Reports of Practical Oncology & Radiotherapy, 2018
This study aims at examining absolute dose verification of step-and-shoot intensity modulated rad... more This study aims at examining absolute dose verification of step-and-shoot intensity modulated radiation treatment (IMRT) of prostate and brain patients by use of ion chambers of two different volumes and thermoluminescent detectors (TLD). Background: The volume of the ion chamber (IC) is very important for absolute dose verification of IMRT plans since the IC has a volume average effect. With TLD detectors absolute dose verification can be done measuring the dose of multiple points simultaneously. Materials and methods: Ion chambers FC65-P of volume 0.65 cc and semiflex of volume 0.125 cc as well as TLDs were used to measure the central axis absolute dose of IMRT quality assurance (QA) plans. The results were compared with doses calculated by a treatment planning system (TPS). The absolute doses of off axis points located 2 cm and 4 cm away from the isocenter were measured with TLDs. Results: The measurements of the 0.125 cc ion chamber were found to be closer to TPS calculations compared to the 0.65 cc ion chamber, for both patient groups. For both groups the root mean square (RMS) differences between doses of the TPS and the TLD detectors are within 3.0% for the central axis and points 2 cm away from the isocenter of each axis. Larger deviations were found at the field edges, which have steep dose gradient. Conclusions: The 0.125 cc ion chamber measures the absolute dose of the isocenter more accurately compared to the 0.65 cc chamber. TLDs have good accuracy (within 3.0%) for absolute dose measurements of in-field points.
Purpose: Cataract formation is an unavoidable complication when radiation therapy, even in small ... more Purpose: Cataract formation is an unavoidable complication when radiation therapy, even in small doses, includes the lens. In this experimental study on rats, the preventive effect of verapamil, a calcium channel blocker, was studied on radiation induced cataract. Methods: Experiment was performed on 40 female, 180-250 g weighted WIstar albino rats. Animals were divided into 3 groups. A control group (n = 10) was observed for 7.5 weeks. Radiation (n =10) and verapamil groups
International Journal of Radiation Oncology*Biology*Physics, 2015
Purpose/Objective(s): Hypofractionated stereotactic body radiation therapy (SBRT) of vertebral me... more Purpose/Objective(s): Hypofractionated stereotactic body radiation therapy (SBRT) of vertebral metastases (VM) is very efficient locally but increases the risk of VM fracture. Local relapses following SBRT are infrequent, but most patients still relapse at distant sites. Preclinical and clinical studies demonstrate that zoledronic acid (ZA) not only reduces fracture risk and activates bone remodeling but also increases immune response and radiosensitivity. This study aimed at evaluating the safety of ZA combined with radiation therapy. Materials/Methods: We conducted a multicenter non dose-escalating phase 1 study combining SBRT (3 x 9 Gy, 90% of prescribed dose to 90% of the PTV) and ZA (12 monthly injections) in VM patients (NCT01219790). Inclusion criteria were VM with a minimum distance of 5 mm between GTV and spinal cord, and creatinine clearance greater than 30 ml/min. Exclusion criteria were previous irradiation of the VM, and symptomatic or progressive neurological dysfunction. GTV, CTV and PTV were defined according to the international consensus of radiosurgery. The main objective was the absence of Grade 3 or higher neurological toxicity at one year. Secondary objectives were acute tolerance, analgesic control, local control and skeletal related events. To detect a 15% rate of late neurotoxicity, we planned to recruit a minimum of 30 patients in order to conclude with a 95 % chance that late neurotoxicity does not exceed this threshold. Results: Thirty-two patients (25 men 7 women, median age 66.4) were treated on 51 VM (9 cervical, 22 thoracic, 17 lumbar, 3 sacral) secondary to solid cancers of the prostate (17), kidney (5), breast (4), lung (3), colon-rectum (2), and sarcoma (2). VM were treated using Robotic Radiosurgery (8), Tomotherapy (18), Novalis (20) or others linear accelerators (5). Grade 3 acute mucosal toxicity was noted in 6 patients. There was no late grade 3 neurological toxicity but two grade 2 cervicobrachial neuralgia have been reported. Median pain score decreased at 3 and 6 months (1.65 and 1.04 respectively versus 2.56 at baseline). Irradiated vertebral collapse was noted in two patients. Local control was obtained in 91% of patients. Conclusion: ZA combined with SBRT to vertebral metastases may increase acute mucosal toxicity, but shows promising long-term safety and efficacy results. ZA may represent an interesting immunomodulatory strategy when combined with SBRT.
OBJECTIVES: In general, breast electron boost treatment planning is made using surgical scars or ... more OBJECTIVES: In general, breast electron boost treatment planning is made using surgical scars or clips placed in the tumor bed. The aim of this study was to compare these two treatments plans in terms of dose optimization. METHODS: Twenty-five patients who had surgical clips placed in the tumor bed during tumor excision were evaluated. At first, surgical clips were not taken into account in these patients (type I). In the secondary stage, the treatment plan (type II) was performed considering surgical clips. Taking type II treatment plan as a basis, type I treatment plan was compared in terms of energy, field size, gantry angle, collimator angle and field center parameters. RESULTS: When compared with Type I plan, changes were observed in the electron energy used in the treatment of 12 patients, the electron fields of 20 patients, the gantry angles of 12 patients, the collimator angles of 6 patients and the field centers of 18 patients when surgical clips were considered. CONCLUSION...
World Congress of Brachytherapy 2012 S 159 tolerated by majority of patients with acceptable degr... more World Congress of Brachytherapy 2012 S 159 tolerated by majority of patients with acceptable degree of acute toxicities. Overall survival data need longer follow-up.
Background The optimum protocol for expander volume adjustment with respect to the timing and app... more Background The optimum protocol for expander volume adjustment with respect to the timing and application of radiotherapy remains controversial. Methods Eighteen New Zealand rabbits were divided into three groups. Metallic port integrated anatomic breast expanders of 250 cc were implanted on the back of each animal and controlled expansion was performed. Group I underwent radiotherapy with full expanders while in Group II, expanders were partially deflated immediately prior to radiotherapy. Control group did not receive radiotherapy. The changes in blood flow at different volume adjustments were investigated in Group II by laser Doppler flowmetry. Variations in the histopathologic properties of the irradiated tissues including the skin, capsule and the pocket floor, were compared in the biopsy specimens taken from different locations in each group. Results A significant increase in skin blood flow was detected in Group II with partial expander deflation. Overall, histopathologic exa...
Does partial expander deflation exacerbate the adverse effects of radiotherapy in two-stage breas... more Does partial expander deflation exacerbate the adverse effects of radiotherapy in two-stage breast reconstruction?
Journal of B.U.ON. : official journal of the Balkan Union of Oncology, 2018
PURPOSE The purpose of this study was to perform pretreatment patient-specific quality assurance ... more PURPOSE The purpose of this study was to perform pretreatment patient-specific quality assurance (QA) for intracranial irradiation using CyberKnife with an ion chamber. METHODS Twenty-five intracranial plans created using the ray-tracing algorithm were used for this study. Computed tomography (CT) images of the water-equivalent RW3 slab phantom with PinPoint ionization chamber were acquired with 1-mm slice thickness and transferred to the MultiPlan treatment planning system (TPS). Four gold fiducial markers embedded into two different plates were used to tracking during the irradiation. Intracranial plans were transferred to CT images of the RW3 phantom. The isodose curves and sensitive volume of ion chamber were overlapped. Point dose measurements were performed three times and the mean point doses were calculated for each plan. The mean doses measured by the PinPoint ion chamber were compared with those of the calculated by MultiPlan TPS in the sensitive volume of PinPoint. RESULT...
Wedge' filters are used to compensate for missing tissue and to optimize isodose distribution... more Wedge' filters are used to compensate for missing tissue and to optimize isodose distribution to target volumes. The original photon energy spectrum changes due to 'wedge' filter because of scattering of primary photons. As such it becomes essential to account for the dependence of the 'wedge' factor on depth and field size in clinical dose calculation. The aim of this study is the determination of 'wedge' factors as a function of field size and phantom depth for Co-60 gamma-ray and X-ray beams in the range of 4, 6 and 15 MV containing 15°-60° brass and tungsten 'wedge' filters. For Co-60 and 4 MV X-ray beams standard 'wedge' filters with angles ranging between 15°-60°; for 6 MV and 15 MV X-ray beams only one 'wedge' filter with an angle of 60° have been used. Wedge factors have been found by the help of the proportion of wedge values to open field values under the same conditions. In order to search field and depth dependence rela...
Reports of Practical Oncology & Radiotherapy, 2018
This study aims at examining absolute dose verification of step-and-shoot intensity modulated rad... more This study aims at examining absolute dose verification of step-and-shoot intensity modulated radiation treatment (IMRT) of prostate and brain patients by use of ion chambers of two different volumes and thermoluminescent detectors (TLD). Background: The volume of the ion chamber (IC) is very important for absolute dose verification of IMRT plans since the IC has a volume average effect. With TLD detectors absolute dose verification can be done measuring the dose of multiple points simultaneously. Materials and methods: Ion chambers FC65-P of volume 0.65 cc and semiflex of volume 0.125 cc as well as TLDs were used to measure the central axis absolute dose of IMRT quality assurance (QA) plans. The results were compared with doses calculated by a treatment planning system (TPS). The absolute doses of off axis points located 2 cm and 4 cm away from the isocenter were measured with TLDs. Results: The measurements of the 0.125 cc ion chamber were found to be closer to TPS calculations compared to the 0.65 cc ion chamber, for both patient groups. For both groups the root mean square (RMS) differences between doses of the TPS and the TLD detectors are within 3.0% for the central axis and points 2 cm away from the isocenter of each axis. Larger deviations were found at the field edges, which have steep dose gradient. Conclusions: The 0.125 cc ion chamber measures the absolute dose of the isocenter more accurately compared to the 0.65 cc chamber. TLDs have good accuracy (within 3.0%) for absolute dose measurements of in-field points.
Purpose: Cataract formation is an unavoidable complication when radiation therapy, even in small ... more Purpose: Cataract formation is an unavoidable complication when radiation therapy, even in small doses, includes the lens. In this experimental study on rats, the preventive effect of verapamil, a calcium channel blocker, was studied on radiation induced cataract. Methods: Experiment was performed on 40 female, 180-250 g weighted WIstar albino rats. Animals were divided into 3 groups. A control group (n = 10) was observed for 7.5 weeks. Radiation (n =10) and verapamil groups
International Journal of Radiation Oncology*Biology*Physics, 2015
Purpose/Objective(s): Hypofractionated stereotactic body radiation therapy (SBRT) of vertebral me... more Purpose/Objective(s): Hypofractionated stereotactic body radiation therapy (SBRT) of vertebral metastases (VM) is very efficient locally but increases the risk of VM fracture. Local relapses following SBRT are infrequent, but most patients still relapse at distant sites. Preclinical and clinical studies demonstrate that zoledronic acid (ZA) not only reduces fracture risk and activates bone remodeling but also increases immune response and radiosensitivity. This study aimed at evaluating the safety of ZA combined with radiation therapy. Materials/Methods: We conducted a multicenter non dose-escalating phase 1 study combining SBRT (3 x 9 Gy, 90% of prescribed dose to 90% of the PTV) and ZA (12 monthly injections) in VM patients (NCT01219790). Inclusion criteria were VM with a minimum distance of 5 mm between GTV and spinal cord, and creatinine clearance greater than 30 ml/min. Exclusion criteria were previous irradiation of the VM, and symptomatic or progressive neurological dysfunction. GTV, CTV and PTV were defined according to the international consensus of radiosurgery. The main objective was the absence of Grade 3 or higher neurological toxicity at one year. Secondary objectives were acute tolerance, analgesic control, local control and skeletal related events. To detect a 15% rate of late neurotoxicity, we planned to recruit a minimum of 30 patients in order to conclude with a 95 % chance that late neurotoxicity does not exceed this threshold. Results: Thirty-two patients (25 men 7 women, median age 66.4) were treated on 51 VM (9 cervical, 22 thoracic, 17 lumbar, 3 sacral) secondary to solid cancers of the prostate (17), kidney (5), breast (4), lung (3), colon-rectum (2), and sarcoma (2). VM were treated using Robotic Radiosurgery (8), Tomotherapy (18), Novalis (20) or others linear accelerators (5). Grade 3 acute mucosal toxicity was noted in 6 patients. There was no late grade 3 neurological toxicity but two grade 2 cervicobrachial neuralgia have been reported. Median pain score decreased at 3 and 6 months (1.65 and 1.04 respectively versus 2.56 at baseline). Irradiated vertebral collapse was noted in two patients. Local control was obtained in 91% of patients. Conclusion: ZA combined with SBRT to vertebral metastases may increase acute mucosal toxicity, but shows promising long-term safety and efficacy results. ZA may represent an interesting immunomodulatory strategy when combined with SBRT.
OBJECTIVES: In general, breast electron boost treatment planning is made using surgical scars or ... more OBJECTIVES: In general, breast electron boost treatment planning is made using surgical scars or clips placed in the tumor bed. The aim of this study was to compare these two treatments plans in terms of dose optimization. METHODS: Twenty-five patients who had surgical clips placed in the tumor bed during tumor excision were evaluated. At first, surgical clips were not taken into account in these patients (type I). In the secondary stage, the treatment plan (type II) was performed considering surgical clips. Taking type II treatment plan as a basis, type I treatment plan was compared in terms of energy, field size, gantry angle, collimator angle and field center parameters. RESULTS: When compared with Type I plan, changes were observed in the electron energy used in the treatment of 12 patients, the electron fields of 20 patients, the gantry angles of 12 patients, the collimator angles of 6 patients and the field centers of 18 patients when surgical clips were considered. CONCLUSION...
World Congress of Brachytherapy 2012 S 159 tolerated by majority of patients with acceptable degr... more World Congress of Brachytherapy 2012 S 159 tolerated by majority of patients with acceptable degree of acute toxicities. Overall survival data need longer follow-up.
Background The optimum protocol for expander volume adjustment with respect to the timing and app... more Background The optimum protocol for expander volume adjustment with respect to the timing and application of radiotherapy remains controversial. Methods Eighteen New Zealand rabbits were divided into three groups. Metallic port integrated anatomic breast expanders of 250 cc were implanted on the back of each animal and controlled expansion was performed. Group I underwent radiotherapy with full expanders while in Group II, expanders were partially deflated immediately prior to radiotherapy. Control group did not receive radiotherapy. The changes in blood flow at different volume adjustments were investigated in Group II by laser Doppler flowmetry. Variations in the histopathologic properties of the irradiated tissues including the skin, capsule and the pocket floor, were compared in the biopsy specimens taken from different locations in each group. Results A significant increase in skin blood flow was detected in Group II with partial expander deflation. Overall, histopathologic exa...
Does partial expander deflation exacerbate the adverse effects of radiotherapy in two-stage breas... more Does partial expander deflation exacerbate the adverse effects of radiotherapy in two-stage breast reconstruction?
Journal of B.U.ON. : official journal of the Balkan Union of Oncology, 2018
PURPOSE The purpose of this study was to perform pretreatment patient-specific quality assurance ... more PURPOSE The purpose of this study was to perform pretreatment patient-specific quality assurance (QA) for intracranial irradiation using CyberKnife with an ion chamber. METHODS Twenty-five intracranial plans created using the ray-tracing algorithm were used for this study. Computed tomography (CT) images of the water-equivalent RW3 slab phantom with PinPoint ionization chamber were acquired with 1-mm slice thickness and transferred to the MultiPlan treatment planning system (TPS). Four gold fiducial markers embedded into two different plates were used to tracking during the irradiation. Intracranial plans were transferred to CT images of the RW3 phantom. The isodose curves and sensitive volume of ion chamber were overlapped. Point dose measurements were performed three times and the mean point doses were calculated for each plan. The mean doses measured by the PinPoint ion chamber were compared with those of the calculated by MultiPlan TPS in the sensitive volume of PinPoint. RESULT...
Wedge' filters are used to compensate for missing tissue and to optimize isodose distribution... more Wedge' filters are used to compensate for missing tissue and to optimize isodose distribution to target volumes. The original photon energy spectrum changes due to 'wedge' filter because of scattering of primary photons. As such it becomes essential to account for the dependence of the 'wedge' factor on depth and field size in clinical dose calculation. The aim of this study is the determination of 'wedge' factors as a function of field size and phantom depth for Co-60 gamma-ray and X-ray beams in the range of 4, 6 and 15 MV containing 15°-60° brass and tungsten 'wedge' filters. For Co-60 and 4 MV X-ray beams standard 'wedge' filters with angles ranging between 15°-60°; for 6 MV and 15 MV X-ray beams only one 'wedge' filter with an angle of 60° have been used. Wedge factors have been found by the help of the proportion of wedge values to open field values under the same conditions. In order to search field and depth dependence rela...
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Papers by GONUL KEMIKLER