SU-E-J-240: The Impact On Clinical Dose-Distributions When Using MR-Images Registered with Stereotactic CT-Images in Gamma Knife Radiosurgery

2014 ◽  
Vol 41 (6Part10) ◽  
pp. 213-213
Author(s):  
H Benmakhlouf ◽  
T Wangerid ◽  
T Kraepelien ◽  
P Forander
Keyword(s):  
Gamma Knife ◽  
Gamma Knife Radiosurgery ◽  
Ct Images ◽  
Mr Images ◽  
Dose Distributions ◽  
Clinical Dose ◽  
The Impact

Gamma Knife radiosurgery for trigeminal neuralgia: the impact of magnetic resonance imaging–detected vascular impingement of the affected nerve

2010 ◽  
Vol 113 (1) ◽  
pp. 53-58 ◽  
Author(s):  
Jason P. Sheehan ◽  
Dibyendu Kumar Ray ◽  
Stephen Monteith ◽  
Chun Po Yen ◽  
James Lesnick ◽  
...  
Keyword(s):  
Pain Relief ◽  
Mr Imaging ◽  
Trigeminal Neuralgia ◽  
Gamma Knife ◽  
Trigeminal Nerve ◽  
Gamma Knife Radiosurgery ◽  
Vascular Compression ◽  
Pain Intensity Score ◽  
The Impact

Object Trigeminal neuralgia is believed to be related to vascular compression of the affected nerve. Radiosurgery has been shown to be reasonably effective for treatment of medically refractory trigeminal neuralgia. This study explores the rate of occurrence of MR imaging–demonstrated vascular impingement of the affected nerve and the extent to which vascular impingement affects pain relief in a population of trigeminal neuralgia patients undergoing Gamma Knife radiosurgery (GKRS). Methods The authors performed a retrospective analysis of 106 cases involving patients treated for typical trigeminal neuralgia using GKRS. Patients with or without single-vessel impingement on CISS MR imaging sequences and with no previous surgery were included in the study. Pain relief was assessed according to the Barrow Neurological Institute (BNI) pain intensity score at the last follow-up. Degree of impingement, nerve diameter preand post-impingement, isocenter placement, and dose to the point of maximum impingement were evaluated in relation to the improvement of BNI score. Results The overall median follow-up period was 31 months. Overall, a BNI pain score of 1 was achieved in 59.4% of patients at last follow-up. Vessel impingement was seen in 63 patients (59%). There was no significant difference in pain relief between those with and without vascular impingement following GKRS (p > 0.05). In those with vascular impingement on MR imaging, the median fraction of vessel impingement was 0.3 (range 0.04–0.59). The median dose to the site of maximum impingement was 42 Gy (range 2.9–79 Gy). Increased dose (p = 0.019) and closer proximity of the isocenter to the site of maximum vessel impingement (p = 0.012) correlated in a statistically significant fashion with improved BNI scores in those demonstrating vascular impingement on the GKRS planning MR imaging Conclusions Vascular impingement of the affected nerve was seen in the majority of patients with trigeminal neuralgia. Overall pain relief following GKRS was comparable in those with and without evidence of vascular compression on MR imaging. In subgroup analysis of those with MR imaging evidence of vessel impingement of the affected trigeminal nerve, pain relief correlated with a higher dose to the point of contact between the impinging vessel and the trigeminal nerve. Such a finding may point to vascular changes affording at least some degree of relief following GKRS for trigeminal neuralgia.

scholarly journals Monte Carlo Dose Calculation Using MRI Based Synthetic CT Generated by Fully Convolutional Neural Network for Gamma Knife Radiosurgery

2021 ◽  
Vol 20 ◽  
pp. 153303382110464
Author(s):  
Jiankui Yuan ◽  
Elisha Fredman ◽  
Jian-Yue Jin ◽  
Serah Choi ◽  
David Mansur ◽  
...  
Keyword(s):  
Neural Network ◽  
Monte Carlo ◽  
Convolutional Neural Network ◽  
Gamma Knife ◽  
Learning Algorithm ◽  
Gamma Knife Radiosurgery ◽  
Dice Similarity Coefficient ◽  
Mr Images ◽  
The Difference ◽  
Synthetic Ct

The aim of this work is to study the dosimetric effect from generated synthetic computed tomography (sCT) from magnetic resonance (MR) images using a deep learning algorithm for Gamma Knife (GK) stereotactic radiosurgery (SRS). The Monte Carlo (MC) method is used for dose calculations. Thirty patients were retrospectively selected with our institution IRB’s approval. All patients were treated with GK SRS based on T1-weighted MR images and also underwent conventional external beam treatment with a CT scan. Image datasets were preprocessed with registration and were normalized to obtain similar intensity for the pairs of MR and CT images. A deep convolutional neural network arranged in an encoder–decoder fashion was used to learn the direct mapping from MR to the corresponding CT. A number of metrics including the voxel-wise mean error (ME) and mean absolute error (MAE) were used for evaluating the difference between generated sCT and the true CT. To study the dosimetric accuracy, MC simulations were performed based on the true CT and sCT using the same treatment parameters. The method produced an MAE of 86.6 ± 34.1 Hundsfield units (HU) and a mean squared error (MSE) of 160.9 ± 32.8. The mean Dice similarity coefficient was 0.82 ± 0.05 for HU > 200. The difference for dose-volume parameter D95 between the ground true dose and the dose calculated with sCT was 1.1% if a synthetic CT-to-density table was used, and 4.9% compared with the calculations based on the water-brain phantom.

scholarly journals A robustness check procedure for hypofractionated Gamma Knife radiosurgery

2018 ◽  
Vol 129 (Suppl1) ◽  
pp. 140-146
Author(s):  
Joshua Chiu ◽  
Steve Braunstein ◽  
Jean Nakamura ◽  
Philip Theodosopoulos ◽  
Penny Sneed ◽  
...  
Keyword(s):  
Gamma Knife ◽  
Treatment Plan ◽  
Gamma Knife Radiosurgery ◽  
Target Coverage ◽  
Quality Assurance Procedure ◽  
Dose Distributions ◽  
Treatment Delivery ◽  
Maximum Tolerance ◽  
Check Procedure ◽  
Robustness Check

OBJECTIVEInterfractional residual patient shifts are often observed during the delivery of hypofractionated brain radiosurgery. In this study, the authors developed a robustness treatment planning check procedure to assess the dosimetric effects of residual target shifts on hypofractionated Gamma Knife radiosurgery (GKRS).METHODSThe residual patient shifts were determined during the simulation process immediately after patient immobilization. To mimic incorporation of residual target shifts during treatment delivery, a quality assurance procedure was developed to sample and shift individual shots according to the residual uncertainties in the prescribed treatment plan. This procedure was tested and demonstrated for 10 hypofractionated GKRS cases.RESULTSThe maximum residual target shifts were less than 1 mm for the studied cases. When incorporating such shifts, the target coverage varied by 1.9% ± 2.2% (range 0.0%–7.1%) and selectivity varied by 3.6% ± 2.5% (range 1.1%–9.3%). Furthermore, when incorporating extra random shifts on the order of 0.5 mm, the target coverage decreased by as much as 7%, and nonisocentric variation in the dose distributions was noted for the studied cases.CONCLUSIONSA pretreatment robustness check procedure was developed and demonstrated for hypofractionated GKRS. Further studies are underway to implement this procedure to assess maximum tolerance levels for individual patient cases.

Stagnant Venous Outflow Predicts Brain Arteriovenous Malformation Obliteration After Gamma Knife Radiosurgery Without Prior Intervention

Neurosurgery ◽  
2019 ◽  
Vol 87 (2) ◽  
pp. 338-347 ◽  
Author(s):  
Yong-Sin Hu ◽  
Cheng-Chia Lee ◽  
Hsiu-Mei Wu ◽  
Huai-Che Yang ◽  
Te-Ming Lin ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Digital Subtraction Angiography ◽  
Gamma Knife ◽  
Gamma Knife Radiosurgery ◽  
Magnetic Resonance Images ◽  
Venous Stasis ◽  
Digital Subtraction ◽  
Venous Outflow ◽  
Therapeutic Decisions ◽  
The Impact

Abstract BACKGROUND Gamma Knife radiosurgery (GKRS) obliterates 65% to 82% of brain arteriovenous malformations (BAVMs). OBJECTIVE To explore the impact of hemodynamics on GKRS outcomes. METHODS We retrospectively (2011-2017) included 98 patients with BAVMs who had received GKRS alone. Two evaluators, blinded to the outcomes, analyzed the pre-GKRS angiography and magnetic resonance images to obtain the morphological characteristics and quantitative digital subtraction angiography (QDSA) parameters. The venous stasis index was defined as the inflow gradient divided by the absolute value of the outflow gradient. Patients’ follow-up magnetic resonance or digital subtraction angiography images were evaluated for the presence of complete obliteration (CO). Cox regression and Kaplan–Meier analyses were conducted to determine the correlations between the parameters and outcomes. RESULTS Among the 98 patients, 63 (63.4%) achieved CO after GKRS at a median latency period of 31 mo. In multivariable analyses with adjustments for age and sex, increased BAVM volume (hazard ratio (HR) 0.949, P = .022) was an independent characteristic predictor, and venous stenosis (HR 2.595, P = .009), venous rerouting (HR 0.375, P = .022), and larger stasis index (HR 1.227, P = .025) were independent angiographic predictors of CO. BAVMs with a stasis index of >1.71 had a higher 36-mo probability of CO than those with a stasis index of ≤1.71 (61.1% vs 26.7%, P < .001). CONCLUSION BAVMs with a larger stasis index, indicating more stagnant venous outflow, may predict obliteration after GKRS. QDSA analysis may help in predicting BAVM treatment outcomes and making therapeutic decisions.

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.

scholarly journals Dosimetric study between a single isocenter dynamic conformal arc therapy technique and Gamma Knife radiosurgery for multiple brain metastases treatment: impact of target volume geometrical characteristics

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Michel Chea ◽  
Karen Fezzani ◽  
Julian Jacob ◽  
Marguerite Cuttat ◽  
Mathilde Croisé ◽  
...  
Keyword(s):  
Brain Metastases ◽  
Gamma Knife ◽  
Irradiation Time ◽  
Geometric Characteristic ◽  
Gamma Knife Radiosurgery ◽  
Major Axis ◽  
Target Volume ◽  
Gradient Index ◽  
Dynamic Conformal Arc Therapy ◽  
The Impact

Abstract Purpose To compare linac-based mono-isocentric radiosurgery with Brainlab Elements Multiple Brain Mets (MBM) SRS and the Gamma Knife using a specific statistical method and to analyze the dosimetric impact of the target volume geometric characteristics. A dose fall-off analysis allowed to evaluate the Gradient Index relevancy for the dose spillage characterization. Material and methods Treatments were planned on twenty patients with three to nine brain metastases with MBM 2.0 and GammaPlan 11.0. Ninety-five metastases ranging from 0.02 to 9.61 cc were included. Paddick Index (PI), Gradient Index (GI), dose fall-off, volume of healthy brain receiving more than 12 Gy (V12Gy) and DVH were used for the plan comparison according to target volume, major axis diameter and Sphericity Index (SI). The multivariate regression approach allowed to analyze the impact of each geometric characteristic keeping all the others unchanged. A parallel study was led to evaluate the impact of the isodose line (IDL) prescription on the MBM plan quality. Results For mono-isocentric linac-based radiosurgery, the IDL around 70–75% was the best compromise found. For both techniques, the GI and the dose fall-off decreased with the target volume. In comparison, PI was slightly improved with MBM for targets < 1 cc or SI > 0.78. GI was improved with GP for targets < 2.5 cc. The V12Gy was higher with MBM for lesions > 0.4 cc or SI < 0.84 and exceeded 10 cc for targets > 5 cc against 6.5 cc with GP. The presence of OAR close to the PTV had no impact on the dose fall off values. The dose fall-off was higher for volumes < 3.8 cc with GP which had the sharpest dose fall-off in the infero-superior direction up to 30%/mm. The mean beam-on time was 94 min with GP against 13 min with MBM. Conclusions The dose fall-off and the V12Gy were more relevant indicators than the GI for the low dose spillage assessment. Both evaluated techniques have comparable plan qualities with a slightly improved selectivity with MBM for smaller lesions but with a healthy tissues sparing slightly favorable to GP at the expense of a considerably longer irradiation time. However, a higher healthy tissue exposure must be considered for large volumes in MBM plans.

scholarly journals Gamma Knife Stereotactic Radiosurgery (GKS) for the treatment of meningiomas – a study of 550 cases

2015 ◽  
Vol 62 (2) ◽  
pp. 130-134
Author(s):  
Radu Perin ◽  
◽  
Rodica Stempurszki ◽  
Vasile Ciubotaru ◽  
Ligia Tataranu ◽  
...  
Keyword(s):  
Gamma Knife ◽  
Gamma Knife Radiosurgery ◽  
Daily Practice ◽  
University Hospital ◽  
Response To Treatment ◽  
Benign Tumors ◽  
Long Time ◽  
Remnant Tumor ◽  
Gamma Knife Stereotactic Radiosurgery ◽  
The Impact

Introduction. Meningiomas are benign tumors which originate from the cells of the arachnoid granules. Meningiomas represent a special pathologic entity for neurosurgeons due to the fact that they can grow silently for a long time, and can affect important neural structures when they become symptomatic. The total resection of meningiomas is curative. For the meningiomas which are not surgically accessible and for reoccurrence. Gamma Knife radiosurgery (GKS) is a very efficient solution. Materials and methods. The study below presents the experience of the authors regarding the use of GKS for the treatment of meningiomas. The authors focus on a population of 550 patients diagnosed and treated for meningiomas over a period of 10 years at the „Bagdasar-Arseni“ University Hospital in Bucharest. This study compares the impact of GKS when performed alone or in association with open microneurosurgery. The authors assessed patients with tumors ranging between 1 and 42 cm3 in volume. GKS is used successfully to treat meningiomas, both independently and in association with open microsurgery. Results. The major complications of the treatment are represented by lack of response to treatment (7% of patients) and transient cerebral edema (22% of patients). A disturbing phenomenon happens in a few meningiomas of the convexity, with malignant edema (<1%). Conclusion. Given the multiple advantages it has, GKS is right now the tip of the spear regarding the therapeutical methods available for meningiomas. These tumors usually are benign in nature; however, a small percentage are malignant. Often, meningiomas cause no symptoms and require no immediate treatment. But the growth of benign meningiomas can cause serious problems. In some cases, such growth can be fatal. Typically, symptomatic meningiomas are treated with either radiosurgery or conventional surgery. When the tumors met in daily practice are larger than the therapeutical resources of the devices used for GKS, an open microsurgical approach may be attempted followed by stereotactic irradiation of the remnant tumor.

Changes of MR Images in Arteriovenous Malformations of Brain after Gamma-knife Radiosurgery

1999 ◽  
Vol 41 (6) ◽  
pp. 1063
Author(s):  
Eui Jong Kim ◽  
Woo Suk Choi ◽  
Young Jin Im ◽  
Joo Hyeong Oh ◽  
Kyung Nam Ryu ◽  
...  
Keyword(s):  
Gamma Knife ◽  
Arteriovenous Malformations ◽  
Gamma Knife Radiosurgery ◽  
Mr Images

Gamma knife radiosurgery for melanoma/renal cell carcinoma brain metastases 1 -10 lesions with optimized margin dose: Improved tumor control and survival

2007 ◽  
Vol 25 (18_suppl) ◽  
pp. 8581-8581
Author(s):  
A. O. Fregene ◽  
P. Mobit ◽  
L. Zamorano ◽  
F. Diaz ◽  
M. Guthikonda ◽  
...  
Keyword(s):  
Renal Cell Carcinoma ◽  
Brain Metastases ◽  
Cell Carcinoma ◽  
Gamma Knife ◽  
Renal Cell ◽  
Karnofsky Performance Status ◽  
Gamma Knife Radiosurgery ◽  
Brain Lesions ◽  
Tumor Control ◽  
The Impact

8581 Background: Radioresistant brain metastases melanoma/renal cell carcinoma cause significant morbidity and mortality: response to whole brain external beam radiotherapy (WBXRT) is minimal, chemotherapy role is investigative, and surgery has its indications and limitations. Reports of survival with Gamma Knife Radiosurgery (GK) is mixed. Reports indicate that 80 to 90% of tumor failure following GK is in the margin: recent multivariate analyses indicate tumor control dependence on margin dose. This study evaluates the impact of better control of brain lesions and consequent reduction of CNS death on overall survival. Methods: Between 10/2002 and 12/2005, 24 consecutive patients with melanoma and renal cell carcinoma male/female radio 14/10, 20 melanoma and 4 renal cell were treated by WBXRT followed by GK radiosurgery utilizing optimized margin dose. Dose was (16 - 20 Gy) to the 50% line with adequate margin to reduce systematic and other associated errors. This was achieved by combining the separate errors associated with the procedure; extent of tumor infiltration beyond gross tumor margin; GK/procedure mechanical precision limitations; MRI image transfer spatial limitations and beam profile margin dose sensitivity. Karnofsky Performance status was 70 - 90%. Follow-up period was 52 months. Results: The mean survival period for the 24 patients with 1 - 10 lesions was 14.11 months: median survival by Kaplan-Meier was 12.0 months. This result is a significant improvement on the 5.5 months reported earlier from this institution for 1 - 5 lesions treated with non-optimized GK dosage; and data by Lavin, et al, at 8 months for predominantly solitary lesions. Conclusions: Melanoma and renal cell carcinoma brain metastases respond very well to GK radiosurgery with optimized margin dose: mean survival for these patients with 1 -3 and 4 - 10 lesions is 14.11 months and comparable to the survival of patients with brain metastases from lung and breast patients: More studies along this line are called for. Patients with multiple metastatic brain lesions from melanoma and renal cell cancers stand to benefit. No significant financial relationships to disclose.

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