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BACKGROUND To evaluate the impact of the planning target volume (PTV) density on treatment planning for lung Stereotactic Body Radiation Therapy (SBRT). MATERIAL AND METHODS The PTV coverage was analyzed in two groups of 40 lung SBRT patients. One group had PTV density 0.5 g/cm3. The treatments were planned in Pinnacle 9.10, using the collapsed cone convolution (CCC) algorithm. The prescribed dose was 60 Gy to the PTV in 4-8 fractions. Respecting constraint for the PTV coverage (D98% > 95%), we compared changes in the isodose line prescription, the number of monitor units (MU), maximum dose (Dmax), irradiated volume covered with 30 Gy (V30Gy), and the optimization planning volume (OPV). RESULTS For the same median values of the PTV coverage (98.3%), the differences are presented with median values between lower and higher density than 0.5 g/cm3. The isodose line prescription was 83 vs. 90% (p

The aim of this study is to compare the dose delivered to the organs at risk (OAR), using static beams (SF) and a dynamic conformational arc (DCA) with flattening filter free (FFF) beams, for lung stereotactic body radiation therapy (SBRT).100 patients with lung cancer were treated with SBRT, using FF beams (TrueBeam STx, 6 MV, IQ = 0.67, 600 MU/min), separated into two groups: DCA (50 patients) and SF (50 patients). These patients were retrospectively re-planned using 6XFFF beams, IQ = 0.63, 1400 MU/min. The beam-on time and dosimetric gain on planning target volume (PTV) and OARs (heart, spinal cord, planning risk volume (PRV) of spinal cord, esophagus, lungs and ribs) were analyzed according to tumor location. The comparison of median values was performed using the non-parametric Wilcoxon test (significance level:PTV coverage was 98.90% versus 98.40% (DCA) and 98.8% versus 98.3% (SF) for the FF and FFF beams, respectively. The median dosimetric gain to the heart, spinal cord, PRV spinal cord, esophagus and lungs was 6% (4-11%) in the central region and 8% (2-23%) in the peripheral region, using FFF (The FFF beams reduce the dose received by all OARs, regardless of the used technique or tumor location, reducing treatment delivery time as well.

Background The use of imaging is indispensable in modern radiation therapy, both for simulation and treatment delivery. For safe and sure utilization, dose delivery from imaging must be evaluated. Objective This study aims to investigate the dose to organ at risk (OAR) delivered by imaging during lung stereotactic body radiation therapy (SBRT) and to evaluate its contribution to the treatment total dose. Material and methods In this retrospectively study, imaging total dose to organs at risk (OARs) (spinal cord, esophagus, lungs, and heart) and effective dose were retrospectively evaluated from 100 consecutive patients of a single institution who had lung SBRT. For each patient, dose was estimated using Monte-Carlo convolution for helical computed tomography (helical CT), Four-Dimensional CT (4D-CT), and kilovoltage Cone-Beam CT (kV-CBCT). Helical CT and kV-CBCT dose were evaluated for the entire thorax acquisition, while 4D-CT dose was analyzed on upper lobe (UL) or lower lobe (LL) acquisition. Treatment dose was extracted from treatment planning system and compared to imaging total dose. Results Imaging total dose maximum values were 117 mGy to the spinal cord, 127 mGy to the esophagus, 176 mGy to the lungs and 193 mGy to the heart. The maximum effective dose was 19.65 mSv for helical CT, 10.62 mSv for kV-CBCT, 25.95 mSv and 38.45 mSv for 4D-CT in UL and LL regions, respectively. Depending on OAR, treatment total dose was higher from 1.7 to 8.2 times than imaging total dose. Imaging total dose contributed only to 0.3% of treatment total dose. Conclusion Imaging dose delivered with 4D-CT to the OARs is higher than those of others modalities. The heart received the highest imaging dose for both UL and LL. Total imaging dose is negligible since it contributed only to 0.3% of treatment total dose.

Purpose: To evaluate the breathing amplitude, tumor motion, patient positioning, and treatment volumes among consecutive four-dimensional computed tomography (4D-CT) scans, during the simulation for lung stereotactic body radiation therapy (SBRT). Material and methods: The variation and shape of the breathing amplitude, patient positioning, and treatment volumes were evaluated for 55 lung cancer patients after consecutive 4D-CT acquisitions, scanned at one-week intervals. The impact of variation in the breathing amplitude on lung tumor motion was determined for 20 patients. The gross tumor volume (GTV) was contoured from a free-breathing CT scan and at ten phases of the respiratory cycle, for both 4D-CTs (440 phases in total). Results: Breathing amplitude decreased by 3.6 (3.4-4.9) mm, tumor motion by 3.2 (0.4-5.0) mm while breathing period increased by 4 (2-6) s, inter-scan for 20 patients. Intra-scan variation was 4 times greater for the breathing amplitude, 5 times for the breathing period, and 8 times for the breathing cycle, comparing irregular versus regular breathing patterns for 55 patients. Using coaching, the breathing amplitude increases 3 to 8 mm, and the breathing period 2 to 6 s. Differences in the contoured treatment volumes were less than 10% between consecutive scans. Patient positioning remained stable, with a small inter-scan difference of 1.1 (0.6-1.4) mm. Conclusion: Decreasing the inter-scan breathing amplitude decreases the tumor motion reciprocally. When the breathing amplitude decreases, the breathing period increases at inter- and intra-scan, especially during irregular breathing. Coaching improves respiration, keeping the initial shape of the breathing amplitude. Contoured treatment volumes and patient positioning were reproducible through successive scans.

To evaluate the amplitude of lung tumor motion and impact of tumor motion on dose delivered to the organs at risk (OARs) during lung stereotactic body radiation therapy (SBRT). This study included 55 patients (30 males and 25 females) with lung cancer who had a small gross tumor volume (GTV). SBRT lung cancer patients were treated with a prescribed dose of 60 Gy in 4 to 8 fractions. Radiotherapy plans were planned in Pinnacle 9.10 with two partial dynamic conformal arcs (DCAs) for the peripheral region (PR) and three to four partial DCAs for the central region (CR). The amplitude of tumor motion and their impact on the maximum dose delivered (Dmax) to the OARs were evaluated in the upper lobe (UL) and lower lobe (LL) in cases of CR and PR tumor’s localizations. The median tumor motions between CR and PR were 4.5 vs 2.2 mm in the UL and 12.5 vs 7.0 mm in the LL. Max dose delivered to the OARs between CR and PR in the UL and LL were as follows: 6.7 vs 8.9 Gy and 9.1 vs 11.7 Gy for the spinal cord; 15.2 vs 0.6 Gy and 22.4 vs 7.6 Gy for the heart; and 11.7 vs 10.8 Gy and 14.8 vs 9.8 Gy for the esophagus, respectively. The dose received by the OARs depends on the amplitude of tumor motion and is relative to the OAR’s location and motion, due to patient respiration and heart contribution.

In this paper, a dosimetric end-to-end test of respiratory gated radiation therapy (RGRT) applied in lung cancer stereotactic body radiation therapy (SBRT) was performed. The test was performed from treatment simulation to treatment delivery using a QUASAR phantom, for regular, slightly irregular and irregular breathing patterns in phase- and amplitude-gated modes. A mechanical and dosimetric verification was performed to evaluate all steps of the proposed treatment workflow. Dose measurements were performed using a PinPoint ion chamber and GafChromic EBT3 films. Mechanical verification confirmed good function of the chosen systems. Dosimetric verification showed good agreement between planned and measured doses, for the phase-gated versus amplitude-gated modes: 1.4 ± 0.4% versus 1.2 ± 0.2% for regular, 2.8 ± 0.3% versus 3.0 ± 0.3% for slightly irregular, and 6.2 ± 0.7% versus 7.4 ± 0.5% for irregular breathing patterns. The gamma passing rates for 3%/3 mm and 2%/2 mm criteria, comparing phase- versus amplitude-gated modes, were 99.0 ± 0.3% versus 99.5 ± 0.2% and 95.2 ± 0.2% versus 96.1 ± 0.2% for the regular, 97.4 ± 0.8% versus 98.0 ± 0.6% and 91.7 ± 0.5% versus 92.4 ± 0.4% for the slightly irregular, and 96.4 ± 0.5% versus 95.3 ± 0.7% and 86.4 ± 0.5% versus 84.6 ± 0.7% for the irregular breathing patterns, respectively. It is concluded that using equipment and workflow for the treatment of lung cancer by means of SBRT in RGRT mode is safe and efficient, for regular and slightly irregular breathing patterns.

Introduction: This study compared phase-gated and amplitude-gated dose deliveries to the moving gross tumor volume (GTV) in lung stereotactic body radiation therapy (SBRT) using Gafchromic External Beam Therapy (EBT3) dosimetry film. Materials and Methods: Eighty treatment plans using two techniques (40 phase gated and 40 amplitude gated) were delivered using dynamic conformal arc therapy (DCAT). The GTV motion, breathing amplitude, and period were taken from 40 lung SBRT patients who performed regular breathing. These parameters were re-simulated using a modified Varian breathing mini phantom. The dosimetric accuracy of the phase- and amplitude-gated treatment plans was analyzed using Gafchromic EBT3 dosimetry film. The treatment delivery efficacy was analyzed for gantry rotation, number of monitor unit (MU), and target position per triggering window. The time required to deliver the phase- and amplitude-gated treatment techniques was also evaluated. Results: The mean dose (range) per fraction was 16.11 ± 0.91 Gy (13.04–17.50 Gy) versus 16.26 ± 0.83 Gy (13.82–17.99 Gy) (P < 0.0001) for phase- and amplitude-gated delivery. The greater difference in the gamma passing rate was 1.2% ±0.4% in the amplitude-gated compared to the phase gated. The gantry rotation per triggering time (tt) was 2° ±1° (1.2°–3°) versus 5° ±1° (3°–6°) (P < 0.0001) and MU per tt was 10 ± 3 MU (6–13 MU) versus 24 ± 7 MU (12–32 MU) (P < 0.0001), for phase- versus amplitude-gated techniques. A 90 beam interruption in the phase-gated technique impacted the treatment delivery efficacy, increasing the treatment delivery time in the phase gated for 1664 ± 202 s 1353–1942 s) compared to 36 interruptions in the amplitude gated 823 ± 79 s (712–926 s) (P < 0.0001). Conclusion: Amplitude-gated DCAT allows for better dosimetric accuracy over phase-gated treatment patients with regular breathing patterns.

Introduction: Gated tangential field-in-field (FIF) technique is used to lower the dose to organs at risk for breast cancer radiotherapy (RT). In this study, the authors investigated the accuracy of the delivered treatment plan with and without gating using a two-dimensional detector array for patient-specific verification purposes.Methods: In this study, a 6MV beams were used for the merged FIF RT (forward Intensity Modulated Radiation Therapy). The respiration signals for gated FIF delivery were obtained from the one-dimensional moving phantom using the real-time position management (RPM) system (Varian Medical Systems, Palo Alto, CA). RPM system used for four-dimensional computed tomography scanner light-speed, GE is based on an infrared camera to detect motion of external 6-point marker. The beams were delivered using a Clinac iX (Varian Medical Systems, Palo Alto, CA) with the multileaf collimator Millennium 120. The MapCheck2 (SunNuclear, Florida) was used for the evaluation of treatment plans. MapCheck2 was validated through a comparison with measurements from a farmer-type ion chamber. Gated beams were delivered using a maximum dose rate with varying duty cycles and analyzed the MapCheck2 data to evaluate treatment plan delivery accuracy.Results: Results of the gamma passing rate for relative and absolute dose differences for all ungated and gated beams were between 95.1% and 100%.Conclusion: Gated FIF technique can deliver an accurate dose to a detector during gated breast cancer RT. There is no significance between gated and ungated patient-specific quality assurance (PSQA); one can use ungated PSQA for verification of treatment plan delivery

The aim of this study was to evaluate thoracic surface motion from chest wall expansion during free breathing (FB) and deep inspiration breath hold (DIBH) methods, measured with and without 4-dimensional computed tomography (4D-CT) simulation, using equipment developed in-house. The respiratory amplitude and chest wall expansion were evaluated at 5 levels of the thorax, (the sterno-clavicular joint (SCJ), the second level, the intermammary line (IML), the fourth level and the caudal end of the xiphoid process (XP)) using radiopaque wires and potentiometers, with a CT scan simultaneously. This study included 25 examinees (10 volunteers performed FB, 10 volunteers performed DIBH and 5 patients performed FB). For low and irregular respiration, coaching was used, and its impact was evaluated for both breathing methods, FB and DIBH. The breathing amplitude performed with FB between volunteers and patients was not detectable at the SCJ; increasing to the abdomen, 3 mm vs 2 mm (p = 0.326) at the second level; 6 mm vs 4 mm (p = 0.042) at the IML; 10 mm vs 8 mm (p0.01) at the fourth level; and 23 mm vs 19 mm (p0.001) at the XP. Contrary to the DIBH, where breathing amplitude was greater at 2 first levels 18 mm (SCJ) and 20 mm (second level), decreasing to the abdomen, 14 mm (IML); 11 mm (fourth level); and 10 mm (XP). Chest wall expansion was not detected at the SCJ, while at other levels measured from 1 to 7 mm. Coaching was improve breathing amplitude, for both methods, FB (3 mm) and DIBH (5 mm). The location of amplification is different depending on the breathing method and the in-house phantom was useful to check the amplification level.

The aim of this study is to investigate the robustness of our institutionally applied clinical target volume (CTV)-to-planning target volume (PTV) margins in cervical cancer patients in terms of an equivalent uniform dose (EUD) based on tumor control probability (TCP). We simulated target motion using 25 IMRT cervical cancer plans to demonstrate the effect of geometrical uncertainties on the EUD and TCP. The different components of the total geometrical uncertainties budget were estimated. The biological effects were compared by calculating the EUDs from the trial DVHs. The impact of geometric uncertainties was calculated as a percentage of the difference between 〖EUD〗_static and 〖EUD〗_motion, where the 〖EUD〗_static is the EUD calculated from the target DVHs and 〖EUD〗_motion is averaged, over a 1000 calculated EUDs for each of the analyzed IMRT treatment plans. The multivariate nonlinear regression was used to find the predicted difference between the static and motion EUD. The estimate of the systematic and random motion errors were Σ_(total(SI,LR,AP)) (mm)=(2.6; 2.5; 1.8) and σ_(total(SI,LR,AP)) (mm)=(3.4; 1.4; 3.4). For average 〈EUD〉_motion=44.3 Gy (over 25 patients) we have found a TCP decrease of about 1%, %(ΔTCP)≈1% for predefined PTV margin. According to the calculated EUD motion-distributions, for particular patients, the CTV does receive the prescribed EUD of 45 Gy. The predicted difference in EUD showed that our isotropic margin of 10 mm is large enough to absorb geometric uncertainties and ensure dose coverage of the moving CTV in the cervical cancer patients.

International audience; Background/Aim. For patients with left-sided breast cancer, a major concern is the dose of radiation delivered to the heart, because of increased risk of exposure and consequently increased risk of major coronary events and side effects. In order to reduce the dose to the heart during breast irradiation, deep inspiration breath-hold (DIBH) technique was implemented in our institution. The aim of this retrospective study was to compare dosimetric parameters of DIBH on the heart, left anterior descending artery (LAD) and ipsilateral lung (IL), compared with free breathing (FB) technique. Methods. Twenty patients who underwent radiotherapy with DIBH at our institution were retrospectively analyzed. Two computed tomography (CT) scans were acquired for each patient, FB-CT and DIBH-CT. Plans consisted of two opposed tangential segmented beams and one direct beam with small dose contribution. Doses to the heart, LAD, and IL were assessed. Results. Dosimetric comparison between FB and DIBH for mean dose to the heart was 5.17 Gy vs. 3.68 Gy, respectively (p < 0.0001), and the mean percentage of the volume receiving 25 Gy was 4.63% vs. 0.85%, respectively (p < 0.0001). Mean dose for LAD was 26.09 Gy vs. 11.89 Gy, respectively (p = 0.00014). Mean percentage of the volume receiving 20 Gy for the IL was 15.16% vs. 13.26% (p = 0.0007) for FB and DIBH, respectively. Conclusion. Implementation of DIBH technique in radiotherapy treatment of patients with left-sided breast cancer statistically significantly reduces the dose delivered to the surrounding organs at risk, particularly to the heart and LAD, with optimal target coverage.

Purpose To evaluate absolute dose between phase- and amplitude-gated modes for lung stereotactic body radiation therapy (SBRT), using the moving targets developed in-house. Methods The moving targets were developed in-house, allowing measurements of absolute dose using Semiflex ion chamber, Pinpoint ion chamber and microDiamond detector. 24 plans were generated in the Pinnacle 16.2 treatment planning system (TPS). 720 partial dynamic conformal arcs (DCA), 120 for phase- and 120 for amplitude-gated mode per detector, were performed to compare dose discrepancy (planned vs measured doses), for all detectors. Single fraction of 15 Gy was delivered with TrueBeam Novalis STx, triggered on the stable phases (phase-gated mode) or near the end-exhalation (amplitude-gated mode), for a breathing period ranging from 2 s to 7 s, using flattened filter free beams (FFF). Results The lowest discrepancy between measured and planned dose was obtained using the microDiamond detector in the phase-gated −0.1 (−0.2 to 0) % and −0.3 (−0.4 to −0.1) % in amplitude-gated mode (p Conclusion Detectors with low discrepancy, PinPoint ion chamber and microDiamond detectors, can be used in routine quality assurance for lung gated delivery in SBRT treatment, for commercial phantom as for phantom developed in-house.

During 2005 and 2006, soil samples were collected from different regions in the Republic of Srpska, in order to evaluate their radioactivity. During the war that lasted from 1994 to 1995, it is known that some locations in the Republic of Srpska were imposed upon by NATO forces. Sampled locations were chosen far away from the bombed places in order to check whether the depleted uranium was dispersed over long distances. The activity concentrations of radionuclides in soil samples were determined by gamma spectrometry (HPGe detector, relative efficiency 23%). Results showed the presence of natural radionuclides 226 Ra , 232 Th , 40 K , 235 U , 238 U as well as the produced radionuclide 137 Cs (from the Chernobyl accident and nuclear probes). In order to evaluate the radiological hazard of the natural radioactivity, the radium equivalent activity, the gamma-absorbed dose rate, the annual effective dose rate and the external hazard index have been calculated.