 MV) using the target current signal. For beam-off latencies, 57.69 ms (6 MV) and 57.73 ms (10 MV) were measured using the PIN diode, compared to 57.33 ms (6 MV) and 56.01 ms (10 MV) using the target current. Conclusions: PIN diodes can be used for accurate determination of the beam-on and beam-off latency characteristics, which could potentially lead to improvements in gated radiotherapy treatments, for example optimizing the gating windows and in estimating dosimetric errors associated with treatment beam latencies. [ABSTRACT FROM AUTHOR]

Background: Raw PET list-mode data contains motion artifacts causing image blurring and decreased spatial resolution. Unless corrected, this leads to underestimation of the tracer uptake and overestimation of the lesion size, as well as inaccuracies with regard to left ventricular volume and ejection fraction (LVEF), especially in small animal imaging.Methods and Results: A respiratory trigger signal from respiration-induced variations in the electro-cardiogram (ECG) was detected. Original and revised list-mode PET data were used for calculation of left ventricular function parameters using both respiratory gating techniques. For adequately triggered datasets we saw no difference in mean respiratory cycle period between the reference standard (RRS) and the ECG-based (ERS) methods (1120 ± 159 ms vs 1120 ± 159 ms; P = n.s.). While the ECG-based method showed somewhat higher signal noise (66 ± 22 ms vs 51 ± 29 ms; P < .001), both respiratory triggering techniques yielded similar estimates for EDV, ESV, LVEF (RRS: 387 ± 56 µL, 162 ± 34 µL, 59 ± 5%; ERS: 389 ± 59 µL, 163 ± 35 µL, 59 ± 4%; P = n.s.).Conclusions: This study showed that respiratory gating signals can be accurately derived from cardiac trigger information alone, without the additional requirement for dedicated measurement of the respiratory motion in rats. [ABSTRACT FROM AUTHOR]

Respiratory gating has been widely applied for respiratory correction or compensation in image acquisition and image-guided interventions. A novel image-based method is proposed to extract respiratory signal directly from 2D ultrasound liver images. The proposed method utilizes a typical manifold learning method, based on local tangent space alignment based technique, to detect principal respiratory motion from a sequence of ultrasound images. This technique assumes all the images lying on a low-dimensional manifold embedding into the high-dimensional image space, constructs an approximate tangent space of each point to represent its local geometry on the manifold, and then aligns the local tangent spaces to form the global coordinate system, where the respiratory signal is extracted. The experimental results show that the proposed method can detect relatively accurate respiratory signal with high correlation coefficient (0.9775) with respect to the ground-truth signal by tracking external markers, and achieve satisfactory computing performance (2.3 s for an image sequence of 256 frames). The proposed method is also used to create breathing-corrected 3D ultrasound images to demonstrate its potential application values. [ABSTRACT FROM AUTHOR]

Accurate localization and uptake quantification of lesions in the chest and abdomen using PET imaging is challenged by respiratory motion occurring during the exam. This work describes how a stack-of-stars MRI acquisition on integrated PET/MRI systems can be used to derive a high-resolution motion model, how many respiratory phases need to be differentiated, how much MRI scan time is required, and how the model is employed for motion-corrected PET reconstruction. MRI self-gating is applied to perform respiratory gating of the MRI data and simultaneously acquired PET raw data. After gated PET reconstruction, the MRI motion model is used to fuse the individual gates into a single, motion-compensated volume with high signal-to-noise ratio (SNR). The proposed method is evaluated in vivo for 15 clinical patients. The gating requires 5–7 bins to capture the motion to an average accuracy of 2 mm. With 5 bins, the motion-modeling scan can be shortened to 3–4 min. The motion-compensated reconstructions show significantly higher accuracy in lesion quantification in terms of standardized uptake value (SUV) and different measures of lesion contrast compared to ungated PET reconstruction. Furthermore, unlike gated reconstructions, the motion-compensated reconstruction does not lead to SNR loss. [ABSTRACT FROM AUTHOR]

In PET/CT thoracic imaging, respiratory motion reduces image quality. A solution consists in performing respiratory gated PET acquisitions. The aim of this study was to generate clinically realistic Monte-Carlo respiratory PET data, obtained using the 4D-NCAT numerical phantom and the GATE simulation tool, to assess the impact of respiratory motion and respiratory-motion compensation in PET on lesion detection and volume measurement. To obtain reconstructed images as close as possible to those obtained in clinical conditions, a particular attention was paid to apply to the simulated data the same correction and reconstruction processes as those applied to real clinical data. The simulations required 140,000 h (CPU) generating 1.5 To of data (98 respiratory gated and 49 ungated scans). Calibration phantom and patient reconstructed images from the simulated data were visually and quantitatively very similar to those obtained in clinical studies. The lesion detectability was higher when the better trade-off between lesion movement limitation (compared to ungated acquisitions) and image statistic preservation is considered (respiratory cycle sampling in 3 frames). We then compared the lesion volumes measured on conventional PET acquisitions versus respiratory gated acquisitions, using an automatic segmentation method and a 40%-threshold approach. A time consuming initial manual exclusion of noisy structures needed with the 40%-threshold was not necessary when the automatic method was used. The lesion detectability along with the accuracy of tumor volume estimates was largely improved with the gated compared to ungated PET images. [ABSTRACT FROM AUTHOR]

Bodily self-consciousness depends on the processing of interoceptive and exteroceptive signals. It can be disrupted by inducing signal conflicts. Breathing, at the crossroad between interoception and exteroception, should contribute to bodily self-consciousness. We induced visuo-respiratory conflicts in 17 subjects presented with a virtual body or a parallelepidedal object flashing synchronously or asynchronously with their breathing. A questionnaire detected illusory changes in bodily self-consciousness and breathing agency (the feeling of sensing one's breathing command). Changes in self-location were tested by measuring reaction time during mental ball drop (MBD). Synchronous illumination changed the perceived location of breathing (body: p = 0.008 vs. asynchronous; object: p = 0.013). It resulted in a significant change in breathing agency, but no changes in self-identification. This was corroborated by prolonged MBD reaction time (body: +0.045 s, 95%CI [0.013; 0.08], p = 0.007). We conclude that breathing modulates bodily self-consciousness. We also conclude that one can induce the irruption of unattended breathing into consciousness without modifying respiratory mechanics or gas exchange. [ABSTRACT FROM AUTHOR]

Purpose To quantify the influence on heart dose metrics of prone left-sided whole-breast irradiation in an end-inspiratory phase (Pr IN ) versus an end-expiratory phase (Pr EX ). Patients and methods Twenty patients underwent CT-simulation in Pr IN and Pr EX . Dynamic intensity-modulated radiotherapy was planned for whole-breast irradiation with a median prescription dose of 40.05 Gy in 15 fractions and maximal sparing of the organs at risk. Dose–volume parameters were analyzed for heart, left anterior descending coronary artery, ipsilateral lung and both breasts. Results Pr IN consistently reduced ( P < 0.001) heart and left anterior descending coronary artery dose metrics compared to Pr EX . Population averages for maximum and mean heart dose were 6.2 Gy and 1.3 Gy for Pr IN versus 21.4 Gy and 2.5 Gy for Pr EX , respectively. Moreover, a maximum heart dose less than 10 Gy was achieved in 80% of patients for Pr IN . Target dose distribution, ipsilateral lung and contralateral breast sparing by radiation dose were similar for both procedures. Conclusions Inspiratory gating consistently reduced heart dose metrics pointing to a possible benefit of breathing-adapted radiotherapy for prone left-sided whole-breast irradiation. [ABSTRACT FROM AUTHOR]

Bodily self-consciousness depends on the processing of interoceptive and exteroceptive signals. It can be disrupted by inducing signal conflicts. Breathing, at the crossroad between interoception and exteroception, should contribute to bodily self-consciousness. We induced visuo-respiratory conflicts in 17 subjects presented with a virtual body or a parallelepidedal object flashing synchronously or asynchronously with their breathing. A questionnaire detected illusory changes in bodily self-consciousness and breathing agency (the feeling of sensing one's breathing command). Changes in self-location were tested by measuring reaction time during mental ball drop (MBD). Synchronous illumination changed the perceived location of breathing (body: p = 0.008 vs. asynchronous; object: p = 0.013). It resulted in a significant change in breathing agency, but no changes in self-identification. This was corroborated by prolonged MBD reaction time (body: +0.045 s, 95%CI [0.013; 0.08], p = 0.007). We conclude that breathing modulates bodily self-consciousness. We also conclude that one can induce the irruption of unattended breathing into consciousness without modifying respiratory mechanics or gas exchange. [ABSTRACT FROM AUTHOR]

Résumé La radiothérapie est utilisée dans les cancers du poumon inopérables, associée ou non à de la chimiothérapie. La radiothérapie classique donne des résultats décevants. De nouvelles techniques permettent une meilleure adaptation au volume tumoral et limitent l’irradiation des tissus sains avec, à terme, la possibilité d’augmenter les doses dans la tumeur et potentiellement d’améliorer la probabilité de survie. Avec la radiothérapie conformationnelle par modulation d’intensité, il est possible de conformer les isodoses à des volumes complexes. Elle est largement utilisée et semble indiquée quand la tumeur est localement évoluée. Ses gains dosimétriques sont démontrés mais les résultats cliniques sont encore hétérogènes. La radiothérapie stéréotaxique permet le traitement de petits volumes cibles par de multiples faisceaux étroits. Elle nécessite des appareils dédiés ou des équipements adaptés sur des accélérateurs classiques. Pour les tumeurs de faible stade, son efficacité est comparable à la chirurgie avec une toxicité acceptable. La curiethérapie endobronchique peut aussi être utilisée pour des tumeurs de faible stade répondant à des critères particuliers. L’hadronthérapie est une technique encore expérimentale. Les hadrons possèdent des propriétés physiques permettant une distribution de dose très précise. Dans les rares études publiées, la toxicité est globalement inférieure aux autres techniques mais pour les tumeurs de faible stade, son efficacité ne semblerait pas supérieure celle de la radiothérapie en conditions stéréotaxiques. Ces techniques sont optimisées par l’imagerie métabolique qui permet de mieux définir la cible et d’évaluer la réponse thérapeutique, la radiothérapie guidée par l’image qui permet un repositionnement plus précis et par les techniques d’asservissement respiratoire qui prennent en compte des mouvements de la cible. Radiotherapy is used for inoperable lung cancers, sometimes in association with chemotherapy. Outcomes of conventional radiotherapy are disappointing. New techniques improve adaptation to tumour volume, decrease normal tissue irradiation and lead to increasing tumour dose with the opportunity for improved survival. With intensity-modulated radiation therapy, isodoses can conform to complex volumes. It is widely used and seems to be indicated in locally advanced stages. Its dosimetric improvements have been demonstrated but outcomes are still heterogeneous. Stereotactic radiotherapy allows treatment of small volumes with many narrow beams. Dedicated devices or appropriate equipment on classical devices are needed. In early stages, its efficacy is comparable to surgery with an acceptable toxicity. Endobronchial brachytherapy could be used for early stages with specific criteria. Hadrontherapy is still experimental regarding lung cancer. Hadrons have physical properties leading to very accurate dose distribution. In the rare published studies, toxicities are roughly lower than others techniques but for early stages its effectiveness is not better than stereotactic radiotherapy. These techniques are optimized by metabolic imaging which precisely defines the target volume and assesses the therapeutic response; image-guided radiation therapy which allows a more accurate patient set up and by respiratory tracking or gating which takes account of tumour respiratory motions. [ABSTRACT FROM AUTHOR]

PET acquisition requires several minutes which can lead to respiratory motion blurring, to increase partial volume effect and SUV under-estimation. To avoid these artifacts, conventional 10-min phase-based respiratory gating (PBRG) can be performed but is time-consuming and difficult with a non-compliant patient. We evaluated an automatic amplitude-based gating method (AABG) which keeps 35% of the counts at the end of expiration to minimize respiratory motion. We estimated the impact of AABG on upper abdominal lesion detectability, quantification and patient management. Methods: We consecutively included 31 patients (82 hepatic and 25 perihepatic known lesions). Each patient underwent 3 acquisitions on a Siemens Biograph mCT (4 rings and time-of-flight): a standard free-breathing whole-body (SWB, 5–7 steps/2.5min per step, 3.3±0.4MBq/kg of 18F-FDG), a 10-min PBRG with six bins and a 5-min AABG method. All gated acquisitions were performed with an ANZAI respiratory gating system. SUVmax and target to background ratio (TBR, defined as the maximum SUV of the lesion divided by the mean SUV of a region of interest drawn in healthy liver) were compared. Results: All 94 lesions in SWB images were detected in the gated images. 10-min PBRG and 5-min AABG acquisitions respectively revealed 9 and 13 new lesions and relocated 7 and 8 lesions. Four lesions revealed by 5-min AABG were missed by 10-min PBRG in 3 non-compliant patients. Both gated methods failed to relocate 2 lesions seen on SWB acquisition. Compared to SWB, TBR increased significantly with 10-min PBRG and with 5-min AABG (respectively 41±59%, p =4.10–3 and 66±75%, p =6.10–5) whereas SUVmax did not (respectively 14±43%, p =0.29 with 10-min PBRG, and 24±46%, p =0.11 with 5-min AABG). Conclusion: The AABG is a fast and a user-friendly respiratory gating method to increase detectability and quantification of upper abdominal lesions compared to the conventional PBRG procedure and the SWB acquisition. [ABSTRACT FROM AUTHOR]

• The greater sensitivity of the new Silicon photomultipliers-based PET systems. • Amplitude-based respiratory motion compensation algorithms may be more widely used in a clinical setting. The objective of this phantom study was to determine whether breathing-synchronized, silicon photomultiplier (SiPM)-based PET/CT has a suitable acquisition time for routine clinical use. Acquisitions were performed in list mode on a 4-ring SiPM-based PET/CT system. The experimental setup consisted of an external respiratory tracking device placed on a commercial dynamic thorax phantom containing a sphere filled with [F-18]-fluorodeoxyglucose. Three-dimensional sinusoidal motion was imposed on the sphere. Data were processed using frequency binning and amplitude binning (the "DMI" and "OFFLINE" methods, respectively). PET sinograms were reconstructed with a Bayesian penalized likelihood algorithm. Respiratory gating from a 150‑ sec acquisition was successful. The DMI and OFFLINE methods gave similar activity profiles but both were slightly shifted in space; the latter profile was closest to the reference acquisition. With SiPM PET/CT systems, the amplitude-based processing of breathing-synchronized data is likely to be feasible in routine clinical practice. [ABSTRACT FROM AUTHOR]

Abstract: With the emergence of the mouse as the predominant model system for studying mammalian brain development, in utero imaging methods are urgently required to analyze the dynamics of brain growth and patterning in mouse embryos. To address this need, we combined synthetic focusing with a high-frequency (38-MHz) annular-array ultrasound imaging system for extended depth-of-field, coded excitation for improved penetration and respiratory-gated transmit/receive. This combination allowed non-invasive in utero acquisition of motion-free 3-D data from individual embryos in approximately 2 min, and data from four or more embryos in a pregnant mouse in less than 30 min. Data were acquired from 148 embryos spanning 5 d of early to mid-gestational stages of brain development. The results indicated that brain anatomy and cerebral vasculature can be imaged with this system and that quantitative analyses of segmented cerebral ventricles can be used to characterize volumetric changes associated with mouse brain development. [Copyright &y& Elsevier]

Purpose: The purpose of this study was to quantify the effects of four-dimensional computed tomography (4DCT), 4D image guidance (4D-IG), and beam gating on calculated treatment field margins in a lung cancer patient population. Materials and Methods: Images were acquired from 46 lung cancer patients participating in four separate protocols at three institutions in Europe and the United States. Seven patients were imaged using fluoroscopy, and 39 patients were imaged using 4DCT. The magnitude of respiratory tumor motion was measured. The required treatment field margins were calculated using a statistical recipe (van Herk M, et al. Int J Radiat Oncol Biol Phys 2000;474:1121–1135), with magnitudes of all uncertainties, except respiratory peak-to-peak displacement, the same for all patients, taken from literature. Required margins for respiratory motion management were calculated using the residual respiratory tumor motion for each patient for various motion management strategies. Margin reductions for respiration management were calculated using 4DCT, 4D-IG, and gated beam delivery. Results: The median tumor motion magnitude was 4.4 mm for the 46 patients (range 0–29.3 mm). This value corresponded to required treatment field margins of 13.7 to 36.3 mm (median 14.4 mm). The use of 4DCT, 4D-IG, and beam gating required margins that were reduced by 0 to 13.9 mm (median 0.5 mm), 3 to 5.2 mm (median 5.1 mm), and 0 to 7 mm (median 0.2 mm), respectively, to a total of 8.5 to 12.4 mm (median 8.6 mm). Conclusion: A respiratory management strategy for lung cancer radiotherapy including planning on 4DCT scans and daily image guidance provides a potential reduction of 37% to 47% in treatment field margins. The 4D image guidance strategy was the most effective strategy for >85% of the patients. [Copyright &y& Elsevier]

Abstract: The aim of this paper is to describe the difficulties encountered when implementing stereotactic radiotherapy of non-small cell lung cancer (T1-T2, N0, M0) using a voluntary breath-hold technique. From 25/03/2010 to 22/02/2011, eight patients with a non-small cell lung cancer were selected for treatment. CT images were obtained with the patient maintaining breath-hold using a spirometer. Treatment was delivered when the patient maintains this level of breath-hold. Treatment was performed with a 4MV and 10MV photon beams from a linear accelerator Varian 2100CS, equipped with a 120 leaves collimator. 60Gy or 48Gy were delivered, in four sessions, to the 80% isodose. The planning target volume (PTV) was defined by adding a 5mm margin to the internal target volume (ITV), the ITV corresponding to the gross tumour volume (GTV) plus a 3mm margin. CTV is considered equal to GTV. The non-understanding of the gating technique, the great number of beams and the limited breath-hold times led to the failure of some treatments. It can be explained by some patients insufficient respiratory abilities and the low dose rate of one of the beams used for treatment, thus forcing some radiation fields to be delivered in two or three times. Implementing such a technique can be limited by the patients’ physical abilities and the materials used. Some solutions were found: a training phase more intense with a coaching of the breath-hold technique more precise, or the use of an abdominal compression device. [Copyright &y& Elsevier]

Abstract: Purpose: To compare respiratory-gated conformal radiotherapy versus conventional conformal radiotherapy for the irradiation of non-small cells lung cancer and breast cancer. Patients and methods: The STIC 2003 project was a comparative, non-randomized, multicenter and prospective study that included in 20 French centers between April 2004 and June 2008, 634 evaluable patients, 401 non-small cells lung cancer and 233 breast cancers. Results: The final results confirmed the feasibility and good reproducibility of the various respiratory-gated conformal radiotherapy systems regardless of tumour location. The results of this study demonstrated a marked reduction of dosimetric parameters predictive of pulmonary, cardiac and esophageal toxicity, especially for non-small cells lung cancer, as a result of the various respiratory gating techniques. These dosimetric benefits were mainly observed with deep inspiration breath-hold techniques (ABC and SDX), which markedly increased the total lung volume compared to the inspiration-synchronized system based on tidal volume (RPM). For non-small cells lung cancer, these theoretical dosimetric benefits were correlated with a significant reduction in clinically acute and late toxicities, especially the pulmonary. For breast cancer, although less clear due to the lower total dose, there was a decrease in the dose delivered to the heart, potentially reducing the risk of cardiac toxicity in the long-term, especially during the irradiation of the left breast, and a reduction in dose to the contra lateral breast. Conclusion: Respiratory-gated radiotherapy appears to be essential to reduce the risk of acute and late toxicities, especially for lungs and heart, during irradiation of non-small cells lung cancer and breast cancers. [Copyright &y& Elsevier]

Abstract: Purpose: To evaluate the different respiratory movement management techniques during irradiation of lung tumours. Patients and methods: Seven patients with one or more primary or secondary lung lesions less than 5cm (11 tumours in total) had three computed tomographies (CT): free-breathing, deep-inspiration breath-hold using a spirometer, and 4-dimensional (4D). From these three acquisitions, five treatment plans were performed: free-breathing (reference method), deep-inspiration breath-hold, and three from the 4D CT: two breathing synchronized treatments (inspiration and expiration) and one treatment taking into account all the tumour motions (definition of the internal target volume [ITV]). Planning target volume (PTV) size and dose delivered to the lungs were compared. Results: Mean PTV with the free-breathing modality was 83±28cm3, which was significantly greater than any of the other techniques (P <0.0001). Compared to the free-breathing PTV, PTV defined with the ITV was reduced by one quarter (63±31cm3), and PTV with the deep-inspiration breath-hold, breathing synchronized inspiration and breathing synchronized expiration techniques were reduced by one third (50 to 54±24 to 26cm3). Deep-inspiration led to significantly increase the healthy lung volume compared to other methods (mean volume of 5500±1500cm3 versus 3540 to 3920cm3, respectively, P <0.0001). The volume of healthy lungs receiving at least 5 and 20Gy (V5 and V5) were significantly higher with the free-breathing method than any of the other methods (P <0.0001). The deep-inspiration breath-hold modality led to the lowest lung V5 and V20. Conclusion: Deep-inspiration breath-hold technique provides the most significant dosimetric advantages: small PTV and large lung volume. However, patients must be able to hold 20seconds of apnea. Respiratory gating also reduces the PTV, but its application often requires the implantation of fiducial, which limit its use. A 4-dimensional CT allows for a personalized and reduced PTV compared to free-breathing CT. [Copyright &y& Elsevier]

Purpose: To investigate respiration-induced heart motion for left-sided breast irradiation using a four-dimensional computed tomography (4DCT) technique and to determine novel indications to assess heart motion and identify breast patients who may benefit from a gated treatment. Methods and Materials: Images of 4DCT acquired during free breathing for 20 left-sided breast cancer patients, who underwent whole breast irradiation with or without regional nodal irradiation, were analyzed retrospectively. Dose distributions were reconstructed in the phases of 0%, 20%, and 50%. The intrafractional heart displacement was measured in three selected transverse CT slices using DLAD (the distance from left ascending aorta to a fixed line [connecting middle point of sternum and the body] drawn on each slice) and maximum heart depth (MHD, the distance of the forefront of the heart to the line). Linear regression analysis was used to correlate these indices with mean heart dose and heart dose volume at different breathing phases. Results: Respiration-induced heart displacement resulted in observable variations in dose delivered to the heart. During a normal free-breathing cycle, heart-induced motion DLAD and MHD changed up to 9 and 11 mm respectively, resulting in up to 38% and 39% increases of mean doses and V25.2 for the heart. MHD and DLAD were positively correlated with mean heart dose and heart dose volume. Respiratory-adapted gated treatment may better spare heart and ipsilateral-lung compared with the conventional non-gated plan in a subset of patients with large DLAD or MHD variations. Conclusion: Proposed indices offer novel assessment of heart displacement based on 4DCT images. MHD and DLAD can be used independently or jointly as selection criteria for respiratory gating procedure before treatment planning. Patients with great intrafractional MHD variations or tumor(s) close to the diaphragm may particularly benefit from the gated treatment. [ABSTRACT FROM AUTHOR]

Abstract: Background and objective: Respiratory-gated techniques are based on controlling the linear accelerator and limiting the beam-on time to only a small portion of the patient’s breathing cycle. For each beam-on, the machine must spend a start-up time (ST) to set up a stable and correct RF field in the waveguide and get the right beam current, etc. That might cause an obvious variation on the beam dosimetric characteristic, including the beam quality and profile, when the duration of ST is un-ignorable to the beam-on time. The purpose of this study is to investigate this kind of impact for various duty cycles (DC) of breathing-gated operation. Materials and method: A respiratory motion phantom and a Real-time Position Management System (RPM) were used to simulate the patient respiration and to control the beam gating. Measurements were performed on a Varian 600C/D linac with 6 MV photons, using different DCs of 5%, 7%, 10%, 12%, 20%, 50%, 75%, and 100% to a 6-s breathing cycle (BC) simulation. The beam quality, flatness, symmetry were evaluated for these conditions. Output reproducibility and dose linearity were measured and evaluated for different MUs at 400 MU/min dose rate and 30% DC as well. Results: For gated delivery in the above selected DCs and BC, the maximum changes in beam quality, symmetry, flatness were −0.181%, 0.124%, −0.17%, compared with non-gated data respectively. The coefficient of dispersion of output was less than 0.3% and good dose linearity was obtained for the tested gating operation condition. Conclusion: For situation similar to our experiment, the duty cycle effect to beam characteristics is ignorable that the beam modeling based on non-gated delivery can be directly used for respiratory gating therapy. Otherwise, the beam characteristics should be carefully checked individually. [Copyright &y& Elsevier]

Abstract: Only 60% of patients with early-stage non-small cell lung cancer (NSCLC), a priori bearing a favorable prognosis, undergo radical resection because of the very frequent co-morbidities occurring in smokers, precluding surgery to be safely performed. Stereotactic radiotherapy consists of the use of multiple radiation microbeams, allowing high doses of radiation to be delivered to the tumour (ranging from 7.5 to 20Gy per fraction) in a small number of fractions (one to eight on average). Several studies with long-term follow-up are now available, showing the effectiveness of stereotactic radiotherapy to control stage I/II non-small cell lung cancer in medically inoperable patients. Local control rates are consistently reported to be above 95% with a median survival of 34 to 45 months. Because of these excellent results, stereotactic radiation therapy is now being evaluated in operable patients in several randomized trials with a surgical arm. Ultimately, the efficacy of stereotactic radiotherapy in early-stage tumours leads to hypothesize that it may represent an opportunity for locally-advanced tumors. The specific toxicities of stereotactic radiotherapy mostly correspond to radiation-induced chest wall side effects, especially for peripheral tumours. The use of adapted fractionation schemes has made feasible the use of stereotactic radiotherapy to treat proximal tumours. Overall, from a technical concept to the availability of specific treatment devices and the publication of clinical results, stereotactic radiotherapy represents a model of implementation in thoracic oncology. [Copyright &y& Elsevier]

Abstract: Purpose: The current IGRT repositioning cannot fully account for the organ deformation and rotation. We introduce a comprehensive solution using gated IMRT with online adaptive replanning to manage both inter- and intra-fractional variations. Methods and materials: The solution includes (1) generating respiration-gated IMRT plans based on 4DCT, (2) acquiring daily gated CT in treatment position prior to the treatment using a diagnostic-quality in-room CT (CTVision, Siemens) with the same gating window as that for the planning CT, (3) performing online repositioning or adaptive replanning based on the gated CT of the day, and (4) delivering the treatment with gating. The entire solution is demonstrated with RT data from 10 selected pancreatic cancer cases. The dosimetric impact of various advanced delivery technologies was investigated. Results: The online adaptive replanning based on the CT of the day combining with gating significantly improves normal tissue sparing during RT for pancreatic cancer. As the complexity of the delivery technology increases from no IGRT to with IGRT, gating and online adaptive replanning, the inter- and intra-fractional variations can be accounted for with increased adequacy. Conclusion: The online adaptive replanning technique based on daily respiration-gated diagnostic-quality CT combined with gated delivery can effectively correct for inter- and intra-fraction variations during radiation therapy. [Copyright &y& Elsevier]

Abstract: The purpose of this study was to define individualized internal target volume (ITV) for hepatocellular carcinoma (HCC) using 4D computed tomography (4DCT), and to determine the geometric and dosimetric benefits of respiratory gating. Gross tumor volumes (GTVs) were contoured on 10 respiratory phases of 4DCT images for 12 patients with HCC. Three treatment plans were prepared using different planning target volumes (PTVs): (1) PTV3D, derived from a single helical clinical target volume (CTV) plus conventional margins; (2) PTV10 phases, derived from ITV10 phases, which encompassed all 10 CTVs plus an isotropic margin of 0.8 cm; (3) PTVgating, derived from ITVgating, which encompassed three CTVs within gating-window at end-expiration plus an isotropic margin of 0.8 cm. The PTV3D was the largest volume for all patients. The ITV-based plans and gating plans spared more normal tissues than 3D plans, especially the liver. Without increasing normal tissue complication probability of the 3D plans, the ITV-based plans allowed for increasing the calculated dose from 50.8 Gy to 54.7 Gy on average, and the gating plans could further escalate the dose to 58.5 Gy. Compared with ITV-based plans, the dosimetric gains with gating plan strongly correlated with GTV mobility in the craniocaudal direction. The ITV-based plans can ensure target coverage with less irradiation of normal tissues compared with 3D plans. Respiratory-gated radiotherapy can further reduce the target volumes to spare more surrounding tissues and allow dose escalation, especally for patients with tumor mobility >1 cm. [Copyright &y& Elsevier]

Abstract: For a long time radiotherapy has been excluded from the therapeutic strategy for hepatocellular carcinoma, given its significant toxicity on the non-tumoral liver parenchyma. Conformal radiation is a recent advance in the field of radiotherapy, allowing dose escalation and combination with other therapeutic options for hepatocellular carcinoma, including trans-arterial chemo-embolization. Conformal radiotherapy is associated with interesting features, especially in cirrhotic patients: wide availability, non-invasiveness, possibility to target multiple localizations anywhere within the liver parenchyma, and favorable tolerance profile even in patients with cirrhosis and/or in a poor medical condition. Recently, radiation delivery has been optimized through several technical developments: respiratory gating and intensity-modulated radiotherapy, which allow a better focalization of the ballistics, stereotactic techniques and proton-beam radiotherapy, whose availability is currently limited in Europe. Given the high response rates of hepatocellular carcinoma to radiation, conformal radiotherapy may be regarded as a curative-intent treatment for hepatocellular carcinoma, similar to surgery and per-cutaneous techniques. Yet the impact of radiotherapy has to be evaluated in randomized trials to better integrate in the complex therapeutic algorithm of hepatocellular carcinoma. [Copyright &y& Elsevier]

Abstract: Background: There is a great deal of excitement regarding respiratory gated radiotherapy (RGRT), however there remain potential errors and controversies surrounding its use. We aim to predict an improvement in the clinical outcome of RGRT in comparison with that of continuous (non-gated) irradiation by analysing toxicity parameters. Materials and methods: The 4DCT scans of 15 patients, with node-positive lung cancer and >5mm of tumour movement, were used for this retrospective analysis. End-inspiration and end-expiration plans were created and the toxicity parameters were compared to continuous (non-gated) 4DCT plans. Results: Median reduction in V20 with inspiratory gating and expiratory gating, using a 10mm set-up margin, was 2.0% (range 0.7% to 3.9%) and 0.6% (range −1.1% to 4.7%), respectively. The reduction in MLD was 2.1Gy (range 0.6 to 3.9Gy) and 1.6Gy (range −1.0 to 3.9Gy), respectively. Conclusions: Although there is a widespread excitement regarding this technique, this study demonstrates that there is limited reduction in toxicity parameters with the use of RGRT in comparison with continuous (non-gated) 4DCT irradiation. Due to the additional potential errors involved in RGRT, we feel that currently, it should only be performed if comparative planning of RGRT plans and continuous (non-gated) 4DCT plans has been undertaken and a likely clinical benefit has been confirmed. [Copyright &y& Elsevier]

Purpose: To evaluate the margins currently used to generate the planning target volume for lung tumors and to determine whether image-guided patient setup or respiratory gating is more effective in reducing uncertainties in tumor position. Methods and Materials: Lung tumors in 7 patients were contoured on serial four-dimensional computed tomography (4DCT) data sets (4–8 4DCTs/patient; 50 total) obtained throughout the course of treatment. Simulations were performed to determine the tumor position when the patient was aligned using skin marks, image-guided setup based on vertebral bodies, fiducials implanted near the tumor, and the actual tumor volume under various scenarios of respiratory gating. Results: Because of the presence of setup uncertainties, the reduction in overall margin needed to completely encompass the tumor was observed to be larger for imaged-guided patient setup than for a simple respiratory-gated treatment. Without respiratory gating and image-guided patient setup, margins ranged from 0.9 cm to 3.1 cm to completely encompass the tumor. These were reduced to 0.7–1.7 cm when image-guided patient setup was simulated and further reduced with respiratory gating. Conclusions: Our results indicate that if respiratory motion management is used, it should be used in conjunction with image-guided patient setup in order to reduce the overall treatment margin effectively. [Copyright &y& Elsevier]

Abstract: Purpose: To evaluate the ability and accuracy of a respiratory gated technique used with contrast enhanced MDCT of the upper abdomen with focus on diagnostic image quality and depiction of organs and major vessels. Materials and methods: Forty-five adult patients who were referred to our institution for follow-up dynamic contrast enhanced abdominal CT imaging were included in this study. Respiratory gated CT scans were performed with the use of a dedicated hardware. A multiphasic CT scan was performed for each patient. Respiratory gated images were obtained between early arterial and portal venous phases during free breathing. Images of respiratory gated (RG) and breathhold (BH) phases were compared qualitatively and quantitatively by two radiologists. Definitive statistical methods were used for evaluating the scoring data, while Mann Whitney U test was used for comparison. Statistical significance was accepted for p values <0.05. Results: Statistical significant difference was found for comparison of scores regarding luminal opacification and contoural integrity of intrahepatic vascular structures with scores of RG scans rated poor to moderate (e.g. 2.86±1.07 for luminal opacification of intrahepatic portal veins as well as border detectability) in comparison to scores of BH scans rated good to excellent (e.g. 1.37±1.31 for luminal opacification, 1.35±1.28 for border detectability of intrahepatic portal veins, p <0.001). Furthermore, statistical significant differences were found for general image noise levels (p <0.001). Conclusions: Further technical advances of RG technique could enable routine use of this technique for selected patient groups. [Copyright &y& Elsevier]

Abstract: The aim of this feasibility study was to evaluate the response to cytotoxic and antiangiogenic treatment of colorectal liver metastasis using respiratory gated contrast enhanced ultrasonography. Seven patients were monitored with contrast enhanced ultrasound. Sulfur hexafluoride filled microbubbles (SonoVue; Bracco S.P.A., Milan, Italy) were used as contrast agent and the scans were performed with a nonlinear imaging technique (power modulation) at low transmit power (MI=0.06). The mean image intensity in the metastatic lesion and in the normal liver parenchyma were measured as a function of time and time-intensity curves from linearized image data were formed. A novel respiratory gating technique was utilized to minimize the effects of respiratory motion on the images. A reference position of the diaphragm (or other echogenic interface) was selected and all frames where the diaphragm deviated from that position were rejected. The wash-in time (start of enhancement to peak) of metastasis and adjacent normal liver parenchyma was measured from time-intensity curves. The ratio of wash-in time of the lesion to that of the normal parenchyma (WITR) was used to compare the perfusion rate. In a reproducibility study (five patients), the average deviation of WITR was found to be 9%. There was an increase in the WITR for patients responding to treatment (mean WITR increase of 17% after first dose of treatment and 75% at the end of the therapy). In four out of five patients (80%) responding to therapy WITR predicted their response from the first treatment. All six patients that responded to therapy by the end of the therapy cycle (6–9 doses) were correctly predicted by using WITR. The WITR may be a new surrogate marker indicative of early tumor response for colorectal cancer patients undergoing cytotoxic and antiangiogenic therapy. (E-mail: maverk@ucy.ac.cy) [Copyright &y& Elsevier]

Purpose: To determine whether lung tumor respiratory excursion at simulation is predictive of excursion during radiation and whether phase offsets between tumor and surrogate markers are constant throughout treatment. Methods and Materials: Respiration-correlated CT scans and two rescans (using a Brilliance Big Bore spiral CT simulator; Philips, Inc.) were obtained from 20 patients at simulation. Gross tumor volume (GTV) was contoured on 10 phases of the respiratory cycle, and excursions were calculated. Diaphragm and xyphoid motion were quantified. Phase offsets, ΔΦ, were calculated for patients with a GTV motion of >3 mm. Interfraction differences in excursions between simulation and rescans and magnitudes of variation in phase offset between fractions were evaluated. Results: Mean GTV excursions at simulation in superior-inferior, anterior-posterior, and medial-lateral directions were 0.67, 0.29, and 0.21 cm, respectively. The magnitude of superior-inferior GTV excursion correlated with tumor location (upper vs. lower lobe, p = 0.011). GTV excursions between simulation and rescan 1 (p = 0.115) and between simulation and rescan 2 (p = 0.071) were stable. Fourteen patients were analyzed for variations in phase offsets. GTV–xyphoid phase offset changed significantly between simulation and rescan 1 (p = 0.007) and simulation and rescan 2 (p = 0.008), with mean ΔΦ values of 13.2% (rescan 1) and 14.3% (rescan 2). Xyphoid–diaphragm offset changed between simulation and rescan 1 (p = 0.004) and between simulation and rescan 2 (p = 0.012), with mean ΔΦ values of 14.5% (rescan 1) and 7.6% (rescan 2). Conclusions: Interfraction consistency in tumor excursion suggests tumor excursion at simulation may direct therapy. Significant variations in phase lag between GTV and other anatomic structures throughout treatment have important implications for techniques that rely on surrogate structures to predict tumor motion [Copyright &y& Elsevier]

Purpose: Respiratory-gated radiotherapy allows for the reduction of the toxicity associated with concomitant chemoradiotherapy, but the smaller fields used could increase the risk of missing the target. A prospective study was performed to evaluate the dosimetric consequences of time-trend changes in patients with lung cancer who were treated with concomitant chemoradiotherapy. Methods and Materials: A total of 24 lung cancer patients eligible for chemoradiotherapy and gated delivery underwent four-dimensional computed tomography (4D-CT) after 15 fractions. This scan was co-registered with the initial planning 4D-CT and a new planning target volume (PTV) was generated on the basis of the tumor visualized after 15 fractions. Coverage of the repeat PTV was evaluated by applying the original plan to the second scan and recalculating the dose. Plan modification was triggered by a 5% reduction in the PTV included within the 95% isodose volume or an unacceptable increase in the critical organ dose. Results: Of the 21 evaluable patients, 15 had an average reduction in the PTV of 8% after 30 Gy. The PTV increased in the remaining 6 patients, but the increase was >20% in only 1 patient. In the latter patient, disease progression was observed, and repeat planning was required. The plans created using the new PTV were acceptable in all the other patients. Conclusion: The role of adaptive radiotherapy appears limited when respiratory-gated radiotherapy is used to reduce the toxicity related to concomitant chemoradiotherapy. The use of more conformal treatment techniques might provide the rationale for repeat imaging as a method to identify patients at risk of dosimetric miss. [Copyright &y& Elsevier]

Purpose: To assess the impact of respiration on myocardial perfusion imaging (MPI) SPECT processed with advanced algorithmic reconstructions. Methods: SPECT studies obtained from a phantom simulation and 49 respiratory-gated, one-day Tc-sestamibi scans were corrected for respiratory-related cardiac movement. Three types of reconstruction algorithms: (a) filtered back projection (FBP), (b) ordered subset expectation maximization in which collimator detector response was incorporated (OSEM-CDR), and (c) OSEM-CDR with additional attenuation and scatter corrections (OSEM-CDR-ACSC) were applied to the corrected and uncorrected sets and analyzed quantitatively and qualitatively. Results: A discrepancy between the corrected and uncorrected bull's eye maps ≥10% was found in 2%, 10%, and 20% of the FBP, OSEM-CDR, and OSEM-CDR-ACSC scans, respectively. In studies with more than 10-mm respiratory motion, the effect of motion was greater in OSEM-CDR and OSEM-CDR-ACSC datasets as compared to FBP processing. Qualitative and quantitative differences between corrected and uncorrected sets were significantly larger in OSEM-CDR and OSEM-CDR-ACSC data than in those of FBP data. Conclusions: Respiratory-related cardiac motion significantly affects MPI-SPECT reconstructed with advanced high-resolution reconstruction algorithms such as OSEM-CDR and OSEM-CDR-ACSC and thus may justifies the application of respiratory gating. [ABSTRACT FROM AUTHOR]

Purpose: The efficiency and precision of respiratory gated radiation therapy for tumors is affected by variations in respiration-induced tumor motion. We evaluated the use of individualized and population-based parameters for such treatment. Methods and Materials: External respiratory signal records and images of respiration-induced tumor motion were obtained from 42 patients undergoing respiratory gated radiation therapy for liver tumors. Gating window widths were calculated for each patient, with 2, 4, and 10 mm of residual motion, and the mean was defined as the population-based window width. Residual motions based on population-based and predefined window widths were compared. Duty times based on whole treatment sessions, at various window levels, were calculated. The window level giving the longest duty time was defined as the individualized most efficient level (MEL). MELs were also calculated based on the first 10 breathing cycles. The duty times for population-based MELs (defined as mean MELs) and individualized MELs were compared. Results: Tracks of respiration-induced tumor motion ranged from 3 to 50 mm. Half of the patients had larger actual residual motions than the assigned residual motions. Duty times were greater when based on individualized, rather than population-based, window widths. The MELs established during whole treatment sessions for 2 mm and 4 mm of residual motion gave significantly increased duty times, whereas those calculated using the first 10 breathing cycles showed only marginal increases. Conclusions: Using individualized window widths and levels provided more precise and efficient respiratory gated radiation therapy. However, methods for predicting individualized window levels before treatment remain to be explored. [Copyright &y& Elsevier]

Purpose: Intrafraction organ motion can produce dosimetric errors in radiotherapy. Commonly, the linear accelerator is gated using real-time breathing phase obtained by way of external sensors. However, the external anatomy does not always correlate well with the internal position. We examined a beam gating technique using signals from implanted wireless transponders that provided real-time feedback on the tumor location without an imaging dose to the patient. Methods and Materials: An interface was developed between Calypso Medical''s four-dimensional electromagnetic tracking system and a Varian Trilogy linear accelerator. A film phantom was mounted on a motion platform programmed with lung motion trajectories. Deliveries were performed when the beam was gated according to the signal from the wireless transponders. The dosimetric advantages of beam gating and the system latencies were quantified. Results: Beam gating using on internal position monitoring provided up to a twofold increase in the dose gradients. The percentage of points failing to be within ±10 cGy of the planned dose (maximal dose, ∼200 cGy) was 3.4% for gating and 32.1% for no intervention in the presence of motion. The mean latencies between the transponder position and linear accelerator modulation were 75.0 ±12.7 ms for beam on and 65.1 ± 12.9 ms for beam off. Conclusion: We have presented the results from a novel method for gating the linear accelerator using trackable wireless internal fiducial markers without the use of ionizing radiation for imaging. The latencies observed were suitable for gating using electromagnetic fiducial markers, which results in dosimetric improvements for irradiation in the presence of motion. [Copyright &y& Elsevier]

Copyright of Zeitschrift für Medizinische Physik is the property of Elsevier GmbH, Urban & Fischer Verlag and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)