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BACKGROUND The standard treatment of locally advanced rectal cancers (LARC) consists on neoadjuvant chemoradiotherapy followed by total mesorectal excision. Different data in literature showed a benefit on tumor downstaging and pathological complete response (pCR) rate using radiotherapy dose escalation, however there is shortage of studies regarding dose escalation using the innovative techniques for LARC (T3-4 or N1-2). AIM To analyze the role of neoadjuvant radiotherapy dose escalation for LARC using innovative radiotherapy techniques. METHODS In December 2020, we conducted a comprehensive literature search of the following electronic databases: PubMed, Web of Science, Scopus and Cochrane library. The limit period of research included articles published from January 2009 to December 2020. Screening by title and abstract was carried out to identify only studies using radiation doses equivalent dose 2 Gy fraction (EQD2) ≥ 54 Gy and Volumetric Modulated Arc Therapy (VMAT), intensity-modulated radiotherapy or image-guided radiotherapy (IGRT) techniques. The authors’ searches generated a total of 2287 results and, according to PRISMA Group (2009) screening process, 21 publications fulfil selection criteria and were included for the review. RESULTS The main radiotherapy technique used consisted in VMAT and IGRT modality. The mainly dose prescription was 55 Gy to high risk volume and 45 Gy as prophylactic volume in 25 fractions given with simultaneous integrated boosts technique (42.85%). The mean pCR was 28.2% with no correlation between dose prescribed and response rates (P value ≥ 0.5). The R0 margins and sphincter preservation rates were 98.88% and 76.03%, respectively. After a mean follow-up of 35 months local control was 92.29%. G3 or higher toxicity was 11.06% with no correlation between dose prescription and toxicities. Patients receiving EQD2 dose > 58.9 Gy and BED > 70.7 Gy had higher surgical complications rates compared to other group (P value = 0.047). CONCLUSION Dose escalation neoadjuvant radiotherapy using innovative techniques is safe for LARC achieving higher rates of pCR. EQD2 doses > 58.9 Gy is associated with higher rate of surgical complications.

Purpose A recent report by the American Association of Physicists in Medicine Task Group 75 and 180 provided imaging dose estimates for image-guided CyberKnife radiotherapy. However, to our knowledge, there have been no concrete demonstrations of imaging intervals that are directly linked to exposure dose. We hypothesized that setting a rational standard may be clearer through a balance of treatment accuracy and reducing imaging doses if the margin of the planned treatment volume is controlled through the imaging interval. This study was conducted to simulate the association between the imaging interval and intra-fraction displacement and to estimate a reasonable internal margin (IM). Methods We retrospectively analyzed data from 21 shell-fixed heads of patients treated with CyberKnife G3 using our dedicated monitoring system. This system comprises pressure sensors that can monitor head displacement every 0.2 s in the absence of any imaging dose. First, the root sum square of head displacements was calculated in 76 treatment fractions with an imaging interval of 10-1440 s. The cumulative frequency of a root sum square displacement (that was less than the IM) was evaluated in image verifications that were undertaken 546,274 times for every imaging interval. Results We found that the mean values and standard deviations (SD) of the displacement were larger in proportion to the imaging interval (p 0.056). The cumulative frequencies of displacement of 0.6 and 1.4 mm (i.e., less than an IM) were 99.2% and 99.1% for imaging intervals of 10 and 360 s, respectively. Conclusions In the current study, we found that imaging intervals were directly proportional to intra-fraction displacement and that there was no correlation in any combination within 720 s. Imaging intervals for an IM of 0.6 mm and 1.4 mm were 10 s and 360 s, respectively, with a 99% confidence interval of intra-fraction displacement. With CyberKnife M6 or a previous version of this system, the imaging dose could be reduced by 0.4760 mSv per 24-minute treatment as the imaging dose ranged from 0.4896 to 0.0136 mSv for imaging intervals of 10 and 360 s with an IM of 0.6 and 1.4 mm, respectively. A rational method that includes X-ray imaging guidance may be achieved with modulation of the imaging interval via the CyberKnife system. This article is protected by copyright. All rights reserved.

The complex and varied motion of the cervix-uterus target during external beam radiotherapy (EBRT) underscores the clinical benefits afforded by adaptive radiotherapy (ART) techniques. These gains have already been realised in the implementation of image-guided adaptive brachytherapy, where adapting to anatomy at each fraction has seen improvements in clinical outcomes and a reduction in treatment toxicity. With regards to EBRT, multiple adaptive strategies have been implemented, including a personalised internal target volume, offline replanning and a plan of the day approach. With technological advances, there is now the ability for real-time online ART using both magnetic resonance imaging and computed tomography-guided imaging. However, multiple challenges remain in the widespread dissemination of ART. This review investigates the ART strategies and their clinical implementation in EBRT delivery for cervical cancer.

Introduction: Adult medulloblastoma is a rare disease. Due to the length of the body areas demanding irradiation, medulloblastoma is a challenging malignancy for the development of advanced radiotherapy techniques. Case Report: We describe a volumetric modulated arc therapy (VMAT) technique applied under image-guided radiation therapy (IGRT) for craniospinal irradiation, offered to a patient with high risk medulloblastoma, together with cisplatin/temozolomide chemotherapy. Three areas of irradiation (cranial, thoracic, and lumbar) were defined, with shifting the gaps between them at a weekly basis (two shifts within the three weeks of therapy). The biological equivalent “normalized total dose” (NTD) to the craniospinal axis and the gaps between the three VMAT-treated areas were calculated for α/β-ratio of 2 Gy, and all the data from dose volume histograms (DVHs) are shown. Conclusion: The technique is reliable delivering with safety and accuracy the desirable radiation dose, with biologically and oncologically acceptable dose-deviations within the field-gaps. The tolerance of the radiochemotherapy regimen was excellent.

Organ motion as a result of respiratory and cardiac motion poses significant challenges for the accurate delivery of radiotherapy to both the thorax and the upper abdomen. Modern imaging techniques during radiotherapy simulation and delivery now permit better quantification of organ motion, which in turn reduces tumour and organ at risk position uncertainty. These imaging advances, coupled with respiratory correlated radiotherapy delivery techniques, have led to the development of a range of approaches to manage respiratory motion. This review summarises the key strategies of image-guided respiratory motion management with a focus on lung and liver radiotherapy.

The meticulous selection and utilisation of image-guided radiotherapy (IGRT) are essential for optimal radiotherapy treatment delivery when using highly conformal treatment techniques in pelvic radiotherapy. Pelvic IGRT has several general IGRT issues to consider (such as choice of match strategy, prioritisation between multiple treatment targets and margin estimates) as well as issues specific to pelvic radiotherapy, in particular large inter-fraction organ variation. A range of interventions, including adaptive treatment strategies, have been developed to address these challenges. This review covers general considerations for the clinical implementation of pelvic IGRT in routine practice and provides an overview of current knowledge regarding pelvic inter-fraction organ motion. Published IGRT evidence for each of the major tumour sites (gynaecological, prostate, bladder, rectal and anal cancer) is summarised, as are state-of-the-art adaptive approaches. General recommendations for the implementation of an institutional pelvic IGRT strategy include. •Ensuring consistency between treatment intent and the IGRT approach utilised. •Ensuring minimum national and international IGRT guidance is followed while considering the benefit of daily volumetric IGRT. •Ensuring the appropriate allied health professionals (namely therapy radiographers/radiation therapists) lead on undertaking IGRT. •Ensuring the IGRT workflow procedure is clear and includes an escalation process for difficult set-ups. •Ensuring a robust IGRT service is in place before implementing advanced adaptive approaches.

Surface guided radiotherapy (SGRT) is becoming a routine tool for patient positioning for specific clinical sites in many clinics. However, it has not yet gained its full potential in terms of widespread adoption. This vision paper first examines some of the difficulties in transitioning to SGRT before exploring the current and future role of SGRT alongside and in concert with other imaging techniques. Finally, future horizons and innovative ideas that may shape and impact the direction of SGRT going forward are reviewed.

Aims In image-guided radiotherapy, daily cone-beam computed tomography (CBCT) is rarely applied to children due to concerns over imaging dose. Simulating low-dose CBCT can aid clinical protocol design by allowing visualisation of new scan protocols in patients without delivering additional dose. This work simulated ultra-low-dose CBCT and evaluated its use for paediatric image-guided radiotherapy by assessment of image registration accuracy and visual image quality. Materials and methods Ultra-low-dose CBCT was simulated by adding the appropriate amount of noise to projection images prior to reconstruction. This simulation was validated in phantoms before application to paediatric patient data. Scans from 20 patients acquired at our current clinical protocol (0.8 mGy) were simulated for a range of ultra-low doses (0.5, 0.4, 0.2 and 0.125 mGy) creating 100 scans in total. Automatic registration accuracy was assessed in all 100 scans. Inter-observer registration variation was next assessed for a subset of 40 scans (five scans at each simulated dose and 20 scans at the current clinical protocol). This subset was assessed for visual image quality by Likert scale grading of registration performance and visibility of target coverage, organs at risk, soft-tissue structures and bony anatomy. Results Simulated and acquired phantom scans were in excellent agreement. For patient scans, bony atomy registration discrepancies for ultra-low-dose scans fell within 2 mm (translation) and 1° (rotation) compared with the current clinical protocol, with excellent inter-observer agreement. Soft-tissue registration showed large discrepancies. Bone visualisation and registration performance reached over 75% acceptability (rated ‘well’ or ‘very well’) down to the lowest doses. Soft-tissue visualisation did not reach this threshold for any dose. Conclusion Ultra-low-dose CBCT was accurately simulated and evaluated in patient data. Patient scans simulated down to 0.125 mGy were appropriate for bony anatomy set-up. The large dose reduction could allow for more frequent (e.g. daily) image guidance and, hence, more accurate set-up for paediatric radiotherapy.

Liver cancers are challenging to treat using image-guided radiotherapy (IGRT) due to motion and deformation of target volumes and organs at risk (OARs), as well as difficulties in visualising liver tumours using cone-beam computed tomography (CBCT) based IGRT. Liver cancer patients may thus benefit from magnetic resonance (MR)-guided daily adaptive re-planning. We evaluated the dosimetric impact of a daily plan adaptation strategy based on daily MR imaging versus CBCT-based IGRT.Ten patients were studied who were treated with CBCT-guided five-fraction stereotactic body radiotherapy (SBRT) and underwent MR imaging before each fraction. Simulated reference plans were created on computer tomography (CT) images and adapted plans were created on the daily MR images. Two plan adaptation strategies were retrospectively simulated: (1) translational couch shifts to match liver, mimicking standard CBCT guidance and (2) daily plan adaptation based on reference plan clinical goals and daily target and OAR contours. Dose statistics were calculated for both strategies and compared.Couch shifts resulted in an average reduction in GTV D99% relative to reference plan values of 5.2 Gy (-12.5% of reference values). Daily plan adaptation reduced this to 0.8 Gy (-2.0%). For six patients who were OAR dose-limited on reference plans, couch shifts resulted in OAR dose violations in 28 out of 28 simulated fractions, respectively; no violations occurred using daily plan adaptation. No OAR dose violations occurred using either strategy for the four cases not OAR dose-limited at reference planning.MR-guided daily plan adaptation ensured OAR dose constraints were met at all simulated treatment fractions while CBCT-based IGRT resulted in a systematic over-dosing of OARs in patients whose doses were limited by OAR dose at the time of reference planning.

Background and purposeWhen treating patients for esophageal cancer (EC) with photon or proton radiotherapy (RT), breathing motion of the target and neighboring organs may result in deviations from the planned dose distribution. The aim of this study was to evaluate the magnitude and dosimetric impact of breathing motion. Results were based on comparing weekly 4D computed tomography (4D CT) scans with the planning CT, using the diaphragm as an anatomical landmark for EC.Material and methodsA total of 20 EC patients were included in this study. Diaphragm breathing amplitudes and off-sets (changes in position with respect to the planning CT) were determined from delineated left diaphragm structures in weekly 4D CT-scans. The potential dosimetric impact of respiratory motion was shown in several example patients for photon and proton radiotherapy.ResultsVariation in diaphragm amplitudes were relatively small and ranged from 0 to 0.8 cm. However, the measured off-sets were larger, ranging from -2.1 to 1.9 cm. Of the 70 repeat CT-scans, the off-set exceeded the ITV-PTV margin of 0.8 cm during expiration in 4 CT-scans (5.7%) and during inspiration in 13 CT-scans (18.6%). The dosimetric validation revealed under- and overdosages in the VMAT and IMPT plans.ConclusionsDespite relatively constant breathing amplitudes, the variation in the diaphragm position (off-set), and consequently tumor position, was clinically relevant. These motion effects may result in either treatments that miss the target volume, or dose deviations in the form of highly localized over- or underdosed regions.

Die Optimierung der Strahlentherapie erfordert zunehmend eine bessere Abgrenzung des Bestrahlungstargets, nicht nur vor Beginn, sondern auch wahrend des Behandlungszeitraums. Die Planung der externen Strahlentherapie beruht seit vielen Jahren auf der Basis der Computertomographie (CT). Im Sinne der bildgefuhrten Radiotherapie („image-guided radiotherapy“, IGRT) werden zunehmend Magnetresonanztomographie (MRT) und funktionelle Hybridbildgebung in die Bestrahlungsplanung integriert. Als Innovation ist die Entwicklung des MR-Linac anzusehen. Die Integration von MRT und Hybridbildgebung (Positronen-Emissions-Tomographie [PET]/CT, PET/MRT) in den Bestrahlungsplanungsprozess ermoglicht auf Grund der besseren morphologischen und funktionellen Information eine prazisere Bestrahlungsplanung. Die Integration von MRT-Daten am MR-Linac auch in die tagliche Lagekontrolle ermoglicht eine Adaption des Bestrahlungsplans an die aktuellen Gegebenheiten. Technische Neuerungen wie der MR-Linac sowie der zunehmende Einsatz von Hybridbildgebung konnen dazu beitragen, dass sich der Trend einer moglichst individuellen Behandlung in der (Radio‑)Onkologie weiter fortsetzt. Am Beispiel des Prostatakarzinoms bietet der Einsatz von Liganden des prostataspezifischen Membranantigens (PSMA) und Hybridbildgebung ein hohes diagnostisches Potenzial fur die Strategie der Therapieplanung. Insbesondere fur die Strahlentherapie des Prostatakarzinoms erscheint der MR-Linac gut geeignet. Ein besonderes Augenmerk ist auf die technische Umsetzung der Lagerung und Datenakquisition zum Zweck der Bestrahlungsplanung zu achten.

Aim To study the impact of bladder and rectum volume changes on prostate positioning and the dosimetric parameters. Background Prostate is a moving organ, and its position is also affected by bladder and rectum volumes. Image-guided radiotherapy (IGRT) is being practiced widely for the treatment of prostate carcinoma (Ca). So, it is important to accurately study the effect of bladder and rectum volume changes in treatment. Materials and methods Thirty patients with Ca prostate were included in this study, and all were treated with 50 Gray (Gy) in 25 fractions for the first phase of treatment. A total of 750 cone-beam computed tomography (CBCT) sessions were performed. Prostate position w.r.t. its day one position was noted, and the bladder and rectum volumes were compared with their volumes on day one. Also, repeat CT was done for five patients after 10 fractions. The initial plan was imported as it was on the repeat CT images, and a hybrid plan was prepared by putting the plan isocenter at the relative anatomical reference point in repeat CT images as it was in primary CT images. The multileaf collimators (MLC) fluence was put as it is, and the dose was calculated using the monitoring units (MU), which were in the initial plan. Doses to bladder, rectum, and the target were analyzed. Results The mean prostate motion in lateral and anterior-posterior direction was found to be 0.71 (±0.69) centimeter cm) and 0.77 (±0.57) cm, respectively. The mean change in bladder and rectum volumes as compared to that in day one CT images was found to be 110.51 (±84.25) cubic centimeters (cc) and 10.89 (±10.17) cc, respectively. No significant variation was observed in the doses to bladder, rectum, and the target volume in a hybrid plan, as compared to that in actual initial plan. Conclusions Bladder and rectum volume affects the position of prostate, rather the dosimetric parameters, and therefore, it can be concluded that daily CBCT should be done for accurate IGRT delivery to the prostate cancer.

The aim of this review article is to present new sophisticated techniques in radiotherapy, which occurred due to the advancement of technology over the past few decades. The paper will provide insight into their advantages and disadvantages, the importance of diagnostic imaging modality, precise contouring, treatment planning and control of patients’ position during radiation treatment. The transition from two-dimensional to three-dimensional radiotherapy has allowed contouring of target volume and organs at risk and accurate information on radiation dosage delivered. With a further desire for more precision and protection of healthy tissues, techniques such as intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) have been developed with the ability to modulate beam intensity. Quality imaging diagnostics is an infallible part of the modern radiotherapy. Image-guided radiotherapy (IGRT) and adaptive radiotherapy enable the delivery of high precision radiation to the target volume and spares organs at risk by correcting interfractional and intrafractional variations. Respiratory gating and tracking technique are useful for tumours that change their position during respiratory cycle. Stereotactic ablative radiotherapy (SABR) is a technique that uses highly conformal high-dose hypofractionated radiation to treat small tumours. In some indication such as the treatment of early stage non small lung cancer, it competes with radical surgery. SABR is also an important therapeutic modality in the management of oligometastatic disease. This paper will briefly discuss proton therapy and its unique physical properties., Cilj ovog preglednog rada je prikazati nove sofisticirane metode radioterapije koje su se razvile zahvaljujući napretku tehnologije unazad par desetljeća. Osvrnut ćemo se na njihove prednosti i nedostatke, važnost slikovne obrade, preciznog konturiranja, planiranja radioterapije i kontrole pozicije pacijenta tijekom radioterapije. Prijelaz s konvencionalne dvodimenzionalne na konformalnu trodimenzionalnu radioterapiju je omogućio konturiranje ciljnog volumena i organa od rizika te praćenje isporučene radioterapijske doze. Daljnjom željom za još većom preciznošću i poštedom zdravih tkiva razvile su se još naprednije tehnike poput radioterapije snopovima promjenjivog intenziteta (IMRT) i volumetrijski modulirane lučne terapije (VMAT) koje imaju mogućnost moduliranja intenziteta snopa. Kvalitetna slikovna dijagnostika je neizostavan dio moderne radioterapije. Radioterapija vođena slikom (IGRT) i adaptivna radioterapija omogućuju isporuku visokopreciznog zračenja na ciljni volumen i poštedu organa od rizika korigiranjem interfrakcionarnih i intrafrakcionarnih varijacija. Gating tehnika i tracking tehnika su korisne kod pomičnih tumora tijekom ciklusa disanja. Stereotaktička ablativna radioterapija (SABR) je tehnika koja koristi visokokonformalno, visokodozno hipofrakcionirano zračenje u liječenju malih tumora. U nekim indikacijama, kao npr. liječenje karcinoma nemalih stanica pluća ranog stadija, ova metoda može zamijeniti kirurški zahvat. Važan je terapijski modalitet u liječenju oligometastatske bolesti. U ovom radu će biti govora i o protonskoj terapiji i njenim jedinstvenim fizikalnim svojstvima.

Highlights • Protocolised evaluation of daily CBCT by RTTs result in re-planning in 10%. • Patients treated with chemoradiotherapy have the highest probability of requiring re-planning. • Most anatomical changes visible on CBCT were detected in treatment week 2, 3 and 4., Introduction During a course of radiotherapy for head-and-neck-cancer (HNC), non-rigid anatomical changes can be observed on daily Cone Beam CT (CBCT). To objectify responses to these changes, we use a decision support system (traffic light protocol). Action levels orange and red may lead to re-planning. The purpose of this study was to evaluate how often re-planning was done for non-rigid anatomical changes, which anatomical changes led to re-planning and in which subgroups of patients treatment adaptation was deemed necessary. Materials and methods A consecutive series of 388 HNC patients were retrospectively selected using the digital log of CBCT scans. The logs were analyzed for the number of new plans on an original planning CT scan (O-pCT) or a new pCT scan (N-pCT). Reasons for re-planning were categorized into: target volume increase/decrease, body contour decrease/increase and local shift of target volume. Subgroup analysis was performed to investigate relative differences of re-planning between treatment modalities. Results For 33 patients the treatment plan was adapted due to anatomical changes, resulting in 37 new plans in total. Re-planning on a N-pCT with complete re-delineation was done 22 times. In fifteen cases a new plan was created after adjustment of contours on the O-pCT. Main reasons for re-planning were target volume increase, body contour decrease and local shifts of target volume. Most re-planning (23%) was seen in patients treated with chemoradiotherapy. Conclusion Visual detection of anatomical changes on CBCT during treatment of HNC, results in re-planning in 1 out of 10 patients.

Purpose: Cone beam CT (CBCT) is used in paediatric image-guided radiotherapy (IGRT) for patient setup and internal anatomy assessment. Adult CBCT protocols lead to excessive doses in children, increasing the risk of radiation-induced malignancies. Reducing imaging dose increases quantum noise, degrading image quality. Patient CBCTs also include ‘anatomical noise’ (e.g. motion artefacts), further degrading quality. We determine noise contributions in paediatric CBCT, recommending practical imaging protocols and thresholds above which increasing dose yields no improvement in image quality. Methods and materials: Sixty CBCTs including the thorax or abdomen/pelvis from 7 paediatric patients (aged 6–13 years) were acquired at a range of doses and used to simulate lower dose scans, totalling 192 scans (0.5–12.8 mGy). Noise measured in corresponding regions of each patient and a 10-year-old phantom were compared, modelling total (including anatomical) noise, and quantum noise contributions as a function of dose. Contrast-to-noise ratio (CNR) was measured between fat/muscle. Soft tissue registration was performed on the kidneys, comparing accuracy to the highest dose scans. Results: Quantum noise contributed 1 mGy. Conclusion: Anatomical noise dominates quantum noise in paediatric CBCT. Appropriate soft tissue contrast and registration accuracy can be achieved for doses as low as 1 mGy. Increasing dose above 1 mGy holds no benefit in improving image quality or registration accuracy due to the presence of anatomical noise.

Early-stage squamous cell cancer (SCC) of the glottis has a good prognosis. Therefore, patients have long survival outcomes and may potentially suffer from late toxicities of radiotherapy. Radiotherapy with a conventional parallel-opposed-pair or anterior-oblique beam arrangements for stage 1 and 2 glottic SCC have field borders that traditionally cover the entire larynx, exposing organs-at-risk (e.g. carotid arteries, contralateral vocal cord, contralateral arytenoid and inferior pharyngeal constrictor muscles) to high radiation doses. The potential long-term risk of cerebrovascular events has attracted much attention to the dose that carotid arteries receive. Swallow and respiratory motion of laryngeal structures has been an important factor that previously limited reduction of the radiation treatment volume. Motion has been evaluated using multiple imaging modalities and this information has been used to calculate PTV margins for generation of more limited target volumes. This review discusses the current literature surrounding dose-effect relationships for various organs-at-risk and the late toxicities that are associated with them. This article also reviews the currently available data and effects of laryngeal motions on dosimetry to the primary target. We also review the current limitations and benefits of a more targeted approach of radiotherapy for early-stage glottic SCCs and the evolution of CT-based IGRT and MR-guided radiotherapy techniques that may facilitate a shift away from a conventional 3D-conformal radiotherapy approach.

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BACKGROUND Image-guided radiotherapy (IGRT) has significantly improved the precision in which radiotherapy is delivered in cancer treatment. Typically, IGRT uses bony landmarks and key anatomical structures to locate the tumor. Recent studies have demonstrated the feasibility of peri-tumor fiducials in enabling even more accurate delineation of target and normal tissue. The use of gold coils as fiducials in gastrointestinal tumors has been extensively studied. However, placement requires expertise and specialized endoscopic ultrasound equipment. This article reports the long-term outcomes of using a standard gastroscopy to inject liquid fiducials for the treatment of oesophageal and gastric tumors with IGRT. AIM To assess the long-term outcomes of liquid fiducial-guided IGRT in a cohort of oesophageal and gastric cancer patients. METHODS A retrospective cohort study of consecutive adults with Oesophagogastric cancers referred for liquid fiducial placement before definitive/neo-adjuvant or palliative IGRT between 2013 and 2021 at a tertiary hospital in Melbourne, Australia was conducted. Up to four liquid fiducials were inserted per patient, each injection consisting of 0.2-0.5mL of a 1:1 mixture of iodized oil (Lipiodol; Aspen Pharmacare) and n-butyl 2-cyanoacrylate (Histoacryl®; B. Braun). A 23-gauge injector (Cook Medical) was used for the injection. All procedures were performed by or under the supervision of a gastroenterologist. Liquid fiducial-based IGRT (LF-IGRT) consisted of computer-assisted direct matching of the fiducial region on cone-beam computerised tomography at the time of radiotherapy. Patients received standard-IGRT (S-IGRT) if fiducial visibility was insufficient, consisting of bone match as a surrogate for tumor position. Radiotherapy was delivered to 54Gy in 30 fractions for curative patients and up to 45Gy in 15 fractions for palliative treatments. RESULTS 52 patients were referred for liquid fiducial placement within the study period. A total of 51 patients underwent liquid fiducial implantation. Of these a total of 31 patients received radiotherapy. Among these, the median age was 77.4 years with a range between 57.5 and 88.8, and 64.5% were male. Twenty-seven out of the 31 patients were able to have LF-IGRT while four had S-IGRT. There were no complications after endoscopic implantation of liquid fiducials in our cohort. The cohort overall survival (OS) post-radiotherapy was 19 mo (range 0 to 87 mo). Whilst the progression-free survival (PFS) post-radiotherapy was 13 mo (range 0 to 74 mo). For those treated with curative intent, the median OS was 22.0 mo (range 0 to 87 mo) with a PFS median of 14.0 mo (range 0 to 74 mo). Grade 3 complication rate post-radiotherapy was 29%. CONCLUSION LF-IGRT is feasible in 87.1% of patients undergoing liquid fiducial placement through standard gastroscopy injection technique. Our cohort has an overall survival of 19 mo and PFS of 13 mo. Further studies are warranted to determine the long-term outcomes of liquid-fiducial based IGRT.

Stereotactic body radiotherapy (SBRT) is an advanced form of radiotherapy (RT) with a growing interest on its application in the treatment of hepatocellular carcinoma (HCC). It can deliver ablative radiation doses to tumors in a few fractions without excessive doses to normal tissues, with the help of advanced modern RT and imaging technologies. Currently, SBRT is recommended as an alternative to curative treatments, such as surgery and radiofrequency ablation. This review discusses the current status of SBRT to aid in the decision making on how it is incorporated into the HCC management.

Lung cancer is one of the most common malignant tumors. It has the highest incidence and mortality rate of all cancers worldwide. Late diagnosis of non-small cell lung cancer (NSCLC) is very common in clinical practice, and most patients miss the chance for radical surgery. Thus, radiotherapy plays an indispensable role in the treatment of NSCLC. Radiotherapy technology has evolved from the classic two-dimensional approach to three-dimensional conformal and intensity-modulated radiotherapy. However, how to ensure delivery of an accurate dose to the tumor while minimizing the irradiation of normal tissues remains a huge challenge for radiation oncologists, especially due to the positioning error between fractions and the autonomous movement of organs. In recent years, image-guided radiotherapy (IGRT) has greatly increased the accuracy of tumor irradiation while reducing the irradiation dose delivered to healthy tissues and organs. This paper presents a brief review of the definition of IGRT and the various technologies and applications of IGRT. IGRT can help ensure accurate dosing of the target area and reduce radiation damage to the surrounding normal tissue. IGRT may increase the local control rate of tumors and reduce the incidence of radio-therapeutic complications.

Purpose: Prostate motion during the radiotherapy course is an important issue. This study investigated the inter-fraction prostate motion in controlled rectal filling condition. Methods: 10 prostate cancer patients underwent image-guided radiotherapy (IGRT) using a cone-beam computed tomography (CBCT) system, after the insertion of fiducial markers (FMs). The planning CT was the reference CT (CTref) used to estimate the reference intermarker distances, and CBCTs were used for off-line comparison with CTref. We evaluated the influence of rectal and bladder volume on prostate shifts. We calculated the required planning target volume (PTV) margins in this patient population. Results: 120 CBCTs were analyzed. Mean prostate displacements (± SD) along the 3 axes (x, y, z) averaged over the 10 patients, were: 0.90 ± 0.84 mm in x, 0.00 ± 2.07 mm in y, -0.80 ± 1.28 mm in z. There is a statistically significant anti-correlation between prostate displacements and: bladder volume variations (P < 0.001) in the y-axis, and rectal volume variations (P < 0.05) in the z-axis. PTV margins obtained for the directions x, y and z are respectively 2.5, 5.6 and 3.9 mm. Conclusion: IGRT in reproducible empty rectum condition allow a high reduction of daily treatment uncertainties.

This comprehensive synopsis summarizes the most relevant information obtained from a systematic analysis of studies of the last decade on radiation proctitis, one of the most feared radioinduced side effects among prostate cancer patients treated with curative external beam radiotherapy. The present review provides a useful support to radiation oncologists for limiting the onset or improving the treatment of radiation proctitis. This work shows that the past decade was a harbinger of significant new evidence in technological advances and technical tricks to avoid radiation proctitis, in addition to dosimetric perspectives and goals, understanding of pathogenesis, diagnostic work-up and treatment. We believe that a well-rounded knowledge of such an issue is fundamental for its appropriate management.

Objectives: Image-guided radiotherapy (IGRT) is a recommended advanced radiation technique that is associated with fewer acute and chronic toxicities. However, one Phase III trial showed worse overall survival in the IGRT arm. The purpose of this observational study is to evaluate the impact of IGRT on overall survival. Methods: We used the Taiwan Cancer Registry Database to enroll cT1-4N0M0 prostate cancer patients who received definitive radiotherapy between 2011 and 2015. We used inverse probability treatment weighting (IPW) to construct balanced IGRT and non-IGRT groups. We compared the overall survival of those in the IGRT and non-IGRT groups. Supplementary analyses (SA) were performed with alternative covariates in propensity score (PS) models and PS approaches. The incidence rates of prostate cancer mortality (IPCM), other cancer mortality (IOCM), and cardiovascular mortality (ICVM) were also evaluated. Results: There were 360 patients in the IGRT arm and 476 patients in the non-IGRT arm. The median follow-up time was 50 months. The 5-year overall survival was 88% in the IGRT arm and 86% in the non-IGRT arm (adjusted hazard ratio [HR] of death = 0.93; 95% CI, 0.61–1.45; p = 0.77). The SA also showed no significant differences in the overall survival between those in the IGRT and non-IGRT arms. Both groups did not significantly differ in terms of IPCM, IOCM, and ICVM. Conclusions: The overall survival of localized prostate cancer patients who underwent IGRT was not inferior to those who did not. Advances in knowledge: We demonstrated that the overall survival for prostate cancer patients with IGRT was not worse than those who did not undergo IGRT; this important outcome comparison has not been previously examined in the general population.

Aim: While delivering radiotherapy it is utmost important to minimize target motion to decrease margins in postoperative gynaecological patients. Hence certain bladder and rectum filling protocols are followed by each institute. During cone beam computed tomography (CBCT) verification, we observed that this motion was more affected by rectal filling. To verify, we retrospectively analysed the vaginal movement and its relation with bladder and rectum filling. Materials and Methods: We evaluated CBCTs of 15 patients of carcinoma endometrium. Bladder and rectum both were contoured offline on each scan. To assess the motion of vagina, two reference points were selected. Posterior movement of bladder and anterior movement of rectum were noted on these points on each scan. Results: Total 150 scans (135 KV-CBCT scans and 15 planning computed tomography) of 15 patients were studied. Stepwise regression analysis reported that bladder wall changes has a nonsignificant relationship with bladder volume among all the individuals. The significant rectal wall changes both at Point X and Y were observed in six patients and only at Point X in three patients. Rest of the patients showed no significant relationship in their CBCT scans. Thus 60% patients showed significant relation between rectal volume and rectal wall changes. Conclusion: Hence we suggest to advice our patients more regarding volume of rectum to decrease vaginal motion. Bladder volume is needed to decrease the dose to small intestine. However prospective data with large number of patients in the study is required to confirm these findings.

The role of radiation therapy (RT) in the treatment of liver malignancies has historically been low, in part due to challenges in delivering ablative doses of RT safely while respecting the radiation dose limits of numerous normal tissues in the upper abdomen, including the liver itself. Challenges to the routine use of RT to treat hepatic malignancies include the low whole liver tolerance to RT and the proximity of liver tumors to other organs at risk (OAR), such as the stomach and bowel. Since the liver moves with breathing and its mean position relative to the vertebral bodies changes daily, delivering highly conformal RT can be challenging.

PurposeFrequency of conventional kV-image guidance is sometimes sacrificed to reduce concomitant risk, leaving deviations of unguided fractions unknown. MV-imaging and treatment dose can be collectively optimized on Halcyon, where fractional MVCBCT provides complete anatomic records for course-wide dose reconstruction. By retrospective dose accumulation, this work simulated the impact of imaging frequency on patient treatment dose on the platform of Halcyon.MethodsFour hundred and sixteen MVCBCT image sets from 16 patients of various tumor sites treated with radiotherapy on Halcyon were retrospectively selected. After applying the image-guided couch shifts of the clinical records, deformable image registration was performed using Velocity software, to deform the planning CTs to the corresponding MVCBCTs, generating pseudo CTs representing the actual anatomies on the treatment day. Fractional treatment dose was reconstructed on pseudo CTs for accumulation, representing the actual patient dose (Ddaily). To simulate weekly image guidance, fractional dose was reconstructed and accumulated by incorporating 1 CBCT-guided corrections and 4 laser-guided setups of each week (Dweekly). Limited by partially imaged volumes and different organs-at-risk of various sites, only target dose-volume parameters were evaluated across all patients.ResultsGTV_D98%, CTV_D98%, PTV_D90%, PTV_D95%, PGTV_D90%, and PGTV_D95% were evaluated, where Dx% means the minimal dose received by x% volume. Pairwise comparisons were made between plan dose and Ddaily, Ddaily and Dweekly respectively. PGTV_D95% of accumulated Dweekly were significantly lower than those of accumulated Ddaily by up to 32.90% of prescription dose, suggesting that weekly-guidance may result in unacceptable under dose to the target. The broad distribution of fractional differences between Ddaily and Dweekly suggested unreliable patient positioning based on aligning surface markers to laser beams, as a popular approach broadly used on conventional Linac systems. Slight target under-dose was observed on daily reconstructed results compared with planned dose, which provided quantitative data to guide clinical decisions such as the necessity of adaptive radiotherapy.ConclusionFractional image guided radiotherapy on Halcyon provides more reliable treatment accuracy than using sacrificed imaging frequency, which also provides complete anatomic records for deformable dose reconstruction supporting more informed clinical decisions.

This report by the Radiation Oncology Discipline of Children’s Oncology Group (COG) describes the practice patterns of pediatric image-guided radiotherapy (IGRT) based on a member survey and provides practice recommendations accordingly. The survey comprised of 11 vignettes asking clinicians about their recommended treatment modalities, IGRT preferences, and frequency of in-room verification. Technical questions asked physicists about imaging protocols, dose reduction, setup correction, and adaptive therapy. In this report, the COG Radiation Oncology Discipline provides an IGRT modality/frequency decision tree and the expert guidelines for the practice of ionizing image guidance in pediatric radiotherapy patients.

Background and purpose External beam radiotherapy for prostate cancer deposits incidental dose to a region surrounding the target volume. Previously, an association was identified between tumor control and incidental dose for patients treated with conventional radiotherapy. We investigated whether such an association exists for patients treated using intensity modulated radiotherapy (IMRT) and tighter margins. Materials and methods Computed tomography scans and three-dimensional treatment planning dose distributions were available from the Dutch randomized HYPRO trial for 397 patients in the standard fractionation arm (39 × 2 Gy) and 407 patients in the hypofractionation arm (19 × 3.4 Gy), mainly delivered using online image-guided IMRT. Endpoint was any treatment failure within 5 years. A mapping of 3D dose distributions between anatomies was performed based on distance to the surface of the prostate delineation. Mean mapped dose distributions were computed for patient groups with and without failure, obtaining dose difference distributions. Random patient permutations were performed to derive p values and to identify relevant regions. Results For high-risk patients treated in the conventional arm, higher incidental dose was significantly associated with a higher probability of tumor control in both univariate and multivariate analysis. The locations of the excess dose mainly overlapped with the position of obturator internus muscles at about 2.5 cm from the prostate surface. No such relationship could be established for intermediate-risk patients. Conclusions An association was established between reduced treatment failure and the delivery of incidental dose outside the prostate for high-risk patients treated using conventionally fractionated IMRT.

BioXmark&reg, (Nanovi A/S, Denmark) is a novel fiducial marker based on a liquid, iodine-based and non-metallic formulation. BioXmark&reg, has been clinically validated and reverse translated to preclinical models to improve cone-beam CT (CBCT) target delineation in small animal image-guided radiotherapy (SAIGRT). However, in phantom image analysis and in vivo evaluation of radiobiological response after the injection of BioXmark&reg, are yet to be reported. In phantom measurements were performed to compare CBCT imaging artefacts with solid fiducials and determine optimum imaging parameters for BioXmark&reg, In vivo stability of BioXmark&reg, was assessed over a 5-month period, and the impact of BioXmark&reg, on in vivo tumour response from single-fraction and fractionated X-ray exposures was investigated in a subcutaneous syngeneic tumour model. BioXmark&reg, was stable, well tolerated and detectable on CBCT at volumes &le, 10 &micro, L. Our data showed imaging artefacts reduced by up to 84% and 89% compared to polymer and gold fiducial markers, respectively. BioXmark&reg, was shown to have no significant impact on tumour growth in control animals, but changes were observed in irradiated animals injected with BioXmark&reg, due to alterations in dose calculations induced by the sharp contrast enhancement. BioXmark&reg, is superior to solid fiducials with reduced imaging artefacts on CBCT. With minimal impact on the tumour growth delay, BioXmark&reg, can be implemented in SAIGRT to improve target delineation and reduce set-up errors.

PurposeDue to the Electron Return Effect (ERE) during Magnetic Resonance Imaging guided Radiotherapy (MRIgRT), rectal gas during pelvic treatments can result in hot spots of over‐dosage in the rectal wall. Determining the clinical impact of this effect on rectal toxicity requires estimation of the amount and mobility (and stability) of rectal gas during treatment. We therefore investigated the amount of rectal gas and local inter‐ and intra‐fractional changes of rectal gas in pelvic cancer patients.MethodsTo estimate the volume of gas present at treatment planning, the rectal gas contents in the planning CT scans of 124 bladder, 70 cervical and 2,180 prostate cancer patients was calculated.To estimate inter‐ and intra‐fractional variations in rectal gas, 174 and 131 T2‐w MRIs for six cervical and eleven bladder cancer patients were used. These scans were acquired during four scan‐sessions (~20‐25 minutes each) at various time‐points. Additionally, 258 T2‐w MRIs of the first five prostate cancer patients treated using MRIgRT at our centre, acquired during each fraction, were analysed. Rectums were delineated on all scans.The area of gas within the rectum delineations was identified on each MRI slice using thresholding techniques. The area of gas on each slice of the rectum was used to calculate the inter‐ and intra‐fractional group mean, systematic and random variations along the length of the rectum.The cumulative dose perturbation as a result of the gas was estimated. Two approaches were explored: accounting or not accounting for the gas at the start of the scan‐session.ResultsIntra‐fractional variations in rectal gas are small compared to the absolute volume of rectal gas detected for all patient groups. I.e., rectal gas is likely to remain stable for periods of 20‐25 minutes. Larger volumes of gas and larger variations in gas volume were observed in bladder cancer patients compared with cervical and prostate cancer patients.For all patients, local cumulative dose perturbations per beam over an entire treatment in the order of 60 % were estimated when gas had not been accounted for in the daily adaption. The calculated dose perturbation over the whole treatment was dramatically reduced in all patients when accounting for the gas in the daily set‐up image.ConclusionRectal gas in pelvic cancer patients is likely to remain stable over the course of an MRIgRT fraction, and also likely to reappear in the same location in multiple fractions, and can therefore result in clinically relevant over‐dosage in the rectal wall. The over‐dosage is reduced when accounting for gas in the daily adaption.

Highlights • Introduction of daily online prostate IGRT was feasible in a national randomised trial. • Dosimetric benefits seen in patients treated with IGRT and reduced CTV-PTV margins. • Overall side effect profiles were acceptable in all groups but lowest with IGRT and reduced margins., Background and purpose Image-guided radiotherapy (IGRT) improves treatment set-up accuracy and provides the opportunity to reduce target volume margins. We introduced IGRT methods using standard (IGRT-S) or reduced (IGRT-R) margins in a randomised phase 2 substudy within CHHiP trial. We present a pre-planned analysis of the impact of IGRT on dosimetry and acute/late pelvic side effects using gastrointestinal and genitourinary clinician and patient-reported outcomes (PRO) and evaluate efficacy. Materials and methods CHHiP is a randomised phase 3, non-inferiority trial for men with localised prostate cancer. 3216 patients were randomly assigned to conventional (74 Gy in 2 Gy/fraction (f) daily) or moderate hypofractionation (60 or 57 Gy in 3 Gy/f daily) between October 2002 and June 2011. The IGRT substudy included a second randomisation assigning to no-IGRT, IGRT-S (standard CTV-PTV margins), or IGRT-R (reduced CTV-PTV margins). Primary substudy endpoint was late RTOG bowel and urinary toxicity at 2 years post-radiotherapy. Results Between June 2010 to July 2011, 293 men were recruited from 16 centres. Median follow-up is 56.9(IQR 54.3–60.9) months. Rectal and bladder dose-volume and surface percentages were significantly lower in IGRT-R compared to IGRT-S group; (p

Aim Advances in therapy have resulted in improved cure rates and an increasing number of long-term Hodgkin's lymphoma (HL) survivors. However, radiotherapy (RT)-related late effects are still a significant issue, particularly for younger patients with mediastinal disease (secondary cancers, heart diseases). In many Centers, technological evolution has substantially changed RT planning and delivery. This consensus document aims to analyze the current knowledge of Intensity-Modulated Radiation Therapy (IMRT) and Image-Guided Radiation Therapy (IGRT) for mediastinal HL and formulate practical recommendations based on scientific evidence and expert opinions. Methods A dedicated working group was set up within the Fondazione Italiana Linfomi (FIL) Radiotherapy Committee in May 2018. After a first meeting, the group adopted a dedicated platform to share retrieved articles and other material. Two group coordinators redacted a first document draft, that was further discussed and finalized in two subsequent meetings. Topics of interest were: 1) Published data comparing 3D-conformal radiotherapy (3D-CRT) and IMRT 2) dose objectives for the organs at risk 3) IGRT protocols and motion management. Results Data review showed that IMRT might allow for an essential reduction in the high-dose regions for all different thoracic OAR. As very few studies included specific dose constraints for lungs and breasts, the low-dose component for these OAR resulted slightly higher with IMRT vs. 3D-CRT, depending on the technique used. We propose a set of dose objectives for the heart, breasts, lungs, and thyroid. The use of IGRT is advised for margin reduction without specific indications, such as the use of breath-holding techniques. An individual approach, including comparative planning and considering different risk factors for late morbidity, is recommended for each patient. Conclusions As HL therapy continues to evolve, with an emphasis on treatment reduction, radiation oncologists should use at best all the available tools to minimize the dose to organs at risk and optimize treatment plans. This document provides indications on the use of IMRT/IGRT based on expert consensus, providing a basis for clinical implementation and future development.

Aim Describe the anatomical changes and tumor displacement due to a rapid response of a patient’s small cell lung cancer (SCLC) during definitive chemoradiotherapy (CRT). Background The treatment for SCLC is based on CRT. If interfractional changes during RT are incorrectly assessed they might compromise adequate coverage of the tumor or increase dose to organs at risk. Image guided RT with cone-beam computed tomography (CBCT) allows to identify daily treatment variations. Material and methods Describe a SCLC case with rapid changes in size, shape and location of the primary tumor during RT. Case report A 62-year-old woman was diagnosed with SCLC with complete obstruction of the anterior and lingular bronchi and incomplete left thorax expansion due to a 12 × 15 cm mass. During CRT (45 Gy in 1.5 Gy per fraction, twice daily) the patient presented rapid tumor response, leading to resolution of bronchi obstruction and hemithorax expansion. Tumor shifted up to 4 cm from its original position. The identification of variations led to two new simulations and planning in a 3-week treatment course. Conclusions The complete radiological response was possible due to systematic monitoring of the tumor during CRT. We recommend frequent on-site image verification. Daily CBCT should be considered with pretreatment tumor obstruction, pleural effusion, atelectasis, large volumes or radiosensitive histology that might resolve early and rapidly and could lead to a miss of the tumor or increased toxicity. Further research should be made in replanning effect in coverage of microscopic disease since it increases uncertainty in this scenario.

Background: To quantify the geometrical changes of each neck nodal level (NNL) and estimate the geometric planning target volume (PTV) margin during image-guided radiotherapy (IGRT) for nasopharyngeal cancer (NPC). Methods: Twenty patients with locally advanced NPC underwent one planning computed tomography (CT plan ) and 6 weekly repeat CT (CT rep ) scans during chemoradiotherapy. Each CT rep was rigidly registered to the CT plan . All the NNLs were manually delineated in each transverse CT section. When comparing the NNL in CT rep with CT plan , their volumes, displacement of the center of the mass, and the shortest perpendicular distance (SPD) were automatically calculated. This was followed by calculation of the systematic and random errors, overlapping index (OI), and dice similarity coefficient (DSC). With PTVs isotropically expanded from NNL by 1, 2, 3, 4, and 5 mm, they were compared with NNL itself; OI >0.95 was defined as the acceptable geometrical coverage. The Mann-Whitney test was used for statistical analysis. Results: All volumes, OI, and DSC of the NNLs (not including level IA) showed a linear decrease over time throughout the treatment course. The volume of NNLs decreased by 1–6% in the first week and 10–21% in the sixth week. The mean SPD was 1.3–1.7 and 1.9–3.5 mm in the first and sixth week respectively. The DSCs for nodal level IB, II, III, and IV were >0.7 and that of level V was 0.95, 2–5 mm was needed to expand the different NNLs. Conclusions: The geometrical changes of each NNL are substantial and the necessary margin of 2–5 mm depended on individual NNL is needed to maintain geometrical coverage throughout the course of IGRT for NPC.

PurposeThe use of ultrasound imaging is not widespread in prostate cancer radiotherapy workflows, despite several advantages (eg, allowing real-time volumetric organ tracking). This can be partially attributed to the need for a trained operator during acquisition and interpretation of the images. We introduce and evaluate an algorithm that can propose a patient-specific transperineal ultrasound probe setup, based on a CT scan and anatomical structure delineations. The use of this setup during the simulation and treatment stage could improve usability of ultrasound imaging for relatively untrained operators (radiotherapists with less than 1yr experience with ultrasound).MethodsThe internal perineum boundaries of three prostate cancer patients were identified based on bone masks extracted from their CT scans. After projection of these boundaries to the skin and exclusion of specific areas, this resulted in a skin area accessible for transperineal ultrasound probe placement in clinical practice. Several possible probe setups on this area were proposed by the algorithm and the optimal setup was automatically selected. In the end, this optimal setup was evaluated based on a comparison with a corresponding transperineal ultrasound volume acquired by a radiation oncologist.ResultsThe algorithm-proposed setups allowed visualization of 100% of the clinically required anatomical structures, including the whole prostate and seminal vesicles, as well as the adjacent edges of the bladder and rectum. In addition, these setups allowed visualization of 94% of the anatomical structures, which were also visualized by the physician during the acquisition of an actual ultrasound volume.ConclusionProvided that the ultrasound probe setup proposed by the algorithm, is properly reproduced on the patient, it allows visualization of all clinically required structures for image guided radiotherapy purposes. Future work should validate these results on a patient population and optimize the workflow to enable a relatively untrained operator to perform the procedure.

Intensity-modulated radiotherapy (IMRT) has become the standard radiotherapy technology utilized for the treatment of prostate cancer, as it permits the delivery of highly conformal radiation dose distributions. Image-guided radiotherapy (IGRT) is an essential companion to IMRT that allows the treatment team to account for daily changes in target anatomy and positioning. In the present review, we will discuss the different sources of geometric uncertainty and review the rationale behind using IGRT in the treatment of prostate cancer. We will then describe commonly employed IGRT techniques and review their benefits and drawbacks. Additionally, we will review the evidence suggesting a potential clinical benefit to utilizing IGRT.

Purpose The purpose of the article was to determine the impact of Dual Registration (DR) image-guided radiotherapy (IGRT) on clinical judgement and treatment delivery for patients with oropharyngeal cancer before implementation. Methods Ninety cone beam computed tomography images from 10 retrospective patients were matched using standard clipbox registration (SCR) and DR. Three IGRT specialist radiographers performed all registrations and evaluated by intraclass correlation to determine inter-rater agreement, Bland-Altman with 95% limits of agreement to determine differences between SCR and DR procedures, changes in clinical judgment, time taken to perform registrations, and radiographer satisfaction. Results Inter-rater agreement between radiographers using both SCR and DR was high (0.867 and 0.917, P ≤ .0001). The 95% limits of agreement between SCR and DR procedures in the mediolateral, cranial–caudal, and ventrodorsal translational directions were −6.40 to +4.91, −7.49 to +6.05, and −7.00 to +5.44 mm, respectively. The mediolateral direction demonstrated significant proportional bias (P ≤ .001) suggesting non-agreement between SCR and DR. Eighty percent of DR matches resulted in a change in clinical judgement to ensure maximum target coverage. Mean registration times for SCR and DR were 94 and 115 seconds, respectively, and radiographers found DR feasible and satisfactory. Conclusion The standard method using SCR in patients with oropharyngeal cancer underestimates the deviation in the lower neck. In these patients, DR is an effective IGRT tool to ensure target coverage of the inferior neck nodes and has demonstrated acceptability to radiotherapy clinical practice.

PURPOSE/OBJECTIVE(S) To quantitatively compare plan quality between mid-inspiration breath-hold (BH) MR-guided radiotherapy (MRgRTBH) and free-breathing (FB) CT-based intensity modulated radiotherapy (CT-IGRTFB) for the ablative treatment of adrenal malignancies. We hypothesized that MRgRTBH would provide improved target coverage and lower organ-at-risk (OAR) doses due to smaller target volumes compared to CT-IGRTFB. MATERIALS/METHODS Twenty adrenal metastasis patients were treated on a 0.35T MR-Linac with real-time sagittal tracking at four frames per second for gated BH delivery. All patients underwent IMRT planning to a median prescription dose of 50 Gy (range: 40-50 Gy) in 5 fractions. For MRgRTBH, the CTV was delineated on the primary 3D TRUFI scan with no internal target volume (ITV). Each patient was retrospectively replanned using a 3-arc, VMAT CT-IGRTFB treatment on a c-arm Linac (HD MLC). 4DCT respiratory evaluation was performed during MRgRTBH simulation. The average intensity projection CT was used to determine the ITV for the CT-IGRTFB plan. All plans used a 5 mm ITV to PTV margin. Target volume metrics used were: target coverage (TC) (PTV V100%/PTV vol), PTV D95%/Rx, PTV D90%/Rx, PTV D80%/Rx, homogeneity index (HI) (PTV D2%/ D98%), high dose conformity (PITV), low dose conformity (D2cm), and gradient (R50%). Additional dose metrics were evaluated for mean ipsilateral kidney and 0.5 cc gastrointestinal (GI) OARs. RESULTS The Wilcoxon signed-rank test showed a statistically significant increase (P 0.05). There were significant reductions (P 0.05) and significant GI OAR sparing (P < 0.05) resulted from the smaller target volumes and reduced OAR-to-PTV proximity. MRgRTBH was shown to be dosimetrically superior for OAR sparing to the small bowel, the large bowel and the duodenum (P < 0.05). Adaptive MRgRTBH was used for all patients, but only initial treatment doses were considered in quantifying the impact of gated BH versus ITV for this study.

AimAlthough manual adjustment of automatic cone beam computed tomography (CBCT) matching may improve the target coverage in certain points of interest, concerns exist that this may lead to dosimetric uncertainties which would negate the theoretical benefit of this approach. The objective of this study is to evaluate the dosimetric impact of manual adjustments made after automatic bony registration on CBCT in prostate patients.MethodsA total of 50 CBCT datasets of ten high-risk prostate cancer patients were randomly chosen. Each CBCT dataset was registered three times. Method (A): Automatic registration, Method (M1): Manual adjustment carried out by two experienced radiation therapists, Method (M2): Manual adjustment carried out by different radiation therapists with varying levels of experience. The clinical target volume (CTV), planning target volume (PTV), the bladder and the rectum were subsequently contoured on each CBCT dataset by a radiation oncologist blinded to the registration methods. The absolute difference of various dosimetric parameters were then analysed and compared with the original planning doses. A comparison of the three matching methods employed was also carried out.ResultsThere was a statistically significant difference in the magnitude of move taken in the inferior superior direction between M1 and M2 method. There were no significant differences observed in any of the dosimetric parameters examined in relation to the rectum, bladder or CTV. The only significant difference observed was the volume of PTV covered by the prescription isodose (95%) which was statistically significant lower in method A compared with both M1 and M2. There was no difference observed between M1 and M2 methods. The mean duration of the automated registration and subsequent analysis was 64 seconds compared with 91 seconds for automated registrations which included the additional manual adjustment.FindingsCBCT-based manual adjustments of automated bony-based registrations during the image-guided radiotherapy verification of prostate cancer patients can improve PTV coverage without impacting negatively on the doses received by the organs at risk. This strategy is associated with a small increase in overall treatment time.

In this study, we compared the registration effectiveness of 4D cone-beam computed tomography (CBCT) and 3D-CBCT for image-guided radiotherapy in 20 Stage IA non–small-cell lung cancer (NSCLC) patients. Patients underwent 4D-CBCT and 3D-CBCT immediately before radiotherapy, and the X-ray Volume Imaging software system was used for image registration. We performed automatic bone registration and soft tissue registration between 4D-CBCT or 3D-CBCT and 4D-CT images; the regions of interest (ROIs) were the vertebral body on the layer corresponding to the tumor and the internal target volume region. The relative displacement of the gross tumor volume between the 4D-CBCT end-expiratory phase sequence and 4D-CT was used to evaluate the registration error. Among the 20 patients (12 males, 8 females; 35–67 years old; median age, 52 years), 3 had central NSCLC and 17 had peripheral NSCLC, 8 in the upper or middle lobe and 12 in the lower lobe (maximum tumor diameter range, 18–27 mm). The internal motion range in three-dimensional space was 12.52 ± 2.65 mm, accounting for 47.8 ± 15.3% of the maximum diameter of each tumor. The errors of image-guided registration using 4D-CBCT and 3D-CBCT on the x (left–right), y (superior–inferior), z (anterior–posterior) axes, and 3D space were 0.80 ± 0.21 mm and 1.08 ± 0.25 mm, 2.02 ± 0.46 mm and 3.30 ± 0.53 mm, 0.52 ± 0.16 mm and 0.85 ± 0.24 mm, and 2.25 ± 0.44 mm and 3.59 ± 0.48 mm (all P < 0.001), respectively. Thus, 4D-CBCT is preferable to 3D-CBCT for image guidance in small pulmonary tumors because 4D-CBCT can reduce the uncertainty in the tumor location resulting from internal motion caused by respiratory movements, thereby increasing the image-guidance accuracy.

Background and purpose: Accurate Cone Beam CT (CBCT) based dose calculations are hindered by limited CBCT image quality. Using retrospective artefact corrections, this paper investigated the accuracy of dose calculations performed directly on CBCT images of lung cancer patients. Materials and methods: Dose calculations were made directly on clinical and artefact corrected CBCT images of 21 lung cancer patients with a re-simulation CT (rCT) image acquired during radiotherapy. The original treatment plan was copied to the rCT and CBCT images and dose was recalculated. Dose comparisons were made using gamma analysis and dose statistics. Gamma comparisons were made using 2%/2 mm and 1%/1 mm criteria, and pass rates of the clinical and improved CBCT images were calculated using the rCT based dose as reference. Results: Dose distributions calculated on the artefact corrected CBCT images had a median 2%/2 mm gamma pass rate of 99.4% when compared to the reference rCT. Doses calculated on the clinical CBCT images had a median 2%/2 mm gamma pass rate of 93.1%. Wilcoxon signed rank test showed the pass rates in the entire CBCT field of view different at p

Background Patients treated with radiotherapy for head and neck (H&N) cancer often experience anatomical changes. The potential compromises to Planning Target Volume (PTV) coverage or Organ at Risk (OAR) sparing has prompted the use of adaptive radiotherapy (ART) for these patients. However, implementation of ART is time and resource intensive. This study seeks to define a clinical trigger for H&N re-plans based on spinal cord safety using kV Cone-Beam Computed Tomography (CBCT) verification imaging, in order to best balance clinical benefit with additional workload. Methods Thirty-one H&N patients treated with Volumetric Modulated Arc Therapy (VMAT) who had a rescan CT (rCT) during treatment were included in this study. Contour volume changes between the planning CT (pCT) and rCT were determined. The original treatment plan was calculated on the pCT, CBCT prior to the rCT, pCT deformed to the anatomy of the CBCT (dCT), and rCT (considered the gold standard). The dose to 0.1 cc (D0.1cc) spinal cord was evaluated from the Dose Volume Histograms (DVHs). Results The median dose increase to D0.1cc between the pCT and rCT was 0.7 Gy (inter-quartile range 0.2–1.9 Gy, p Conclusions An adaptive re-plan can be triggered using spinal cord doses calculated on the CBCT/dCT. Implementing this trigger can reduce patient appointments and radiation dose by eliminating up to 90% of additional un-necessary CT scans, reducing the workload for radiographers, physicists, dosimetrists, and clinicians.

The the position error plays an important role in the therapy of breast cancer with intensity-modulated radiation therapy(IMRT) by image-guided technique. In order to explore the methods of reducing the position error, fifteen breast cancer patients with image-guided radiotherapy were selected in this study. The images of patients were scanned using the Versa HD imaging system. The position errors were obtained and analyzed by comparing the images between the simulating CT images and the Versa HD images in four directions, X (left and right), Y (head and foot), Z (belly back) and RTN (rotation angle). It is found that the frequencies of the absolute values of the X, Y, and Z direction position errors exceed 1mm are 40%, 66.6%, and 60%, respectively, and the frequencies of which exceed 2mm are 26.6%, 26.6%, and 60%. The average values of the errors of X, Y, Z, and RTN are 0.91mm, 1.45mm, 2.57mm, and 0.39deg, respectively. The position error takes place most in the Y direction, and least in the X direction. According to the differences between the simulating CT images and the Versa HD images, the position errors were obtained and analyzed. The relations between the errors and the directions can by applied in the real-time correction of the treatment of breast cancer patients with image guidance technique.

Many advancements taking place in the field of radiation therapy come in the form of increasingly powerful devices and specialized treatments that aim to increase precision, visualization, and facility throughput. Although these devices are very effective at their respective roles within radiotherapy, they are expensive and require specialized vaults to shield the public and the radiation worker from the ionizing radiation. A proposed device, known as the Simple XRT, is designed to circumvent the inherent drawbacks of the current devices. The Simple XRT uses a 6 MV linear accelerator that utilizes diagnostic quality computed tomography (CT) image guidance. Simple XRT will serve as a cost-effective device for treating most cancer indications.

Purpose: To propose a novel method to improve the mega-voltage CT (MVCT) image quality for helical TomoTherapy while maintaining the stability on dose calculation.Materials and Methods: The Block-Matching 3D-transform (BM3D) and Discriminative Feature Representation (DFR) methods were combined into a novel BM3D + DFR method for their respective advantages. A phantom (Catphan504) and three serials of clinical (head & neck, chest, and pelvis) MVCT images from 30 patients were acquired using the helical TomoTherapy system. The contrast-to-noise ratio (CNR) and edge detection algorithm (canny) was employed for image quality comparisons between the original and BM3D + DFR enhanced MVCT. A simulated rectangular field of 6 MV X-ray beams were vertically delivered on the original and post-processed MVCT serials of the same CT density phantom, and the dose curves on both serials were compared to test the effects of image enhancement on dose calculation accuracy.Results: In total, 466 transversal MVCT slices were acquired and processed by both BM3D and the proposed BM3D + DFR methods. Compared to the original MVCT image, the BM3D + DFR method presented a remarkable improvement in terms of the soft tissue contrast and noise reduction. For the phantom image, the CNR of the region of interest (ROI) was improved from 1.70 to 4.03. The average CNR of ROIs for 10 patients from each anatomical group, were increased significantly from 1.45 ± 1.51 to 2.09 ± 1.68 for the head & neck (p < 0.001), from 0.92 ± 0.78 to 1.36 ± 0.85 for the chest (p < 0.001), and from 1.12 ± 1.22 to 1.76 ± 1.31 for the pelvis (p < 0.001), respectively. The canny edge detection operator showed that BM3D + DFR provided clearer organ boundaries with less chaos. The root-mean-square of the dosimetry difference on the iso-center passed horizontal dose profile curves and vertical percentage depth dose curves were only 0.09% and 0.06%, respectively.Conclusions: The proposed BM3D + DFR method is feasible to improve the soft tissue contrast for the original MVCT images with coincidence in dose calculation and without compromising resolution. After integration in clinical workflow, the post-processed MVCT may be better applied on image-guided and adaptive helical TomoTherapy.