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Showing 25 results for Surgery
M.t. Bahreyni Toossi, A.r. Khoshbin Khoshnazar,
Volume 2, Issue 2 (9-2004)
Abstract
Background: Radiosurgery is a focal brain irradiation technique that delivers, usually in a single session, high dose of ionizing radiation. The presence of lateral electronic disequilibrium and steep dose gradients in small fields demands special attention to the selection of a suitable detector with respect to its size, composition and response. Materials and Methods : Small circular fields were produced by home-made collimators attached to a 9MV Neptun 10 PC linac ranging from 12.5mm to 25 mm at isocenter level in 2.5 mm
increment. Stereotactic beam data including percent depth dose, off axis ratio and output factor were measured using p-type silicon chip detector in a water phantom. Beam data were plotted for all available collimator sizes. Results: Percent depth dose values at depth of 100 cm show 10 percent increase with enlargement of the field sizes from 12.5 mm to 25mm. Small overestimation of output factor has been observed using diode detector. Conclusion: It is concluded for stereotactic radiosurgery with higher energy photon diode
detector could be a good and reasonable choice to measure percent depth dose and off axis ratio. Regarding the output factor, it is better to compare the results with those obtained by other
detectors. Iran . J. Radiat. Res., 2004 2 (2): 79-84
M.t. Bahreyni Toossi, A.r. Khoshbin Khoshnazar,
Volume 2, Issue 3 (12-2004)
Abstract
Background: A set of hardware stereotactic radiosurgery is designed and constructed. The scope of this article is to describe how we have designed and developed stereotactic collimation assembly for a 9 MV Neptun 10 PC linac. Materials and methods: One collimator holder and six collimators were made, with their
radiation field diameter between 12.5 mm to 25 mm at isocenter level. Beam data, such as depth dose percent, off axis ratio and output factor of the collimators were measured. Isocentric
accuracy and dose delivery, accuracy tests were also performed using locally made isocentric alignment control device, target simulator and plexiglass phantom. Results: Average isocenter shifts resulting from gantry and couch motion were respectively 1.5 mm and 2 mm. Simulating a stereotactic radiosurgery with the help of a plexiglass phantom showed less than one percent radiation leakage to critical organs such as eyes and thyroid. Conclusion: Stereotactic collimation assembly in conjunction with the rest of constructed equipments can be employed to set up SRS treatment, provided safety and to compensate operations are taken into account. Iran . J. Radiat. Res., 2004 2 (3): 135-140
K.n. Esnaashari, M. Allahverdi, H. Gharaati, M. Shahriari,
Volume 5, Issue 1 (6-2007)
Abstract
Background: Stereotactic radiosurgery is an important clinical tool for the treatment of small lesions in the brain, including benign conditions, malignant and localized metastatic tumors. A dosimetry study was performed for Elekta ‘Synergy S ’ as a dedicated Stereotactic radiosurgery unit, capable of generating circular radiation fields with diameters of 1-5 cm at isocentre using the BEAM/EGS4 Monte Carlo code. Materials and Methods: The linear accelerator Elekta “Synergy S” equipped with a set of 5 circular collimators from 10 mm to 50 mm in diameter at isocentre distance was used. The cones were inserted in a base plate mounted on the collimator linac head . A PinPoint chamber and Wellhofer water tank chamber were selected for clinical dosimetry of 6 MV photon beams. The results of simulations using the Monte Carlo system BEAM/EGS4 to model the beam geometry were compared with dose measurements . Results: An excellent agreement was found between Monte Carlo calculated and measured percentage depth dose and lateral dose profiles which were performed in water phantom for circular cones with 1, 2, 3, 4 and 5 cm in diameter. The comparison between calculation and measurements showed up to 0.5 % or 1mm difference for all field sizes. The penumbra (80-20%) results at 5 cm depth in water phantom and SSD=95 ranged from 1.5 to 2.1 mm for circular collimators with diameter 1 to 5 cm . Conclusion: This study showed that BEAMnrc code has been accurate in modeling Synergy S linear accelerator equipped with circular collimators.
Dr. P.k. Bagri, D. Singh, P. Kumari, S. Kumari, S. Beniwal, H.s. Kumar,
Volume 12, Issue 4 (10-2014)
Abstract
Background: Inflammatory myofibroblastic tumor (IMT) is a tumor composed of myofibroblasts and a mixed inflammatory infiltrate that rarely undergoes malignant transformation. The most common sites of involvement include the lung, liver and orbit, but it has been reported to occur in nearly every site of the body, including oral cavity and soft tissue. Although common in other sites, such a tumor in rarer location including inguinal region is likely to be missed/misdiagnosed and hence need to be reported. Case Report: We present an unusual case of a 50 year old male with bilateral inguinal swelling attended our institute few days back with history of local excision twice, but still showing recurrence. He was treated by wide local excision with bilateral orchiectomy this time. Histopathological report revealed inflammatory myofibroblastic tumor with malignant transformation. Adjuvant radiotherapy was also given and patient taken in followup. At one year of serial follow-ups, the patient is disease-free both clinically and on investigations, indicating successful combined surgery and radiotherapy in the treatment of malignant IMT. Conclusion: IMT of the inguinal region is very rare. Its clinical presentation may resemble malignant tumor, so IMT should be kept as differential diagnosis. The recommended treatment is complete surgical resection with adjuvant corticosteroid. Adjuvant radiotherapy may be considered depending upon the location of the tumor.
Dr. T. Veselsky, J. Novotny Jr., V. Pastykova,
Volume 16, Issue 1 (1-2018)
Abstract
Background: To determine the basic physical and dosimetric properties of a new synthetic single-crystal diamond detector and its application for relative small field dosimetry. Materials and Methods: The pre-irradiation dose required to stabilize detector response, dose rate dependence, photon and electron energy dependence, temperature dependence and angular dependence of MicroDiamond detector response were evaluated. Output factors on Leksell Gamma Knife Perfexion and on CyberKnife were measured to assess detector feasibility in small radiation field dosimetry. For all measurements, the detector was connected to Unidos electrometer set to 0 voltage. Results: Relative output factors measured on Leksell Gamma Knife Perfexion for 4 mm and 8 mm collimators were in agreement with Monte Carlo reference values from the manufacturer, with deviations of 0.3% and 2.1%, respectively. For CyberKnife and fixed circular collimators, the difference in output factor values did not exceed 2% from vendor-supplied values, even for the smallest radiation field with a diameter of 5 mm. Conclusion: Our results indicate that the MicroDiamond detector is a promising tool for relative small field dosimetry. For output factor measurements on Leksell Gamma Knife Perfexion and CyberKnife, the detector can be used with minimal response corrections applied (correction factors not larger than 2%).
J. Zhang, S.g. Wu, J.y. Sun, F.y. Li, X.x. Guan, Dr. Z.y. He,
Volume 16, Issue 3 (7-2018)
Abstract
Background: To compare the following techniques for hypofractionated whole-breast irradiation (WBI) with simultaneous integrated boost (SIB) after breast-conserving surgery (BCS): three-dimensional conformal radiation therapy plus electron boost (3DCRT-EB), intensity-modulated radiation therapy (IMRT) plus EB (IMRT-EB), field-in-field IMRT plus EB (FIF-IMRT-EB), FIF-IMRT plus IMRT boost (FIF-IMRT-IB), IMRT plus IMRT boost (IMRT-IB), and volumetric-modulated arc therapy (VMAT) plus VMAT boost (VMAT-VB). Materials and Methods: Twenty patients with left breast cancer were enrolled. The prescribed dose was 40.05 Gy in 15 fractions to the whole breast and an SIB to the tumor bed of 3.2 Gy/fraction (total, 48 Gy). Target-volume coverage, dose-conformity index, homogeneity index (HI), doses to organs at risk (OAR), and costs were compared. Results: FIF-IMRT-EB performed the best, while FIF-IMRT-IB, IMRT-IB, and VMAT-VB performed the worst. The mean dose to the planning target volume for breast evaluation (PTV Eval-breast) was significantly lower for IMRT-EB and FIF-IMRT-EB than for the other plans. For both PTV Eval-breast and PTV Eval-boost, VMAT-VB had the lowest target-volume coverage for 95% of the prescription dose and the highest target-volume coverage for >105% of the prescription dose. Among the six plans, VMAT-VB had the best HI for PTV Eval-boost and the highest doses to all OAR, except the coronary artery. Plans with EBs had lower mean doses for the contralateral lung and contralateral breast than plans with IMRT boosts. FIF-IMRT-EB had a low cost; plans with IMRT boosts had the highest costs. Conclusion: FIF-IMRT-EB may be the most suitable irradiation technique for hypofractionated WBI with SIB after BCS.
Sh. Rafieian, S. Farzanefar, Dr. M. Abbasi,
Volume 16, Issue 4 (10-2018)
Abstract
A 17-year-old boy with hyperparathyroidism exhibited a large cyst in the left hemi-thorax on his chest X-ray. The cyst was identified as a hydatid cyst. He was referred for biphasic methoxy isobutyl isonitrile (MIBI) parathyroid scan. A discrete ectopic parathyroid was detected in the left upper mediastinum in addition to accumulation of the MIBI tracer in the cyst wall. Using radio-guided occult lesion localization with an injection of 3 mCi 99m Tc - MIBI in the morning of the operation day, an ectopic adenoma was detected with a gamma probe within the thymus, resected with a consequent decline of serum high parathyroid hormone (PTH). This report is remarkable in two different aspects: the importance of radio-guided localization of ectopic adenoma, which in this case was within the thymus, and the accumulation of MIBI in hydatid cyst wall, as a unique report of this condition.
X.s. Hu, S.m. Wen, J. Bie, F. Xian, W.w. He, Dr. D. Li,
Volume 17, Issue 4 (10-2019)
Abstract
Background: To compare radical surgery with definitive radiotherapy for upper third esophageal squamous cell carcinoma. Materials and Methods: A total of 191 patients were included in the study. Patients’ clinicopathologic features, and survival time were recorded. Kaplan-Meier (K-M) analysis was adopted to analyze Overall survival (OS), Disease-free survival(DFS), Progression-free survival(PFS), and a Cox multivariate model was used to adjust potential confound factors. Results: The K-M survival analysis showed that treatments, location of lesion, and length of lesion were all associated with the OS (P<0.005). In the surgery group, K-M survival showed that T stage (T1 vs T2, P=0.012, T1 vs T3, P=0.002), location (upper vs upper merged middle, P<0.001), and length lesion (<5 cm vs >5 cm, P=0.015), affected the OS，T stage (T1 vs T2, P=0.018, T1 vs T3, P=0.020) and location of lesion (upper vs upper merged middle, P=0.007) was associated with DFS. The Cox model showed that none of these parameters independently influenced the OS and DFS. In the radiotherapy group, K-M survival showed that supraclavicular lymph node metastasis (P=0.007), concurrent chemo-radiotherapy (P=0.012), and sex (P=0.047) influenced the OS，adjuvant chemotherapy (P=0.013) and age (P=0.013) influenced PFS, The Cox model showed that supraclavicular lymph node metastasis (P=0.018) independently influenced OS and adjuvant chemotherapy (P=0.046) independently influenced PFS. Conclusion: Surgery has better therapeutic effect than radiotherapy. Patients with an upper merged middle lesion and advanced T stage for surgery, male, local advanced and without concurrent chemo-radiotherapy for radiotherapy have a poor prognosis.
Md, Y. Mori, H. Nakazawa, C. Hashizume, T. Tsugawa, T. Murai,
Volume 17, Issue 4 (10-2019)
Abstract
Background: As the optic pathways are thought to be the structures most vulnerable to irradiation, skull base tumors involving them are especially challenging to treat. Stereotactic radiosurgery (SRS) / stereotactic radiotherapy (SRT) is an effective and safe option for the treatment of them. Characteristics of dosimetry of SRT for skull base tumors by Gamma Knife were evaluated in comparison with those by other modalities. Materials and Methods: Original Novalis (NV) multi-beam-intensity-modulated-SRT(MB-IM-SRT) plan and additional simulation plans of Gamma Knife (GK) and TomoTherapy (TT) were compared in 20 cases. For target covering, 95% dose was assigned for 95% of the planning target volume (PTV) (D[95%]=28.5 Gy / 5 fractions). Conformity index (CI), homogeneity index (HI=D95% / maximum dose of PTV)), gradient index (GI=V[47.5% dose] / V[95% dose] of body), and the doses to organs at risk (OARs) were evaluated. Results: CI and GI were significantly better with GK than NV or TT. HI was significantly smaller (less homogeneous) with GK. D[1 ml] and V[20 Gy] of brainstem were significantly smaller with GK than NV or TT. V[20Gy] of whole brain was also significantly smaller with GK. D[0.1 ml] and V[20 Gy] of optic pathways were smaller with GK than NV or TT, though the differences did not reach statistical significance. Conclusion: If a higher internal dose gradient is interpreted as an advantage for tumor ablation, GK SRT might be expected to be a more effective and safer treatment for skull base benign tumors adjacent to the optic pathways and brainstem when they are not large.
S. Ahn, J.s. Park, J.h. Song, Y.k. Hong, Ph.d., S.s. Jeun,
Volume 18, Issue 4 (10-2020)
Abstract
Background: Pineal parenchymal tumor (PPT) is extremely rare and histologically heterogeneous, and the optimal treatment strategy is controversial. This study examined clinical outcomes of patients with PPT treated with cyberknife radiosurgery (CKRS) as a primary treatment modality after tumor biopsy. Materials and Methods: Between 2009 and 2018, there were six patients diagnosed with PPT who were treated with single or hypofractionated cyberknife radiosurgery (CKRS) after undergoing endoscopic third ventriculostomy (ETV) and tumor biopsy. Two tumors were pineocytoma (PC) and four were pineal parenchymal tumor of intermediate differentiation (PPTID). The marginal dose was 18 Gy, and the median target volume was 3.05 (range 1.4-7.4) cc. The median follow-up period was 55 (range 18 -141) months. Results: Five patients were alive, and all of their tumors were locally controlled during follow-up periods. Two tumors disappeared completely, two other tumors partially regressed, and another tumor showed no interval change after CKRS. One patient with PPTID showed local progression 14 months after CKRS and died 21 months after CKRS. There were no acute or late complications related to CKRS. Conclusion: This study suggested that CKRS can be used as a primary treatment modality after ETV and tumor biopsy for PPT with favorable clinical outcomes. However, alternative treatment modalities need to be considered for higher risk groups of patients with PPTID.
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