3D-CRT Treatment Research Articles

Determination of the dose calculations accuracy of 3D-CRT treatment planning

Determination of the dose calculations accuracy of 3D-CRT treatment planning

Dosimetry and Biochemical Comparison of Early Radiation-Induced Lung Toxicity in Breast Cancer Patients Treated with 3D-CRT and IMRT: the Role of Serum Interleukin-6 and Pulmonary Surfactant Protein-D.

Radiation-induced lung disease is a potentially fatal, dose-limiting toxicity commonly seen after radiotherapy of thoracic malignancies, including breast cancer. To evaluate and compare the early lung toxicity induced by 3D-CRT and IMRT radiotherapy treatment modalities in breast cancer female patients using biochemical, dosimetry and clinical data. this study included 15 normal healthy controls, 15 breast cancer patients treated with IMRT, and 15 breast cancer patients treated with 3D-CRT. One blood sample was obtained from the control group and 3 blood samples were withdrawn from cases before RT, after RT and after 3 months of RT. IMRT delivered higher radiation dose to the breast tumor and lower doses to the lung as an organ at risk. There was a non-significant increase in the serum levels of IL-6 before IMRT and 3D-CRT compared with its levels in the control group. There were significant increases in serum levels of IL-6 after RT (IMRT and 3DCRT) compared with its levels before RT. There was a non-significant decrease in the serum levels of IL-6 after 3 months of RT (IMRT and 3D-CRT) compared with its serum levels immediately after RT. There was a non-significant increase in the serum levels of SP-D before RT (IMRT and 3D-CRT) compared with its levels in the control group. There were significant-increases in serum levels of SP-D after RT (IMRT and 3D-CRT) compared with its levels before RT. There was a non-significant decrease in the serum levels of SP-D after 3 months of radiotherapy (IMRT and 3D-CRT) compared with its serum levels immediately after RT. serum of levels IL-6 and SP-D can be used to diagnose the occurrence of early lung toxicity due to radiotherapy and the rate of recovery from radiation pneumonitis is apparent in case of IMRT than 3D-CRT.

Study of PRESAGE® dosimeter for end-to-end 3D radiotherapy verification using an anthropomorphic phantom with bespoke dosimeter insert.

Modern radiotherapy techniques have advanced and become more sophisticated. End-to-end 3D verification of the complex radiotherapy dose distribution in an anthropomorphic phantom can ensure the accuracy of the treatment delivery. The phantoms commonly used for dosimetry are homogeneous solid water phantom which lacks the capability to measure the 3D dose distribution for heterogeneous tissues necessary for advanced radiotherapy techniques. Therefore, we developed an end-to-end 3D radiotherapy dose verification system based on MAX-HD anthropomorphic phantom (Integrated Medical Technologies Inc., Troy, New York) with bespoke intracranial insert for PRESAGE® dosimeter. In this study, several advanced radiotherapy treatment techniques of various levels of complexity; 3D-CRT, IMRT and VMAT treatment, were planned for a 20mm diameter of a spherical target in the brain region and delivered to the phantom. The dosimeters were read out using an in-house developed optical computed tomography (OCT) imaging system known as 3DmicroHD-OCT. It was found that the measured dose distribution of the PRESAGE® when compared with the measured dose distribution of EBT film and Monaco TPS has a maximum difference of less than 3% for 3D-CRT, IMRT and VMAT treatment plans. The gamma analysis results of PRESAGE® in comparison to EBT film and Monaco TPS show pass rates of more than 95% for the criteria of 3% dose difference and 3mm distance-to-agreement. This study proves the capability of PRESAGE® and bespoke MAX-HD phantom in conjunction with the 3DmicroHD-OCT system to measure 3D dose distribution for end-to-end dosimetry verification.

Quality Assessment Radiotherapy Planning of Breast Cancer Patients with Built-In Metal Port Implants

Purpose: To evaluate the quality of radiation planning for breast cancer patients with implants with a built-in metal port. Conduct a quantitative analysis of the quality of planning, assess the dose load on critical organs for this category of patients.Material and methods: Homogeneity and conformity indices were calculated, and dose loads in critical organs were assessed for irradiation plans using 3D conformal RT (3D CRT) technology for 23 breast cancer patients with a built-in metal port implants. Calculations were carried out both taking into account (outlining) the metal port and artifacts from it on CT images, and without taking it into account.Results: Based on the results of the analysis of the calculated values of conformity and homogeneity indices, doses in critical organs of irradiation plans for 23 patients with breast cancer, it was shown that the presence of a metal port and artifacts from it affects the nature of the dose distribution.Conclusions: When creating a 3D CRT treatment plan, it is necessary to delineate the metal port and artifacts and assign true densities.

ИСПОЛЬЗОВАНИЕ ВОДНОГО БОЛЮСА ПРИ ЛУЧЕВОЙ ТЕРАПИИ ПАЦИЕНТОВ С ИЗОЛИРОВАННЫМИ ПОВЕРХНОСТНЫМИ ПРОЯВЛЕНИЯМИ Т-КЛЕТОЧНОЙ ЛИМФОМЫ КОЖИ

Purpose: To demonstrate the effectiveness of water bolus, combined with individual immobilization for the treatment of lesions in the pedal region of the foot on a patient with isolated cutaneous T-cell lymphoma lesions. Material and methods: Construction of individual immobilization devices, simultaneously functioning as a bolus, in two clinical cases of T-cell cutaneous lymphoma radiation therapy in the pedal region of the foot, along with 3D-CRT and VMAT treatment planning, accompanied by retrospective evaluation of interfractional motion. Results: The proposed methodology demonstrates the effectiveness of the individual immobilization devices in minimizing interfractional motion, as well as the benefit of the bolus effect of the device in achieving optimal dose distribution in the treatment of superficial T-cell lymphoma lesions.

A dosimetric comparison of 3D-CRT, IMRT and IMAT treatment techniques - assessment from radiation protection point of view.

The purpose was to assess the impact of irradiation technique type and beam energy on the mixed radiation field around the medical linear accelerator (linac) in terms of radiation quality and related radiation protection quantities. Seven radiotherapeutic plans with Alderson-Rando anthropomorphic phantom [different techniques: conventional three-dimensional conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT) and intensity modulated arc therapy (IMAT), different beams: 6 MV or 18 MV, and their arrangements) were prepared for the case of prostate malignancy. Recombination chambers REM-2 and GW2 were positioned on the treatment couch 100 cm from the beam axis at the height of the isocentre. Recombination chambers REM-2 and GW2 were used for recombination index of radiation quality Q4 determination, measurement of total tissue dose Dt and calculation of gamma and neutron components to Dt. Estimation of Dt and Q4 allowed for the ambient dose equivalent H*(10) calculations for each plan. For plans prepared with 6 MV beams, Q4 values within the limits of uncertainty were equal to one, which confirms the correctness of the measurement method. For plans implemented with 18 MV beams, the value of Q4 was in the range of 3.7-5.7. Comparison between treatment techniques indicates that the lowest exposure resulting from out-of-field doses comes from 6 MV IMAT (0.7 mSv), whereas the highest one is from 18 MV IMRT (55.1 mSv). With the recombination chambers technique it was confirmed that the choice of beam energy directly affects the generation of photoneutrons. The treatment plan technique can have a significant impact on the out-of-field dose.

A dosimetric evaluation of intensity modulated radiotherapy and three-dimensional conformal radiotherapy for prostate cancer in Ghana.

External beam radiotherapy incorporates treatment techniques such as three-dimensional conformal radiotherapy (3DCRT), intensity-modulated radiotherapy (IMRT), image-guided radiotherapy and volumetric modulated arc therapy to deliver high-energy radiation to cancer. The use of IMRT for cancer treatment is also associated with significant costs for patients in low-middle-income countries. The purpose of this study was to compare the dosimetric properties of 3DCRT and IMRT treatment plans for the external beam irradiation of patients with prostate cancer (Pca) to ascertain the superiority of IMRT in terms of dose homogeneity, conformity and dose limitation to organs at risk (OAR) in a resource-limited setting. One hundred and sixty treatment plans for 80 patients were created using 3DCRT and IMRT on the Eclipse treatment planning system (version 13.6). Data were collected and assessed from the dose-volume histogram of each plan. The conformity and homogeneity index (HI) for each of the plans were calculated. The doses to the OAR were also recorded and evaluated. The mean HIs for the IMRT and 3DCRT treatment techniques were 0.04 ± 0.02 (range: 0.01-0.011) and 0.09 ± 0.02 (range: 0.04-0.016), respectively. The mean conformity index (CI) for IMRT and 3DCRT techniques were 1.257 ± 0.112 (range: 0.99-1.58) and 1.302 ± 0.196 (range: 1.10-2.26). IMRT had a better significant mean HI and CI compared to 3DCRT. Generally, for this study, IMRT had better organ sparing compared to 3DCRT. The mean doses for the OARs ranged from 4.3-74.6 Gy for IMRT and 3.1-75.9 Gy for the 3DCRT technique. Overall, this study demonstrates that IMRT may offer an enhanced therapeutic profile, potentially reducing toxicity to the patient and ensuring more precise dose delivery to the target volume compared to 3DCRT in PCa external beam irradiation.

Dosimetric Comparison of Hippocampal Sparing Whole Brain Radiotherapy by Volumetric Modulated Arc Therapy, Linac-based Intensity-modulated Radiation Therapy and 3-D Conformal Radiation Therapy: A Cross-sectional Study

Introduction: Brain metastases are treated with Whole-Brain Radiotherapy (WBRT) using the 3-D Conformal Radiation Therapy (3DCRT) technique. Attempts have been made to perform dosimetric analysis of WBRT with hippocampal sparing using 3DCRT, Volumetric Modulated Arc Therapy (VMAT), and Linac-based Intensity Modulated Radiation Therapy (linac-based IMRT), anticipating technical challenges during contouring and treatment planning. Aim: To perform a dosimetric analysis and comparison ofhippocampal sparing cranial irradiation by 3DCRT, VMAT, and IMRT treatment plans in brain metastases patients. Materials and Methods: The analytical cross-sectional dosimetric study was conducted from November 2022 to September 2023 at Government Medical College, Kottayam, Kerala, India. Ten patients treated for brain metastases with WBRT using 3DCRT were considered for dosimetric analysis. The Planning Target Volume (PTV) dosimetry and hippocampal dosimetry were studied for all ten patients. The important dosimetric parameters included volume receiving 100% dose, Target Coverage (TC), Homogeneity Index (HI) in PTV dosimetry, the mean hippocampal dose, and maximal hippocampal dose in hippocampal dosimetry. The hippocampus and hippocampal avoidance volume were contoured. Treatment plans for 3DCRT, VMAT, and Linac-based IMRT were generated for each patient’s prescription dose of 30 Gy in 10 fractions. The non-parametric Kruskal-Wallis test was used for data analysis. Results: The mean whole brain Planned Target Volume (PTV) was 1190 cm3 . The mean hippocampal avoidance volume was 30 cm3 , which occupied 2.5% of the whole brain PTV. The average median dose received by the hippocampus was 30.05 Gy, 17.1 Gy, and 17.5 Gy for 3DCRT, Linac-based IMRT, and VMAT, respectively. The mean dose for the hippocampus was 31.03 Gy, 17.7 Gy, and 17.5 Gy for 3DCRT, Linac-based IMRT, and VMAT, respectively (p<0.001). VMAT offered better hippocampal sparing compared to IMRT and 3DCRT. On average, VMAT offered a 2% improvement, and 3DCRT offered a 5% improvement in TC compared to IMRT. The HI of 3DCRT was 0.09, IMRT 0.199, and VMAT 0.150. Conclusion: VMAT and LINAC-based IMRT permit hippocampal-sparing WBRT with adequate target volume coverage and acceptable homogeneity when compared to 3DCRT plans. Thus, the dosimetric study suggests that modern radiotherapy techniques should be advocated for hippocampal-sparing WBRT.

Novel hybrid treatment planning approach for irradiation a pediatric craniospinal axis

This study presents a new treatment planning approach merging 3D-CRT and VMAT fields into a hybrid treatment plan (HybTP), in order to achieve an optimum dose coverage of the planning target volume (PTV) and protection of OAR. Craniospinal axis irradiation (CSI) treated with 3D conformal radiotherapy (3D-CRT) is associated with high doses to the heart and eye lenses but provides better sparing of lungs and kidneys compared to volumetric modulated arc therapy (VMAT). VMAT treatment spares eye lenses and the heart, but lungs and kidneys are not as effective as 3D-CRT. Thus, a combination of both techniques (HybTP) may be optimal in sparing all these organs at risk (OAR). The results of HybTP are compared with helical tomotherapy (HT), intensity modulated radio therapy (IMRT), VMAT, and 3D-CRT plans. Hybrid, HT, VMAT, IMRT, and 3D-CRT treatment plans for a male child (age 6 years) with medulloblastoma were created and compared. A total dose of 35.2 Gy (PTV) with a dose per fraction of 1.6 Gy was prescribed. The following dose acceptance criteria were defined:(1)Mean PTV dose should be 100% of the prescribed dose, while the maximum dose should not exceed 107%.(2)At least 98% of the PTV should receive 95% of the prescribed dose.(3)The cribriform plate should be covered by the 95% isodose line.(4)The acceptance criteria for the OARs were: lenses Dmax<10 Gy, lungs Dmean<7 Gy, kidneys Dmean<15 Gy, heart Dmean<26 Gy, and heart V25<10%.The plans were compared regarding dose homogeneity index (HI) and conformity index (CI), PTV coverage, (particularly at cribriform plate) and doses at OARs. Best conformity was achieved with HT (CI = 0.98) followed by VMAT (CI = 0.96), IMRT (CI = 0.91), HybTP (CI = 0.86), and 3D-CRT (CI = 0.83). The homogeneity index varied marginally. For both HT and IMRT the HI was 0.07, and for 3D-CRT, VMAT and HybTP the HI was between 0.13 and 0.15. The cribriform plate was sufficiently covered by HybTP, VMAT, and 3D-CRT. The dose acceptance criteria for OARs were met by HT and HybTP. VMAT did not meet the criteria for lung (Dmean = right 10.4 Gy/left 10.2 Gy), 3D-CRT did not meet the criteria for eye lenses (Dmax = right 32.3 Gy/left 33.1), and heart (V25≈44%) and IMRT did not meet the criteria for lung (Dmean = right 11.1 Gy/left 11.2 Gy) and eye lenses (Dmax = right 12.2 Gy/left 13.1). HybTP meets all defined acceptance criteria and has proved to be a reasonable alternative for CSI. With HybTP that combines VMAT at the brain and heart with 3D-CRT posterior spinal fields (to spare lungs and kidneys), both appropriate coverage of the PTV and sparing of OAR can be achieved.

Robustness analysis of surface-guided DIBH left breast radiotherapy: personalized dosimetric effect of real intrafractional motion within the beam gating thresholds.

The robustness of surface-guided (SG) deep-inspiration breath-hold (DIBH) radiotherapy (RT) for left breast cancer was evaluated by investigating any potential dosimetric effects due to the residual intrafractional motion allowed by the selected beam gating thresholds. The potential reduction of DIBH benefits in terms of organs at risk (OARs) sparing and target coverage was evaluated for conformational (3DCRT) and intensity-modulated radiation therapy (IMRT) techniques. Atotal of 192 fractions of SGRT DIBH left breast 3DCRT treatment for 12patients were analyzed. For each fraction, the average of the real-time displacement between the isocenter on the daily reference surface and on the live surface ("SGRT shift") during beam-on was evaluated and applied to the original plan isocenter. The dose distribution for the treatment beams with the new isocenter point was then calculated and the total plan dose distribution was obtained by summing the estimated perturbed dose for each fraction. Then, for each patient, the original plan and the perturbed one were compared by means of Wilcoxon test for target coverage and OAR dose-volume histogram (DVH) metrics. Aglobal plan quality score was calculated to assess the overall plan robustness against intrafractional motion of both 3DCRT and IMRT techniques. Target coverage and OAR DVH metrics did not show significant variations between the original and the perturbed plan for the IMRT techniques. 3DCRT plans showed significant variations for the left descending coronary artery (LAD) and the humerus only. However, none of the dose metrics exceeded the mandatory dose constraints for any of the analyzed plans. The global plan quality analysis indicated that both 3DCRT and IMRT techniques were affected by the isocenter shifts in the same way and, generally, the residual isocenter shifts more likely tend to worsen the plan in all cases. The DIBH technique proved to be robust against residual intrafractional isocenter shifts allowed by the selected SGRT beam-hold thresholds. Small-volume OARs located near high dose gradients showed significant marginal deteriorations in the perturbed plans with the 3DCRT technique only. Global plan quality was mainly influenced by patient anatomy and treatment beam geometry rather than the technique adopted.

Comparison of 3D-conformal and intensity-modulated radiation therapy for left-sided breast cancer

Background: We compared 3D-conformal radiation therapy (3D-CRT) and intensity-modulated radiation therapy (IMRT) planning for left-sided post-mastectomy patients. Aim: To compare the dose coverage of the planning target volume (PTV) and dose delivered to organs at risk (OAR) of 3D-CRT and IMRT plans. Setting: Department of Oncology, central South Africa. Methods: Twenty-six archived CT scans of patients with left-sided breast cancer were included. The 3D-CRT and IMRT plans were designed for each patient and compared using the Monaco © planning system (version 5.11.02). Statistical analysis was performed for PTV coverage (V 95% , V 98% , V 105% ) and radiation doses to the heart, ipsilateral lung, combined lungs, contralateral breast, and oesophagus. Results: The V 98% and V 105% target volume dose coverage for the 3D-CRT plans were 67.07% and 0.21%, respectively, compared to 92.32% and 1.10% of the IMRT plans. However, the IMRT plans’ mean volume of PTV, receiving 95% of the prescribed dose (PD), was 7.68% compared to the 3D-CRT’s 32.93%. The IMRT plans resulted in a V 22 Gy &lt; 10% for the heart, with a value of 4.15%. The V 18.87 Gy &lt; 45% values for the ipsilateral and combined lungs were 28.09% and 13.70%, respectively. The 3D-CRT plans showed a lower dose to the oesophagus (5.07 Gy) and contralateral breast (V 5 Gy &lt; 15% = 3.51%). Conclusion: It was shown that 3D-CRT and IMRT treatment planning can effectively achieve clinical goals for post-mastectomy left-sided breast cancer radiotherapy. Contribution: The findings underscore the continuing relevance of 3D-CRT planning in oncology for optimal PTV dose coverage and low OAR dose.

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.

Comparison the Difference of Thyroid Function Status between 2D &amp; 3D CRT Treatment Technique in HNC Patients

Introduction: Thyroid gland is an important endocrine gland which regulates metabolic activities in our body as well as regulates vital body functions including breathing, heart rate, central and peripheral nervous systems, body weight, menstrual cycle, cholesterol levels and much more. As thyroid gland placed in the same field area treated by radiation therapy of non-thyroid head and neck cancer patient, so it is a challenge to preserve the normal thyroid function after completion of treatment. Objective: To assess the comparison the difference of thyroid function status between 2D &amp; 3D CRT treatment technique in HNC patients. Methods: It was a quasi-experimental study was conducted at National Institute of Cancer Research &amp; Hospital (NICRH), Mohakhali, Dhaka, Bangladesh from November 2016 and ended in October’2017. Total of 60 patients with above mentioned criteria were selected and each arm got 30 patients. Patient with histopathology report proven carcinoma of head and neck receiving radiotherapy were selected from tumor board of NICRH. The present study were carried out on patients with biopsy proven malignancies of head and neck who attended the Radiotherapy Department for radiotherapy and who met the selection criteria of the study. Results: Total study population was 60 among which 30 were in arm A (2D) and 30 were in arm B (3D). Majorities of the patients in arm A were 41-50 years old (46.7%). The mean age of the arm A patients was 52.27 (±7.38) years and that of the arm B was 49.50 (± 13.55) years. Thirty patients of head &amp; neck cancers were included in arm A of the study, i.e. 2D arm. Out of which 21 (70%) were male and rest 9 (30%) were female. Thirty patients of head &amp; neck cancers were included in arm B of the study, i.e. 3D arm. Out of which 23 (76.7%) were male and rest 7 (23.3%) were female. Most of the patients in both arms were farmers (40% in arm A and 60% in arm B). There were 9(30%) oropharyngeal, 8(26.7%) hypopharyngeal and 13(43.3%) ........

Validation of esophageal cancer treatment methods from 3D-CRT, IMRT, and Rapid Arc plans using custom Python software to compare radiobiological plans to normal tissue integral dosage.

The aim was to develop in-house software that is able to calculate and generate the biological plan evaluation of the esophagus treatment plan using the Niemierko model for normal tissue complication probability and tumor control probability. The Niemierko model can be applied for esophagus cancer treatment plan to estimate the tumor control probability (TCP) and the normal tissue complication probability (NTCP) using different planning techniques. The equivalent uniform dose (EUD) and effective volume parameters were compared with organ at risk. Subsequently, EUD and TCP parameter were compared with tumor volume for all five different planning techniques. Ten cases for esophageal cancer were included in this study. For each patient, five treatment plans were generated. The Anisotropic analytical algorithms (AAA) were used for dose calculation for the three-dimensional conformal radiation therapy (3D-CRT), intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) techniques. The in-house developed radiobiological plan evaluation software using python programming is used for this study which takes a dose volume histogram (DVH) text file as an input file for biological plan evaluation. EUD, NTCP, TCP and effective volume were calculated from the Niemierko model using the in-house developed python based software and compared with treatment monitor units (MU) with all five different treatment plan. The best technique is quantified as benchmarked out of other different qualities of treatment. The four field 3D-CRT treatment plan is found to be the best suited from the perspective of biological plan index evaluation among the other planning techniques.

Radiation technique and outcomes following moderately hypofractionated treatment of low risk prostate cancer: a secondary analysis of RTOG 0415.

While moderately hypofractionated radiotherapy (MHRT) for prostate cancer (PC) is commonly delivered by intensity modulated radiation therapy, IMRT has not been prospectively compared to three-dimensional conformal radiotherapy (3D-CRT) in this context. We conducted a secondary analysis of the phase III RTOG 0415 trial comparing survival and toxicity outcomes for low-risk PC following MHRT with IMRT versus 3D-CRT. RTOG 0415 was a phase III, non-inferiority trial randomizing low-risk PC patients to either MHRT or conventionally fractionated radiation with stratification by RT technique. A secondary analysis for differences in overall survival (OS), biochemical recurrence free survival (BRFS), or toxicity by EPIC scores and Common Terminology Criteria for Adverse Events (CTCAE) was performed. 1079 patients received the allocated intervention with a median follow up of 5.8 years. 79.1% of patients were treated with IMRT and radiation technique was balanced between arms. Across all patients, RT technique was not associated with significant differences in BRFS, OS, or rates of acute and late toxicities. For patients completing MHRT, there was a difference in the late GU toxicity distribution between 3D-CRT and IMRT but no difference in late grade 2 or greater GU or GI toxicity. Stratifying patients by RT technique and fractionation, no significant differences were observed in the minimal clinically important difference (MCID) in EPIC urinary and bowel scores following RT. RT technique did not impact clinical outcomes following MHRT for low-risk PC. Despite different late GU toxicity distributions in patients treated with MHRT by IMRT or 3D-CRT, there was no difference in late Grade 2 or greater GU or GI toxicity or patient reported toxicity. Increases in late GU and GI toxicity following MHRT compared to CFRT, as demonstrated in the initial publication of RTOG 0415, do not appear related to a 3D-CRT treatment technique.

Impact of dose distribution on rotational setup errors in radiotherapy for prostate cancer.

This study aimed to assess the impact of rotational setup errors on the target volume's dose distribution during radiotherapy for prostate cancer. A 6D robotic couch was used to describe the rotational setup error, and the dosage change in the target volume was analyzed using the planning evaluation factors. Treatment plans for three-dimensional conformal radiotherapy (3DCRT), intensity-modulated radiotherapy (IMRT), and volumetric modulated arc radiotherapy (VMAT) were established after contouring the target volume and surrounding normal tissues on tomography obtained from the humanoid phantom. A 6D robotic couch was employed in the radiation room to describe the rotational setup errors of ±1° to ±5° in roll, yaw, and pitch, and cone beam computed tomography (CBCT) images were obtained. Furthermore, the dose distribution was extracted from the 3DCRT, IMRT, and VMAT treatment plans, dose mapping was performed on CBCT that depicts the rotational setup error. Target coverage(TC) decreased by 0.39% to 2.17% in roll, 0.43% to 2.59% in yaw, and 0.70% to 4.12% in pitch, respectively. In the comparison using the Radiation Therapy Oncology Group (RTOG) protocol criteria, when the rotational setup error of VMAT pitch was -2° or more, more than +1°, a target coverage of 95% or lower was shown, indicating the greatest effect among rotational setup errors. Furthermore, in 3DCRT, IMRT, and VMAT, the rotational setup error showed the greatest effect in pitch, and the dose change was larger in VMAT than in 3DCRT and IMRT. Therefore, specific rotational error due to pitch during radiotherapy for prostate cancer requires special consideration. Moreover, the more sophisticated and complex algorithms, such as VMAT, applied, the greater the dose change of target coverage due to rotational error; therefore, caution is required.

Volumetric modulated arc therapy (VMAT) comparison to 3D-conformal technique in lung stereotactic ablative radiotherapy (SABR).

Stereotactic ablative radiotherapy (SABR) can be a curative option for non-small cell lung cancer (NSCLC) and oligometastatic lung disease. Volumetric modulated arc therapy (VMAT) has offered further advancements in terms of radiation dose shaping without compromising treatment times however there is potential for greater low-dose exposure to the lung. This study was to assess whether VMAT lung SABR would result in any increase to the dosimetry parameters compared with three-dimensional conformal radiotherapy (3D-CRT) that could confer increased risk of radiation pneumonitis. A total of 53 and 30 3D-CRT treatment plans of patients treated with 48 Gy in 4 fractions were compared. No statistically significant difference in planning target volumes between the VMAT 29.9 cc (range 12.4-58.5 cc) and 3D-CRT 31.2 cc (range 12.3-58.3 cc) P=0.79. The mean of total lung V5, ipsilateral lung V5 and contralateral lung V5 all showed a trend of being smaller in the VMAT treatment group- 14% versus 15.8%, 25.6% versus 30.4% and 1.6% versus 2.2%, respectively, but all were not statistically significant differences. Mean of the mean lung dose MLD, again showed a trend of being lower in the VMAT treatments but was also non-significant, 2.6 Gy versus 3.0 Gy, P=1.0. Mean V20 was the same in both cohorts, 3.3%. The dosimetry for 3D-CRT and VMAT plans were not significantly different including V5, and therefore we conclude that VMAT treatment is unlikely to be associated with an increased risk of radiation pneumonitis.

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.

On the risk of secondary cancer from thymoma radiotherapy

Objective. This study aims at quantifying the lifetime attributable risk of secondary fatal cancer (LARFAC) to patients receiving adjuvant radiotherapy treatment for thymoma, a neoplasm where cure rates and life expectancy are relatively high, patient age at presentation relatively low and indications for radiotherapy controversial depending on the disease stage. Approach. An anthropomorphic phantom was scanned, organs were contoured and a standard 6 MV 3DCRT treatment plan was produced for thymoma treatment. The phantom was loaded with thermoluminescent dosimeters (TLDs) and treated by linear accelerator per plan. The TLDs were subsequently read for out-of-field dose distribution while in-field dose distribution was obtained from the planning system. Sex and age-specific lifetime radiogenic cancer risk was calculated as the sum of in-field risk and out-of-field risk. The latter risk was estimated using hybrid ICRP 2007 103-BEIR VII tables of organ-specific risks based on the linear-no threshold (LNT) model and applicable at low doses, while the former using mathematical risk models applicable at high doses. Main results. The LARFAC associated with a prescribed dose of 50 Gy to target volume in 25 fractions was in the approximate range of 1%–3%. The risk was higher for young and female patients. The largest contributing organ to this risk were the lungs by far. Using the LNT model inappropriately to calculate risk at therapeutic doses (in-field) would overestimate the risk up to tenfold. Significance. The LARFAC to patient from thymoma radiotherapy was quantified taking into consideration the inapplicability of the LNT model at therapeutic doses. The risk is not negligible; the information may be relevant to patients and clinicians.

Automation of radiation treatment planning for rectal cancer.

PurposeTo develop an automated workflow for rectal cancer three‐dimensional conformal radiotherapy (3DCRT) treatment planning that combines deep learning (DL) aperture predictions and forward‐planning algorithms.MethodsWe designed an algorithm to automate the clinical workflow for 3DCRT planning with field aperture creations and field‐in‐field (FIF) planning. DL models (DeepLabV3+ architecture) were trained, validated, and tested on 555 patients to automatically generate aperture shapes for primary (posterior–anterior [PA] and opposed laterals) and boost fields. Network inputs were digitally reconstructed radiographs, gross tumor volume (GTV), and nodal GTV. A physician scored each aperture for 20 patients on a 5‐point scale (>3 is acceptable). A planning algorithm was then developed to create a homogeneous dose using a combination of wedges and subfields. The algorithm iteratively identifies a hotspot volume, creates a subfield, calculates dose, and optimizes beam weight all without user intervention. The algorithm was tested on 20 patients using clinical apertures with varying wedge angles and definitions of hotspots, and the resulting plans were scored by a physician. The end‐to‐end workflow was tested and scored by a physician on another 39 patients.ResultsThe predicted apertures had Dice scores of 0.95, 0.94, and 0.90 for PA, laterals, and boost fields, respectively. Overall, 100%, 95%, and 87.5% of the PA, laterals, and boost apertures were scored as clinically acceptable, respectively. At least one auto‐plan was clinically acceptable for all patients. Wedged and non‐wedged plans were clinically acceptable for 85% and 50% of patients, respectively. The hotspot dose percentage was reduced from 121% (σ = 14%) to 109% (σ = 5%) of prescription dose for all plans. The integrated end‐to‐end workflow of automatically generated apertures and optimized FIF planning gave clinically acceptable plans for 38/39 (97%) of patients.ConclusionWe have successfully automated the clinical workflow for generating radiotherapy plans for rectal cancer for our institution.