Intensity-modulated Radiotherapy Technique Research Articles

Impact of Radiation on Dysphagia-Related Structures: A Dosimetric and Clinical Comparative Analysis of Three-Dimensional Conformal Radiotherapy (3D-CRT) and Intensity-Modulated Radiation Therapy (IMRT) Techniques in Patients With Head and Neck Cancer

Impact of Radiation on Dysphagia-Related Structures: A Dosimetric and Clinical Comparative Analysis of Three-Dimensional Conformal Radiotherapy (3D-CRT) and Intensity-Modulated Radiation Therapy (IMRT) Techniques in Patients With Head and Neck Cancer

DOSIMETRIC COMPARISON OF INTENSITY-MODULATED RADIATION THERAPY (IMRT) AND VOLUMETRIC-MODULATED ARC THERAPY (VMAT) IN RECTAL CANCER PATIENTS: A COMPREHENSIVE ANALYSIS

This study aimed to conduct a thorough dosimetric comparison between two advanced radiotherapy techniques, Intensity-Modulated Radiation Therapy (IMRT) and Volumetric-Modulated Arc Therapy (VMAT), to ascertain the superior modality in terms of dose distribution and organ-at-risk sparing for rectal cancer patients. Thirty-three patients with ECOG performance status 1, aged between 18 to 60 years, diagnosed with Stage II to III rectal cancer, were included in this prospective study. Each patient underwent treatment planning with IMRT and VMAT techniques using Varian system simulation computed tomography scans. The dosimetric analysis encompassed the evaluation of target volume dose homogeneity, conformity, and doses to at-risk organs. The dosimetric comparison was conducted utilizing seven-field IMRT and dual arc VMAT plans. Statistical analysis was performed using paired t-tests and SPSS 20 software. Treatment plan constraints adhered to the RTOG 9406 guidelines, ensuring adequate planning target volume (PTV) coverage, homogeneity index, conformity index, and dose limits for organs at risk, including small bowel V20 (<200cc), bladder V45 (<21Gy), and femoral head V50 (≤30 Gy). Volumetric arc therapy plans demonstrated superior dose homogeneity to fixed-field intensity-modulated plans (p-value = 0.04), particularly in femoral head dose-limiting toxicity (p-value = 0.00). However, intensity-modulated therapy exhibited equivalent or superior performance in other evaluated parameters. Our findings suggest that while VMAT offers advantages in PTV coverage homogeneity and femoral head dose-limiting toxicity, IMRT remains competitive and potentially preferable in certain dosimetric aspects. The choice between IMRT and VMAT should be carefully considered based on individual patient characteristics and treatment goals. This comprehensive dosimetric comparison contributes valuable insights into optimizing radiotherapy planning for rectal cancer patients, potentially guiding clinical decision-making and improving treatment outcomes.

A Randomised Phase II Trial to Evaluate the Feasibility of Radiotherapy Dose Escalation, Facilitated by Intensity-Modulated Arc Radiotherapy Techniques, in High-Risk Neuroblastoma

BACKGROUND AND PURPOSEFor high-risk neuroblastoma, planning target volume coverage is often compromised to respect adjacent kidney tolerance. This trial investigated whether intensity-modulated arc radiotherapy techniques (IMAT) could facilitate dose escalation better than conventional techniques. MATERIALS AND METHODSChildren with high-risk abdominal neuroblastoma referred for radiotherapy to the primary tumour site and involved regional lymph nodes were randomised to receive either standard dose (21 Gy in 14 fractions) or escalated dose (36 Gy in 24 fractions) radiotherapy. Dual planning with both a conventional anterior-posterior parallel opposed pair radiotherapy technique and an IMAT technique was performed. The quality of target volume and organ-at-risk delineation, and dosimetric plans, were externally reviewed. Dosimetric parameters were used to judge the superior technique for treatment. This feasibility trial was not powered to detect improvement in outcome with dose escalation. RESULTSBetween 2017 and 2020, 50 patients were randomised and dual-planned. The IMAT technique was judged more favourable in 48 patients. In all patients randomised to receive 36 Gy, IMAT would have permitted delivery of the full dose (median D50% 36.0 Gy, inter-quartile range 36.0–36.1 Gy) to the target volume, whereas dose compromise would have been required with conventional planning (median D50% 35.6 Gy, inter-quartile range 28.7–35.9 Gy). CONCLUSIONIMAT facilitates safe dose escalation to 36 Gy in patients receiving radiotherapy for neuroblastoma. The value of dose escalation is now being evaluated in a current prospective phase III randomised trial.

Measurement and Incorporation of Laryngeal Motion Using cine-MRI on an MR-Linear Accelerator to Generate Radiation Therapy Plans for Early-stage Squamous Cell Cancers of the Glottis

IntroductionSwallow-related motion of the larynx is most significant in the cranio-caudal directions and of short duration. Conventional target definition for radical radiotherapy includes coverage of the whole larynx. This study longitudinally examined respiration- and swallow-related laryngeal motions using cine-MRI. We further analysed the dosimetry to organs at risk by comparing 3D-conformal radiotherapy (3D-CRT), Volumetric-Modulated Arc Therapy (VMAT) and Intensity-Modulated Radiotherapy (IMRT) techniques. MethodsFifteen patients with T1-2 N0 glottic squamous cell carcinomas were prospectively recruited for up to three cine-MRI scans on the Elekta Unity MR-Linear accelerator, at the beginning, middle and end of a course of radical radiotherapy. Swallow frequency and motion of the hyoid bone, cricoid and thyroid cartilages and vocal cords were recorded during swallow and rest. Adapted treatment volumes consisted of GTV + 0.5-1 cm to a CTV with an additional ITV for personalised resting-motion. Swallow-related motion was deemed infrequent and was not accounted for in the ITV. We compared radiotherapy plans for 3D-CRT (whole larynx), VMAT (whole larynx), VMAT and IMRT (ITV for resting motion). ResultsResting- and swallow- motions were most prominent in the craniocaudal plane. There were no significant changes in the magnitudes of motions over the course of radiotherapy. There was a trend for a progressive reduction in the frequency of swallow. Treatment of partial-larynx volumes with intensity-modulated methods significantly reduced the dose to carotid arteries compared to whole-larynx. Robustness analysis demonstrated that when accounting for intra-fraction swallow, the total dose delivered to the ITV/PTV was maintained above 95%. ConclusionsSwallow-related motions are infrequent and accounting for resting motion in an ITV is sufficient. VMAT/IMRT techniques that treat more conformal targets can significantly spare critical organs at risk such as the carotid arteries and thyroid gland, potentially reducing the risk of carotid artery stenosis related and other complications long-term.

Investigation of the effect of bolus on skin dose in breast cancer treatment with tomotherapy and LINAC radiotherapy devices

In postmastectomy radiation therapy (PMRT), it is important that the chest wall skin is included in the target volume and receives an adequate dose. This study aims to investigate the effect of bolus on skin dose in breast cancer treatment with Tomotherapy and LINAC radiotherapy devices and to examine the accuracy of the surface dose calculated by treatment planning system (TPS) with thermoluminescence dosimetry (TLD). Female Alderson Rando Phantom's chest wall is virtually divided into 9 regions. Computed tomography (CT) images of the phantom were obtained with a section thickness of 3 mm. Two plans, with and without bolus, were created for each of the helical tomotherapy (HT), intensity-modulated radiotherapy (IMRT) and field-in-field (FiF) techniques. A bolus thickness of 0.5 cm was used for all bolus plans. Doses calculated from TPSs were obtained for 88 predetermined points on the chest wall. After irradiation, doses measured with TLDs were obtained. The effect of bolus use on the chest wall surface was examined. The increase in surface dose due to bolus use was 50.35%, 55.35% and 68.56% for HT, IMRT and FiF techniques in TPS, respectively. This increase in TLD measurements was 58.18%, 30.90% and 46.31% for HT, IMRT and FiF techniques, respectively. The best agreement between TPS and TLD doses for bolus and non-bolus plans was found in the HT technique. The difference between TPS and TLD doses decreased within the three treatment techniques due to bolus use. Since the chest wall skin cannot receive the required dose in IMRT and FiF techniques, bolus use is recommended until acute skin reactions occur. There is no need to use a bolus for the HT technique.

Dosimetric comparison of 3D-Conformal and IMRT techniques used in radiotherapy of gastric cancer: A retrospective study

This study aimed to compare three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) planning techniques commonly used in gastric cancer radiotherapy with dose volume histograms. Computed tomography (CT) images of 20 gastric cancer patients were retrospectively analyzed. 3D-CRT, 5F- IMRT and 7F- IMRT treatment plans were created for each patient. The 3 plans were compared on dose volume histogram (DVH). 3D-CRT, 5F-IMRT and 7F-IMRT plans achieved a prescribed dose of 45 Gy for 95% of PTV volume. D95 values were 45.06±0.47 Gy for 3DCRT, 46.39±0.38 Gy for 5F-IMRT and 45.20±0.11 Gy for 7F-IMRT. In 3D-CRT, 5F-IMRT and 7F-IMRT techniques, the 13 Gy receiving volumes of the right kidney were found to be 35.08+9.59, 36.25+7.97 and 37.03+9.03 respectively. Moreover, the volume of the right kidney receiving a 20 Gy and 30 Gy dose received less dose with 5F-IMRT than with 7F-IMRT. Since each patient's critical organs are at different distances from the target and each technique has its own advantages in terms of critical organs, we suggest that the useful technique should be decided by clinical consensus.

Biological Dose Escalation—Do We Have a New Window of Opportunity in High-Grade Glioma?—A Feasibility Study

Despite multimodality treatment in high-grade glioma (HGG) involving maximal safe resection and adjuvant chemoradiotherapy, the prognosis remains dismal. In this study, we aimed to evaluate a method of biological enhancement by combining dose escalation with a condensed overall treatment time, aiming for maximal cytoreduction as a surrogate for improved outcomes. Hypofractionation has the dual advantage of enhanced cell kill with reduced overall treatment time. To this effect, we have employed a study involving hypofractionated simultaneous integrated boost (SIB) versus conventional treatment. As a secondary objective, we evaluated volumetric modulated arc therapy (VMAT) and intensity modulated radiotherapy (IMRT) in terms of optimal delivery technique for SIB boost. Forty patients were randomized into two arms, the study arm received 60 Gy in 25 fractions and the standard arm received 60 Gy in 30 fractions with concurrent and adjuvant temozolomide. The patients were assessed radiologically for tumor cytoreduction and acute toxicity parameters weekly during treatment, 6 weeks post-treatment, and 3 monthly follow-up. All patients were planned using VMAT and IMRT techniques in the study arm for the comparison of treatment time and dosimetric efficiency. However, the treatment was performed through VMAT technique. Data were analyzed using simple descriptive statistics including Student's t-tests, proportion tests, and Pearson correlation for association. The total sample size was estimated at 40, with 20 samples per group, providing a statistical power of 81% and a significance level (p-value) of 0.05. It was observed that tumor cytoreduction was significantly enhanced in a subgroup of patients in the study arm with smaller volume residual disease (p = 0.04) that was found at 6 weeks post-treatment evaluation. The tolerance, toxicity, and compliance were comparable in both arms. During the dosimetric evaluation, it was determined that VMAT had a significantly lower hot spot compared to the IMRT plan (64.22 Gy vs. 64.75 Gy, p = 0.02). It was also observed that the delivery with VMAT was faster and involved a lesser number of monitor units (555.7 MU vs. 679.6MU, p = 0.001). The hypofractionated SIB radiotherapy using the VMAT technique can provide a feasible method of biological dose enhancement without compromising toxicity and might have the future potential to improve local control in HGG.

Radiotherapy Planning in Synchronous Bilateral Breast Cancer Irradiation: A Dosimetric Study

Background: The large radiation field and surrounding normal structures make treatment planning and dose delivery of synchronous bilateral breast cancer (SBBC) much more difficult than it is for unilateral breast cancer. Intensity-modulated radiation therapy (IMRT) or volumetric-modulated arc therapy (VMAT) can produce acceptable normal tissue sparing while improving target dose coverage compared to 3D-CRT. With this context in mind, we carried out a study to examine the dosimetric variations of IMRT and VMAT techniques using a single isocenter for planning cases of SBBC. Patients and methods: Five patients were considered for this study. All the patients had undergone bilateral mastectomy. Dose prescribed was 50 Gy in 25 fractions. VMAT and IMRT plans were created for each patient. All the plans made were mono-isocentric. Dosimetric data of the target and organs at risk (OAR) were compared. Results: There is a trend towards better PTV coverage using VMAT compared to IMRT (V95 IMRT=94.8720, V95 VMAT=95.8740; P=0.316). VMAT plans significantly improved the dose homogeneity as V105% decreased from 2.886% to 0.312% using VMAT plans (P=0.001). IMRT plans showed trend towards higher lung Dmean and V20Gy than VMAT plans. The irradiation dose to the heart was significantly higher in the IMRT plan than VMAT plan, resulting in Dmean of 15.836 Gy vs 13.580 Gy (P=0.026), V25Gy of 16.498% vs 13.832% (P=0.046) and V30 Gy of 9.774% vs 7.022% (P= 0.043). Conclusion: The single isocentric VMAT technique can be performed conveniently in SBBC. It improves target volume coverage with optimal normal tissue sparing. It is a feasible approach while planning synchronous bilateral breast irradiation.
  

Dosimetric Impact of Voluntary Deep Inspiration Breath Hold (DIBH) in Mediastinal Hodgkin Lymphomas: A Comparative Evaluation of Three Different Intensity Modulated Radiation Therapy (IMRT) Delivery Methods Using Voluntary DIBH and Free Breathing Techniques.

Hodgkin lymphomas are radiosensitive and curable tumors that often involve the mediastinum. However, the application of radiation therapy to the mediastinum is associated with late effects including cardiac and pulmonary toxicities and secondary cancers. The adoption of conformal IMRT and deep inspiration breath- hold (DIBH) can reduce the dose to healthy normal tissues (lungs, heart and breast). We compared the dosimetry of organs at risk (OARs) using different IMRT techniques for two breathing conditions, i.e., deep inspiration breath hold (DIBH) and free breathing. Twenty-three patients with early-stage mediastinal Hodgkin lymphomas were accrued in the prospective study. The patients were given treatment plans which utilized full arc volumetric modulated arc therapy (F-VMAT), Butterfly VMAT (B-VMAT), and fixed field IMRT (FF-IMRT) techniques for both DIBH and free breathing methods, respectively. All the plans were optimized to deliver 95% of the prescription dose which was 25.2 Gy to 95% of the PTV volume. The mean dose and standard error of the mean for each OAR, conformity index (CI), and homogeneity index (HI) for the target using the three planning techniques were calculated and compared using Student's t-test for parametric data and Wilcoxon signed-rank test for non-parametric data. The HI and CI of the target was not compromised using the DIBH technique for mediastinal lymphomas. The mean values of CI and HI for both DIBH and FB were comparable. The mean heart doses were reduced by 2.1 Gy, 2.54 Gy, and 2.38 Gy in DIBH compared to FB for the F-VMAT, B-VMAT, and IMRT techniques, respectively. There was a significant reduction in V5Gy, V10Gy, and V15Gy to the heart (p < 0.005) with DIBH. DIBH reduced the mean dose to the total lung by 1.19 Gy, 1.47 Gy, and 1.3 Gy, respectively. Among the 14 female patients, there was a reduction in the mean right breast dose with DIBH compared to FB (4.47 Gy vs. 3.63 Gy, p = 0.004). DIBH results in lower heart, lung, and breast doses than free breathing in mediastinal Hodgkin Lymphoma. Among the different IMRT techniques, FF-IMRT, B-VMAT, and F-VMAT showed similar PTV coverage, with similar conformity and homogeneity indices. However, the time taken for FF-IMRT was much longer than for the F-VMAT and B-VMAT techniques for both breathing methods. B-VMAT and F-VMAT emerged as the optimal planning techniques able to achieve the best target coverage and lower doses to the OARs, with less time required to deliver the prescribed dose.

Approaches for Stereotactic Radiosurgery (SRS)/Stereotactic Radiotherapy (SRT) in brain metastases using different radiotherapy modalities (Feasibility study).

SRS and SRT are precise treatments for brain metastases, delivering high doses while minimizing doses to nearby organs. Modern linear accelerators enable the precise delivery of SRS/SRT using different modalities like three-dimensional conformal radiotherapy (3DCRT), intensity-modulated radiotherapy (IMRT), and Rapid Arc (RA). This study aims to compare dosimetric differences and evaluate the effectiveness of 3DCRT, IMRT, and Rapid Arc techniques in SRS/SRT for brain metastases. 10 patients with brain metastases, 3 patients assigned for SRT, and 7 patients for SRS. For each patient, 3 treatment plans were generated using the Eclipse treatment planning system using different treatment modalities. No statistically significant differences were observed among the three techniques in the homogeneity index (HI), maximum D2%, and minimum D98% doses for the target, with a p >  0.05. The RA demonstrated a better conformity index of 1.14±0.25 than both IMRT 1.21±0.26 and 3DCRT 1.37±0.31. 3DCRT and IMRT had lower Gradient Index values compared to RA, suggesting that they achieved a better dose gradient than RA. The mean treatment time decreased by 26.2% and 10.3% for 3DCRT and RA, respectively, compared to IMRT. In organs at risk, 3DCRT had lower maximum doses than IMRT and RA, but some differences were not statistically significant. However, in the brain stem and brain tissues, RA exhibited lower maximum doses compared to IMRT and 3DCRT. Additionally, RA and IMRT had lower V15Gy, V12Gy, and V9Gy values compared to 3DCRT. While 3D-CRT delivered lower doses to organs at risk, RA and IMRT provided better conformity and target coverage. RA effectively controlled the maximum dose and irradiated volume of normal brain tissue. Overall, these findings indicate that 3DCRT, RA, and IMRT are suitable for treating brain metastases in SRS/SRT due to their improved dose conformity and target coverage while minimizing dose to healthy tissues.

Hypofractionated Partial Breast Irradiation With Intensity-Modulated Radiotherapy in Early Breast Cancer or Carcinoma In Situ: An Investigational Short-Term Analysis.

This study aimed to analyze the treatment outcomes and adverse effects of moderately hypofractionated partial breast irradiation (PBI) in patients with early breast cancer. In total, 473 patients with early breast cancer or carcinoma in situ were diagnosed with Tis or T1N0 disease and underwent PBI following breast-conserving surgery. All histologic tumor types, close surgical margins within 1 mm of the tumor, and multifocal tumors were included in this study. A radiation dose of 50 Gy in 20 fractions was delivered over 4 weeks using intensity-modulated radiotherapy technique. Dosimetric data, recurrence patterns, survival outcomes, and adverse events were retrospectively analyzed. During a median follow-up of 28.9 months, seven patients (1.5%) experienced ipsilateral breast tumor recurrence (IBTR). Two patients had regional recurrence, four patients developed contralateral breast cancer, and no distant metastases were observed. The locoregional recurrence rate in the ipsilateral breast was 1.8%. Two deaths occurred during the follow-up period, but were not attributed to breast cancer. The 2-year disease-free survival and 2-year overall survival rates were was 94.0% and 99.8%, respectively. Acute adverse events occurred in 131 patients (27.1%), and were distributed among all grades, with only two patients (0.4%) experiencing grade 3 events. Late adverse events were noted in 16 patients (3.4%), and were distributed among all grades, including grade 3 events in four patients (0.8%). No grade 4 or 5 events were observed. Hypofractionated PBI demonstrated favorable IBTR rates in patients with early breast cancer, with low incidence of acute and late toxicities in the short-term analysis.

Dose measurement of optic chiasm and parotid organs using OCTAVIUS 4D phantom: a dynamic IMRT method for nasopharyngeal cancer treatment

IntroductionIn intensity-modulated radiation therapy (IMRT) techniques, although the dose conformity increases, the out-of-field doses would not decrease. This study aimed to assess the dose error calculated by the treatment planning system (TPS) in the out-of-field regions using the dynamic IMRT (D-IMRT) method in nasopharyngeal cancer (NPC) patients. MethodsThe out-of-field doses were measured for the chiasm and parotid organs using the D-IMRT technique (6 MV energy) with Monaco TPS. Computed tomography (CT) images of 10 NPC patients (54–77 years, mean: 61.6 ± 12.2 years) were considered and countered using 7-field and 11-field methods. The OCTAVIUS 4D phantom was utilized for dose assessment. ResultsAccording to the OCTAVIUS measurements, the Monaco TPS dose errors ranged from −58.8 to 105.5%. The average dose error for optic chiasm and parotid organs was −25% and 8.5%, respectively, with several cases falling within tolerance (±5%). ConclusionThere were considerable dose calculation errors by Monaco TPS for organs located in out-of-field regions (optic chiasm and parotid) during IMRT for NPC patients. Therefore, accurate dose estimation in the out-of-field regions should be considered in clinical practices.

Palliative radiotherapy for leptomeningeal metastases after photon-based intensity-modulated radiotherapy in a nasopharyngeal cancer patient.

Leptomeningeal metastasis is a rare in nasopharyngeal carcinoma, affecting less than 5% of patients with a poor prognosis. The aim of this case report was to present management of palliative radiotherapy in leptomeningeal metastasis of nasopharyngeal carcinoma patient. A 33-year-old female presented with nasopharyngeal carcinoma with stage III, T3N3M0, WHO type III. The patient has received chemoradiation with photon-based intensity-modulated radiotherapy (IMRT) technique at the dose of 70 Gy in 33 fractions and showed a satisfactory outcome in 12 months follow-up. Later, at 18 months after chemoradiation completion, the patient complained of worsening bilateral sciatic pain, particularly during coughing, with slight limitations in bilateral hip flexion observed during straight leg raises. The whole spine contrast-enhanced magnetic resonance imaging (MRI) examination showed nodular enhancement of leptomeningeal thickening at the T4 level of the spinal cord lower than S3. Palliative radiation therapy utilized a three-dimensional conformal radiation therapy (3D-CRT) technique producing 35 Gy in 14 fractions placed in a field spanning the T4-S3 vertebral bodies. Methotrexate was administered intravenously every two weeks for three cycles to ensure central nervous system penetration. After four months of follow-up, no evidence of disease was found at the primary site and metastatic areas on subsequent physical examination or imaging with MRI and there was satisfactory improvement in neurologic symptoms. In conclusion, leptomeningeal metastases with primary nasopharyngeal carcinoma are rare and typically cause neurological impairments in patients. Hematogenous or cerebrospinal fluid-mediated spread of the cancer is considered the most likely pathway for leptomeningeal dissemination. Strategic modalities, such as radiotherapy with chemotherapy, may improve outcomes in symptoms and quality of life.

Dosimetrically motivated beam-angle optimization for non-coplanar arc radiotherapy with and without dynamic collimator rotation.

Non-coplanar techniques have shown to improve the achievable dose distribution compared to standard coplanar techniques for multiple treatment sites but finding optimal beam directions is challenging. Dynamic collimator trajectory radiotherapy (colli-DTRT) is a new intensity modulated radiotherapy technique that uses non-coplanar partial arcs and dynamic collimator rotation. To solve the beam angle optimization (BAO) problem for colli-DTRT and non-coplanar VMAT (NC-VMAT) by determining the table-angle and the gantry-angle ranges of the partial arcs through iterative 4π fluence map optimization (FMO) and beam direction elimination. BAO considers all available beam directions sampled on a gantry-table map with the collimator angle aligned to the superior-inferior axis (colli-DTRT) or static (NC-VMAT). First, FMO is performed, and beam directions are scored based on their contributions to the objective function. The map is thresholded to remove the least contributing beam directions, and arc candidates are formed by adjacent beam directions with the same table angle. Next, FMO and arc candidate trimming, based on objective function penalty score, is performed iteratively until a desired total gantry angle range is reached. Direct aperture optimization on the final set of colli-DTRT or NC-VMAT arcs generates deliverable plans. colli-DTRT and NC-VMAT plans were created for seven clinically-motivated cases with targets in the head and neck (two cases), brain, esophagus, lung, breast, and prostate. colli-DTRT and NC-VMAT were compared to coplanar VMAT plans as well as to class-solution non-coplanar VMAT plans for the brain and head and neck cases. Dosimetric validation was performed for one colli-DTRT (head and neck) and one NC-VMAT (breast) plan using film measurements. Target coverage and conformity was similar for all techniques. colli-DTRT and NC-VMAT plans had improved dosimetric performance compared to coplanar VMAT for all treatment sites except prostate where all techniques were equivalent. For the head and neck and brain cases, mean dose reduction-in percentage of the prescription dose-to parallel organs was on average 0.7% (colli-DTRT), 0.8% (NC-VMAT) and 0.4% (class-solution) compared to VMAT. The reduction in D2% for the serial organs was on average 1.7% (colli-DTRT), 2.0% (NC-VMAT) and 0.9% (class-solution). For the esophagus, lung, and breast cases, mean dose reduction to parallel organs was on average 0.2% (colli-DTRT) and 0.3% (NC-VMAT) compared to VMAT. The reduction in D2% for the serial organs was on average 1.3% (colli-DTRT) and 0.9% (NC-VMAT). Estimated delivery times for colli-DTRT and NC-VMAT were below 4 min for a full gantry angle range of 720°, including transitions between arcs, except for the brain case where multiple arcs covered the whole table angle range. These times are in the same order as the class-solution for the head and neck and brain cases. Total optimization times were 25%-107% longer for colli-DTRT, including BAO, compared to VMAT. We successfully developed dosimetrically motivated BAO for colli-DTRT and NC-VMAT treatment planning. colli-DTRT and NC-VMAT are applicable to multiple treatment sites, including body sites, with beneficial or equivalent dosimetric performances compared to coplanar VMAT and reasonable delivery times.

Dosimetry of intensity-modulated radiation therapy and volumetric-modulated arc therapy techniques after modified radical mastectomy for breast cancer and hypofractionated intensity-modulated radiotherapy.

The aim of this study was to compare the advantages and disadvantages of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) in patients with left-sided breast cancer who underwent hypofractionated IMRT after a modified radical mastectomy. Twenty patients who required adjuvant radiotherapy after modified radical mastectomy were randomly selected, and a specified dose of 43.5 Gy/15 F was used to plan for IMRT or VMAT. Dose-volume histograms (DVHs) were utilized to evaluate the dose distribution of the planning target volumes (PTVs) and organs at risk (OARs). VMAT demonstrated a greater and more uniform dose distribution of PTVs and lower number of monitor units. No significant differences were found in V5 of the affected lung and heart between the two techniques (P > 0.05). The V10, V20, V30, and Dmean of the affected lung and V10, V20, V30, V40, Dmean, and Dmax of the whole heart were better in the VMAT than in the IMRT (P < 0.05). The Dmean and Dmax of the left anterior descending (LAD) branch of the coronary artery of the heart were better in the VMAT (P < 0.05), and the use of the VMAT effectively reduced the cardiopulmonary dose. A significant advantage of V30 and Dmean was also found in VMAT (P < 0.05). These findings indicate that VMAT has higher clinical significance than IMRT, because it improved the dose distribution in the target area, reduced the cardiopulmonary dose, protected the OARs (e.g. thyroid), and shortened the treatment duration.

Photon Dose Distribution Analysis Using Three-Dimensional Conformal Radiation Therapy (3DCRT) And Intensity Modulated Radiotherapy (IMRT) Techniques in Cervical Cancer Cases Based on Histogram Volume Dose Curve (DVH)

Radiotherapy is one of the effective treatment methods for cervical cancer, although it is faced with great challenges in delivering an accurate dose of radiation. The purpose of this study was to compare the effectiveness of two cervical cancer treatment techniques, namely Three-Dimensional Conformal Radiation Therapy (3DCRT) and Intensity Modulated Radiotherapy (IMRT) in terms of conformity, homogeneity, and protection of Organs at Risk (OAR). The study used primary data from DVH 3DCRT and IMRT techniques collected from 15 cervical cancer patients. Conformity index (CI) and homogeneity (HI) were evaluated, and dose at OAR was assessed according to QUANTEC rules. The results showed the average CI value for the 3DCRT technique was (96,7 ± 1,5) x 10-2, while for IMRT it was (98,8 ± 0,8) x 10-2. In addition, the average HI score for the 3DCRT technique was (9,6 ± 1,5) x 10-2, and for IMRT it was (6,8 ± 1,9) x 10-2. In the 3DCRT technique, V50 for the rectum ranges from 0 – 57%, V65 for the bladder is 0%, and V50 for the left and right femoral heads ranges from 0 – 15.92% and 0 – 10.86%. While in the IMRT technique, V50 for the rectum ranges from 0 – 40,56%, V65 for bladder is 0%, and V50 for the left and right femoral heads ranges from 0 – 0,3% and 0 – 1,05%. The results of this study showed that the IMRT technique was better and more effective in treating cervical cancer than the 3DCRT technique. The IMRT technique has a higher CI value, indicating a better level of conformity, as well as a lower HI value, signifying a higher level of homogeneity. In addition, the IMRT technique is also able to provide better OAR protection.

An Analytical Study to Determine Dose-Volume Threshold for Radiation Induced Hypothyroidism.

Objective: To determine radiation dose volume threshold in predicting the development of hypothyroidism in cancer patients following neck irradiation. Methods: This is a cross sectional follow up study for patients who had been previously irradiated, prior to enrolment in the study. We have done thyroid dose-volumetric analysis on 120 histologically proven cancer patients in the age group of 18-75 years who received neck irradiation as a part of their definitive or adjuvant radiotherapy with three-dimensional conformal or intensity-modulated radiotherapy technique (3D -CRT or IMRT) and completed at least six months post-radiotherapy. Primary tumor sites included carcinoma or lymphoma of the head and neck, breast, cervical, and upper thoracic esophagus, requiring neck irradiation. Results: The proportion of patients who tested positive for Radiation induced hypothyroidism (RIHT) was found to be 40%, with clinical hypothyroidism and subclinical hypothyroidism being 25.8% and 14.2%, respectively. Time to develop hypothyroidism peaks around two years. Mean thyroid gland dose (Dmean) >28 Gy, thyroid gland volume receiving 40 Gy dose (i.e. V40) >49% and age <50 years were found to be significant risk factors for the development of RIHT on binary logistic regression. RT dose >50 Gy and thyroid gland volume spared from 40 Gy (i.e. VS40) < 2.12cm3 were statistically significant predictors for RIHT on chi-square and (Receiver operating characteristic) ROC curve analysis respectively but not on regression analysis. Conclusion: Dose-volume threshold for the thyroid gland as Dmean <28 Gy and V40 <49% may prevent the development of RIHT.

Prosedur Teknik Penyinaran Metode Intensity Modulated Radiation Therapy(IMRT) Kelenjar Getah Bening Pada Kasus Limfoma Hodgkin (LH) Di Rumah Sakit Umum Pusat DR.Hasan Sadikin

Latar Belakang: Lymph node cancer in the case of Hodkin's Lymphoma is a type of cancer. Lymphoma is a solid tumor of the immune system. Hodgkin lymphoma (HL) accounts for about 10% of all lymphomas. The Intensity Modulated Radiation Therapy (IMRT) technique is one of the cancer treatment techniques in Hodgkin's Lymphoma cases. The aim of this research is to determine the procedure and reasons for using the IMRT technique in lymph node cancer in Hodkin's Lymphoma cases.Metode: This research is qualitative research with a case study approach using retrospective data. The research time is from 24 to 30 May 2023 and the research location is in the Department of Radiation Oncology, RSUP Dr. Hasan Sadikin Bandung. The research subjects consisted of Radiation Oncologists, Medical Physics, Radiotherapists. Researchers collected data from patient medical records, made interview transcripts and carried out data reduction and processed it using open coding, and provided it in the form of quotations and then drew conclusions.Hasil: The procedure for irradiating Hodgkin's Lymphoma using the IMRT technique at the RSHS Department of Radiation Oncology begins with positioning the patient on the examination table with a fixation device and arranging the patient according to the reference point of the CT Simulator and making a thermoplastic mask then carrying out verification and irradiation. The IMRT technique has the advantage of using MLC so that the radiation is modulated according to the contour of the target and the disadvantage of precise dose distribution in limiting the radiation dose to organs at risk.Kesimpulan: In the case of the Department of Radiation Oncology, Dr. Hasan Sadikin Hospital, Bandung, the IMRT technique was used with consideration, namely that the IMRT technique already uses MLC which creates individual blocks automatically according to the projections depicted on the TPS.&#x0D;  

Hypoglossal nerve delineation in nasopharyngeal carcinoma patients may reduce the radiation dose and damage to the nerve

This study aims to establish a delineation guideline for the contouring of the hypoglossal nerve by dividing the nerve into different segments, and to test the possibility of a radiation dose reduction to the hypoglossal nerve in NPC patients receiving radiotherapy. Twenty NPC patients were selected arbitrarily. The hypoglossal nerves were delineated using anatomic landmarks and divided into the cisternal, intracanalicular, carotid, and transverse segments. The tumor coverage by radiation and dose-volume parameters of the nerve with and without various dose constraints to the hypoglossal nerve were compared. The hypoglossal nerve, which is invisible on CT images, can be delineated accurately with the assistance of several anatomic landmarks. Without a dose constraint to the hypoglossal nerve, the carotid space, intracanalicular, and transverse segments had high radiation dose-volumes. The dose-volume to the nerve, however, can be reduced when the nerve was defined and a dose constraint was given. The delineation of the hypoglossal nerve with its different segments is feasible. The carotid space, intracanalicular, and transverse segments received the highest dose, where the nerve damage was most likely located. The dose to the nerve can be reduced to less than 70 Gy using the intensity-modulated radiotherapy technique.

Radiation Induced Lumbar Plexopathy (RILP) in Patients of Cancer Cervix Treated by IMRT Technique: A Study of Dosimetry and Clinical Correlation

To assess the Dosimetric parameters of lumbo sacral plexus in carcinoma cervix patients treated with concurrent chemo-radiation by Intensity modulated radiotherapy (IMRT) technique & to clinically correlate these Dosimetric parameters with the lumbo sacral plexus toxicity. Total twenty-four patients were included in this study between December 2020 to December 2021. They were all treated by Intensity modulated radiotherapy (IMRT) technique. Radiotherapy dose delivered was 50Gy in 25 fractions at 2Gy/#, it was followed by 3 applications of intracavitary brachytherapy of 7Gy/ fraction each. The lumbo-sacral plexus was delineated according to guidelines given by Sun and Xi et al. No dose constraint was prescribed to the lumbo-sacral plexus prior to the treatment. Magnetic resonance imaging (MRI) of bilateral lumbo-sacral plexus test was done prior to the treatment and 12 months' post treatment. Dose received by the lumbo-sacral plexus was calculated DVH parameters was evaluated. The lumbo-sacral plexus toxicity was assessed by the 10-point questionnaire pre-treatment & post treatment and was compared. Assessment of toxicity was done by RTOG (Radiation Therapy Oncology Group) scoring criteria. Out of the 24 patients treated, 7 patients had gross nodes which were treated with a boost dose of 60 Gy. Out of these patients 9 patients (37.5%) developed signs and symptoms of radiation induced lumbar plexopathy (RILP). Among these patients, the most common symptom was weakness in the lower limbs followed by impaired leg movement and activities interfering daily activities such as walking, squatting and getting up from the chair. Other positive findings included stiffness, lower limb pain, lower back ache radiating the lateral aspect of the thigh and numbness of the lower limbs. Total prescribed dose to 95% of the planned target volume ranged from 49.2Gy - 61.9 Gy (median - 57 Gy). The mean volume of the LS plexus was 128 cc (range, 92- 143 cc). The mean of the D-max of LS plexus was 56.2 Gy (range, 43.2 Gy- 61.9 Gy). The V30 Gy was received by 84 % of LS plexus, whereas V40, V50, V60 was received by 64 %, 13 % and 4%. The most common significant findings on MRI post treatment were unilateral thickening of the nerve roots followed by hyperintensity in T2 weighted image and STIR sequencing. Mild contrast uptake and edema were present in the nerve roots. Radiation induced lumbar plexopathy (RILP) is one of the late complications after chemoradiotherapy in patients of carcinoma cervix, which is often misdiagnosed or missed on follow up. Therefore, lumbar plexus must be contoured in all pelvic malignancies which are treated by chemoradiotherapy with IMRT technique as it prevents dose dumping in that region. Further studies with longer follow up are needed.