МРТ (магнитно-резонансная томография) играет важнейшую роль при планировании радиохирургического лечения. С помощью МРТ создается контур мишени для облучения и критических структур. Этот метод визуализации позволяет с высокой точностью определить границы патологического очага, однако существуют определенные факторы (неоднородность постоянного магнитного поля, нелинейность поля градиента и т. д.), из-за которых МРТ-изображения более восприимчивы к пространственным искажениям в сравнении с изображениями, полученными посредством компьютерной томографии (КТ). Определение геометрических искажений на МРТ-изображениях – важнейший этап обеспечения точности радиохирургического лечения. Один из способов определения дисторсии заключается в выполнении МРТ- и КТ-сканирования специального фантома, внутри которого находятся пластиковые стержни и дальнейшем анализе положения стержней на МРТ- и КТ-изображениях. Как правило, сравнение МРТ- и КТ-изображений фантома проводится визуально, что является довольно субъективной и неточной оценкой. Цель нашей работы заключалась в разработке программного обеспечения (ПО) для автоматизации выполнения данного теста по гарантии качества МРТ-исследования. С помощью разработанного программного обеспечения было проведено сравнение МРТ в двух режимах T1 и T2 с результатами КТ. Было показано, что отклонения МРТ Т1 и Т2 от КТ превышали 1 мм в 3.5 % случаев и 0.1 % соответственно. Был проведен анализ направлений и величин отклонений по всему объему фантома. Наибольшие отклонения наблюдаются в нижней правой части аксиального среза фантома и преимущественно направлены к верхней левой части среза в случае Т1 и к верху среза в случае Т2. Данные результаты позволяют проводить планирование радиохирургического лечения. Использование данного ПО в клинической практике поможет ускорить проведение теста и устранить субъективные оценки смещений.

Hypothalamic hamartoma (HH) is a dysplastic lesion fused with hypothalamus and followed by epilepsy, precocious puberty and behavioral disorders. Up to 50% of patients become free of seizures after surgery, but various complications occur in 1/4 of cases. Radiofrequency thermocoagulation, laser interstitial thermal therapy and stereotactic radiosurgery (SRS) are alternative treatment options.OBJECTIVE:To define the indications for SRS in patients with HH and to clarify the irradiation parameters.MATERIAL AND METHODS:Twenty-two patients with HH and epilepsy underwent SRS at the Moscow Gamma-knife Center. A retrospective analysis included 19 patients with sufficient follow-up data. Median age of patients was 11.5 years (range 1.3-25.8). The diameter of irradiated HHs ranged between 5.5 and 40.9 mm. In 8 (36%) cases, the volume of hamartoma exceeded 3 cm3. Mean prescribed dose was 18±2.0 Gy, mean prescribed isodose - 48±4.2%. Median follow-up period was 14.8 months (range 3.4 - 96.1).RESULTS:Three (15.8%) patients were free of seizures. One patient (5.3%) improved dramatically after treatment with compete resolution of generalized seizures and experienced only rare emotional seizures (Engel IB). Eleven (57.8%) patients reported lower incidence of seizures. Severity and incidence of seizures were the same in 4 patients (21.1%). The best results were achieved in mean target dose over 20-22 Gy, minimal target dose over 7-10 Gy, covering by the prescribed dose of at least 70-80% of hamartoma volume, as well as in patients with the prescribed dose of 12 Gy delivered to almost entire volume of tumor. None patient had any complications after SRS.CONCLUSION:SRS is safe regarding neurological, endocrine or visual disturbances. Careful patient selection for SRS makes it an effective option for HH-related epilepsy. The best candidates for SRS are children with seizures aged over 1 year, hamartoma <3 cm3 and area of fusion with hypothalamus <150 mm2.

This work presents experimental measurements performed using GAFChromic EBT3 dosimetry film and diamond detector T60019 to validate penEasy Monte Carlo based model developed previously for the Leksell Gamma Knife Perfexion. The relative dose profiles along X and Z coordinate axes, for each collimator size 4, 8, and 16 mm, and the relative output factors have been investigated. The penEasy model has been validated comparing the calculated output factors and dose profiles with the corresponding experimental results. The differences between the calculated output factors and the corresponding data measured with diamond detector were found to be 1.8 and 2.1% for the 8 and 4 mm collimator, respectively. Excellent agreement was found between penEasy and EBT3 results. The differences in the output factors were found to be 0.4% and −0.7% for the 8 and 4 mm collimators, respectively. The relative dose profiles were found to be in good agreement for both detectors and penEasy data. The gamma index test returns values (3%, 1 mm) < 1 for all profiles comparison calculated between penEasy and EBT3 film.

The study objective is to present the results of the treatment of metastatic brain patients by the staged radiosurgery with the Gamma Knife.Materials and methods. The retrospective analysis included 31 patients (13 men and 18 women) with brain metastases, whose radiosurgery treatment was carried out in 2 sessions. The operation was contraindicated in all patients due to the risk of neurological deficits or due to the high anesthesiological risk.Results. Local control of metastases growth was achieved in 31 (96.9 %) of 32 foci 3 months after treatment, and in 92.5 and 83.8 %, after 6 and 12 months, respectively. The age <50 years were associated with higher progression-free survival respectively. The median time of grade I–II radiation complications was 3.0 months, complications were observed in 11 (45.8 %) of 24 patients. Radiation complications of grade II (perifocal edema) were observed in 8 (33.3 %) patients, grade III (radionecrosis) – in 2 (8.3 %) patients. Overall survival at 6 and 12 months was 55.6 and 40.8 %, respectively (median 6.9 months), in patients receiving antitumor drug treatment – 80.0 and 56.8 %, respectively. All patients who did not received antitumor drug therapy died within 6 months.Conclusion. Two-stage radiosurgery, carried out in 2 sessions with an interval of 2–4 weeks, provides satisfactory local control with an acceptable level of post-radiation complications. This method of treatment can be used in patients with large brain metastases who are not subject to surgical treatment.

Central neurocytoma is a rare benign brain tumor. These tumors may be giant and accompanied by compression of ventricular system and surrounding structures. Modern treatment of brain neurocytoma includes extended resection and restoration of normal CSF circulation. Surgical treatment does not often lead to total resection of these tumors. Redo resection was preferred in patients with tumor progression for a long time. In the last decade, various authors report stereotactic irradiation for continued tumor growth to ensure local growth control. This study was aimed at evaluation of postoperative outcomes in patients with brain neurocytomas, as well as treatment of tumor progression in long-term period.OBJECTIVETo analyze recurrence-free survival in patients with brain neurocytomas, risk factors of recurrence-free survival, effectiveness of various treatments for tumor progression and delayed complications.MATERIAL AND METHODSLong-term postoperative follow-up data of patients with brain neurocytomas are reported in the manuscript. We analyzed recurrence-free survival and risk factors of recurrence-free survival, treatment outcomes in patients with progression of brain neurocytomas, long-term complications and their prevention.RESULTSFollow-up included 84 out of 115 patients with brain neurocytoma after surgical treatment in 2008-2017. Follow-up period ranged from 2 to 10 years (mean 6 years) after resection. Most patients had regression of neurological symptoms after surgery. Continued tumor growth within 12-96 months after surgery occurred in 26 (30.19%) out of 84 patients (19 cases after partial resection and 7 cases after total resection according to MRI data). Two-year recurrence-free survival was 94%, 5-year survival - 83%. Risk factors of continued tumor growth were resection quality and Ki-67 index. Redo resection was performed in 7 cases. Eleven patients underwent stereotactic irradiation for tumor progression. Indications for stereotactic irradiation of central neurocytoma are MR data on continued growth of lateral ventricle tumor without signs of ICH and CSF flow impairment. There were no cases of hemorrhage inside the residual tumor and CSF flow impairment in early postoperative period after redo resection. In all cases (n=11), stereotactic irradiation (mean follow-up 2.5 years) ensured satisfactory control of tumor growth with reduction of the neoplasm in 4 cases and no tumor growth in 7 cases.CONCLUSIONResection of central neurocytoma ensures long-term recurrence-free period. The main causes of tumor recurrence are partial resection and high proliferative activity (Ki-67 index over 5%). Redo resection is advisable for tumor progression followed by CSF flow impairment. In case of continued growth of neurocytoma without signs of intracranial hypertension, stereotactic irradiation with various fractionation modes ensures effective and safe control of tumor growth.

Glioma is one of the most common primary tumors among adults. Glioblastoma multiforme (GBM) is the most aggressive form of glioma with very poor prognosis. The median patient survival is about 15 months. Treatment of glioma requires a complex approach combining surgical resection, chemotherapy and radiation therapy. Definition of the tumor border is the important step of radiation therapy treatment planning. The rapid development of the diagnostic methods made it possible to address this challenging task. However, the optimal treatment volume is still a matter of debate due to the complex biological behavior and high invasiveness of the tumor. Furthermore, the subjective interpretation of the visual information by the expert existed. So far, the application of machine learning in image analysis is a promising tool for glioma segmentation in multimodal MRI imaging. This review aims to summarize recent works using machine learning in high — and low — grade glioma segmentation.

UNLABELLED:The study purpose was to evaluate the impact of gamma knife radiosurgery (GKRS) alone on the overall survival and rate of intracranial recurrences in brain metastasis patients.MATERIAL AND METHODS:Treatment outcomes in 502 patients (211 males and 291 females with 2782 brain metastases (BMs)) were retrospectively reviewed. Most patients (n=142; 28.2%) were diagnosed with breast cancer. Multiple BMs were detected in 259 patients (51.6%). The median of the total tumor volume and ВM number was 5.9 cm3 (0.09-44.5 cm3) and 4 (1-36), respectively. The mean marginal radiation dose was 21 Gy (15-24 Gy). The mean follow-up period was 10.6 months (0.2-47.2 months).RESULTS:The overall survival rate for 12 and 24 months was 37.6 and 19.1%, respectively. The median overall survival after GKRS was 8.6 months (95% confidence interval (CI) 7.0-10.0). Local control of metastatic lesions was achieved in 78.8% of patients. The median local recurrence-free survival was 6.8 months after radiosurgery. The development of new (distant) metastases was observed in 49.5% of patients. The median distant metastasis-free time was 8.8 months. The Karnofsky performance score (KPS) of ≥80 (HR 0.3935, 95% CI 0.2429-0.6376; p=0.0002), BM number of <3 (HR 0.6138, 95% CI 0.3993-0.9943; p=0.0269), and BMs of breast and lung cancers (HR 0.5442, 95% CI 0.3642-0.8071; p=0.0027) are predictors of better survival. In the case of intracranial metastasis recurrence, repeated radiosurgery provides the median overall survival of 19.6 months versus 9.6 months in patients without radiosurgery (HR 0.4026, 95% CI 0.2381-0.6809).CONCLUSION:Radiosurgical treatment of patients with multiple BMs provides the median overall survival of 8.6 months. A good functional status, non-extensive metastasis of the brain, and radiosensitive morphology of the primary tumor are the predictors of better survival. Repeated radiosurgical treatment for intracranial recurrences provides longer overall survival compared to that in patients without repeated radiosurgical treatment.

The dependence of the initial electron-beam parameters on absorbed dose distributions have been investigated using a CyberKnife radiotherapy accelerator (Accuray, United States). To describe the initial electron-beam characteristics, simulations of the linear electron accelerator are performed and the electron distributions in the beam of a linac output are analyzed. The radial distributions of electrons are assumed exponential, whereas the energy electron distributions are approximated by monoenergetic and rectangular spectra. There is no significant dependence of depth-dose curves in a phantom on the shape of the electron beam. Importantly, a clear dependence of the radiation field profile on the size of the electron beam is observed not just in the penumbra region, but also in the open part.

INTRODUCTION:Cerebral arteriovenous malformations (AVMs) are the congenital anomalies of development of cerebral vessels during the embryonic period. The conventional therapy for AVMs currently includes endovascular management, microneurosurgical resection, and stereotactic irradiation.MATERIAL AND METHODS:A total of 315 patients with brain AVMs were subjected to stereotactic radiotherapy in 2005-2011. 238 (76%) patients had previous subarachnoid hemorrhage (SAH) within different time (6 months to 5 years) before the therapy; 214 (68%) patients had headaches; 113 (36%) patients had focal neurological symptoms caused by localization; and 82 (26%) patients had seizures. Twenty-three patients were subjected to surgical resection of an intracerebral hematoma prior to radiotherapy and 119 (36%) patients received endovascular treatment including partial embolization of the stroma of AVM. 267 patients received single-fraction radiosurgical irradiation. In patients with large AVMs, we used the hypofractionation technique consisting in target irradiation with several (usually 2-7) fractions; the radiation dose per fraction exceeds 2 Gy. Forty-six patients were irradiated in the hypofractionation mode; two patients had a course of stereotactic radiotherapy in the standard fractionation mode. The marginal dose of radiosurgical irradiation was 13-30 Gy (the average dose was 24 Gy). The main group of patients (38 individuals) with large AVMs was treated using hypofractionation of 35 Gy per 5 fractions.RESULTS:Control angiography was carried out in 225 patients who had been followed up for at least 2 years after therapy showed that complete obliteration was achieved in 83% of cases. The rate of symptomatic radiation reactions was less than 10%. The higher risk of developing obliteration was observed for AVMs less than 2 cm3 in size at marginal doses more than 24 Gy. In the hypofractionation group consisting of 27 patients with complete follow-up data, obliteration was observed in 10 (37%) patients. The rate of symptomatic reactions was less than 35%.CONCLUSIONS:The radiosurgical method is a minimally invasive choice of treatment for patients with brain AVM, which allows one to achieve sufficiently high degree of obliteration with the minimum complication rate. The hypofractionation procedure is the method of choice for treating large AVMs. Stereotactic irradiation using the Novalis linear accelerator makes it possible to treat patients with AVMs of virtually any location and volume.

During recent decade development of frameless techniques of fixation enabled introduction of stereotactic radiation therapy in metastatic brain lesions and made possible irradiation of large foci involving or proximal to eloquent and critical brain areas. This paper focuses on comparative analysis of effectiveness of hypofractionation (HRST) and radiosurgery (SRS) using CyberKnife system in cerebral metastases. Since November 2009 till June 2011 54 patients with cerebral metastases were treated using CyberKnife system. Age of patients ranged between 25 and 77 years (mean 54 years). 16 patients received radiosurgical treatment (mean total dose was 22.5-35 Gy, number of fractions varied from 2 to 7, mean volume of irradiation was 22.69 cm3) and 8 patients were treated by HRST with RS of selected foci (mean total dose reached 23 and 30 Gy, mean volume of irradiation was 1.02 cm3 and 11.19 cm3, respectively). Indices of overall regression and stabilization of disease for HRST and SRS groups were 81% and 79%, respectively. With mean follow-up period of 12.3 (1-16.1) months median survival for SRS and HRST reached 6.38 (1-15.8) and 6.2 (0.2-16.1) months and median recurrence-free survival was 3.6 (1-13.6) and 5.5 (2-14.2) months, respectively. Obtained results confirmed biological advantages of fractionated stereotactic radiotherapy of large cerebral tumors in comparison with radiosurgery. Prospective studies with rigid criteria of inclusion are required to determine optimal dose/volume/fractionation interrelations in stereotactic radiation treatment of cerebral metastases.