Dosimetric study of RapidArc plans and conventional intensity modulated radiotherapy for prostate cancer involving seminal vesicles and pelvis lymph nodes

Purpose: The main purpose of this study is to (1) identify the continual diversity between conventional fixed field intensity modulation radiotherapy (IMRT) and RapidArc (RA) for high-risk prostate cancer; and (2) determine potential benefits and drawbacks of using for this type of treatment.Methods: A cohort of 20 prostate cases including prostate, seminal vesicles and pelvic lymph nodes was selected for this study. The primary planning target volume (PTVP) and boost planning target volume (PTVB) were contoured. The total prescription dose was 75.6 Gy (45 Gy to PTVP and an additional 21.6 Gy to PTVB). Two plans were generated for each PTV: multiple 7-fields for IMRT and two arcs for RA.Results: A Sigma index (IMRT: 2.75 ± 0.581; RA: 2.8 ± 0.738) for PTVP and (IMRT: 2.0 ± 0.484; RA: 2.1 ± 0.464) for PTVB indicated similar dose homogeneity inside the PTV. Conformity index (IMRT: 0.96 ± 0.047; RA: 0.95 ± 0.059) for PTVP and (IMRT: 0.97 ± 0.015; RA: 0.96 ± 0.014) for PTVB was comparable for both the techniques. IMRT offered lower mean dose to organ at risks (OARs) compared to RA plans. Normal tissue integral dose in IMRT plan resulted 0.87% lower than RA plans. All the plans displayed significant increase (2.50 times for PTVP and 1.72 for PTBB) in the average number of necessary monitor units (MUs) with IMRT beam. Treatment delivery time of RA was 2 ‒ 6 minutes shorter than IMRT treatment.Conclusion: For PTV including pelvic lymph nodes, seminal vesicles and prostate, IMRT offered a greater degree of OARs sparing. For PTV including seminal vesicles and prostate, RA with two arcs provided comparable plan with IMRT. RA also improved the treatment efficiency due to smaller number of MUs required.</p

Dosimetric study of RapidArc plans and conventional intensity modulated radiotherapy for prostate cancer involving seminal vesicles and pelvis lymph nodes

Purpose: The main purpose of this study is to (1) identify the continual diversity between conventional fixed field intensity modulation radiotherapy (IMRT) and RapidArc (RA) for high-risk prostate cancer; and (2) determine potential benefits and drawbacks of using for this type of treatment.Methods: A cohort of 20 prostate cases including prostate, seminal vesicles and pelvic lymph nodes was selected for this study. The primary planning target volume (PTVP) and boost planning target volume (PTVB) were contoured. The total prescription dose was 75.6 Gy (45 Gy to PTVP and an additional 21.6 Gy to PTVB). Two plans were generated for each PTV: multiple 7-fields for IMRT and two arcs for RA.Results: A Sigma index (IMRT: 2.75 ± 0.581; RA: 2.8 ± 0.738) for PTVP and (IMRT: 2.0 ± 0.484; RA: 2.1 ± 0.464) for PTVB indicated similar dose homogeneity inside the PTV. Conformity index (IMRT: 0.96 ± 0.047; RA: 0.95 ± 0.059) for PTVP and (IMRT: 0.97 ± 0.015; RA: 0.96 ± 0.014) for PTVB was comparable for both the techniques. IMRT offered lower mean dose to organ at risks (OARs) compared to RA plans. Normal tissue integral dose in IMRT plan resulted 0.87% lower than RA plans. All the plans displayed significant increase (2.50 times for PTVP and 1.72 for PTBB) in the average number of necessary monitor units (MUs) with IMRT beam. Treatment delivery time of RA was 2 ‒ 6 minutes shorter than IMRT treatment.Conclusion: For PTV including pelvic lymph nodes, seminal vesicles and prostate, IMRT offered a greater degree of OARs sparing. For PTV including seminal vesicles and prostate, RA with two arcs provided comparable plan with IMRT. RA also improved the treatment efficiency due to smaller number of MUs required

Advantage of using deep inspiration breath hold with active breathing control and image-guided radiation therapy for patients treated with lung cancers

Purpose: The aim of this study was to evaluate the irradiated volume and doses to the target, heart, left lung, right lung and spinal cord, the number of segments and treatment time by using moderated deep inspiration breath hold (mDIBH) with active breathing control (ABC) and image-guided radiotherapy (IGRT) for patients treated with lung cancers.Methods: The suitability of this technique for lung patient treated with ABC was investigated and the solutions to achieve better treatments were discussed. Eleven lung cancer patients (3 left-sided and 8 right sided lesions) with stages I-III underwent standard free breath (FB) and ABC computed tomography (CT) scans in the treatment supine position. This can be achieved by applying respiratory manoeuvres, such as mDIBH, during which the threshold volume utilized is defined as 75-80% of the maximum aspiratory capacity. Five to seven, 6-MV photon beams with optimized gantry angles were designed according to the tumor location to conform to the PTV while sparing as much heart, spinal cord, and contra lateral lung as possible. For eleven patients, treatment planning using mDIBH CT data with intensity modulated radiation therapy (IMRT) was then reoptimized on the free breathing data set for comparison. The studied parameters of the plans for each patient were evaluated based on the average of the minimum, mean, and maximum difference in dose, the range of difference, and the p-value using two-tailed paired t test assuming equal variance.Results: The average volume of the planning target volume (PTV) in 11 patients increased to 1.32% in ABC compared to FB. The average volume of heart in 11 patients decreased to 2.9% in ABC compared to free breathing IMRT. In the case of lungs, the volume increased to 27.5% and 25.85% for left and right lungs, respectively. The range of mean difference in dose to the PTV in 11 patients was -54 cGy to 230 cGy with ABC technique when compared with free breathing. The range of mean dose difference of heart in 11 patients observed were -88 cGy to 66 cGy (p &lt; 0.0410) between ABC and FB. The range of maximum dose difference to the spinal cord in 11 patients were -1592 cGy to 190 cGy (p &lt; 0.041) with ABC technique when compared with FB IMRT. Monitor units (MUs) were -22.9% less in ABC compared to FB. Segments were more in ABC compared to FB for about 16.39% on an average. The average of minimum, mean and maximum difference in dose to the right lung and left lung were less in ABC compared with FB.Conclusion: In most of the cases, IGRT with ABC significantly reduces the mean dose to heart, right lung, left lung, and spinal cord compared with FB. Discrepancy observed in few cases made the statistical data inconsistent. Depending on anatomy and arbitrary phase of the breathing cycle, the results may vary and for better outcome of the results optimum treatment procedures need to follow.

Quality control test for electronic portal imaging device using QC-3 phantom with PIPSpro

Purpose:A Quality control (QC) test suitable for routinely daily use has been established for electronic portal imaging device (EPID) using PIPSpro software version 4.4 (Standard Imaging, Middleton, WI). It provides an objective and quantitative test for tolerable image quality on the basis of the high contrast spatial resolution, the contrast-to-noise ratio (CNR) and noise.Methods: The test uses a QC-3 phantom consisting of five sets of high contrast rectangular bar patterns with spatial frequeinces of 0.10, 0.20, 0.25, 0.43 and 0.75 lp/mm using 6MV and 15MV photon energy for accquiring high quality images. A “base line” value for the relative square wave modulation transfer function (RMTF), CNR and Noise data was obtained during a one week calibration period and one month test period.Results: Subsequent measurements shows significant deviations from baseline values, resulting in warning messages “potential problems in system performance”. The QC test uses high contrast spatial resolution and CNR for the system with acceptable performance. Conclusion: The method provides an automatic, objective, and sensitive measure of the system's imaging performance. This is a useful implementation during acceptance testing, commissioning, and routine quality control

Commissioning and quality assurances of the Intrabeam Intra-Operative radiotherapy unit

Purpose: The authors report comprehensive commissioning and quality assurance (QA) procedures for Intrabeam, Intra-Operative radiotherapy (IORT) unit. The Intrabeam system miniature X-ray source is a 50 kV and 40 µA unit. Methods: The authors’ tests include measurements of output, beam deflection, isotropy, kVp and mAs measurements, quality index, isodose, reproducibility, linearity, depth dose verification, and 3D dose distribution. IC ionization chamber and the UNIDOSE dosimeter were used for the output commissioning. Probe adjuster/ionization chamber holder (PAICH) was used to check the mechanical straightness of the probe. For radiation tests, NACP parallel plate chamber, Standard Imaging electrometer, 30 × 30 × 30 cm3 IAEA water phantom, solid water slabs, EDR-2 Films with RIT software, and ionization based survey meters were used. Unfors Xi platinum edition kVp meter was used to measure the kVp and mAs. Results: In mechanical QA test, X-Beam position (-0.09 mm), Y-Beam position (0.01 mm), and radial position (0.11 mm) errors were within the tolerance level. Isotropy test with PDA, survey meter, ion chamber, and film measurements also produced results within the specifications. Output measurements with PAICH and external chamber measurements were matched. Beam quality, linearity, and reproducibility values were ascertained at 50KV and 40 µA and found to be within limits. Isodose, 3D dose distribution, transverse, and horizontal profiles showed the good isotropy of the source. Conclusion: The authors’ methodology provides comprehensive commissioning and calibration procedures for the Intrabeam system

Dosimetric study of RapidArc plans with flattened beam (FB) and flattening filter-free (FFF) beam for localized prostate cancer based on physical indices

Purpose: To identify the continual diversity between flattening photon beam (FB) and Flattening Filter Free (FFF) photon beams for localized prostate cancer; and to determine potential benefits and drawbacks of using unflattened beam for this type of treatment.Methods: Eight prostate cases including seminal vesicles selected for this study. The primary planning target volume (PTVP) and boost planning target volume (PTVB) were contoured. The total prescription dose was 78 Gy (56 Gy to PTVP and an additional 22 Gy to PTVB). For all cases, treatment plans using 6MV with FB and FFF beams with identical dose-volume constraints, arc angles and number of arcs were developed. The dose volume histograms for both techniques were compared for primary target volume and critical structures.Results: A low Sigma index (FFF: 1.65 + 0.361; FB: 1.725 + 0.39) indicating improved dose homogeneity in FFF beam. Conformity index (FFF: 0.994 + 0.01; FB: 0.993 + 0.01) is comparable for both techniques. Minimal difference of Organ at risk mean dose was observed. Normal tissue integral dose in FB plan resulted 1.5% lower than FFF plan. All the plans displayed significant increase (1.18 times for PTVP and 1.11 for PTBB) in the average number of necessary MU with FFF beam.Conclusion: Diversity between FB and FFF beam plans were found. FFF beam accelerator has been utilized to develop clinically acceptable Rapid Arc treatment plans for prostate cancer with 6 MV.---------------------------------Cite this article as: Rout BK, Muralidhar KR, Ali M, Shekar MC, Kumar A. Dosimetric study of RapidArc plans with flattened beam (FB) and flattening filter-free (FFF) beam for localized prostate cancer based on physical indices. Int J Cancer Ther Oncol 2014; 2(4):02046.  DOI: 10.14319/ijcto.0204.

Radiotherapy for large cutaneous angiosarcoma of face with RapidArc (VMAT)

Angiosarcoma is a rare malignancy of vascular origin. It can affect any part of the body, head and neck region being probably the most common site of diagnosis. We present here a case of Angiosarcoma of face in a 67-year-old elderly gentleman who was treated with RapidArc – volumetric modulated arc therapy (VMAT) for recurrence after surgery, radiotherapy and chemotherapy. As an alternative to Electron Beam Therapy, RapidArc with skin bolus can be considered for large complex shaped targets with irregular surface and tissue inhomogeneity. RapidArc plan can achieve adequate target coverage with acceptable dose homogeneity and conformity

Advantage of using deep inspiration breath hold with active breathing control and image-guided radiation therapy for patients treated with lung cancers

Purpose: The aim of this study was to evaluate the irradiated volume and doses to the target, heart, left lung, right lung and spinal cord, the number of segments and treatment time by using moderated deep inspiration breath hold (mDIBH) with active breathing control (ABC) and image-guided radiotherapy (IGRT) for patients treated with lung cancers.Methods: The suitability of this technique for lung patient treated with ABC was investigated and the solutions to achieve better treatments were discussed. Eleven lung cancer patients (3 left-sided and 8 right sided lesions) with stages I-III underwent standard free breath (FB) and ABC computed tomography (CT) scans in the treatment supine position. This can be achieved by applying respiratory manoeuvres, such as mDIBH, during which the threshold volume utilized is defined as 75-80% of the maximum aspiratory capacity. Five to seven, 6-MV photon beams with optimized gantry angles were designed according to the tumor location to conform to the PTV while sparing as much heart, spinal cord, and contra lateral lung as possible. For eleven patients, treatment planning using mDIBH CT data with intensity modulated radiation therapy (IMRT) was then reoptimized on the free breathing data set for comparison. The studied parameters of the plans for each patient were evaluated based on the average of the minimum, mean, and maximum difference in dose, the range of difference, and the p-value using two-tailed paired t test assuming equal variance.Results: The average volume of the planning target volume (PTV) in 11 patients increased to 1.32% in ABC compared to FB. The average volume of heart in 11 patients decreased to 2.9% in ABC compared to free breathing IMRT. In the case of lungs, the volume increased to 27.5% and 25.85% for left and right lungs, respectively. The range of mean difference in dose to the PTV in 11 patients was -54 cGy to 230 cGy with ABC technique when compared with free breathing. The range of mean dose difference of heart in 11 patients observed were -88 cGy to 66 cGy (p &lt; 0.0410) between ABC and FB. The range of maximum dose difference to the spinal cord in 11 patients were -1592 cGy to 190 cGy (p &lt; 0.041) with ABC technique when compared with FB IMRT. Monitor units (MUs) were -22.9% less in ABC compared to FB. Segments were more in ABC compared to FB for about 16.39% on an average. The average of minimum, mean and maximum difference in dose to the right lung and left lung were less in ABC compared with FB.Conclusion: In most of the cases, IGRT with ABC significantly reduces the mean dose to heart, right lung, left lung, and spinal cord compared with FB. Discrepancy observed in few cases made the statistical data inconsistent. Depending on anatomy and arbitrary phase of the breathing cycle, the results may vary and for better outcome of the results optimum treatment procedures need to follow.  </p

Quality control test for electronic portal imaging device using QC-3 phantom with PIPSpro

Purpose:A Quality control (QC) test suitable for routinely daily use has been established for electronic portal imaging device (EPID) using PIPSpro software version 4.4 (Standard Imaging, Middleton, WI). It provides an objective and quantitative test for tolerable image quality on the basis of the high contrast spatial resolution, the contrast-to-noise ratio (CNR) and noise.Methods: The test uses a QC-3 phantom consisting of five sets of high contrast rectangular bar patterns with spatial frequeinces of 0.10, 0.20, 0.25, 0.43 and 0.75 lp/mm using 6MV and 15MV photon energy for accquiring high quality images. A “base line” value for the relative square wave modulation transfer function (RMTF), CNR and Noise data was obtained during a one week calibration period and one month test period.Results: Subsequent measurements shows significant deviations from baseline values, resulting in warning messages “potential problems in system performance”. The QC test uses high contrast spatial resolution and CNR for the system with acceptable performance. Conclusion: The method provides an automatic, objective, and sensitive measure of the system's imaging performance. This is a useful implementation during acceptance testing, commissioning, and routine quality control.</p