3DCRT Technique Research Articles

Dosimetric comparison of 3-dimensional conformal radiotherapy (3D-CRT) and volumetric-modulated arc therapy (VMAT) in locally advanced cancer cervix

AbstractIntroduction:Dosimetric advantages of volumetric-modulated arc therapy (VMAT) over three-dimensional conformal radiotherapy (3D-CRT) are not established in a head-on comparison of a uniform group of locally advanced carcinoma of the cervix (LACC). Therefore, we conducted a dosimetric comparison of these two techniques in LACC patients.Materials and methods:Computed tomography (CT) data of histologically proven de novo LACC, including Stage IIB–IIIB and earlier stages deemed inoperable, were included in this prospective observational dosimetric study. Planning was initially done by 3D-CRT technique (dose of 45–50·4 Gy @ 1·8–2 Gy/# was used in the actual treatment), followed by VMAT planning and appropriate dosimetric comparisons were done in 39 cases.Results:For planning target volume coverage, D95, D98 and D100 (p < 0·0001 for all parameters) and V95 and V100 (p = 0·002 and <0·0001, respectively) were significantly improved with VMAT. The conformity index (CI) was significantly better with VMAT (p = 0·03), while 3D-CRT had a significantly better homogeneity index (HI)(p = 0·003). Dose to the urinary bladder was significantly reduced with VMAT compared to 3D-CRT for V20–V50, except V10. The doses to the rectum and abdominal cavity were significantly reduced with VMAT compared to 3D-CRT plans for all parameters (V10–V50). The number of organs at risks (OARs) for which constraints were met was higher with VMAT plans than with 3D-CRT plans, with at least four out of the five OARs protected in 46·1 versus 5·1% and all constraints achieved in 15·4% versus none.Conclusion:We conclude that in dosimetric terms, VMAT is superior to 3D-CRT for LACC.

Is Butterfly VMAT technique advantageous in hodgkin lymphoma patients with neck and mediastinal involvement?

Amaç: Bu çalışmada, erken evre Hodgkin lenfoma (HL) tanılı bilateral boyun ve mediasten yerleşimli genç kadın ve erkek olgularda, üç boyutlu konformal radyoterapi (3DCRT) ile volumetric modulated arc therapy (VMAT) ve butterfly VMAT tekniklerinin dozimetrik olarak karşılaştırılması amaçlanmıştır.
 Gereç ve Yöntemler: Erken evre HL'lı 20 hastaya radyoterapi uygulandı. Tüm plan verileri, hedef hacim ve kritik organ doz hacim histogramları karşılaştırıldı. Her üç teknik için konformite indeksi, homojenite indeksi ve % V107 farklılıkları değerlendirildi.
 Bulgular: Sağ meme maksimum, V25, V30 ve sol meme maksimum, V20, 25, 30 değerleri ise 3DCRT planlamada diğer VMAT planlarında elde edilen değerlerden daha yüksek idi. Bu da istatistiksel olarak anlamlı bulundu. Akciğer V5 değerleri 3DCRT planlamasında, VMAT planlarından daha düşüktü ve V20, 25,30 değerleri ise VMAT planlarından istatistiksel olarak daha yüksekti. Sağ ve sol parotis ortalamaları, V5,20 25, 30 değerleri butterfly VMAT planlamasında diğer planlara göre anlamlı olarak daha düşüktü. Sağ parotis V20, V25 değerinin butterfly VMAT planlamasında, ikili karşılaştırmalarda VMAT planından daha düşük olduğu bulunmuştur.
 Sonuçlar: Memede 20 Gy ve üzerinde VMAT, butterfly VMAT, 20 Gy ve altında ise 3DCRT tekniğinin daha avantajlı olduğu görülmektedir. Parotis dozları açısından ise butterfly VMAT’ın daha avantajlı olduğu görülmektedir.

Dosimetric comparison of three-dimensional conformal radiotherapy and static and dynamic intensity-modulated radiotherapy for the treatment of early-stage glottic cancer

The aim of this study was to compare dosimetric variations using the three-dimensional conformal radiotherapy (3DCRT), dynamic intensity-modulated radiation therapy (D-IMRT), and static intensity-modulated radiation therapy (S-IMRT) techniques for glottic cancer. Ten patients with early-stage glottic cancer were retrospectively selected and evaluated. The 3DCRT and IMRT treatment plans were performed using the solution commercialized by Varian with the Eclipse treatment planning system (TPS). For each patient, five different treatment plans were created and compared with respect to the doses received by the organs at risk (OARs) including the carotid arteries, thyroid gland, and spinal cord; the dose homogeneity index (DHI); conformity indexes (CI); and total monitor unit (MU) counts required for the treatment. The Mann-Whitney U test was used for statistical analyses. Statistically significant differences for the 3DCRT, D-IMRT, and S-IMRT techniques were observed for the planning target volume (PTV) mean and maximum doses. The results of this study indicated an increase in DHI for 3DCRT compared with D-IMRT and S-IMRT. Furthermore, the S-IMRT technique led to the superior decreased dose to the OAR. The 3DCRT plans performed better at the Dmax of the spinal cord and MU counts. The D-IMRT and S-IMRT techniques allowed more homogeneous dose distributions in PTV. Considering the dose to OAR, S-IMRT was more appropriate rather than 3DCRT and D-IMRT.

Impact of sentinel lymph-node biopsy and FDG-PET in staging and radiation treatment of anal cancer patients

To assess the role of sentinel lymph-node biopsy (SLNB) and FDG-PET in staging and radiation treatment (RT) of anal cancer patients. This retrospective study was performed on 80 patients (male: 32, female: 48) with a median age of 60 years (39–89 years) with anal squamous cell carcinoma who were treated from March 2008 to March 2018 at the IRCCS San Raffaele Hospital. Patients without clinical evidence of inguinal LNs metastases and/or with discordance between clinical evidence and imaging features were considered for SLNB. FDG-PET was performed in 69/80 patients. Patients with negative imaging in inguinal region and negative SLNB could avoid RT on groin to spare inguinal toxicity. CTV included GTV (primary tumour and positive LNs) and pelvic ± inguinal LNs. PTV1 and PTV2 corresponded to GTV and CTV, respectively, adding 0.5 cm. RT dose was 50.4 Gy/28 fractions to PTV2 and 64.8 Gy/36 fractions to PTV1, delivered with 3DCRT (n = 24) or IMRT (n = 56), concomitant to Mitomycin-C and 5-FU chemotherapy. FDG-PET showed inguinal uptake in 21/69 patients (30%) and was negative in 48/69 patients (70%). Lymphoscintigraphy was performed in 11/21 positive patients (4 patients SLNB confirmed inguinal metastases, 6 patients false positive and 1 patient SLN not found), and in 29/48 negative patients (5/29 showed metastases, 23/29 true negative and 1 SLN not found). Sensitivity, specificity, positive and negative predictive value of FDG-PET were 62%, 79%, 40% and 82%, respectively. Median follow-up time from diagnosis was 40.3 months (range: 4.6–136.4 months): 69 patients (86%) showed a complete response, 10 patients (13%) a partial response, 1 patient (1%) a stable disease. Patients treated on groin (n = 54) versus not treated (n = 26) showed more inguinal dermatitis (G1–G2: 50% vs. 12%; G3–G4: 17% vs. 0%, p < 0.05). For patients treated on groin, G3–G4 inguinal dermatitis, stomatitis and neutropenia were significantly reduced with IMRT against 3DCRT techniques (13% vs. 36%, p = 0.10; 3% vs. 36%, p = 0.003; 8% vs. 29%, p = 0.02, respectively). SLNB improves the FDG-PET inguinal LNs staging in guiding the decision to treat inguinal nodes. IMRT technique significantly reduced G3-G4 toxicities when patients are treated on groin.

A Retrospective Analysis of Dose Distribution and Toxicity in Patients with Left Breast Cancer Treated with Adjuvant Intensity-Modulated Radiotherapy: Comparison with Three-Dimensional Conformal Radiotherapy.

BackgroundA better understanding of the organs-at-risk (OAR) dose metrics and the related toxicity induced by radiotherapy (RT) for left breast cancer (BC) will improve the quality of life. This study addressed the issue for left-BC patients treated with intensity-modulated radiotherapy (IMRT) compared to three-dimensional conformal radiotherapy (3D-CRT).Patients and MethodsBetween 2012 and 2018, 308 left-BC patients underwent adjuvant RT at our hospital. Before June 2015, 134 patients were treated with 3D-CRT. Thereafter, 174 patients underwent IMRT. The patient’s characteristics in the IMRT group did not significantly different compared to those in the 3D-CRT group.ResultsAmong the total study population, the incidence of ≥grade 2 radiation dermatitis (RID) was 17.3%. Higher volumes receiving 105% (≥5.7%) and 107% (≥1%) of prescribed dose and 3D-CRT technique were associated with a higher risk of RID. Regarding lung toxicity, the mean lung dose (≥10.2Gy) and V20 (≥20%) of ipsilateral lung were significantly associated with the incidence of RT-induced pulmonary changes. By dosimetry analysis, IMRT achieved better dose conformity and delivered lower mean doses to heart and ipsilateral lung compared to 3D-CRT. Furthermore, propensity sore and multivariate analysis showed that IMRT technique helped to reduce RT-induced dermatitis and lung toxicity.ConclusionOur data suggest that the volume of OAR exposed to higher doses is a predictor of RT-induced toxicity. Adjuvant RT with IMRT technique offered better dose conformity and spared high-dose levels to OARs to reduce radiation-related morbidity for BC patients.

Dosimetric Evaluation of 3-Dimensional Conformal Radiotherapy Technique in Postoperative Patients with Gastric Carcinoma: When Is IMRT Really Needed?

Background and purpose: Adjuvant Chemoradiotherapy is the standard of care for postoperative gastric cancers with high risk features. The purpose of the current study is to do a dosimetric analysis in the postoperative setting by using 3-Dimensional Conformal Radiotherapy (3D-CRT) to a total dose of 45 Gy in 25 fractions over 5 weeks. A subsequent comparison with the 3D-CRT and IMRT of other published data is presented.Materials and Methods: Sixty postoperative patients who underwent radiation with 3D-CRT technique were included in this analysis. All patients received concurrent 5-Flurouracil or Capecitabine chemotherapy along with radiation. Radiation plans were analysed in terms of PTV coverage, conformity index (CI), homogeneity index (HI), organs at risk (OARs) and dose volume histogram (DVH) parameters. Results: DVH statistics for PTV: Dmean was 45.2±0.8 Gy, D98 was 42.9 ±1 Gy, D95 was 43.4±0.8 Gy, and D2 was 47.7±1.1 Gy. Mean CI for all plans was 1.23±0.43 and HI was 1.09±0.03. DVH parameters for OARs: right kidney, Dmean = 11.9±5.1 Gy, V18 was 21.5±13.8%, V15 was 27.2±14.9% and left kidney, Dmean was 17.7±5.8 Gy, V18 was 33.5±13.8%, V15 was 43.2±15.5%. Dmean for liver was 27.7±6.4 Gy and V20 was 69.2±15.8%. D195cc for the bowel bag was 36.3±10.8 Gy. Conclusion: The results of this study and subsequent comparison with existing literature suggests that 3D-CRT provides adequate homogenous target volume dose coverage and OAR protection, comparable to IMRT. More than the radiotherapy technique, it was the anastomotic site and the tumor location that determined the OAR doses.

Teknik 3D Conformal Radioterapi (3DCRT) Pada Keganasan Sinus Paranasal Dengan Modalitas Linac

Background: Radiotherapy is a radiation therapy action using ionizing radiation. To obtain the maximum dose of radiation in the tumour and the lowest possible dose on critical organs required a technique of radiation technique 3 Dimensional Conformal Radiotherapy (3DCRT). Radiotherapy Unit Radiology Installation Dr Sardjito Hospital Yogyakarta using 3DCRT technique. This research aims to know the radiotherapy procedure on paranasal sinus cancer using 3DCRT technique, to know the implementation of bolus beam modifier and dose optimization with the addition of electron radiation.Methods: The type of research in this thesis is qualitative research with case study approach. The research was conducted at Radiotherapy Unit Radiology Installation Dr Sardjito Hospital Yogyakarta after published Ethical Clearance. Methods of data collection in this study are observation, interviews, and documentation.Result: The results of this study indicate that the radiotherapy procedure in paranasal sinus cancer using 3DCRT technique can produce a homogeneous dose distribution, the implementation of bolus beam modifier is capable of generating dosage homogeneity on uneven target surfaces, and the distribution of doses with electron radiation on the target in the surface area can be optimal.Conclusion: With these techniques, the goal of radiotherapy can be achieved is to give the maximum dose in the tumour and the minimum dose possible in healthy tissue located in the vicinity.

Conformal radiotherapy plans for palliative bone metastasis - comparison of dosimetric parameters

Background:Palliative radiotherapy offers significant relief in the huge physical distress of patients with bony metastasis. The enormous potential of conformal techniques has not been tested in palliative settings. However,the increasing life span of patients with metastatic disease demands to optimize the radiotherapy techniques to provide maximal durable symptomatic relief. Despitean increase in the utilization of the 3DCRT technique for palliative bony metastasis, the optimal beam arrangement remains unknown. Materials and Methods:Ten patients of vertebral bony metastasis were retrospectively selected and four virtual 3DCRT plans were generated for each patient. The field approaches were a single field, two fields, three fields and five field approaches. For PTV, D90, D50, Dmean, Conformity index (CI) were evaluated.Dmean was evaluated for the esophagus, bowel, kidneys, and combined lungs. Dose-volume histograms were computed for the various treatment plans and compared. Statistical analysis was done by ANOVA test. Results:A total of forty radiotherapy plans were generated. PTV parameters were significantly better with two field plans over one field plans in terms of D90 (p= 0.002), D50 (p= 0.02), Dmean(p=0.0009). Dmeanwassignificantly better with three field approach compared to two field approach (p=0.0006). The Dmeanwas significantly increased for organs at risk in two fields and three field plans.Five field approach did not showan advantage in terms of dosimetry of PTV but there was a significant rise in the dose to Organs at risk (OAR’s). Conclusion:The three field plans showed better dose distribution to the PTV with an acceptable increase in the dose to OAR’s.

Analyzing the Positional uncertainties in 3dcrt ca breast Patients with Free Breathing and Active Breath Coordinator Gating Immobilization Devices

Aim: The aim of this study is to rule out the difference in positional setup errors when using immobilization device such as thermoplastic mould for free breathing and vacloc with ABC gating in ca breast patient treating with 3DCRT technique. Objective: The study is to compare the patient setup uncertainties using two different immobilization device, one with standard thermoplastic mould and other with vacuum cushion with active breath control gating in our clinical setup. Methodology: fourteen patients with ca breast are taken for the study. seven patients are undergone immobilization using standard thermoplastic moulding and remaining seven patients undergone, vacuum cushion with active breath control DIBH (deep inspiration breath hold) gating. CT was taken and 3dcrt plan were done according to the standard protocol. Prior to the treatment CBCT was taken, matching was done in XVI with the reference images, to rule out any positional shifts. Positional Shifts on all 3 axes such x, y, z is noted with rotational shift. Comparison were done on systematic error (?), random error (?), mean displacement vector (R), mean setup error (M). Result: immobilization device used by vacloc with DIBH ABC gating shows very less shifts in all direction, especially longitudinal direction compared with mould one, which we are using routinely in our department.

Radiation dose homogeneity and critical organs in radiotherapy treatment of prostate cancer

Present study compares two different 3D radiotherapy techniques: three-dimensional conformal radiotherapy (3D-CRT) and 3D external-beam radiation dose fields from computerized treatment plans, produced for 30 prostate cancer patients. All of the patients were the subject of treatment at the National Cancer Institute in Egypt. Evaluation was made of dose homogeneity within the target volume and the dose to critical organs (organs at risk, OAR). The plans were based on CT scans, all for cases of localized prostate cancer (all stage T2N0M0), with the CT scans transferred to the treatment planning systems. Comparison of the two different 3D radiation techniques was made in terms of isodose distributions and dose-volume histograms. The percentage of the planning target volume receiving 95% (V95) and 107% (V107) of the prescribed dose were obtained. For the 3D-CRT technique, the mean values for these were respectively 90.6% and 5.7% while for the other 3D technique they were 94.9% and 3.8%. In examining the dose received by the OAR, use of the 3D-CRT technique was found to provide the preferred dose distribution, with much greater sparing of the bladder, rectum and head of both femora. For the rectum the mean V70, V75 and D95 values (the latter referring to doses to 95% of the treatment volume) for the 3D-CRT technique were 35.5%, 32.2% and 34% while for the other 3D technique these were 8.4%, 0.2% and 12% respectively. For the bladder, the mean V40 and V65 values obtained using the 3D-CRT technique were 80.8% and 74.9% while for the alternative 3D technique they were 20.4% and 17% respectively. Thus for the particular cohort, the 3D-CRT technique provided superior target coverage and reduction of dose to the OAR.

Dosimetric Comparison of 3D-CRT, IMRT, IMAT and Helical Tomotherapy for Thoracic Esophageal Carcinoma

In this study, we compared the dose-volume parameters for treatment of thoracic esophageal cancer with treatment plans for 3D-CRT, IMRT, IMAT and HT. 15 thoracic esophagus patients who were treated in our clinic between 2017-2018 years were selected. PTV volumes were between 205 and 445.4 cc with an average of 355.2 cc. 3D-CRT, IMRT, IMAT and HT radiotherapy plans were created for each patient using the same contours and the same dose planning prescription. Total dose of 50.4 Gy for all patients was planed with 180 cGy dose per a fraction in total 28 fractions. For PTV; when the four treatment techniques were compared, HI values were 3D-CRT 0.84 ± 0.0, IMRT 0.57 ± 0.05, IMAT 0.06 ± 0.013, HT 0.08 ± 0.03 (p &amp;lt;0.05). CI values were found for 3D-CRT as 1.84 ± 0.2, for IMRT as 1.25 ± 0.05, for IMAT as 1.19 ± 0.04, for HT as 1.2 ± 0.06 (p &amp;lt;0.05). IMRT and IMAT techniques provided better OAR protection compared to other techniques in all lung and heart comparisons. The lowest doses for Dmax and D1% of Spinal Cord were provided by HT technique. We found that IMRT, IMAT and HT techniques have lower critical organ doses than 3D-CRT technique for treating torasic esophageal cancer. Considering the current evidence of the relationship between radiation-induced cardiac toxicity in the literature and the dose-volume parameters after treatment for esophageal cancer in our study, we can say that dose plans are better for IMRT and IMAT plans than 3D-CRT and HT in terms of lung and heart doses.

The risk for developing a secondary cancer after breast radiation therapy: Comparison of photon and proton techniques

Background and purposeTo compare secondary malignancy risks of modern proton and photon therapy techniques for locally advanced breast cancer. Methods and materialsWe utilized dosimetric data from 34 [10 photon-VMAT, 10 photon-3DCRT, 14 pencil beam scanning proton (PBS)] breast cancer patients who received comprehensive nodal irradiation. Employing a model based on organ equivalent dose to account for both inhomogeneous organ dose distributions and non-linear functional dose relationships, we estimated excess absolute risk, excess relative risk, and lifetime attributable risk (LAR) for secondary malignancies. The model uses dose distribution, number of fractions, age at exposure, attained age, the linear-quadratic dose response relationship for cell survival, repopulation factor, as well as gender specific age dependencies, and initial slopes of dose response curves. ResultsThe LAR for carcinoma at age 70 was estimated to be up to 3.64% for esophagus with an advantage of 3DCRT over PBS and VMAT. For the ipsilateral lung, risks were lowest for PBS (up to 5.56%), followed by 3DCRT (up to 6.54%) and VMAT (up to 7.7%). For the contralateral lung, there is a clear advantage of 3DCRT and PBS techniques (risk <0.86%) over VMAT (up to 4.4%). The risk for the contralateral breast is negligible for 3DCRT and PBS but was estimated as up to 1.2% for VMAT. Risks for the thyroid are overall negligible. Independently performed comparative treatment plans on 10 patients revealed that the risk for the contralateral lung and breast using VMAT can be more than an order of magnitude higher compared to PBS. Sarcoma risks were estimated as well showing similar trends but were overall lower compared to carcinoma. ConclusionConventional (3DCRT) techniques led to the lowest estimated risks of, thyroid and esophageal secondary cancers while PBS demonstrated a benefit for secondary lung and contralateral breast cancer risks, with the highest risks overall associated with VMAT techniques.

Predictors of Weight Loss in Patients With Head and Neck Cancer Receiving Radiation or Concurrent Chemoradiation Treated at a Tertiary Cancer Center.

Radiation therapy (RT) has remained the mainstay treatment approach for head and neck cancers. Weight loss due to tumor or tumor-related factors remains a major health issue among head and neck cancer patients. A total of 357 patients were identified for the study. Possible weight-loss predictors were determined in the patients undergoing RT based on the patient demographics, tumor site, and treatment characteristics. The mean age of patients was 52 years, whereas the median age was 51 years (range, 18-87). Two hundred and thirteen (66%) patients had oral cavity cancers, 43 (14%) had oropharyngeal cancer, 26 (8%) had hypopharyngeal cancer, 13 (6%) had larynx cancer, and 19 (6%) had other site involvement. A total of 192 patients received 3-dimensional conformal radiation therapy (3DCRT), whereas 127 patients received intensity modulated radiation therapy-image guided radiation therapy (IMRT-IGRT), 212 (66%) received concurrent chemotherapy, and 107 (34%) patients did not receive concurrent chemotherapy. A total of 127 (40%) of the patients gained weight during the first week of RT; on the other hand, maximum weight loss among patients was occurred during the third and fourth weeks of RT. Analysis by logistic regression determined there is significant weight loss (>10%) in patients receiving radical RT as compared with adjuvant RT. Better outcomes were observed in patients receiving RT by IMRT-IGRT technique as compared with 3DCRT technique.

Results of the ACCEL trial: Dosimetry in accelerated partial breast irradiation

PurposeTo report the achieved dosimetry in the ACCEL trial and compare the results to reported dosimetry from the major accelerated partial breast irradiation (APBI) phase III trials. MethodsThe ACCEL trial was a single arm, phase II, prospective cohort study. A five-field, inverse-planned, IMRT strategy was employed using a class solution technique to increase planning consistency including high dose conformity and low normal tissue dose to the ipsilateral breast. ResultsBetween 2016 and 2019, 283 patients were treated with 27 Gy in five fractions in consecutive days. The average PTV conformity index was 1.1. For the ipsilateral breast, the median (range) volume receiving 95% and 50% of the prescription dose was 9.7% (3.2–22.4) and 30.3% (11.1–54.6), respectively. Compared to major APBI phase III trial constraints, this reduction in irradiated volume at the 95% and 50% isodose levels represents a reduction of 209 cm3 and 265 cm3, respectively. ConclusionThe IMRT planning strategy employed in the ACCEL trial demonstrated consistent and superior dosimetry by comparison to conventionally used 3D CRT techniques. Future APBI trials should update dosimetric constraints.

Dosimetric comparison between different radiotherapy protocols for prostate cancer using Geant4 Monte Carlo simulation

We aimed to evaluate absorbed doses received by organs at risk (OARs) following prostate treatment with external beam radiotherapy (EBRT), using different techniques (3D-CRT and box), number of fields (4 and 6 fields) and photon energies (6 and 10 MV). The MIRD5 adult male anthropomorphic phantom in GEANT4 package was used. However, the prostate, rectum and both femoral heads were not available, hence, were created within the phantom. A dose of 75 Gy was prescribed to the prostate, in all simulated treatments. Field size of 6.4 × 5.9 cm2 was used in all techniques. For 3D-CRT technique, beams with similar shape to the prostate were used, while for box technique, square-shaped beams were used. Absorbed doses to OARs (rectum, urinary bladder and both femoral heads) were then evaluated. The 3D-CRT technique resulted in lower dose to OARs compared to box technique. Also, the findings show an inverse relationship between number of fields and the OARs doses. There was no dose difference between the OARs with different beam energies. In conclusion, the 6-field 3D-CRT technique with 6 MV photon beam is an ideal treatment option for prostate cancer.

Case of Adenoid Cystic Carcinoma of Lacrimal Gland Treated by Eye Sparing Radiation Therapy using 3DCRT Technique

Case of Adenoid Cystic Carcinoma of Lacrimal Gland Treated by Eye Sparing Radiation Therapy using 3DCRT Technique

Anovel approach to SBRT patient quality assurance using EPID-based real-time transit dosimetry : Astep to QA with in vivo EPID dosimetry.

Intra- and inter-fraction organ motion is amajor concern in stereotactic body radiation therapy (SBRT). It may cause substantial differences between the planned and delivered dose distribution. Such delivery errors may lead to medical harm and reduce life expectancy for patients. The project presented here investigates and improves arapid method to detect such errors by performing online dose verification through the analysis of electronic portal imaging device (EPID) images. To validate the method, arespiratory phantom with inhomogeneous insert was examined under various scenarios: no-error and error-simulated measurements. Simulation of respiratory motions was practiced for target ranges up to 2 cm. Three types of treatment planning technique - 3DCRT (three-dimensional conformal radiation therapy), IMRT (intensity modulated radiation therapy), and VMAT (volumetricmodulated arc therapy - were generated for lung SBRT. Atotal of 54plans were generated to assess the influence of techniques on the performance of portal dose images. Subsequently, EPID images of 52SBRT patients were verified. Both for phantom and patient cases, dose distributions were compared using the gamma index method according to analysis protocols in the target volume. The comparison of error-introduced EPID-measured images to reference images showed no significant differences with 3%/3 mm gamma evaluation, though target coverage was strongly underestimated. Gamma tolerance of 2%/2 mm reported noticeable detection in EPID sensitivity for simulated errors in 3DCRT and IMRT techniques. The passing rates for 3DCRT, IMRT, and VMAT with 1%/1 mm in open field were 84.86%, 92.91%, and 98.75%, and by considering MLC-CIAO + 1 cm (threshold 5%), were 68.25%, 83.19%, and 95.29%, respectively. This study demonstrates the feasibility of EPID for detecting the interplay effects. We recommend using thin computed tomography slices and adding sufficient tumor margin in order to limit the dosimetric organ motion in hypofractionated irradiation with preserved plan quality. In the presence of respiratory and gastrointestinal motion, tighter criteria and consequently using local gamma evaluation should be considered, especially for VMAT. This methodology offers asubstantial step forward in in vivo dosimetry and the potential to distinguish errors depending on the gamma tolerances. Thus, the approach/prototype provides afast and easy quality assurance procedure for treatment delivery verification.

Impact of 6 MV photons and mixed beam (6 MV and 15 MV) photons on the dose distribution in high-grade gliomas using three-dimensional conformal radiotherapy technique - A Retrospective Analysis

Background and Aim: The present study focused on the impact of 6 MV photons and mixed beam (6 MV and 15 MV) photons on dose distribution in high-grade gliomas using three-dimensional conformal radiotherapy (3DCRT) technique. The suitability of using different photon beam energies was evaluated with respect to dose distribution. Materials and Methods: A total of 24 patients of high-grade glioma treated on linear accelerator were enrolled and evaluated in this retrospective study. All patients had undergone total/subtotal resection of tumor. These patients were treated with postoperative adjuvant external beam radiotherapy on a linear accelerator using 3DCRT technique. Treatment plans were generated using 6 MV and a combination of both 6 MV and 15 MV photon beams. All plans were generated using suitable planning objectives, and dose constraints which were identical across the plans, except the beam energy. The plans were analyzed in terms of their target coverage, conformity, and normalized dose range. Results: In 16 patients out of 24, the treatment plans were generated using 6 MV photons, the normalization dose was well within 5%–7% of the dose prescribed. In the remaining 8 patients, the normalized dose was >107%, and in these cases, the use of mixed beam plans yielded a better dose distribution with normalized dose between 101% and 105%. Conformity index (CI) values were between 1.2 and 1.98. CI mean was 1.59. Conclusions: The use of mixed beams in 3DCRT technique may be considered as an alternative, especially in a scenario where pure 6 MV photons do not yield homogeneous dose distribution within the normalized range, and in centers where intensity-modulated radiation therapy and field-in-field technique are not available.

Should we consider thyroid gland as an organ at risk in carcinoma breast patients receiving adjuvant radiation by conformal technique? A single institute dosimetric study

The most common malignancy among Indian women is carcinoma of the breast. In the management of breast cancer (BC), radiation therapy (RT) is given to breast or chest wall and supraclavicular lymph nodal (SCLN) area, with at least part of the thyroid receiving RT dose.There is an increased incidence of hypothyroidism (HT) among BC patients after RT involving the SCLN area. Moreover, the incidence of HT in India is higher than in the West. The aim of our study is to dosimetrically evaluate the thyroid doses during RT for BC. This is a single institute prospective study (n = 131). Radiation was planned by three-dimensional conformal radiation therapy (3D-CRT) technique and dose-volume parameters for thyroid gland were noted. The median thyroid gland volume was 7.4 cc. The median of the mean dose to thyroid gland was 2068 cGy, V10 was 42%, and V40 was 33%. In other studies, BC patients with smaller thyroid gland were more prone to HT (volume <8 cc). In our study, we have seen that the median thyroid volume was 7.4 cc. Our study showed a lower mean dose to the thyroid gland and smaller volume thyroid glands than in the literature. As the incidence of HT is higher in India, compared to the west and our patients had small volume thyroid glands, they could be at higher risk of developing HT RT. So BC patients should be monitored for HT and should be given a dose constraint while planning RT.

The Effect of Absorbed Dose to Organs at Risk Following Craniospinal Irradiation Using Different Radiotherapy Techniques

Introduction: In medulloblastoma patients craniospinal irradiation is an important element the treatment. Our study aimed to evaluate the effect of absorbed dose to organs at risk using the hybrid intensity-modulated radiation therapy (IMRT) versus three-dimensional conformal radiotherapy (3DCRT) for craniospinal irradiation (CSI) in average risk medulloblastoma patients. Materials and Methods: In this study, thirteen medulloblastoma patients were included. The prescribed total dose to the planning target volume (PTV) was 23, 40 Gy in 13 fractions. Two radiotherapy techniques, three dimensional conformal radiotherapy (3DCRT) and hybrid intensity modulated radiotherapy (IMRT) were used to treat these patients. The coverage of the Target was evaluated using the D mean, D95%, D2%, D98% and V95%. Other parameters were also compared such as Integral dose (ID), Homogeneity index (HI) and doses to the organs at risk (OARs). Results: There was no significant difference in the mean dose received by the PTV-Brain or the dose received by 95% and 98% of PTV volume using the two techniques. For PTV-Spine, the percentage volume receiving 95% of the total dose increased significantly in the hybrid IMRT technique compared to the conformal technique. So, hybrid IMRT plan achieved the best coverage for PTV spine. Lower dose for OAR was delivered by 3DCRT, except the heart and thyroid, hybrid IMRT achieved better sparing. All plans resulted in the same dose homogeneity index (DHI) for PTV-Brain. For PTV-Spine, hybrid IMRT technique achieved better dose homogeneity compared to 3DCRT technique (1.09 vs. 1.12; p > 0.05). Conclusions: hybrid IMRT technique can be realized on conformal technique because it achieved better dose coverage for the (PTV) and organ at risk (OAR). 3DCRT reduced mean dose to most OARS, except the heart and thyroid. Therefore, the hybrid IMRT technique may be a CSI treatment alternative to 3DCRT.