Conformal Radiotherapy Treatment Planning Research Articles

Pulmonary fibrosis prevalence after adjuvant radiotherapy of Iranian patients with breast cancer: A single-center cross-sectional study.

This study aims to investigate the incidence rate of pulmonary fibrosis as a late radiotherapy complication and identify the associated dosimetric and demographic factors using radiological findings between Iranian patients with breast cancer. Breast cancer patients treated at the education hospital of Shohada-e Tajrish Hospital, Tehran, Iran, from 2017 to 2021 were considered. Patients have included for whom a secondary chest CT scan was available at least six months after radiotherapy. Dose-volume histogram (DVH) parameters of three-dimensional conformal radiotherapy (3D-CRT) treatment plans were exported. Demographic features and data on underlying lung diseases, diabetes, and smoking history were extracted. A total of 250 patients were included in the study with a mean age of 46.1 ± 7.5 yrs and a mean body mass index (BMI) of 24.5 ± 4.2 kg/m2. Pulmonary fibrosis was detected for sixty-two cases. A significant relationship was obtained between the ipsilateral lung DVH parameters of patients with pulmonary fibrosis (P value < 0.05). The V5Gy, V10Gy, V13Gy, V20Gy, V30Gy, MLD, and DMax for individuals with pulmonary fibrosis were significantly higher than those without this injury. Pulmonary fibrosis was distinguished for 25% of the breast cancer cases at least six months after adjuvant radiotherapy. A significant relationship between the DVH parameters, underlying lung disease, diabetes, radiotherapy fields (i.e., Breast + LN + SC or Breast/Chest-wall only), age, and BMI with the frequency of the ipsilateral pulmonary fibrosis was obtained. V13Gy and V30Gy of the ipsilateral lung may be the most predictor of pulmonary fibrosis incidence.

Establishment of local diagnostic reference levels for breast cancer CT protocols in radiotherapy in a single Moroccan center

The objective of this study was to establish local diagnostic reference levels (LDRLs) for breast cancer computed tomography imaging in radiotherapy (CT-RT) at a single hospital in Morocco. Data were collected from 106 adult breast cancer patients aged between 33 and 78 yr during five months. Data were obtained using a Hitachi Supria 16-slice CT simulator at a regional oncology center in Morocco. CT-RT images are intended for 3D conformal radiotherapy treatment planning. Dose length product (DLP) and volumetric computed tomography dose index (CTDIvol) were evaluated by determining the 75th percentile as diagnostic reference levels for CT-RT breast cancer. LDRLs for CT-RT breast cancer have been determined in terms of DLP and CTDIvol, and they were 330.4 mGy.cm and 6.8 mGy, respectively. The DRLs were compared with other Europeans study. DRLs for this study were lower than those for the United Kingdom (UK), Croatia and Slovenia. The results of this study can be a reference for the establishment of local and national DRLs in Morocco and the optimization of CT-RT breast cancer procedures.

Incidental nodal irradiation in patients with esophageal cancer undergoing (chemo)radiation with 3D-CRT or VMAT

The extent of elective nodal irradiation (ENI) in patients undergoing definitive chemoradiotherapy (dCRT) for esophageal squamous cell carcinoma (ESCC) remains unclear. The aim of this dosimetric study was to evaluate the extent of incidental nodal irradiation using modern radiation techniques. A planning target volume (PTV) was generated for 30 patients with node-negative esophageal carcinoma (13 cervical/upper third, 7 middle third, 10 lower third/abdomen). Thereby, no elective nodal irradiation (ENI) was intended. Both three-dimensional conformal radiotherapy (3D-CRT) and volumetric-modulated arc therapy (VMAT) treatment plans (50 Gy in 25 fractions) were calculated for all patients. Fifteen nodal stations were contoured according to the definitions of the AJCC and investigated in regard to dosimetric parameters. Compared to 3D-CRT, VMAT was associated with lower dose distribution to the organs at risk (lower Dmean, V20 and V30 for the lungs and lower Dmean and V30 for the heart). For both techniques, the median Dmean surpassed 40 Gy in 12 of 15 (80%) nodal stations. However, VMAT resulted in significantly lower Dmeans and equivalent uniform doses (EUD) compared to 3D-CRT for eight nodal stations (1L, 2L, 2R, 4L, 7, 8L, 10L, 15), while differences did not reach significance for seven nodal station (1R, 4R, 8U, 8M, 10R, 16). For dCRT of ESCC, the use of VMAT was associated with significantly lower median (incidental) doses to eight of 15 regional lymph node areas compared to 3D-CRT. However, given the small absolute differences, these differences probably do not impair (regional) tumor control rates.

Three-dimensional conformal radiotherapy breast cancer planning: An evaluation study comparing two techniques using homemade phantom

Anthropomorphic phantoms, which can provide equivalent human tissue densities, are one of the best solutions for verifying the quality of radiotherapy treatment plans produced by treatment planning systems. The goal of this work was to develop and fabricate a breast phantom to estimate radiation doses to the breast, lung, and surface using radiochromic films (EBT3) for basically two techniques of three-dimensional conformal radiotherapy (3D-CRT) treatment planning. Thirty-two acrylic slices were used to construct the phantom. Cork and Teflon were used to mimic the lung and bone, respectively. Four slots were drilled for dosimetry purposes to allow access to the areas of ionization chamber installation. Both wedged and open of two tangential beams techniques were applied. With a mean deviation of 1.02 ± 1.1, the variation between estimated point doses and measurements using the three ionization chambers ranged from 2.9 to 1.4%. Using 0, 5 and 10 mm boluses, the mean percentage doses on the target surface were 54.7, 88.6 and 91.7% of the prescribed dose (PD), respectively. The homemade phantom was appropriate for conducting quality control (QC) tests for 3D-CRT planning techniques for breast radiotherapy.

Verification of monitoring unit calculations for the 3D conformal radiotherapy treatment planning system

The present work aims to validate an Independent Calculation of Monitoring Units (ICMU) software developed to accurately calculate the number of Monitoring Units (MU) used in radiation treatment. The calculation was performed for the photon beam with a variety of nominal energies (6 MV − 18 MV) and filed size ranging from 3 × 3 cm2 to 40 × 40 cm2. Two set-up conventions of treatment techniques were tested, a constant source to surface distance (SSD) and an isocentric set-up with a constant source to axis distance (SAD). The ICMU software was written in C-sharp (C #), using the equivalent square field size concept to calculate the radiation field quantities and connects to a database containing measurements quantities such as Tissue Phantom ratio (TPR) and Output Factors (OFs). The ICMU was successfully validated by comparing it to the Treatment Planning System (TPS) or CMS Monitor Unit Calculations (CMS_MU). The required standards were satisfactorily met (5.0%).

Independent verification of treatment planning system calculations

Abstract Purpose According to the available international recommendations, at least one independent verification of the calculations of number of monitor unit (MU) is required for every patient treated by teleradiotherapy. The aim of this study was to estimate the differences of dose distributions calculated with two treatment planning systems: Eclipse (Varian) and Oncentra MasterPlan (Elekta). Materials and methods The analysis was performed for 280 three-dimensional conformal radiotherapy treatment (3D-CRT) plans with photon beams from Varian accelerators: CL 600C/D X6 MV (109 plans), CL 2300C/D X6 MV (43 plans), and CL 2300C/D X15 MV (128 plans). The mean doses in the planning target volume (PTV) and doses at the isocenter point obtained with Eclipse and Oncentra MasterPlan (OMP) were compared with Wilcoxon matched-pairs signed rank test. Additionally, the treatment planning system (TPS) calculations were compared with dosimetric measurements performed in the inhomogeneous phantom. Results Data were analysed for 6 MV plans and for 15 MV plans separately, independently of the treatment machine. The dose values calculated in Eclipse were significantly (p &lt;0.001) higher compared to calculations of OMP system. The average difference of the mean dose to PTV was (1.4 ± 1.0)% for X6 MV and (2.5 ± 0.6)% for X15 MV. Average dose disparities at the isocenter point were (1.3 ± 1.9)% and (2.1 ± 1.0)% for X6 MV and X15 MV beams, respectively. The largest differences were observed in lungs, air cavities, and bone structures. Moreover the variation in dosimetric measurements was less as compared to Eclipse calculations. Conclusions OMP calculations were introduced as the independent MU verification tool with the first action level range equal to 3.5%.

Erken Evre Glottik Larenks Kanserli Hastalarda Radyoterapi Tekniğinin Karotis Arter Dozu Üzerine Etkisi

Objective: The aim of this study was to compare two radiotherapy techniques in early stage glottic laryngeal cancer patients in terms of radiotherapy dose applied to the carotid artery.Material - Methods: In this study, we included 10 early-stage (T1/2) glottic larynx cancer patients. Both intensity-modulated radiotherapy (IMRT) and 3-dimension conformal radiotherapy (3DCRT) treatment plans were prepared for each patient. Treatment volumes (CTV, PTV) were created for all patients. The entire larynx was described as CTV to include both false and true vocal cords, anterior-posterior commissures, arytenoids, aryepiglottic folds, subglottic region. For planning target volüme (PTV), while 5-mm was added to CTV in all directions, 3-mm margin was given to protect the carotid artery and spinal cord in posterolaterally. Spinal cord and carotid artery were contoured as the organ at risk (OAR). The doses of the target volumes, the OAR volumes, the homogeneity index (HI) were compared. Results: PTV parameters (Dmin, Dmean, Dmax, D90, D95) was compared in the 2 different technique. IMRT in comparison to 3DCRT significantly reduced the high-dose volumes (V30, V35, V50) of carotid artery (p &amp;lt; 0.001), but not to the low dose volume (V10). CI was similar (0.9 vs. 0.9, p = 0.3) compared to 3DCRT. However, HI was significantly improved with IMRT (0.1 vs. 0.08, p &amp;lt; 0.001). The maximum dose of the spinal cord was lower in 3DCRT compared to IMRT (18 Gy vs. 44Gy). Conclusion: IMRT is a superior radiotherapy (RT) technique in patients with T1/T2 glottic cancer in terms of protecting carotid artery.

Dosimetric Evaluation of Intensity Modulated Radiotherapy and Three-Dimensional Conformal Radiotherapy Treatment Plans for Prostate Cance

Dosimetric Evaluation of Intensity Modulated Radiotherapy and Three-Dimensional Conformal Radiotherapy Treatment Plans for Prostate Cance

Physician review of image registration and normal structure delineation.

IntroductionImage registration and delineation of organs at risk (OARs) are key components of three‐dimensional conformal (3DCRT) and intensity‐modulated radiotherapy (IMRT) treatment planning. This study hypothesized that image registration and OAR delineation are often performed by medical physicists and/or dosimetrists and are not routinely reviewed by treating physicians.MethodsAn anonymous, internet‐based survey of medical physicists and dosimetrists was distributed via the MEDPHYS and MEDDOS listserv groups. Participants were asked to characterize standard practices for completion and review of OAR contouring, target volume contouring, and image registration at their institution along with their personal training in these areas and level of comfort performing these tasks. Likert‐type scales are reported as Median [Interquartile range] with scores ranging from 1 = “Extremely/All of the time” to 5 = “Not at all/Never.”ResultsTwo hundred and ninety‐seven individuals responded to the survey. Overall, respondents indicated significantly less frequent physician review (3 [2–4] vs 2 [1–3]), and less confidence in the thoroughness of physician review (3 [2–4] vs 2 [1–3], P < 0.01) of OAR contours compared to image registration. Only 19% (95% CI 14–24%) of respondents reported a formal process by which OAR volumes are reviewed by physicians in their clinic. The presence of a formal review process was also associated with significantly higher perceived thoroughness of review of OAR volumes compared to clinics with no formal review process (2 [2–3] vs 3 [2–4], P < 0.01).ConclusionDespite the critical role of OAR delineation and image registration in the 3DCRT and IMRT treatment planning process, physician review of these tasks is not always optimal. Radiotherapy clinics should consider implementation of formal processes to promote adequate physician review of OARs and image registrations to ensure the quality and safety of radiotherapy treatment plans.

Computed Tomography/Magnetic Resonance Imaging (CT/MRI) Image Registration and Fusion Assessment for Accurate Glioblastoma Radiotherapy Treatment Planning

Background: In this study, computed tomography/magnetic resonance imaging (CT/MRI) image registration and fusion in the 3D conformal radiotherapy treatment planning of Glioblastoma brain tumor was investigated. Good CT/MRI image registration and fusion made a great impact on dose calculation and treatment planning accuracy. Indeed, the uncertainly associated with the registration and fusion methods must be well verified and communicated. Unfortunately, there is no standard procedure or mathematical formalism to perform this verification due to noise, distortion, and complicated anatomical situations. Objectives: This study aimed at assessing the effective contribution of MRI in Glioma radiotherapy treatment by improving the localization of target volumes and organs at risk (OARs). It is also a question to provide clinicians with some suitable metrics to evaluate the CT/MRI image registration and fusion results. Methods: Quantitative image registration and fusion evaluation were used in this study to compare Eclipse TPS tools and Elastix CT/MRI image registration fusion. Thus, Dice score coefficient (DSC), Jaccard similarity coefficient (JSC), and Hausdorff distance (HD) were found to be suitable metrics for the evaluation and comparison of the image registration and fusion methods of Eclipse TPS and Elastix. Results: The programmed tumor’s volumes (PTV) delineated on CT slices were approximately 1.38 times smaller than those delineated on CT/MRI fused images. Large differences were observed for the edema and the brainstem. It was also found that MRI considerably optimized the dose to be delivered to the optic nerve and brainstem. Conclusions: Image registration and fusion is a fundamental step for suitable and efficient Glioma treatment planning in 3D conformal radiotherapy that ensure accurate dose delivery and unnecessary OAR irradiation. MRI can provide accurate localization of targeted volumes leading to better irradiation control of Glioma tumor.

A Comparative Study of 3-D Conformal Radiotherapy Treatment Plans with and Without Deep Inspiration Breath-Hold Technique for Left-Sided Breast Cancer

Introduction: The rate of cardiac diseases have increased among patients who underwent radiotherapy for left-sided breast cancer. The study’s aim was evaluate the dose to organs at risk in free-breathing 3-dimensional conformal (FB-3DCRT) against 3-dimensional conformal deep inspiration breath-hold (3DCRT-DIBH) in patients with left-sided breast cancer. Material and Methods: In total, 15th female patients diagnosed with left-sided breast cancer were included in this study from December 2017 to December 2018. All selected patients were subjected to FB and DIBH computed tomography (CT) scans. The 3DCRT plans were created on both DIBH and FB scans for each selected patient. Various doses were obtained from dose-volume histograms and then compared. The data were analyzed in SPSS software (version 20) (IBM; IL). P-value less than 0.05 was considered statistically significant. Results: The results obtained from the DIBH and FB conditions were compared. The average maximum dose and V95% for planning target volume was approximate for both DIBH and FB, and the average mean doses to the heart, left anterior descending artery, and left lung were decreased by 40.50% (P=0.0003), 54.30% (P=0.02),and 18.50% (P=0.0002) in DIBH, respectively. Moreover, the heart V25% and V30% were decreased by 36% (P=0.06) and 35.8 % (P=0.03) in DIBH, respectively. Regarding the left lung, a decrease by 18.10% in V10% (P=0.0006) and 18% in V20% (P=0.0002) was also observed in DIBH. Conclusion: The 3DCRT-DIBH for patients with left-sided breast cancer maintained the benefits of radiotherapy while minimizing cardiac risks. All patients completed their treatment smoothly.

Evaluation of conformal radiotherapy treatment planning of breast cancer patients: Preliminary case study patients from Persahabatan Central Hospital

Persahabatan Central Hospital has served radiotherapy treatment for cancer patients using linac, Elekta Precise and XiO treatment planning system (TPS) since May 2017. This study collected 91 breast cancer patients treated from May 2017 until January 2019. Most patients were preceded by surgery either mammae radical mastectomy (MRM) (83.5%) or breast conservative surgery (BCS) (16.5%). Conformal treatment planning generally performed with 2 tangential fields and most included oblique fields for treating axillary lymph nodes. Percentage of patients with clinical tumor volumes >400 cm3 was 29%, in the range of 200-400 cm3 was 36%, and the rest was <200 cm3. The lung volume irradiated with dose ≥20 Gy was used as one of parameters for treatment optimization. The mrm patient number with lung volume irradiated >30% was 9 persons (11.8%), in the range of 20-30% was 65 persons (85.5%), and <20% was 2 persons (2.6%). For the bcs patients, the number followed these criteria with lung volume of 20-30% was 13 persons (86.7%), and <20% was 2 persons (13.3%). Most breast cancer patients treated with radiotherapy were advanced stage preceded by mrm, treatment planning was difficult for achieving lung volume <30% that irradiated with the dose ≥20 Gy.

Comparison of dose calculation algorithms model: Convolution, superposition, and fast superposition in 3-D Conformal Radiotherapy (3D-CRT) treatment plan

The important task of radiotherapy is to make sure that the radiation dose to the target tumour is accurate as prescribed and the dose to the organ at risk is minimized. Therefore, the aim of this study is to compare and evaluate the efficiency of the dose calculation algorithms: namely convolution, superposition, and fast superposition which installed in Treatment Planning System (TPS) (CMS XiO, USA). In this study, we modified protocols described in IAEATecdoc-1583, where four typical treatment techniques such as single field, multiple field, wedge field, and multi-leaf collimated (MLC) field were analysed from the system. The measurement data for calculated dose and measured dose were taken from thorax CIRS anthropomorphic phantom. The assessment of algorithms was done by comparing the point dose calculated with the measured dose. The study shows that the superposition algorithm produced relative error less than ± 3% which passed 100% of all reference points, whilst the convolution algorithm and fast superposition presented relative error more than ± 3% which passed 82% and 91% of reference points, respectively. In conclusion, the evaluation of radiotherapy treatment plan shall take into account the type of dose calculation algorithm model in order to optimize radiotherapy treatment and ensure the radiation safety to the patient.

P298] The influence of variations of the beam quality for high energy photon beams on tissue inhomogeneity correction factors for radiotherapy treatment plans

Purpose The purpose of this study was to assess the effect of variations of the beam quality (TPR20,10) for photon beams on tissue inhomogeneity correction factors (ICFs). Methods A total of 90 three-dimensional conformal radiotherapy (3DCRT) treatment plans for three locations (3DCRT lung, gynaecological, prostate) and 15 SRS lung plans were considered for this study. For 3DCRT plans, the ICFs were calculated for a range of beam qualities. For 6 MV, the range of TPR20,10 was 0.670 ± 3%, and for 15 MV, the range of TPR20,10 was 0.760 ± 3%. The stereotactic plans were prepared with two 6 MV beams from a Varian TrueBeam accelerator - one generated with a flattening filter (X6, TPR20,10 = 0.688) and one flattening filter free (X6FFF, TPR20,10 = 0.632). Calculations were performed using Eclipse treatment planning system (TPS) with the anisotropic analytical algorithm (AAA). ICFs were also measured in a CIRS Tissue Simulation Phantom (thorax with lungs) for two fields 5 × 5 and 10 × 10 for X6 and X6FFF beams. PTW Farmer and semiflex ionization chambers were used for measurements. Results Calculations for 3DCRT plans showed that the 6% variations in energy (TPR20,10) lea to average changes of ICFs of 2.0% (6 MV) and 2.6% (15 MV) for lung cases. For gynaecological and prostate patients, the mean differences of ICFs were less than 1%. The difference of 5.6% of TPR20,10 values between X6 and X6 FFF for lung SRS treatment plans led to a difference of ICFs of less than 2%. Measurements with the CIRS phantom also demonstrated differences of ICFs consistently less than 5% between X6 and X6 FFF beams. Conclusions The influence of energy on inhomogeneity correction factors is rather small. Correction factors measured on one accelerator may be used for another accelerator with similar energy provided quality control tests are performed.

Comparison of 3D-CRT and IMRT techniques in radiotherapy for post-prostatectomy patients with a higher risk of nodal involvement

Background. Irradiation of a larger volume of the target may lead to an increase of the doses delivered to the surrounding organs at risk (OAR) for post-prostatectomy patients with a higher risk of nodal involvement. It was anticipated that IMRT significantly improved OAR sparing. The aim of this study was to provide a dosimetric comparison between conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) treatment plans for patients with prostate cancer irradiated to the prostate bed and pelvic lymph-nodal area. Materials and methods. The 3D-CRT and IMRT plans were created for ten patients after prostatectomy. The treatment plans were generated for the prostate bed (PTV1) and the pelvic lymph nodes (PTV2). The sum of PTV1 and PTV2 was irradiated to a mean dose of 46 Gy in 23 fractions, and additionally PTV1 was irradiated to a mean dose of 18 Gy in 9 fractions. Target coverage and the doses delivered to the pelvic bones, the rectum, the bladder, the bowel bag, and the femurs, were compared between techniques. The Wilcoxon signed-rank test was used to compare the dosimetric parameters. Results. The dosimetric quality of 3D-CRT and IMRT plans were comparable for target coverage (the mean value of PTV1 V95%, the mean value of PTV2 V95% all > 99%). The IMRT plans resulted in significant reductions in the pelvic bones V30[%], V40[%], the rectum V40[%], V50[%], V60[%], the bladder V40[%], V50[%], V60[%], the bowel bag V45[cc] and the femurs V40[%]. Conclusions . The analysis presented in this paper demonstrates that the IMRT technique reduces the delivered dose to the OARs. Most interesting was the possibility of reducing the delivered dose to the pelvic bones and the bowel bag. This allowed us to expect a decreased risk of acute hematologic toxicity and acute gastrointestinal toxicity.

O21. Verification of prostate conformal radiotherapy treatment planning done on an XiO treatment planning system

Introduction Prostate three-dimensional conformal radiotherapy treatment (3D-CRT) planning presents many challenges for the dosimetrist, partly due to the array of parameters available for plan-evaluation. The aim of this study is to determine the parameter(s) contributing most to prostate 3D-CRT treatment plan quality. From this contribution an in-house protocol for the evaluation of prostate 3D-CRT plans was created. Materials and methods Nineteen different dosimetrists each created a prostate 3DCRT treatment plan for the same patient on the XiO treatment planning systems of Equra Health, from which the data of three physical and eight dosimetric parameters were extracted. Exploratory principal component analysis (PCA) performed on this small data-set determined the inter-relation between the parameters contributing most to variation. From this analysis principal components indicating treatment plan quality for prostate 3D-CRT were obtained. Dose-verification on the eight Siemens Primus linear accelerators of Equra Health was performed using Gafchromic EBT2 film placed within an anthropomorphic RANDO phantom. The dose delivered to the applicable organs at risk (OARs) was also measured in this plane. Results The average field size provided the highest relation of variation, while three additional parameters (V65 of the rectum, the number of beams and the maximum dose) indicated sufficient variation worth considering. Film-analysis indicated an area of approximately 8 × 10 cm 2 in size which had 97% agreement for all the Siemens Primus linear accelerators used. The dose to the rectum was found to be high. As a result, a protocol has been drafted to give guidance for planning of prostate 3DCRT within Equra Health. Conclusion Exploratory PCA can be used to identify the relationships between planning parameters within a small data-set. This procedure could also be performed to optimize the treatment planning for other types of cancer.

Comparison of the effects of two different dose algorithms in cardiac dose parameters for hodgkin lymphoma patients receiving mediastinal radiotheraphy

Objective: This study aimed to compare pencil beam (PB) and convolution superposition (CS) dose calculation algorithms with respect to cardiac dose-volume parameters V5, V25, V30 and MHD (median heart dose) in Hodgkin lymphoma (HL) patients who received mediastinal radiotherapy (RT). Material and Methods: Ten eligible cases with the diagnosis of HL who completed mediastinal RT at Dokuz Eylul University Department of Radiation Oncology before 01.01.2011 formed the study population. Related 3D conformal RT treatment plans were obtained from the Treatment Planning System (TPS) (Nucletron Oncentra Master Plan Version 3.3 SP3 program). Calculations were done for 6 and 18 MV-X beam energy, respectively by using PB and CS algorithms in the TPS. Two algorithms were compared in terms of cardiac dose-volume parameters (V5, V25, V30 and MHD). Results: Mean relative difference for both V25 and V30 was found to be significantly higher in favor of PB algorithm in both 6 MV-X and 18 MV-X photon energy. Mean relative differences were 1.75% (p=0.012) and 6.76% (p=0.028) for the V25 and V30 parameters, respectively in 6 MV-X and 3.25% (p=0.021) and 13.95% (p=0.007) for the V25 and V30 parameters, respectively in 18 MV-X energy. Conclusion: When PB algorithm is used in RT treatment planning of HL patients for the mediastinal region where tissue inhomogeneity is relatively high, heart V25 and V30 parameters were shown to result in higher values compared to CS algorithm in our study. It is more appropriate to prefer CS algorithm instead of PB algorithm since it increases accuracy of calculations in the treatment planning of mediastinal RT.

SU‐E‐T‐742: The Risk of Secondary Malignancies as An Evaluation Factor in the Comparison of Prostate Cancer Intensity Modulated Radiotherapy (IMRT) and Conformal Radiotherapy (CRT) Treatment Plans

Purpose:To examine the clinical efficacy of both MLC‐based IMRT, and 3D‐Conformal Radiation Therapy modalities (CRT) to treat prostate cancer using radiobiological measures. Furthermore, to investigate the risk for developing secondary malignancies in bladder and rectum due to radiotherapy from the corresponding modalities.Methods:Treatment plans for prostate cancer were developed using IMRT and CRT for ten patients. For the IMRT plans, two different treatment protocols were used (RTOG and FCCC). For the evaluation of these plans, the complication‐free tumor control probability, the total probability of injury, the total probability of control/benefit, and the biologically effective uniform dose were employed. Furthermore, based on the dosimetric data of IMRT and CRT, the risk for secondary malignancies was calculated for bladder and rectum.Results:The average risk for secondary malignancy was lower for the bladder (0.37%) compared to the rectum (0.81%) based on all the treatment plans of the ten prostate cancer patients. The highest average risk for secondary malignancy for bladder and rectum was for the 6X 3D modality (0.46% and 1.12%, respectively) and the lowest was for the 18X IMRT RTOG modality (0.33% and 0.56%, respectively). The response probability was lower for the bladder than for the rectum in all the plans. For the bladder the highest value was for the 18X IMRT FCCC (0.03%) and the lowest was for the 18X 3D modality (0.0%). For the rectum, the highest value was for the 6X IMRT RTOG (3.52%) and the lowest was for the 18X IMRT FCCC modality (0.41%).Conclusion:By using radiobiological measures it is shown that the IMRT FCCC plans had the lowest risks for normal tissue complications, whereas the IMRT RTOG had the highest. Regarding the risk for secondary malignancies, the CRT plans showed the highest values both in bladder and rectum.

Feasibility of using intravenous contrast-enhanced computed tomography scans in oesophagus cancers

Introduction The goal of this study is to investigate the feasibility of using intravenous contrast-enhanced computed tomography scans in 3-dimensional conformal radiotherapy treatment planning (3DCRT) for oesophagus cancers. Material and methods Eighteen patients treated for esophagus cancer had a 3D scan with (CT_int) and without (CT_no_int) intravenous injection of contrast product. 45 Gy to 50 Gy were planned. Organs at risk (OAR) were contoured on CT_no_int and CT_int. Target volume (PTV) was created on CT_int then copy/paste on CT_no_inj. Treatment planning was done on CT_no_int then copy/paste on CT_int. Esophagus tumors were planned with 3D-CRT using 4 to 5 coplanar beams with 6 or 16 MV energies. The position of the prescription point was kept on both plans. The used algorithm is the algorithm AAA V10 (Varian). 95% (V95), 100% (V100) and 102% (V102) isodoses volumes, min, max and average PTV doses, monitor units (MU), heart and healthy lungs delivered doses were compared. The differences (D), and the standards deviation (SD), between the average values by CT on all the patients were calculated and noted D (SD). The Wilcoxon statistical test was used. Results Results show a weak difference on total MU on both plans: 0.2% (0.7%) (ns). Average differences related to PTV doses are respectively 0.1% (1.1%), 2.4% (16.4%) and −0.1% (0.7%) (ns) for max, min and average doses. The comparison of isodoses volume shows an important standard deviation: 0% (5%) (ns), −2% (30%) and 1% (61%) respectively for V95, V100 and V102. For the heart, the differences are equals to 2% (14%) (ns) and 1% (17%) for V30Gy and V40Gy. No difference was shown concerning healthy lungs delivered doses: 0%(4%), 0% (4%) (ns) and −1% (7%) for V5Gy, V20Gy and V30Gy respectively. Conclusion The study shows no statistical differences between both plans with and without contrast product. As a consequence, treatment planning on an intravenous contrast-enhanced scanner in esophagus cancers is possible without major achievement or the treatment planning quality. The goal of this study is to investigate the feasibility of using intravenous contrast-enhanced computed tomography scans in 3-dimensional conformal radiotherapy treatment planning (3DCRT) for oesophagus cancers. Eighteen patients treated for esophagus cancer had a 3D scan with (CT_int) and without (CT_no_int) intravenous injection of contrast product. 45 Gy to 50 Gy were planned. Organs at risk (OAR) were contoured on CT_no_int and CT_int. Target volume (PTV) was created on CT_int then copy/paste on CT_no_inj. Treatment planning was done on CT_no_int then copy/paste on CT_int. Esophagus tumors were planned with 3D-CRT using 4 to 5 coplanar beams with 6 or 16 MV energies. The position of the prescription point was kept on both plans. The used algorithm is the algorithm AAA V10 (Varian). 95% (V95), 100% (V100) and 102% (V102) isodoses volumes, min, max and average PTV doses, monitor units (MU), heart and healthy lungs delivered doses were compared. The differences (D), and the standards deviation (SD), between the average values by CT on all the patients were calculated and noted D (SD). The Wilcoxon statistical test was used. Results show a weak difference on total MU on both plans: 0.2% (0.7%) (ns). Average differences related to PTV doses are respectively 0.1% (1.1%), 2.4% (16.4%) and −0.1% (0.7%) (ns) for max, min and average doses. The comparison of isodoses volume shows an important standard deviation: 0% (5%) (ns), −2% (30%) and 1% (61%) respectively for V95, V100 and V102. For the heart, the differences are equals to 2% (14%) (ns) and 1% (17%) for V30Gy and V40Gy. No difference was shown concerning healthy lungs delivered doses: 0%(4%), 0% (4%) (ns) and −1% (7%) for V5Gy, V20Gy and V30Gy respectively. The study shows no statistical differences between both plans with and without contrast product. As a consequence, treatment planning on an intravenous contrast-enhanced scanner in esophagus cancers is possible without major achievement or the treatment planning quality.

Comparison of Heart and Coronary Artery Doses Associated With Intensity-Modulated Radiotherapy Versus Three-Dimensional Conformal Radiotherapy for Distal Esophageal Cancer

To compare heart and coronary artery radiation exposure using intensity-modulated radiotherapy (IMRT) vs. four-field three-dimensional conformal radiotherapy (3D-CRT) treatment plans for patients with distal esophageal cancer undergoing chemoradiation. Nineteen patients with distal esophageal cancers treated with IMRT from March 2007 to May 2008 were identified. All patients were treated to 50.4 Gy with five-field IMRT plans. Theoretical 3D-CRT plans with four-field beam arrangements were generated. Dose-volume histograms of the planning target volume, heart, right coronary artery, left coronary artery, and other critical normal tissues were compared between the IMRT and 3D-CRT plans, and selected parameters were statistically evaluated using the Wilcoxon rank-sum test. Intensity-modulated radiotherapy treatment planning showed significant reduction (p < 0.05) in heart dose over 3D-CRT as assessed by average mean dose (22.9 vs. 28.2 Gy) and V30 (24.8% vs. 61.0%). There was also significant sparing of the right coronary artery (average mean dose, 23.8 Gy vs. 35.5 Gy), whereas the left coronary artery showed no significant improvement (mean dose, 11.2 Gy vs. 9.2 Gy), p = 0.11. There was no significant difference in percentage of total lung volume receiving at least 10, 15, or 20 Gy or in the mean lung dose between the planning methods. There were also no significant differences observed for the kidneys, liver, stomach, or spinal cord. Intensity-modulated radiotherapy achieved a significant improvement in target conformity as measured by the conformality index (ratio of total volume receiving 95% of prescription dose to planning target volume receiving 95% of prescription dose), with the mean conformality index reduced from 1.56 to 1.30 using IMRT. Treatment of patients with distal esophageal cancer using IMRT significantly decreases the exposure of the heart and right coronary artery when compared with 3D-CRT. Long-term studies are necessary to determine how this will impact on development of coronary artery disease and other cardiac complications.