CTNI-44. DOSIMETRIC IMPACT OF TUMOR TREATING FIELDS ON CONCURRENT RADIATION THERAPY FOR PEDIATRIC BRAIN TUMORS

2021 ◽  
Vol 23 (Supplement_6) ◽  
pp. vi69-vi70
Author(s):  
Enzhuo Quan ◽  
Eun Han ◽  
Christine Chung ◽  
Tina Briere ◽  
Zsila Sadighi ◽  
...  
Keyword(s):  
Brain Tumors ◽  
Tumor Volume ◽  
Volumetric Modulated Arc Therapy ◽  
Skin Dose ◽  
Target Coverage ◽  
Dose Distributions ◽  
Tumor Treating Fields ◽  
Early Results ◽  
Treatment Plans ◽  
The Impact

Abstract INTRODUCTION Early results suggest that tumor treating fields (TTF) concurrent with radiotherapy (RT) for glioblastoma yields acceptable dosimetry in adults; the impact on RT dose distribution in children is unknown. This study was undertaken to evaluate the dosimetric impact of TTF on concurrent photon RT for children with brain tumors. METHODS CT scans of an anthropomorphic pediatric head phantom (approximately 15-year-old) and an infant-head-sized spherical phantom were acquired with and without TTF attached. For each phantom, simulated supratentorial tumor targets were initially contoured on CT datasets acquired without TTF attached. Treatment plans using volumetric modulated arc therapy were created to deliver 60Gy and 50Gy to the gross tumor volume (GTV) and clinical tumor volume (CTV), respectively, in 30 fractions. The dose distributions of the same treatment plans were then re-computed with TTF attached. Target coverage metrics were compared between dose distributions with and without TTF. To measure skin dose, treatment plans were delivered with thermoluminescent dosimeters placed on the phantoms at various locations, with and without TTF attached. RESULTS The presence of TTF slightly reduced target coverage. For the two phantoms studied, D95 of the CTV was reduced by 0.65% and 1.03%, and D95 of the GTV was reduced by 0.7% and 1.05%, respectively. Electrodes under the direct beam path increased skin dose by an average of 43.3% (0.3Gy – 20.7Gy), but all skin dose measurements stayed within tolerances. TTF electrodes out of the RT field did not cause an increase in measured dose. CONCLUSIONS The dosimetric impact of TTF on pediatric head phantoms receiving concurrent RT resembles that reported in adult studies. Although the tumor dose is not significantly affected, the skin dose notably increases due to the bolus effect from the TTF electrodes, which may be mitigated by skin-sparing planning and shifting of the device during RT.

The impact of reference isocentre position on set-up errors in head-and-neck image-guided radiotherapy

2017 ◽  
Vol 17 (1) ◽  
pp. 104-113
Author(s):  
Helena Lenko ◽  
Primož Peterlin
Keyword(s):  
Head And Neck ◽  
Volumetric Modulated Arc Therapy ◽  
Patient Positioning ◽  
Lateral Direction ◽  
Image Guided Radiotherapy ◽  
Position Correction ◽  
Treatment Plans ◽  
Set Up ◽  
The Impact ◽  
Head And Neck Radiotherapy

AbstractAimTo examine and quantify set-up errors in patient positioning in head-and-neck radiotherapy and to investigate the impact of the choice of reference isocentre—on the patient neck or patient skull—on the magnitude of set-up errors.Materials and methodsSet-up position corrections obtained using online kV 2D/2D matching were recorded automatically for every treatment fraction. 3,413 treatment records for 117 patients treated with volumetric modulated arc therapy during 2013 and 2014 on a single treatment machine in our clinic were analysed. In 79 treatment plans the reference isocentre was set to the patient skull, and in 47 to the neck.ResultsStandard deviation of group systematic error in the vertical, longitudinal and lateral direction and the couch rotation were found to be 2·5 mm, 2·1 mm, 1·9 mm and 0·43° (skull) and 2·5 mm, 1·8 mm, 1·7 mm and 0·49° (neck), respectively. Random error of the vertical, longitudinal, lateral and rotational position correction was 1·8 mm, 1·5 mm, 1·6 mm and 0·62° (skull) and 1·9 mm, 1·6 mm, 1·5 mm and 0·60° (neck), respectively. Positional shifts in different directions were found to be uncorrelated.ConclusionsNeither reference isocentre set-up shows a clear advantage over the other in terms of interfraction set-up error.

scholarly journals Dosimetric Impact of Deep Learning-Based CT Auto-Segmentation on IMRT Treatment Planning for Prostate Cancer

2021 ◽  
Author(s):  
Maria Kawula ◽  
Dinu Purice ◽  
Minglun Li ◽  
Gerome Vivar ◽  
Seyed-Ahmad Ahmadi ◽  
...  
Keyword(s):  
State Of The Art ◽  
Pearson Correlation ◽  
Automatic Segmentation ◽  
Volumetric Modulated Arc Therapy ◽  
Target Volume ◽  
Ct Images ◽  
Pass Rate ◽  
Dice Similarity Coefficient ◽  
Dose Distributions ◽  
The Impact

Abstract Background The evaluation of the automatic segmentation algorithms is commonly performed using geometric metrics, yet an evaluation based on dosimetric parameters might be more relevant in clinical practice but is still lacking in the literature. The aim of this study was to investigate the impact of state-of-the-art 3D U-Net-generated organ delineations on dose optimization in intensity-modulated radiation therapy (IMRT) for prostate patients for the first time. Methods A database of 69 computed tomography (CT) images with prostate, bladder, and rectum delineations was used for single-label 3D U-Net training with dice similarity coefficient (DSC)-based loss. Volumetric modulated arc therapy (VMAT) plans have been generated for both manual and automatic segmentations with the same optimization settings. These were chosen to give consistent plans when applying perturbations to the manual segmentations. Contours were evaluated in terms of DSC, average and 95% Hausdorff distance (HD). Dose distributions were evaluated with the manual segmentation as reference using dose volume histogram (DVH) parameters and a 3%/3mm gamma-criterion with 10% dose cut-off. A Pearson correlation coefficient between DSC and dosimetric metrics, gamma index and DVH parameters, has been calculated. Results 3D U-Net based segmentation achieved a DSC of 0.87(0.03) for prostate, 0.97(0.01) for bladder and 0.89(0.04) for rectum. The mean and 95% HD were below 1.6(0.4) and below 5(4) mm, respectively. The DVH parameters V 60/65/70 Gy for the bladder and V 50/65/70 Gy for the rectum showed agreement between dose distributions within ±5% and ±2%, respectively. The DVH parameters for prostate and prostate+3mm margin (surrogate clinical target volume) showed good target coverage for the 3D U-Net segmentation with the exception of one case. The average gamma pass-rate was 85\%. A comparison between geometric and dosimetric metrics showed no strong statistically significant correlation between these metrics. Conclusions The 3D U-Net developed for this work achieved state-of-the-art geometrical performance. The study highlighted the importance of dosimetric evaluation on top of standard geometric parameters and concluded that the automatic segmentation is sufficiently accurate to assist the physicians in manually contouring organs in CT images of the male pelvic region, which is an important step towards a fully automated workflow in IMRT.

Clinical experience using Delta 4 phantom for pretreatment patient-specific quality assurance in modern radiotherapy

2018 ◽  
Vol 18 (02) ◽  
pp. 210-214
Author(s):  
R. P. Srivastava ◽  
C. De Wagter
Keyword(s):  
Quality Assurance ◽  
Treatment Planning ◽  
Volumetric Modulated Arc Therapy ◽  
Planning System ◽  
Treatment Planning System ◽  
Patient Specific ◽  
Dose Distributions ◽  
Gamma Index ◽  
Calculated Dose ◽  
Treatment Plans

AbstractPurposeIn advanced radiotherapy techniques such as intensity-modulated radiation therapy (IMRT), the quality assurance (QA) process is essential. The aim of the study was to assure the treatment planning dose delivered during delivery of complex treatment plans. The QA standard is to perform patient-specific comparisons between planned doses and doses measured in a phantom.Materials and methodThe Delta 4 phantom (Scandidos, Uppsala, Sweden) has been used in this study. This device consists of diode matrices in two orthogonal planes inserted in a cylindrical acrylic phantom. Each diode is sampled per beam pulse so that the dose distribution can be evaluated on segment-by-segment, beam-by-beam, or as a composite plan from a single set of measurements. Ninety-five simple and complex radiotherapy treatment plans for different pathologies, planned using a treatment planning system (TPS) were delivered to the QA device. The planned and measured dose distributions were then compared and analysed. The gamma index was determined for different pathologies.ResultsThe evaluation was performed in terms of dose deviation, distance to agreement and gamma index passing rate. The measurements were in excellent agreement between with the calculated dose of the TPS and the QA device. Overall, good agreement was observed between measured and calculated doses in most cases with gamma values above 1 in >95% of measured points. Plan results for each test met the recommended dose goals.ConclusionThe delivery of IMRT and volumetric-modulated arc therapy (VMAT) plans was verified to correspond well with calculated dose distributions for different pathologies. We found the Delta 4 device is accurate and reproducible. Although Delta4 appears to be a straightforward device for measuring dose and allows measure in real-time dosimetry QA, it is a complex device and careful quality control is required before its use.

scholarly journals Impact of prescription isodose level and collimator selection on dose homogeneity and plan quality in robotic radiosurgery

2021 ◽  
Author(s):  
Alexandra Hellerbach ◽  
Markus Eichner ◽  
Daniel Rueß ◽  
Klaus Luyken ◽  
Mauritius Hoevels ◽  
...  
Keyword(s):  
Treatment Time ◽  
Target Dose ◽  
Dose Distributions ◽  
Robotic Radiosurgery ◽  
Treatment Plans ◽  
Dose Homogeneity ◽  
Physical Limitations ◽  
The Impact ◽  
Prescription Isodose ◽  
Selection Of

Abstract Purpose In stereotactic radiosurgery (SRS), prescription isodoses and resulting dose homogeneities vary widely across different platforms and clinical entities. Our goal was to investigate the physical limitations of generating dose distributions with an intended level of homogeneity in robotic SRS. Methods Treatment plans for non-isocentric irradiation of 4 spherical phantom targets (volume 0.27–7.70 ml) and 4 clinical targets (volume 0.50–5.70 ml) were calculated using Sequential (phantom) or VOLOTM (clinical) optimizers (Accuray, Sunnyvale, CA, USA). Dose conformity, volume of 12 Gy isodose (V12Gy) as a measure for dose gradient, and treatment time were recorded for different prescribed isodose levels (PILs) and collimator settings. In addition, isocentric irradiation of phantom targets was examined, with dose homogeneity modified by using different collimator sizes. Results Dose conformity was generally high (nCI ≤ 1.25) and varied little with PIL. For all targets and collimator sets, V12Gy was highest for PIL ≥ 80% and lowest for PIL ≤ 65%. The impact of PIL on V12Gy was highest for isocentric irradiation and lowest for clinical targets (VOLOTM optimization). The variability of V12Gy as a function of collimator selection was significantly higher than that of PIL. V12Gy and treatment time were negatively correlated. Plans utilizing a single collimator with a diameter in the range of 70–80% of the target diameter were fastest, but showed the strongest dependence on PIL. Conclusion Inhomogeneous dose distributions with PIL ≤ 70% can be used to minimize dose to normal tissue. PIL ≥ 90% is associated with a marked and significant increase in off-target dose exposure. Careful selection of collimators during planning is even more important.

scholarly journals P14.80 Advances in radiotherapy for brain tumors (benign, malignant and pediatrics tumors)

2019 ◽  
Vol 21 (Supplement_3) ◽  
pp. iii86-iii86
Author(s):  
M Theodorou
Keyword(s):  
At Risk ◽  
Brain Metastasis ◽  
Brain Tumors ◽  
Tumor Volume ◽  
Organs At Risk ◽  
Low Grade ◽  
Pediatric Tumors ◽  
Low Grade Gliomas ◽  
Target Definition ◽  
Treatment Plans

Abstract BACKGROUND New techniques in radiation oncology such as VMAT (volumetric modulated arc therapy), IGRT (image guidance radiotherapy) compare 3D-conformal technique offering better coverage of the target and more safety for the organs at risk for brain tumors such as Glioblastomas, low grade gliomas, pediatric tumors, meningiomas, pituitary adenomas, brain metastasis. MATERIAL AND METHODS Compare 3D-conformal treatment plans with VMAT -IGRT plan for Glioblastoma, pituitary adenoma, pediatric tumors, low grade gliomas, brain metastasis. Clinical target definition occur with Fusion of planing-MRI with Planing-CT inclusive preoperative and postoperative MRI to exact delineation of GTV (gross tumor volume), CTV (clinical target definition, PTV (planing tumor volume). contouring of organs at risk such as brainstemm, chiasm, N. opticus right and left, eye right and left, lens right and left, brain, cerebellum, internal ears. RESULTS VMAT treatment plans offer higher coverage of the target, higher homogenize radiation index and less radiation for the organs at risk. Due to the good safety of the organs at risk less toxicity during radiation was mentioned specially for neuroaxisradiation for medulloblastoma in children. The toleration during radiotherapy with VMAT technique is is much better than 3D conformal technique CONCLUSION VMAT technique offers higher radiation dose to the target and less radiation to the organs at risk with better toleration of treatment and less toxicity inclusive late side effects such as radionecrosis.

scholarly journals Impact of intra-fractional motion on dose distributions in lung IMRT

2020 ◽  
pp. 1-5
Author(s):  
Mikhail A. Chetvertkov ◽  
Oleg N. Vassiliev ◽  
Jinzhong Yang ◽  
He C. Wang ◽  
Amy Y. Liu ◽  
...  
Keyword(s):  
Lung Cancer ◽  
Organs At Risk ◽  
Intensity Modulated Radiotherapy ◽  
Median Number ◽  
Clinical Treatment ◽  
Dose Distributions ◽  
Median Reduction ◽  
Treatment Plans ◽  
The Mean ◽  
The Impact

Abstract Aim: To investigate the impact of intra-fractional motion on dose distribution in patients treated with intensity-modulated radiotherapy (IMRT) for lung cancer. Materials and methods: Twenty patients who had undergone IMRT for non-small cell lung cancer were selected for this retrospective study. For each patient, a four-dimensional computed tomography (CT) image set was acquired and clinical treatment plans were developed using the average CT. Dose distributions were then recalculated for each of the 10 phases of respiratory cycle and combined using deformable image registration to produce cumulative dose distributions that were compared with the clinical treatment plans. Results: Intra-fractional motion reduced planning target volume (PTV) coverage in all patients. The median reduction of PTV covered by the prescription isodose was 3·4%; D98 was reduced by 3·1 Gy. Changes in the mean lung dose were within ±0·7 Gy. V20 for the lung increased in most patients; the median increase was 1·6%. The dose to the spinal cord was unaffected by intra-fractional motion. The dose to the heart was slightly reduced in most patients. The median reduction in the mean heart dose was 0·22 Gy, and V30 was reduced by 2·5%. The maximum dose to the oesophagus was also reduced in most patients, by 0·74 Gy, whereas V50 did not change significantly. The median number of points in which dose differences exceeded 3%/3 mm was 6·2%. Findings: Intra-fractional anatomical changes reduce PTV coverage compared to the coverage predicted by clinical treatment planning systems that use the average CT for dose calculation. Doses to organs at risk were mostly over-predicted.

Early Outcomes of Coronary Endarterectomy in Patients Undergoing Coronary Artery Bypass Surgery

2016 ◽  
Vol 19 (2) ◽  
pp. 059
Author(s):  
Amin Bagheri ◽  
Ahmad Masoumi ◽  
Jamshid Bagheri
Keyword(s):  
Coronary Artery ◽  
Coronary Artery Bypass ◽  
Coronary Artery Bypass Surgery ◽  
Bypass Surgery ◽  
Artery Bypass ◽  
Adverse Outcomes ◽  
Supraventricular Arrhythmia ◽  
Coronary Endarterectomy ◽  
Early Results ◽  
The Impact

<strong>Background:</strong> Coronary endarterectomy (CE) is performed as an adjunct to coronary artery bypass surgery (CABG); however, the efficacy of this technique is still controversial. We aimed to evaluate the impact of CE combined with CABG when compared with isolated CABG.<br /><strong>Methods:</strong> Patients who underwent CABG between July 2007 and June 2014 were included. 70 of 2452 patients (2.8%) underwent CE in addition to CABG. Early results were compared with isolated CABG and predictors of adverse outcome were measured in stepwise multivariate logistic regression analyses.<br /><strong>Results:</strong> The incidence of comorbidities including prior myocardial infarction, diabetes mellitus, and three-vessel coronary disease in CE patients was higher; however, mortality (4.3% versus control 3.6%; P = .762) and postoperative complications were not significantly increased in this group of patients (except supraventricular arrhythmia). Although age greater than 70 years, impaired ejection fraction, intraoperative intraaortic balloon pump, and prolonged cardiopulmonary bypass time were important predictors of adverse outcomes, CE was not associated with increased mortality or postoperative morbidities. <br /><strong>Conclusion:</strong> Despite the higher risk profile of patients who underwent CE, this technique was not identified as an independent risk factor for adverse postoperative outcomes.

scholarly journals Dosimetric comparison of MR-linac-based IMRT and conventional VMAT treatment plans for prostate cancer

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Vanessa Da Silva Mendes ◽  
Lukas Nierer ◽  
Minglun Li ◽  
Stefanie Corradini ◽  
Michael Reiner ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Target Volume ◽  
Planning System ◽  
Treatment Planning System ◽  
Target Coverage ◽  
Treatment Delivery ◽  
Ptv Margin ◽  
Delivery Times ◽  
Low Field ◽  
Treatment Plans

Abstract Background The aim of this study was to evaluate and compare the performance of intensity modulated radiation therapy (IMRT) plans, planned for low-field strength magnetic resonance (MR) guided linear accelerator (linac) delivery (labelled IMRT MRL plans), and clinical conventional volumetric modulated arc therapy (VMAT) plans, for the treatment of prostate cancer (PCa). Both plans used the original planning target volume (PTV) margins. Additionally, the potential dosimetric benefits of MR-guidance were estimated, by creating IMRT MRL plans using smaller PTV margins. Materials and methods 20 PCa patients previously treated with conventional VMAT were considered. For each patient, two different IMRT MRL plans using the low-field MR-linac treatment planning system were created: one with original (orig.) PTV margins and the other with reduced (red.) PTV margins. Dose indices related to target coverage, as well as dose-volume histogram (DVH) parameters for the target and organs at risk (OAR) were compared. Additionally, the estimated treatment delivery times and the number of monitor units (MU) of each plan were evaluated. Results The dose distribution in the high dose region and the target volume DVH parameters (D98%, D50%, D2% and V95%) were similar for all three types of treatment plans, with deviations below 1% in most cases. Both IMRT MRL plans (orig. and red. PTV margins) showed similar homogeneity indices (HI), however worse values for the conformity index (CI) were also found when compared to VMAT. The IMRT MRL plans showed similar OAR sparing when the orig. PTV margins were used but a significantly better sparing was feasible when red. PTV margins were applied. Higher number of MU and longer predicted treatment delivery times were seen for both IMRT MRL plans. Conclusions A comparable plan quality between VMAT and IMRT MRL plans was achieved, when applying the same PTV margin. However, online MR-guided adaptive radiotherapy allows for a reduction of PTV margins. With a red. PTV margin, better sparing of the surrounding tissues can be achieved, while maintaining adequate target coverage. Nonetheless, longer treatment delivery times, characteristic for the IMRT technique, have to be expected.

scholarly journals The impact of tumour regression in locally advanced carcinoma cervix during external beam radiotherapy and the need for adaptive planning

2016 ◽  
Keyword(s):  
Ct Scan ◽  
Locally Advanced ◽  
Target Volume ◽  
Ct Images ◽  
Tumour Regression ◽  
Target Coverage ◽  
Carcinoma Cervix ◽  
Advanced Carcinoma ◽  
The Impact ◽  
Planning Ct

Aim: To study the impact of tumour regression occurring during IMRT for locally advanced carcinoma cervix and study dose distribution to target volume and OARs and hence the need for any replanning. Materials and Methods: 40 patients undergoing IM-IGRT and weekly chemotherapy were included in the study. After 36 Gy, a second planning CT-scan was done and target volume and OARs were recontoured. First plan (non-adaptive) was compared with second plan (adaptive plan) to evaluate whether it would still offer sufficient target coverage to the CTV and spare the OARs after having delivered 36 Gy. Finally new plan was created based on CT-images to investigate whether creating a new treatment plan would optimize target coverage and critical organ sparing. To measure the response of the primary tumour and pathologic nodes to EBRT, the differences in the volumes of the primary GTV and nodal GTV between the pretreatment and intratreatment CT images was calculated. Second intratreatment IMRT plans was generated, using the delineations of the intratreatment CT images. The first IMRT plan (based on the first CT-scan or non adaptive plan) was compared with second IMRT plan (based on the second CT-scan or adaptive plan). Results: 35% patients had regression in GTV in the range of 4.1% to 5%, 20% in the range of 1.1%-2%, 15% in the range of 2.1%-3% and 20% in the range of 6%-15%. There was significant mean decrease in GTV of 4.63 cc (p=0.000). There was a significant decrease in CTV on repeat CT done after 36 Gy by 23.31 cc (p=0.000) and in PTV by 23.31 cc (p=0.000). There was a statistically significant increase in CTV D98, CTV D95, CTV D50 and CTV D2 in repeat planning CT done after 36 Gy. There was no significant alteration in OARs doses. Conclusion: Despite tumour regression and increased target coverage in locally advanced carcinoma cervix after a delivery of 36 Gy there was no sparing of OARs. Primary advantage of adaptive RT seems to be in greater target coverage with non-significant normal tissue sparing.

scholarly journals Management of colorectal cancer in the era of COVID-19: Challenges and suggestions

2021 ◽  
Vol 104 (2) ◽  
pp. 003685042110106
Author(s):  
Walid Alam ◽  
Youssef Bouferraa ◽  
Yolla Haibe ◽  
Deborah Mukherji ◽  
Ali Shamseddine
Keyword(s):  
Colorectal Cancer ◽  
Treatment Protocols ◽  
Cancer Management ◽  
Increased Risk ◽  
Huge Impact ◽  
Treatment Plans ◽  
Virus Exposure ◽  
Risk Of Exposure ◽  
Colorectal Cancer Patients ◽  
The Impact

The Coronavirus (COVID-19) pandemic had a huge impact on all sectors around the world. In particular, the healthcare system has been subject to an enormous pressure that has surpassed its ability in many instances. Additionally, the pandemic has called for a review of our daily medical practices, including our approach to colorectal cancer management where treatment puts patients at high risk of virus exposure. Given their higher median age, patients are at an increased risk for severe symptoms and complications in cases of infection, especially in the setting of immunosuppression. Therefore, a review of the routine colorectal cancer practices is needed to minimize risk of exposure. Oncologists should weigh risk of exposure versus the patient’s oncologic benefits when approaching management. In addition, treatment protocols should be modified to minimize hospital visits and admissions while maintaining the same treatment efficacy. In this review, we will focus on challenges that colorectal cancer patients face during the pandemic, while highlighting the priority in each case. We will also discuss the evidence for potential modifications to existing treatment plans that could reduce infectious exposure without compromising care. Finally, we will discuss the impact of the socio-economic difficulties faced by Lebanese patients due to a poor economy toppled by an unexpected pandemic.

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