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Background: Mobility of lung tumors is induced by respiration and causes inadequate dose coverage. Objective: This study quantified lung tumor motion, velocity, and stability for small (≲5 cm) and large (>5 cm) tumors to adapt radiation therapy techniques for lung cancer patients. Material and Methods: In this retrospective study, 70 patients with lung cancer were included that 50 and 20 patients had a small and large gross tumor volume (GTV). To quantify the tumor motion and velocity in the upper lobe (UL) and lower lobe (LL) for the central region (CR) and a peripheral region (PR), the GTV was contoured in all ten respiratory phases, using 4D-CT. Results: The amplitude of tumor motion was greater in the LL, with motion in the superior-inferior (SI) direction compared to the UL, with an elliptical motion for small and large tumors. Tumor motion was greater in the CR, rather than in the PR, by 63% and 49% in the UL compared to 50% and 38% in the LL, for the left and right lung. The maximum tumor velocity for a small GTV was 44.1 mm/s in the LL (CR), decreased to 4 mm/s for both ULs (PR), and a large GTV ranged from 0.4 to 9.4 mm/s. Conclusion: The tumor motion and velocity depend on the tumor localization and the greater motion was in the CR for both lobes due to heart contribution. The tumor velocity and stability can help select the best technique for motion management during radiation therapy. [ABSTRACT FROM AUTHOR]

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: p < 0.05). 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 (p < 0.05). The dose received by the ribs decreases by 5–6 Gy, using FFF beams. The median gain in beam-on time ranged from 31% to 34% for SF and from 44 to 52% for DCA using FFF beams. The FFF beams reduce the dose received by all OARs, regardless of the used technique or tumor location, reducing treatment delivery time as well. [ABSTRACT FROM AUTHOR]

To evaluate the impact of the planning target volume (PTV) density on treatment planning for lung Stereotactic Body Radiation Therapy (SBRT). The PTV coverage was analyzed in two groups of 40 lung SBRT patients. One group had PTV density <0.5 g/cm3, while the other 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). 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 < 0.0001), the MUs were 2294 vs. 1655 MU (p < 0.0001), Dmax was 74.26 vs. 68.09 Gy (p < 0.0001), V30Gy was 117.03 vs. 104.81 cc (p = 0.04), and OPV was 28.48 vs. 39.35 cc (p < 0.001). By overriding the ITV density to 0.8 g/cm3, the isodose line prescription decreases. The Dmax and MUs decrease by 7%, V30Gy by 34%, and OPV by 70%. To obtain similar PTV coverage for PTV which is <0.5 g/cm3, a larger margin irradiating a large OPV was used. More MUs and a higher maximum dose were delivered. For the PTV density of ≤0.36 g/cm3, overriding is recommended to reduce the dose and irradiated volume. [ABSTRACT FROM AUTHOR]

Introduction: In this study, we aimed to evaluate internal (lung, heart and diaphragm) and external (nine glass marbles) marker motion in correlation with lung tumor motion and determine potential surrogate for respiratory gating radiation therapy (RGRT) depending on tumor localization, upper lobe (UL) versus lower lobe (LL). Material and Methods: We included 58 patients (34 male and 24 female) with small lung cancer (≤ 5cm), who underwent stereotactic body radiation therapy (SBRT). All patients were scanned and contoured in all ten phases (Varian Eclipse 13.7) after four-dimensional computed tomography simulation (4D-CT). The motions of internal and external markers were analyzed and correlated with tumor motion. Pearson correlation coefficient (PCC) was used to evaluate the correlation between internal and external marker motion and tumor motion. Results: The median (range) values of tumor motion were 3.2 (0.6-11.0) and 8.6 (4.0-24.0) mm in the UL and LL, respectively. The median (range) values of organs motion and PCC comparing UL vs. LL were 2.0 (0.3-9.1) vs. 6.0 (2.8-13.9) mm and 0.46 (0.30-0.95) vs. 0.79 (0.50-0.94) for the lung, respectively, 11.9 (2.5- 16.3) vs. 12.5 (5.0-22.5) mm and 0.68 (0.11-0.93) vs. 0.89 (0.30-0.99) for the diaphragm, respectively, and 3.9 (2.5-6.3) vs. 7.6 (4.5-8.6) mm and 0.49 (0.20-0.70) vs. 0.59 (0.36-0.83) for the heart, respectively. The external marker motion and correlation coefficient for UL and LL were 2.5 (0.9-7.4) vs. 2.3 (1.0-5.9) mm and 0.54 (0.09-0.96) vs. 0.73 (0.27-0.94), respectively. Conclusion: Lung and diaphragm motion correlate better with tumor motion than the external marker. Diaphragm motion can be an excellent indicator for treatment based on RGRT. [ABSTRACT FROM AUTHOR]

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 (4DCT), 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. [ABSTRACT FROM AUTHOR]

Purpose: To study the impact of fused (18)F-fluoro-deoxy-D-glucose (FDG)-hybrid positron emission tomography (PET) and computed tomography (CT) images on conformal radiotherapy planning for esophageal carcinoma patients. Methods and Materials: Thirty-four esophageal carcinoma patients were referred for concomitant radiotherapy and chemotherapy with radical intent. Each patient underwent CT and FDG-hybrid PET for simulation treatment in the same treatment position. PET images were coregistered using five fiducial markers. Target delineation was initially performed on CT images, and the corresponding PET data were subsequently used as an overlay to CT data to define the target volume. Results: (18)F-fluorodeoxy-D-glucose-PET identified previously undetected distant metastatic disease in 2 patients, making them ineligible for curative conformal radiotherapy. The gross tumor volume (GTV) was decreased by CT and FDG image fusion in 12 patients (35%) and increased in 7 patients (21%). The GTV reduction was > or =25% in 4 patients owing to a reduction in the length of the esophageal tumor. The GTV increase was > or =25% with FDG-PET in 2 patients owing to the detection of occult mediastinal lymph node involvement in 1 patient and an increased length of the esophageal tumor in 1 patient. Modifications of the GTV affected the planning treatment volume in 18 patients. Modifications of the delineation of the GTV and displacement of the isocenter of the planning treatment volume by FDG-PET also affected the percentage of total lung volume receiving >20 Gy in 25 patients (74%), with a dose reduction in 12 patients and dose increase in 13. Conclusion: In our study, CT and FDG-PET image fusion appeared to have an impact on treatment planning and management of esophageal carcinoma. The affect on treatment outcome remains to be demonstrated. [ABSTRACT FROM AUTHOR]