Verification of dose distribution in high dose-rate brachytherapy for cervical cancer using a normoxic N-vinylpyrrolidone polymer gel dosimeter.

The polymer gel dosimeter has been proposed for use as a 3D dosimeter for complex dose distribution measurement of high dose-rate (HDR) brachytherapy. However, various shapes of catheter/applicator for sealed radioactive source transport used in clinical cases must be placed in the gel sample. The absorbed dose readout for the magnetic resonance (MR)-based polymer gel dosimeters requires calibration data for the dose-transverse relaxation rate (R2) response. In this study, we evaluated in detail the dose uncertainty and dose resolution of three calibration methods, the multi-sample and distance methods using the Ir-192 source and the linear accelerator (linac) method using 6MV X-rays. The use of Ir-192 sources increases dose uncertainty with steep dose gradients. We clarified that the uniformly irradiated gel sample improved the signal-to-noise ratio (SNR) due to the large slice thickness of MR images and could acquire an accurate calibration curve using the linac method. The curved tandem and ovoid applicator used for intracavitary irradiation of HDR brachytherapy for cervical cancer were reproduced with a glass tube to verify the dose distribution. The results of comparison with the treatment planning system (TPS) calculation by gamma analysis on the 3%/2 mm criterion were in good agreement with a gamma pass rate of 90%. In addition, the prescription dose could be evaluated accurately. We conclude that it is easy to place catheter/applicator in the polymer gel dosimeters, making them a useful tool for verifying the 3D dose distribution of HDR brachytherapy with accurate calibration methods.

Impact of Percutaneous Transluminal Renal Angioplasty on Autonomic Nervous System and Natriuresis in Hypertensive Patients With Renal Artery Stenosis.

Background We investigated the early postoperative effect of percutaneous transluminal renal angioplasty on ambulatory blood pressure (BP) and the circadian characteristics of natriuresis and autonomic nerve activity. Methods and Results A total of 64 patients with hypertension with hemodynamically significant renal artery stenosis (mean age, 60.0±21.0 years; 31.3% fibromuscular dysplasia) who underwent angioplasty were included, and circadian characteristics of natriuresis as well as heart rate variability indices, including 24-hour BP, low-frequency and high-frequency (HF) components, and the percentage of differences between adjacent normal R-R intervals >50 ms were evaluated using an oscillometric device, TM-2425, both at baseline and 3 days after angioplasty. In both the fibromuscular dysplasia and atherosclerotic stenosis groups, 24-hour systolic BP (fibromuscular dysplasia, -19±14; atherosclerotic renal artery stenosis, -11±9 mm Hg), percentage of differences between adjacent normal R-R intervals >50 ms, HF, brain natriuretic peptide, and nighttime urinary sodium excretion decreased (all P<0.01), and heart rate increased (both P<0.05) after angioplasty. In both groups, revascularization increased the night/day ratios of percentage of differences between adjacent normal R-R intervals >50 ms (both P<0.01) and HF, and decreased those of low frequency/HF (all P<0.05) and nighttime urinary sodium excretion (fibromuscular dysplasia, 1.17±0.15 to 0.78±0.09; atherosclerotic renal artery stenosis, 1.37±0.10 to 0.99±0.06, both P<0.01). Multiple logistic regression analysis indicated that a 1-SD increase in baseline low frequency/HF was associated with at least a 15% decrease in 24-hour systolic BP after angioplasty (odds ratio, 2.30 [95% CI, 1.03-5.67]; P<0.05). Conclusions Successful revascularization results in a significant BP decrease in the early postoperative period. Intrarenal perfusion might be a key modulator of the circadian patterns of autonomic nerve activity and natriuresis, and pretreatment heart rate variability evaluation seems to be important for treatment success.

Three-dimensional Winston-Lutz test using reusable polyvinyl alcohol-iodide (PVA-I) radiochromic gel dosimeter.

Medical linear-accelerator-based stereotactic radiosurgery (SRS) using a stereotactic apparatus or image-guided radiotherapy system for intracranial lesions is performed widely in clinical practice. In general, Winston-Lutz (WL) tests using films or electric portal imaging devices (EPIDs) have been performed as pre-treatment and routine quality assurance (QA) for the abovementioned treatment. Two-dimensional displacements between the radiation isocentre and mechanical isocentre are analysed from the test; therefore, it is difficult to identify the three-dimensional (3D) isocentre position intuitively. In this study, we developed an innovative 3D WL test for SRS-QA using a novel radiochromic gel dosimeter based on a polyvinyl alcohol-iodide (PVA-I) complex that can be reused after annealing. A WL gel phantom that was consisted of the PVA-I gel dosimeter poured into a tall acrylic container and an embedded small tungsten sphere was used as a position detector. A flatbed scanner was used to analyse the isocentre position. The measured 3D isocentre accuracy from the gel-based WL test was within 0.1 mm compared with that obtained from the EPID-based WL test. Furthermore, excellent reusability of the WL gel phantom was observed in long-term SRS isocentre verification, in which clinical SRS cases involving repeated irradiation and annealing were analysed. These results demonstrate the high accuracy and reliable evaluation of the isocentre position using an innovative test. In addition, the clinical-based routine SRS-QA using the PVA-I gel dosimeter demonstrates a highly convenience while affording an easy and fast analysis process.

Associations Between Arterial Stiffness Indices and Chronic Kidney Disease Categories in Essential Hypertensive Patients.

BACKGROUND: This study investigated the association between arterial stiffness indices and asymptomatic chronic kidney disease (CKD) risk categories in hypertensive patients. METHODS: Arterial stiffness indices, including 24-hour brachial and aortic systolic blood pressure (SBP) and pulse wave velocity (PWV), were measured by an oscillometric Mobil-O-Graph device, brachial-ankle PWV (baPWV) by a volume-plethysmographic method, and renal resistive index (RI) by ultrasonography, in 184 essential hypertensive patients (66.0 ± 17.1 years, 47.3% male). CKD was categorized into 3 stages based on the Kidney Disease Improving Global Outcomes (KDIGO) criteria, using a combination of estimated glomerular filtration and albuminuria. RESULTS: The 24-hour aortic PWV (aPWV), baPWV, and RI increased with worsening severity of CKD risk category (all P < 0.01 for trend). Multivariate logistic regression analysis found that a 1 SD increase of nighttime aortic SBP (odds ratio [OR] 1.52), PWV (OR 4.80), or RI (OR 1.75) was an independent predictor of high or very-high CKD stage (all P < 0.05). After adjustment for potential confounders, day-to-night change in brachial SBP as well as in aPWV differed among groups (P < 0.05, respectively). In a multivariate regression model, day-to-night changes in aortic SBP and PWV, and RI were independently associated with day-to-night brachial SBP change. CONCLUSIONS: In hypertension, circadian hemodynamics in high CKD stage are characterized by higher nighttime values of aortic SBP and PWV and disturbed intrarenal hemodynamics. Further, the blunted nocturnal BP reduction in these patients might be mediated via disturbed intrarenal hemodynamics and circadian hemodynamic variation in aortic SBP and arterial stiffness.

Insight into the Role of Angiopoietins in Ageing-Associated Diseases.

Angiopoietin (Ang) and its receptor, TIE signaling, contribute to the development and maturation of embryonic vasculature as well as vascular remodeling and permeability in adult tissues. Targeting both this signaling pathway and the major pathway with vascular endothelial growth factor (VEGF) is expected to permit clinical applications, especially in antiangiogenic therapies against tumors. Several drugs targeting the Ang-TIE signaling pathway in cancer patients are under clinical development. Similar to how cancer increases with age, unsuitable angiogenesis or endothelial dysfunction is often seen in other ageing-associated diseases (AADs) such as atherosclerosis, Alzheimer's disease, type 2 diabetes, chronic kidney disease and cardiovascular diseases. Thus, the Ang-TIE pathway is a possible molecular target for AAD therapy. In this review, we focus on the potential role of the Ang-TIE signaling pathway in AADs, especially non-cancer-related AADs. We also suggest translational insights and future clinical applications of this pathway in those AADs.

Zero-spindle spectral drill: real-time spectral measurement in a fixed Fabry-Pérot cavity.

An optical configuration for Fabry-Pérot cavity scanning using a geometric phase shifter, known as the "spectral drill," is improved to acquire a spectrum in real-time. Previously, the resonance condition of the spectral drill is swept by the mechanical rotation of a phase plate comprising a geometric phase shifter, and the acquisition time is limited. In this work, using a q-plate and a camera instead of phase plate rotation and a photo detector, we remove all the spinning mechanics and increase the acquisition rate by a factor 720. This technique will be applied to locking laser frequency.

Verification of dose distribution in high-dose-rate brachytherapy using a nanoclay-based radio-fluorogenic gel dosimeter.

Dose distributions have become more complex with the introduction of image-guided brachytherapy in high-dose-rate (HDR) brachytherapy treatments. Therefore, to correctly execute HDR, conducting a quality assurance programme for the remote after-loading system and verifying the dose distribution in the patient treatment plan are necessary. The characteristics of the dose distribution of HDR brachytherapy are that the dose is high near the source and rapidly drops when the distance from the source increases. Therefore, a measurement tool corresponding to the characteristic is required. In this study, using an Iridium-192 (Ir-192) source, we evaluated the basic characteristics of a nanoclay-based radio-fluorogenic gel (NC-RFG) dosimeter that is a fluorescent gel dosimeter using dihydrorhodamine 123 hydrochloride as a fluorescent probe. The two-dimensional dose distribution measurements were performed at multiple source positions to simulate a clinical plan. Fluorescence images of the irradiated NC-RFG were obtained at a high resolution (0.04 mm pixel-1) using a gel scanner with excitation at 465 nm. Good linearity was confirmed up to a dose range of 100 Gy without dose rate dependence. The dose distribution measurement at the five-point source position showed good agreement with the treatment planning system calculation. The pass ratio by gamma analysis was 92.1% with a 2%/1 mm criterion. The NC-RFG dosimeter demonstrates to have the potential of being a useful tool for quality assurance of the dose distribution delivered by HDR brachytherapy. Moreover, compared with conventional gel dosimeters such as polymer gel and Fricke gel dosimeters it solves the problems of diffusion, dose rate dependence and inhibition of oxygen-induced reactions. Furthermore, it facilitates dose data to be read in a short time after irradiation, which is useful for clinical use.

Impact of Percutaneous Revascularization on Left Ventricular Mass and Its Relationship to Outcome in Hypertensive Patients With Renal Artery Stenosis.

BACKGROUND: We investigated the effects of percutaneous transluminal renal angioplasty on left ventricular (LV) mass, and the impact of LV mass reduction on outcomes. METHODS: A total of 144 hypertensive patients with renal artery stenosis (RAS) (mean age 69 years; 22.2% fibromuscular dysplasia (FMD)) who underwent angioplasty were included. Echocardiography was performed at baseline and after 1 year, and patients were thereafter followed up for a median of 5.6 years for primary composite outcomes. RESULTS: In both the FMD and atherosclerotic stenosis (ARAS) groups, LV mass decreased after angioplasty, but the decrease in LV mass index (-15.4 ± 18.3% vs. -0.8 ± 27.8%, P < 0.01) as well as the regression rate of LV hypertrophy was greater in FMD. Multiple logistic regression analysis indicated that FMD (odds ratio (OR) 2.94, P < 0.01), severe RAS (≥90%) (OR 2.94, P < 0.05), and higher LV mass index at baseline (OR 2.94 for 1 SD increase, P < 0.001) were independent predictors of LV mass index decrease of at least 20%. The primary composite outcomes occurred in 45 patients (31.3%). In FMD, lower LV mass index after 1 year (hazard ratio 2.81 for 1 SD increase, P < 0.05) or regression of LV mass (hazard ratio 0.75 for 5% decrease, P = 0.054) showed a tendency to be associated with better outcomes; however, these associations were not found in ARAS. CONCLUSIONS: Hypertensive patients with ARAS have less regression of LV mass in response to angioplasty than those with FMD, and LV mass regression is less useful as a surrogate marker of outcomes especially in ARAS.

Association Between Circadian Hemodynamic Characteristics and Target Organ Damage in Patients With Essential Hypertension.

BACKGROUND: This study investigated the association between circadian hemodynamic characteristics and asymptomatic hypertensive organ damage. METHODS: Circadian hemodynamics, including 24-hour brachial and aortic systolic blood pressure (SBP), pulse wave velocity (PWV), augmentation index (AIx@75), cardiac index, and total vascular resistance (TVR), were evaluated using an oscillometric device, Mobil-O-Graph, in 284 essential hypertensive patients (67.8 ± 16.0 years, 54% female). Hypertensive target organ damage (TOD), namely carotid wall thickening, left ventricular hypertrophy, and albuminuria, was assessed in all patients. RESULTS: Office SBP and 24-hour brachial and aortic SBP all increased with increasing number of organs involved (all P < 0.01 for trend). After multivariate logistic regression analysis, 24-hour brachial SBP (odds ratio [OR] = 1.04 for 1 mm Hg increase, P < 0.001) as well as aortic SBP (OR = 1.03 for 1 mm Hg increase, P < 0.05) maintained significance. Percent decrease during nighttime in brachial SBP, PWV, and TVR, but not cardiac index, showed a significant graded relationship with the number of organs involved. In a multivariate stepwise regression model, the nighttime values of brachial SBP, PWV, and TVR emerged as independent predictors of the presence of TOD. CONCLUSION: In essential hypertension, 24-hour aortic SBP could be a marker of subclinical TOD, and further, the blunted nocturnal BP reduction in TOD patients might be mediated by disturbed circadian hemodynamic variations in aortic SBP, vascular resistance, and arterial stiffness.

Dose distribution verification in high-dose-rate brachytherapy using a highly sensitive normoxic N-vinylpyrrolidone polymer gel dosimeter.

Rapid technological advances in high-dose-rate brachytherapy have led to a requirement for greater accuracy in treatment planning system calculations and in the verification of dose distributions. In high-dose-rate brachytherapy, it is important to measure the dose distribution in the low-dose region at a position away from the source in addition to the high-dose range in the proximity of the source. The aim of this study was to investigate the accuracy of a treatment plan designed for prostate cancer in the low-dose range using a normoxic N-vinylpyrrolidone-based polymer gel (VIPET gel) dosimeter containing inorganic salt as a sensitizer (iVIPET). The dose response was evaluated on the basis of the transverse relaxation rate (R2) measured by magnetic resonance scanning. In the verification of the treatment plan, gamma analysis showed that the dose distributions obtained from the polymer gel dosimeter were in good agreement with those calculated by the treatment planning system. The gamma passing rate according to the 2%/2 mm criterion was 97.9%. The iVIPET gel dosimeter provided better accuracy for low doses than the normal VIPET gel dosimeter, demonstrating the potential to be a useful tool for quality assurance of the dose distribution delivered by high-dose-rate brachytherapy.

Influence of magnesium chloride on the dose-response of polyacrylamide-type gel dosimeters.

We investigated the effect of magnesium chloride (MgCl2) on the nuclear magnetic resonance dose-response of polyacrylamide-type (PAGAT, NIPAM, and VIPET) gel dosimeters containing acrylamide, N-isopropylacrylamide, and N-vinylpyrrolidone as a monomer, respectively. The dose-transverse relaxation rates (1/T2 = R2) obtained from magnetic resonance imaging data revealed that a substantial increase in the dose-R2 response occurred as the concentration of MgCl2 in the gel dosimeters increased. The sensitivity of the PAGAT gel with 1.0 M MgCl2 was found to be approximately one order higher than that of the same gel without MgCl2. In addition, the water equivalences of the gels with MgCl2 were evaluated over a wide range of photon energies. The results indicated that MgCl2 acts as a powerful sensitizer to radiation-induced free-radical polymerization in polyacrylamide-type gel dosimeters, but does not interfere with the desirable properties of basic polyacrylamide-type gel dosimeters (i.e., the dose rate and dose integration).

Circadian hemodynamic characteristics in hypertensive patients with primary aldosteronism.

OBJECTIVE: The present study aimed to compare circadian hemodynamic characteristics in hypertensive patients with and without primary aldosteronism. METHODS: Circadian hemodynamics, including 24-h brachial and central blood pressure (BP), SBP variability indices, central pulse wave velocity (PWV), augmentation index (AIx@75), cardiac index, and total vascular resistance (TVR), were evaluated using an oscillometric device, Mobil-O-Graph, in 60 patients with primary aldosteronism (63.4±13.3 years, 47% women) and 120 age-matched and sex-matched patients with essential hypertension. RESULTS: Office SBP, PWV, AIx@75, and BP variability indices were similar between groups; however, 24-h brachial (124 ±â€Š14 vs 130 ±â€Š11 mmHg) as well as central (112 ±â€Š12 vs 120 ±â€Š10 mmHg) SBP was higher (both P < 0.01), and the difference between 24-h brachial and central SBP (11 ±â€Š5 vs 9 ±â€Š3 mmHg, P < 0.05), an index of pressure amplification, was smaller in primary aldosteronism than in essential hypertension. In both groups, cardiac index decreased from daytime to night-time (both P < 0.01), but this decrease was smaller in primary aldosteronism (P < 0.05). During daytime, TVR in primary aldosteronism was higher than that in essential hypertension (P < 0.05), and the significant increase of TVR from daytime to night-time was lost in primary aldosteronism. In a multivariate stepwise regression model, primary aldosteronism emerged as an independent predictor of 24-h central SBP as well as the difference between 24-h brachial and central SBP. CONCLUSION: Our results demonstrated that circadian hemodynamics in primary aldosteronism patients are characterized by increased central SBP, smaller disparity between brachial and central SBP, and disturbed circadian hemodynamic variation.

Association between renal function and outcomes after percutaneous transluminal renal angioplasty in hypertensive patients with renal artery stenosis.

OBJECTIVE: We investigated the impact of renal function on outcomes after percutaneous transluminal angioplasty. METHODS: A total of 139 hypertensive patients with atherosclerotic renal artery stenosis (mean age, 70 years, 80.6% men) who underwent renal percutaneous transluminal angioplasty were included. Renal function was evaluated on the basis of estimated glomerular filtration rate (eGFR) and albuminuria/proteinuria, and classified into three categories according to eGFR (≥45, 30-44, and <30 ml/min/1.73 m) and albuminuria/proteinuria [normal-to-mild: albumin/creatinine ratio (ACR) less than 3.0, protein/creatinine ratio (PCR) less than 15; moderate: ACR 3.0-30.0, PCR 15-50; severe: ACR > 30.0, PCR > 50 mg/mmol]. RESULTS: During a median follow-up of 5.4 years, 36.0% of patients developed the primary composite end point, including cardiovascular and renal outcomes. In multivariate Cox regression analysis, eGFR less than 30 (hazard ratio 3.47, P < 0.01) as well as severe albuminuria/proteinuria (hazard ratio 2.63, P < 0.05) was an independent predictor of worse outcome. In the subgroup without events within 1 year after angioplasty (n = 117), the outcome differed among the three renal functional categories at 1 year based on eGFR (log-rank χ = 16.28, P < 0.001) as well as on albuminuria/proteinuria (log-rank χ = 8.30, P < 0.05). At 1 year, 24 patients (20.1%) showed at least 20% decrease in eGFR, and their outcome was worse than that in those with at least 20% increase (n = 23) (hazard ratio 3.50, P < 0.05). Multiple logistic regression analysis indicated that pretreatment moderate-to-severe albuminuria/proteinuria was an independent predictor of at least 20% eGFR decrease (odds ratio 2.82, P < 0.05). CONCLUSION: Impaired renal function, and in particular, a poor response of eGFR to angioplasty, is associated with worse outcome. Therapeutic effectiveness of renal angioplasty seems to be limited in patients with albuminuria/proteinuria.

Investigation of the non-thermal effects of exposing cells to 70-300 GHz irradiation using a widely tunable source.

This study investigated the effects of millimeter wave (MMW) irradiation with a wide range of frequencies on the proliferation and activity of normal human skin fibroblast (NB1RBG) and human glioblastoma (A172) cells. Very few studies have focused on low-power, long-term irradiation of cells with a widely tunable source. Our research examined non-thermal effects on cells exposed to radiation at low power with tunable frequencies from 70 GHz to 300 GHz. A widely tunable MMW source was set within a cell culture incubator. To avoid the effect of heat generation due to irradiation, the intensity was maintained below 10 µW and the device was arranged such that the irradiation came from underneath the cells. Irradiation was performed by sweeping from 70 GHz to 300 GHz in 1.0 GHz steps. The MMW source was positioned 100 mm away from the container in which the cells were cultured. Cells were exposed to MMWs for either 3, 70 or 94 h. Measurements of cell proliferation were made using the alternating current measurement method. We found no difference in proliferation between cells exposed to MMWs and unexposed cells. A colorimetric method using novel tetrazolium compound: MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt] was used for cell activity and cytotoxicity assays. We found no difference in cellular activity or toxicity between MMW-exposed cells and sham cells. Our study thus found no non-thermal effect as a result of exposure of cells to 70 GHz to 300 GHz of radiation.

[Polymer Gel Dosimeter].

With rapid advances being made in radiotherapy treatment, three-dimensional (3D) dose measurement techniques of great precision are required more than ever before. It is expected that 3D polymer gel dosimeters will satisfy clinical needs for an effective detector that can measure the complex 3D dose distributions. Polymer gel dosimeters are devices that utilize the radiation-induced polymerization reactions of vinyl monomers in a gel to store information about radiation dose. The 3D absorbed dose distribution can be deduced from the resulting polymer distribution using several imaging modalities, such as MRI, X-ray and optical CTs. In this article, the fundamental characteristics of polymer gel dosimeter are reviewed and some challenging keys are also suggested for the widely spread in clinical use.

Computational investigation of suitable polymer gel composition for the QA of the beam components of a BNCT irradiation field.

This study investigated the optimum composition of the MAGAT polymer gel which is to be used in the quality assurance measurement of the thermal neutron, fast neutron and gamma ray components in the irradiation field used for boron neutron capture therapy at the Kyoto University Reactor. Simulations using the PHITS code showed that when combined with the gel, 6Li concentrations of 0, 10 and 100ppm were found to be potentially usable.

The usefulness of monomeric periostin as a biomarker for idiopathic pulmonary fibrosis.

The natural course of idiopathic pulmonary fibrosis (IPF) is variable. Predicting disease progression and survival in IPF is important for treatment. We previously demonstrated that serum periostin has the potential to be a prognostic biomarker for IPF. Our aim was to use monomeric periostin in a multicenter study to evaluate its efficacy in diagnosing IPF and predicting its progression. To do so, we developed a new periostin kit to detect only monomeric periostin. The subjects consisted of 60 IPF patients in a multicenter cohort study. We applied monomeric periostin, total periostin detected by a conventional kit, and the conventional biomarkers-KL-6, SP-D, and LDH-to diagnose IPF and to predict its short-term progression as estimated by short-term changes of %VC and % DL, CO. Moreover, we compared the fraction ratios of monomeric periostin to total periostin in IPF with those in other periostin-high diseases: atopic dermatitis, systemic scleroderma, and asthma. Monomeric periostin showed the greatest ability to identify IPF comparable with KL-6 and SP-D. Both monomeric and total periostin were well correlated with the decline of %VC and % DL, CO. Clustering of IPF patients into high and low periostin groups proved useful for predicting the short-term progression of IPF. Moreover, the relative ratio of monomeric periostin was higher in IPF than in other periostin-high diseases. Measuring monomeric periostin is useful for diagnosing IPF and predicting its short-term progression. Moreover, the ratio of monomeric periostin to total periostin is elevated in IPF compared to other periostin-high diseases.

[Evaluation of 3D Dose Distribution and Clinical Applications Using Polymer Gel Dosimeter].

Evaluation of dosimetric impact of the interplay effect between multi-leaf collimator (MLC) movement and tumor respiratory motion during volumetric modulated arc therapy (VMAT) delivery using polymer gel dosimeter was taken as an example in this article. An excellent gas barrier PAN (polyacrylonitrile) bottle filled with polyacrylamide-based gel dosimeter contained magnesium chloride as a sensitizer (iPAGAT dosimeter) was set to the QUASAR™ respiratory motion phantom (Modus), and was moved with motion amplitudes (peak-to-peak amplitude) of 1 and 2 cm with a 4 second period during VMAT delivery by the Novalis Tx linear accelerator (Varian/BrainLAB). Two spherical GTVs with 2 cm diameter and two PTVs were defined considering the respiratory motion and setup uncertainties. Three-dimensional (3D) dose distribution in iPAGAT dosimeter was read out by the 3T MRI system, and was evaluated by the dose profiles, gamma analysis and the dose-volume histogram (DVH) using in-house developed software. As a result, interplay effect was negligible since dose coverage of GTV was sufficient during VMAT delivery with simulated respiratory motion.

[Polymer Gel Dosimetry for the High-Dose-Rate Brachytherapy Using Ir-192 Source].

High-dose-rate (HDR) brachytherapy is performed with the remote after-loading system (RALS) to transport an Ir-192 source directly to inside or near the tumor. Quality assurance (QA) of equipment should be performed at sufficient frequency to ensuring safety and quality of HDR brachytherapy treatment. Polymer gel dosimeters have been attracting attention in recent years as a QA tools of HDR brachytherapy, because they can measure the three-dimensional steep dose gradients around HDR sources. In this paper, we introduce our preliminary results using VIPET polymer gel dosimeters for Ir-192 HDR brachytherapy dosimetry.