Apparatus dependence of normal brain tissue dose in stereotactic radiosurgery for multiple brain metastases

2011 ◽  
Vol 114 (6) ◽  
pp. 1580-1584 ◽  
Author(s):  
Lijun Ma ◽  
Paula Petti ◽  
Brian Wang ◽  
Martina Descovich ◽  
Cynthia Chuang ◽  
...  
Keyword(s):  
Single Case ◽  
Normal Brain ◽  
Target Dose ◽  
Brain Volumes ◽  
Contrast Enhanced Ct ◽  
Dose Volume ◽  
Dose Planning ◽  
Target Volumes ◽  
Gamma Knife Perfexion ◽  
Relationship Of

Object Technical improvements in commercially available radiosurgery platforms have made it practical to treat a large number of intracranial targets. The goal of this study was to investigate whether the dose to normal brain when planning radiosurgery to multiple targets is apparatus dependent. Methods The authors selected a single case involving a patient with 12 metastatic lesions widely distributed throughout the brain as visualized on contrast-enhanced CT. Target volumes and critical normal structures were delineated with Leksell Gamma Knife Perfexion software. The imaging studies including the delineated contours were digitally exported into the CyberKnife and Novalis multileaf collimator–based planning systems for treatment planning using identical target dose goals and dose-volume constraints. Subsets of target combinations (3, 6, 9, or 12 targets) were planned separately to investigate the relationship of number of targets and radiosurgery platform to the dose to normal brain. Results Despite similar target dose coverage and dose to normal structures, the dose to normal brain was strongly apparatus dependent. A nonlinear increase in dose to normal brain volumes with increasing number of targets was also noted. Conclusions The dose delivered to normal brain is strongly dependent on the radiosurgery platform. How general this conclusion is and whether apparatus-dependent differences are related to differences in hardware design or differences in dose-planning algorithms deserve further investigation.

Advances in the radiosurgical treatment of large inoperable arteriovenous malformations

2007 ◽  
Vol 23 (6) ◽  
pp. E6 ◽  
Author(s):  
Jesse Jones ◽  
Sunyoung Jang ◽  
Christopher C. Getch ◽  
Alan G. Kepka ◽  
Maryanne H. Marymont
Keyword(s):  
Arteriovenous Malformations ◽  
Latency Period ◽  
Peripheral Dose ◽  
Target Delineation ◽  
Dose Volume ◽  
Dose Planning ◽  
Target Volumes ◽  
Risk Of Hemorrhage ◽  
Higher Doses

✓ Radiosurgery has proven useful in the treatment of small arteriovenous malformations (AVMs) of the brain. However, the volume of healthy tissue irradiated around large lesions is rather significant, necessitating reduced radiation doses to avoid complications. As a consequence, this can produce poorer obliteration rates. Several strategies have been developed in the past decade to circumvent dose–volume problems with large AVMs, including repeated treatments as well as dose, and volume fractionation schemes. Although success on par with that achieved in lesions smaller than 3 ml remains elusive, improvements over the obliteration rate, the complication rate or both have been reported after conventional single-dose stereotactic radiosurgery (SRS). Radiosurgery with a marginal dose or peripheral dose < 15 Gy rarely obliterates AVMs, yet most lesions diminish in size posttreatment. Higher doses may then be reapplied to any residual nidi after an appropriate follow-up period. Volume fractionation divides AVMs into smaller segments to be treated on separate occasions. Doses > 15 Gy irradiate target volumes of only 5–15 ml, thereby minimizing the radiation delivered to the surrounding brain tissue. Fewer adverse radiological effects with the use of fractionated radiosurgery over standard radiosurgery have been reported. Advances in AVM localization, dose delivery, and dosimetry have revived interest in hypofractionated SRS. Investigators dispensing ≥ 7 Gy per fraction minimum doses have achieved occlusion with an acceptable number of complications in 53–70% of patients. The extended latency period between treatment and occlusion, about 5 years for emerging techniques (such as salvage, staged volume, and hypofractionated radiotherapy), exposes the patient to the risk of hemorrhage during that period. Nevertheless, improvements in dose planning and target delineation will continue to improve the prognosis in patients harboring inoperable AVMs.

scholarly journals Volumetric and dosimetric impact of Post-Surgical MRI guided radiotherapy for Glioblastoma: A pilot study

BJR|Open ◽  
2021 ◽  
Author(s):  
Marcus Tyyger ◽  
Suchandana Bhaumik ◽  
Michael Nix ◽  
Stuart Currie ◽  
Chandran Nallathambi ◽  
...  
Keyword(s):  
Normal Brain ◽  
Dose Volume Histogram ◽  
Target Delineation ◽  
Post Surgery ◽  
Dose Volume ◽  
Target Volumes ◽  
Ct Simulation ◽  
Organ At Risk ◽  
Mri Guided ◽  
Dedicated Mri

Objectives: Glioblastoma (GBM) radiotherapy (RT) target delineation requires MRI, ideally concurrent with CT simulation (pre-RT MRI). Due to limited MRI availability, <72 h post-surgery MRI is commonly used instead. Whilst previous investigations assessed volumetric differences between post-surgical and pre-RT delineations, dosimetric impact remains unknown. We quantify volumetric and dosimetric impact of using post-surgical MRI for GBM target delineation. Methods: Gross tumour volumes (GTVs) for five GBM patients receiving chemo-RT with post-surgical and pre-RT MRIs were delineated by three independent observers. Planning target volumes (PTVs) and RT plans were generated for each GTV. Volumetric and dosimetric differences were assessed through: absolute volumes, volume-distance histograms, and dose-volume histogram statistics. Results: Post-surgical MRI delineations had significantly (p < 0.05) larger GTV and PTV volumes (median 16.7 and 64.4 cm3 respectively). Post-surgical RT plans, applied to pre-RT delineations, had significantly decreased (p < 0.01) median PTV doses (ΔD99% = −8.1 Gy and ΔD95% = −2.0 Gy). Median organ at risk (OAR) dose increases (brainstem ΔD5% =+0.8, normal brain mean dose =+2.9 and normal brain ΔD10% = 5.3 Gy) were observed. Conclusion: Post-surgical MRI delineation significantly impacted RT planning, with larger normal-appearing tissue volumes irradiated and increased OAR doses, despite a reduced coverage of the pre-RT defined target. Advances in knowledge: We believe this is the first investigation assessing the dosimetric impact of using post-surgical MRI for GBM target delineation. It highlights the potential of significantly degraded RT plans, showing the clinical-need for dedicated MRI for GBM RT.

A comprehensive evaluation of the quality and complexity of prostate IMRT and VMAT plans generated by an automated inverse planning tool

2021 ◽  
pp. 1-7
Author(s):  
Dean Wilkinson ◽  
Kelly Mackie ◽  
Dean Novy ◽  
Frances Beaven ◽  
Joanne McNamara ◽  
...  
Keyword(s):  
Dose Level ◽  
Comprehensive Evaluation ◽  
Volumetric Modulated Arc Therapy ◽  
Intensity Modulated Radiotherapy ◽  
Target Volume ◽  
Planning Tool ◽  
Inverse Planning ◽  
Dose Planning ◽  
Target Volumes ◽  
Lymph Node Irradiation

Abstract Introduction: The Pinnacle3 Auto-Planning (AP) package is an automated inverse planning tool employing a multi-sequence optimisation algorithm. The nature of the optimisation aims to improve the overall quality of radiotherapy plans but at the same time may produce higher modulation, increasing plan complexity and challenging linear accelerator delivery capability. Methods and materials: Thirty patients previously treated with intensity-modulated radiotherapy (IMRT) to the prostate with or without pelvic lymph node irradiation were replanned with locally developed AP techniques for step-and-shoot IMRT (AP-IMRT) and volumetric-modulated arc therapy (AP-VMAT). Each case was also planned with VMAT using conventional inverse planning. The patient cohort was separated into two groups, those with a single primary target volume (PTV) and those with dual PTVs of differing prescription dose levels. Plan complexity was assessed using the modulation complexity score. Results: Plans produced with AP provided equivalent or better dose coverage to target volumes whilst effectively reducing organ at risk (OAR) doses. For IMRT plans, the use of AP resulted in a mean reduction in bladder V50Gy by 4·2 and 4·7 % (p ≤ 0·01) and V40Gy by 4·8 and 11·3 % (p < 0·01) in the single and dual dose level cohorts, respectively. For the rectum, V70Gy, V60Gy and V40Gy were all reduced in the dual dose level AP-VMAT plans by an average of 2·0, 2·7 and 7·3 % (p < 0·01), respectively. A small increase in plan complexity was observed only in dual dose level AP plans. Findings: The automated nature of AP led to high quality treatment plans with improvement in OAR sparing and minimised the variation in achievable dose planning metrics when compared to the conventional inverse planning approach.

RADT-20. SINGLE INSTITUTION REVIEW OF LARGE VOLUME HIGH GRADE GLIOMA PATIENTS TREATED WITH RADIOTHERAPY

2021 ◽  
Vol 23 (Supplement_6) ◽  
pp. vi45-vi45
Author(s):  
Vishal Manik ◽  
Angela Swampillai ◽  
Omar Al-Salihi ◽  
Kazumi Chia ◽  
Lucy Brazil
Keyword(s):  
Large Volume ◽  
Brain Volume ◽  
Collaborative Study ◽  
High Grade Glioma ◽  
Study Data ◽  
Molecular Profile ◽  
Normal Brain ◽  
High Grade ◽  
Total Brain Volume ◽  
Dose Volume

Abstract AIM Not uncommonly, we come across significantly large high grade glioma cases (HGGs). With standard delineation protocols, we end up irradiating a large volume of normal brain. Emami & QUANTEC data define normal brain tolerance doses, however they are often of limited use in clinic practice. Thus, we reviewed our patients with significant tumor volumes to derive a safe dose/ volume level for brain. METHODOLOGY Patients with HGGs over the last 3 years were extracted from Mosaiq™ information system. The output was sorted with respect to clinical target volumes from lowest to highest. The top 25 percentile i.e. patients with a CTV of &gt; 412cc (n=53) were identified for this study. Data was collected with respect to clinical, tumor characteristics and radiotherapy parameters. RESULTS Median age of population was 53 and majority (n=38) were males. Nine patients had multi-focal tumors while six had bilateral extension. Majority of the study group had Glioblastoma Multiforme (n=44), whereas 6 had Grade 3 tumors. Most of the patients could only have a biopsy (n=27). Molecular profile showed 42 were Isocitrate-Dehydrogenase negative and 26 were unmethylated tumors. Stupp’s & Perry’s regimen were the commonly used protocols, however patients (n=7) with significant volumes near critical structures were treated with doses in the range of 50.4 – 55Gy in 30 fractions. The CTV volumes in the population ranged from 412 – 1223 cc while total brain volume range was 1112 – 1667 cc. Median of 43.5% of brain volume was covered in the PTV, while median of 5% of brain volume outside the PTV was treated to BED2 of 100Gy. Median survival was 12.4 months. CONCLUSION Our study shows reasonable tolerance of radiotherapy doses of &gt; 50 Gy to larger volumes of brain. We propose a multi-center collaborative study to derive a new standardized dose volume tolerance.

Microsurgical exposure of the petrous portion of the carotid artery

1977 ◽  
Vol 47 (5) ◽  
pp. 713-726 ◽  
Author(s):  
Wayne S. Paullus ◽  
T. Glenn Pait ◽  
Albert L. Rhoton
Keyword(s):  
Carotid Artery ◽  
Single Case ◽  
Collateral Flow ◽  
Content Type ◽  
Cervical Portion ◽  
Temporary Occlusion ◽  
Petrous Portion ◽  
Tensor Tympani Muscle ◽  
Trigeminal Nerves ◽  
Relationship Of

✓ Occlusion of the cervical portion of the internal carotid artery (ICA) has been treated by vein graft bypass from the common carotid to the supraclinoid segment. However, this procedure has the disadvantages of requiring temporary occlusion of collateral flow, the short length of ICA available for anastomosis, and the retraction required for exposure of the supraclinoid area. In an attempt to find a more suitable bypass site for grafting, the petrous portion of 50 carotid arteries was studied in cadavers. It was found that there was a 1-cm length of the horizontal segment of the petrous carotid that could be exposed in the floor of the middle fossa lateral to the trigeminal nerve. This segment was covered by dura only or a thin layer of cartilage in approximately half of the specimens. In the remainder, there was often a thin shell of bone covering the artery, which could be drilled away. The petrous portion of the carotid artery had branches in only 38% of specimens, a Vidian branch in 30%, and a periosteal branch in 8%. The carotico-tympanic artery, previously reported to be the most common branch, was not found in a single case. These branches allow the retrograde flow needed to maintain the patency of this segment following proximal occlusions. The relationship of the carotid artery to structures that might be injured in exposing the petrous portion of the artery was reviewed; these structures include the cochlea, middle ear, Eustachian tube, tensor tympani muscle, geniculate ganglion, and facial, greater petrosal, and trigeminal nerves.

The effect of set-up uncertainties, contour changes, and tissue inhomogeneities on target dose-volume histograms

2002 ◽  
Vol 29 (10) ◽  
pp. 2305-2318 ◽  
Author(s):  
B. C. John Cho ◽  
Marcel van Herk ◽  
Ben J. Mijnheer ◽  
Harry Bartelink
Keyword(s):  
Target Dose ◽  
Dose Volume Histograms ◽  
Dose Volume ◽  
Set Up
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