Remote Afterloading System Research Articles

A potential usefulness of ultra-high-resolution computed tomography in quality assurance of remote after-loading system for cervical cancer.

Intracavitary brachytherapy with a remote after-loading system (RALS) is performed as a part of radical radiation therapy in cervical cancer. The radiation source is delivered directly through an applicator placed inside the uterus or vagina. Thorough quality control is important to prevent accidents that can lead to serious irradiation error, and an applicator check is one such quality control measure. We experienced a clinical situation in which a small volume of water was observed in the lumen of a post-sterilized applicator on treatment-planning CT. Although the submersion test was negative and no air bubbles emerged from the applicator, ultra-high-resolution computed tomography (U-HRCT) showed a linear crack reaching the inside of the applicator. This abnormality was not identified on treatment-planning CT, which has lower spatial resolution than U-HRCT. In addition, no linear cracks were seen on U-HRCT images of eight other applicators considered to be free from damage. U-HRCT may have superior potential to detect applicator damage and could be useful for quality assurance of the RALS procedure.

Dosimetric Comparison of Isodose Surface Volume and Total Reference Air Kerma (TRAK) based Volume in Cervical Cancer Brachytherapy.

We aim to compare TRAK & TPS based isodose volumes in cervical cancer brachytherapy and assess the feasibility, accuracy and potential future implications of TRAK in this regard and as a newer emerging tool to assess treatment intensity in cervical cancer brachytherapy. one hundred patients with histologically proven squamous cell carcinoma of cervix uteri were assessed for brachytherapy (after completion of external radiation) and prospectively enrolled for the study. 60 Gy, 75 Gy, and 85 Gy isodose volumes were obtained from the TPS (VTPS) for 50, 25 & 25 patients with Manchester, Fletcher & interstitial implant respectively, receiving various fractionation schedules by Ir192 HDR remote after-loading system. Using the formula Vpred=4965(TRAK/dref)3/2+170(TRAK/dref)-1.5 the TRAK based isodose surface volumes (Vpred) were derived. Reference doses (dref) were calculated based on accumulated EBRT and brachytherapy doses. The two sets of volume were compared with respect to applicator type, standard, and optimised plan. Surrogate point A dose was also correlated. VTPS - Vpred were 5.24 ± 2.7%, all volumes being predicted within 10%. Correlation of TRAK vs VTPS60/ VTPS75/ VTPS85 showed R2 of 0.994, 0.987 and 0.971 respectively. There was no significant difference in predicted volumes with respect to applicator type. The surrogate point A showed mean volume and standard deviation of 7.44 ± 13.4%, 17.63 ± 16.38 and 3.5 ± 0.95 for Manchester optimised, Fletcher optimised and standard plans respectively. TRAK with point A (R2=0.5632), bladder (R2=0.2015) and rectal doses (R2=0.121) yielded no correlation. Volumes calculated by TRAK correlate with TPS obtained volumes significantly and the formula predicting isodose surface volumes within 10% accuracy for ICBT applications and not for pure interstitial implants. However, TRAK fails to correlate with surrogate point A, bladder and rectal doses hence has questionable utility as a marker for biological response & treatment intensity.

Use of Thermoluminescence Dosimetry for QA in High-Dose-Rate Skin Surface Brachytherapy with Custom-Flap Applicator

Surface brachytherapy (BT) lacks standard quality assurance (QA) protocols. Commercially available treatment planning systems (TPSs) are based on a dose calculation formalism that assumes the patient is made of water, resulting in potential deviations between planned and delivered doses. Here, a method for treatment plan verification for skin surface BT is reported. Chips of thermoluminescent dosimeters (TLDs) were used for dose point measurements. High-dose-rate treatments were simulated and delivered through a custom-flap applicator provided with four fixed catheters to guide the Iridium-192 (Ir-192) source by way of a remote afterloading system. A flat water-equivalent phantom was used to simulate patient skin. Elekta TPS Oncentra Brachy was used for planning. TLDs were calibrated to Ir-192 through an indirect method of linear interpolation between calibration factors (CFs) measured for 250 kV X-rays, Cesium-137, and Cobalt-60. Subsequently, plans were designed and delivered to test the reproducibility of the irradiation set-up and to make comparisons between planned and delivered dose. The obtained CF for Ir-192 was (4.96 ± 0.25) μC/Gy. Deviations between measured and TPS calculated doses for multi-catheter treatment configuration ranged from -8.4% to 13.3% with an average of 0.6%. TLDs could be included in clinical practice for QA in skin BT with a customized flap applicator.

Questionnaire Report on the Independent Use of a Computed Tomography System Installed in the Room for High-dose-rate Remote Afterloading System

Questionnaire Report on the Independent Use of a Computed Tomography System Installed in the Room for High-dose-rate Remote Afterloading System

Technical note: Analysis of brachytherapy source movement by high-speed camera.

To assess the accuracy of the movement of a brachytherapy source using a high-speed camera for evaluating source position, dwell time, and transit dose. A high-speed camera was used to record the source position of an Ir-192 source relative to a ruler within a custom positioning jig in a remote afterloading system. The analyzed frames can be used to assess dwell positions and times. Treatment plans had multiple dwell times equal to 0.1, 0.5, 1.0, and 2.0 s in 2.5- and 5-mm step sizes. Images were acquired at a rate of 146 frames/s. Acquired images were processed to automatically track the actual source using the correlation between a template image and each frame. The brachytherapy dose calculation formalism (AAPM TG43-U1) was applied to each frame to evaluate the transit dose contribution to the total dose. The differences in measured source positions from the nominal for dwell times equal to 0.1, 0.5, 1.0, and 2.0 s in treatment plans were approximately ≤1mm. The corresponding differences in measured dwell times from the nominal values at 5 mm steps were -15, -9, -5, and 5 ms, respectively. The source velocities at 5mm steps were approximately 393mm/s. The dose differences at 5mm from the source movement with and without the transit dose for these dwell times were 38%, 7%, 3%, and 2%, respectively. Recording a brachytherapy source using a high-speed camera allowed the evaluation of positional and dwell time accuracies as well as dosimetry assessments, such as the transit dose, based on the application of AAPM TG-43U1.

Japanese structure survey of radiation oncology in 2015.

This article describes the ongoing structure of radiation oncology in Japan in terms of equipment, personnel, patient load and geographic distribution to identify and overcome any existing limitations. From May 2016 to August 2018, the Japanese Society for Radiation Oncology conducted a questionnaire based on the Japanese national structure survey of radiation oncology in 2015. Data were analyzed based on the institutional stratification by the annual number of new patients treated with radiotherapy per institution. The estimated annual numbers of new and total (new plus repeat) patients treated with radiation were 225 000 and 271 000, respectively. Additionally, the estimated cancer incidence was 891 445 cases with approximately 25.2% of all newly diagnosed patients being treated with radiation. The types and numbers of treatment devices actually used included linear accelerator (linac; n = 936), Gamma Knife (n = 43), 60Co remote afterloading system (RALS; n = 21), and 192Ir RALS (n = 129). The linac system used dual-energy functions in 754 units, 3D conformal radiotherapy functions in 867, and intensity-modulated radiotherapy (IMRT) functions in 628. There were 899 Japan Radiological Society/Japanese Society for Radiation Oncology-certified radiation oncologists (RO), 1213.9 full-time equivalent (FTE) ROs, 2394.2 FTE radiotherapy technologists (RTT), 295.7 FTE medical physicists, 210.2 FTE radiotherapy quality managers, and 906.1 FTE nurses. The frequency of IMRT use significantly increased during this time. In conclusion, the Japanese structure of radiation oncology has clearly improved in terms of equipment and utility although there was a shortage of personnel in 2015.

Quality assurance tool for determination of position and transit time of a Co-60 source in high dose rate brachytherapy

In this study, three holders were designed, constructed and characterized to perform quality assurance on the source position and transit time in remote afterloading systems with Co-60 sources for high dose rate brachytherapy. The holders design focused on achieving accuracy, low cost, and a time efficient tool for use in clinical settings. Sensitivities greater than 0.6%/mm and maximum precisions better than 0.14 mm for the source position were obtained. The transit time was determined for the holders with a relative precision better than 19%.

High dose rate 192Ir versus high dose rate 60Co brachytherapy: an overview of systematic reviews of clinical responses of gynecological cancers from 1984 to 2020

The Purpose. Radioisotope of 192Iradium (192Ir) has a half-life (74 days) and is not easily accessible in developing countries. As a result, by the time source shipment clearance and the customs paperwork are completed, a large proportion of useful activity had already been decayed away. In fact, 60Cobalt (60Co) remote afterloading systems are commercially available by many venders. As a result, it may well become an alternative source to 192Ir and conform many of these challenges. The aim of this study is that to report clinical responses of different types of gynaecological cancers treated with high dose rate (HDR) 192Ir and HDR60Co brachytherapy in order to check whether HDR 60Co could be used as an alternative brachytherapy, source to HDR 192Ir. Materials and Methods. A retrospective study of clinical responses of different types of gynaecological cancers, staged from I to IV according to recommendations of International Federation of Gynaecology and Obstetrics (FIGO), treated by brachytherapy alone, radiotherapy alone (combined brachytherapy and radiotherapy) and combined radiotherapy and chemotherapy (brachytherapy, radiotherapy and chemotherapy) between 1984 and December 2020 was conducted. The patients were treated with external beam radiotherapy 45–51 Gy boosted with HDR 192Ir and HDR 60Co afterloading brachytherapy of 18–30 Gy to point A. The results. The study scrutinized the data of 11086 patients with different types of gynaecological cancers. Most of the patients, 70 percent of them, were diagnosed with gynaecological cancers in stages II and III. For patients treated with 192Ir brachytherapy source 5-years overall survival rate (OS), local control, 2-years, 5-years and 10-years disease free survival (DFS), complications of gastro-intestine (GI) and complications of genito-urinary (GU) were 63.5%, 92%, 72.6%, 64.07%, 43.75%, 3.9% and 5.92%, but for those treated with 60Co they were 57.7%, 86.63%, 82.5%, 53.35%, 43.75%, 4.8% and 3.7%, respectively. Conclusions. The use of HDR 60Co brachytherapy has the capacity to produce overall survival rate and disease control in patients with carcinoma of the gynaecology comparable to that reported for HDR 192Ir brachytherapy. Currently, the toxicity and damage of the normal tissues and radiation-related second cancers are of a similar incidence to that of standard HDR 192Ir brachytherapy. Source exchange frequency is not a serious concern because it requires less frequency of replacement, and commissioning can be accomplished within years; hence, replacing HDR 192Ir with HDR 60Co brachytherapy achieves significant cost saving. Therefore, we recommend that 60Co source ought to be the first choice for low resource radiotherapy setting as it offers economic advantages over 192Ir and have comparable clinical outcomes to that of 192Ir source.

A Case of Buccal Mucosal Cancer with Function Preserved by Mold Irradiation

Surgical resection or brachytherapy has been used for curative treatment of oral cancer. Although only limited facilities perform brachytherapy, treatment results are as good as those of surgical resection and allow functional preservation. We report here the use of high-dose-rate brachytherapy with a remote after-loading system for mold irradiation for buccal mucosal cancer, in which function is expected to be impaired by surgical treatment. The patient was a woman in her 80s who visited a dental clinic complaining of pain in the left buccal mucosa. She was referred to our department, where a tumor with a rough surface of 39 mm×22 mm was found on the left buccal mucosa. Computed tomography showed a contrast-enhanced soft-tissue mass on the left cheek, with a thickness of 20 mm. Subsequent biopsy of the lesion revealed squamous cell carcinoma, and the tumor was classified as cT2N0M0 （stage Ⅱ）. Surgical resection would be expected to cause dysfunction through the skin on the cheek, therefore simultaneous chemoradiotherapy was planned. The thickness of the oral mucosa should be less than 15 mm, but was 20 mm in this case, making brachytherapy unsuitable. We therefore created a mold device using the occlusion plate to extend the buccal mucosa and maintain contact with the source of radiation, allowing irradiation of the tumor. Mold irradiation was performed using 192-Ir at a total dose of 60 Gy. The patient remains recurrence-free as of 2 years 6 months after mold irradiation.

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.

Japanese structure survey of radiation oncology in 2013.

ABSTRACTThis paper describes the ongoing structure of radiation oncology in Japan in terms of equipment, personnel, patient load and geographic distribution to identify and overcome any existing limitations. From December 2014 to July 2017, the Japanese Society for Radiation Oncology conducted a questionnaire based on the Japanese national structure survey of radiation oncology in 2013. Data were analyzed based on institutional stratification by the annual number of new patients treated with radiotherapy per institution. The estimated annual numbers of new and total (new plus repeat) patients treated with radiation were 216 000 and 257 000, respectively. Additionally, the estimated cancer incidence was 862 452 cases with ~25.0% of all newly diagnosed patients being treated with radiation. The types and numbers of treatment devices actually used included linear accelerator (LINAC; n = 880), Gamma Knife (n = 45), 60Co remote afterloading system (RALS; n = 23) and 192Ir RALS (n = 128). The LINAC system used dual-energy functions in 675 units, 3D conformal radiotherapy functions in 785 and intensity-modulated radiotherapy (IMRT) functions in 494. There were 831 Japan Radiological Society/Japanese Society for Radiation Oncology-certified radiation oncologists, 1130.6 full-time equivalent (FTE) radiation oncologists, 2214.6 FTE radiotherapy technologists, 196.6 FTE medical physicists, 183.8 FTE radiotherapy quality managers and 856.7 FTE nurses. The frequency of IMRT use significantly increased during this time. In conclusion, the Japanese structure of radiation oncology has clearly improved in terms of equipment and utility although there was a shortage of personnel in 2013.

High-dose-rate intracavitary brachytherapy for non-palpable and non-visible recurrent vaginal stump tumors after hysterectomy

Purpose: The purpose of this study was to evaluate patients who were treated with high-dose-rate (HDR) intracavitary brachytherapy for non-palpable and non-visible recurrent vaginal stump that occurred after hysterectomy. Materials and Methods: This retrospective study included 11 patients aged 52–81 (median, 61) years. The HDR brachytherapy was performed using a remote after-loading system (RALS). The dose per fraction was planned at mainly 4 Gy/fraction, twice per week, for a total of 32 Gy. Results: CR and PR were diagnosed on cytology or visual examination in nine (82%) patients and in one (9%) patient, respectively. SD was noted in one (9%) patient. Isolated stump recurrence developed in five patients and the three-year LC rate was 53%. There was no severe acute and late toxicity. Conclusion: Local salvage is possible with a three-year LC rate of 53% with regard to non-palpable and non-visible limited vaginal recurrence of gynecological cancer that responds to HDR brachytherapy (4 Gy/fraction, total 32 Gy).

Japanese structure survey of radiation oncology in 2012.

ABSTRACTThis paper describes the ongoing structure of radiation oncology in Japan in terms of equipment, personnel, patient load and geographic distribution to identify and overcome any existing limitations. From March 2013 to August 2016, the Japanese Society for Radiation Oncology conducted a questionnaire based on the Japanese national structure survey of radiation oncology in 2012. Data were analyzed based on the institutional stratification by the annual number of new patients treated with radiotherapy per institution. The estimated annual numbers of new and total (new plus repeat) patients treated with radiation were 213 000 and 251 000, respectively. Additionally, the estimated cancer incidence was 865 238 cases with ~24.6% of all newly diagnosed patients being treated with radiation. The types and numbers of treatment devices actually used included linear accelerator (LINAC; n = 864), telecobalt (n = 0), Gamma Knife (n = 44), 60Co remote afterloading system (RALS; n = 23) and 192Ir RALS (n = 130). The LINAC system used dual-energy functions in 651 units, 3D conformal radiotherapy functions in 759 and intensity-modulated radiotherapy (IMRT) functions in 466. There were 792 Japan Radiological Society/Japanese Society for Radiation Oncology-certified radiation oncologists, 1061.6 full-time equivalent (FTE) radiation oncologists, 2124.2 FTE radiotherapy technologists, 181.3 FTE medical physicists, 170.9 FTE radiotherapy quality managers and 841.5 FTE nurses. The frequency of IMRT use significantly increased during this time. In conclusion, the Japanese structure of radiation oncology has clearly improved in terms of equipment and utility although there was a shortage of personnel in 2012.

Japanese Structure Survey of Radiation Oncology in 2011.

ABSTRACTWe evaluated the evolving structure of radiation oncology in Japan in terms of equipment, personnel, patient load and geographic distribution to identify and overcome any existing limitations. From March 2012 to August 2015, the Japanese Society for Radiation Oncology conducted a questionnaire based on the Japanese national structure survey of radiation oncology in 2011. Data were analyzed based on the institutional stratification by the annual number of new patients treated with radiotherapy per institution. The estimated annual numbers of new and total (new plus repeat) patients treated with radiation were 211 000 and 250 000, respectively. Additionally, the estimated cancer incidence was 851 537 cases with approximately 24.8% of all newly diagnosed patients being treated with radiation. The types and numbers of treatment devices actually used included linear accelerator (LINAC; n = 836), telecobalt (n = 3), Gamma Knife (n = 46), 60Co remote afterloading system (RALS; n = 24), and 192Ir RALS (n = 125). The LINAC system used dual-energy functions in 619 units, 3D conformal radiotherapy functions in 719 and intensity-modulated radiotherapy (IMRT) functions in 412. There were 756 JRS or JASTRO-certified radiation oncologists, 1018.5 full-time equivalent (FTE) radiation oncologists, 2026.7 FTE radiotherapy technologists, 149.1 FTE medical physicists, 141.5 FTE radiotherapy quality managers and 716.3 FTE nurses. The frequency of IMRT use significantly increased during this time. To conclude, although there was a shortage of personnel in 2011, the Japanese structure of radiation oncology has clearly improved in terms of equipment and utility.

High-dose-rate brachytherapy for high-grade vaginal intraepithelial neoplasia: a dosimetric analysis.

PurposeDue to the rarity of vaginal intraepithelial neoplasia (VAIN), it is impossible to define the best treatment approach or to assess vaginal morbidity. However, brachytherapy (BT) could be a valuable choice for VAIN grade 3 (VAIN3). The aim of this paper was to report a single-institution study of the application of high-dose-rate BT and to evaluate clinical outcomes as well as to investigate the dose-effect relationship for vaginal stenosis.Material and methodsWe retrospectively collected hospital records and treatment plans of 14 consecutive women treated in our department from August 2010 to August 2016, with HDR-BT delivered using iridium-192 by a remote after-loading system. Doses in 3D-planned treatment based on computed tomography (CT) were prescribed in high-risk clinical target volume (HR-CTV) at the vaginal wall. Vaginal stenosis was defined as vaginal shortening/narrowing according to CTCAE4.1. The International Commission on Radiation Units & Measurements (ICRU) bladder and rectal points were used for dose report analysis. The posterior-inferior border of the symphysis points was used to derive reference points. The median age of the enrolled women was 60 years, and the median total radiation dose delivered was 35 Gy.ResultsDuring a median period of 15 days, the treatment was well tolerated, and no interruption was necessary. Acute toxicity was minimal, whereas late toxicity appeared in 4 patients as G2 and in 3 patients as G3 vaginal stenosis. Patients with stenosis G ≥ 2 received a higher median dose to the rectal point and were mainly over 60 years old.ConclusionsPatients with VAIN3 seemed to benefit from BT. It is generally assumed that the vagina is radio-resistant, and no constraints have yet been set, but sexual dysfunction after BT is an important cause of long-term distress. Finding applicable dose limits to the vagina could improve patients’ quality of life.

Japanese structure survey of radiation oncology in 2010.

We evaluated the evolving structure of radiation oncology in Japan in terms of equipment, personnel, patient load, and geographic distribution to identify and overcome any existing limitations. From March 2011 to June 2013, the Japanese Society for Radiation Oncology conducted a questionnaire based on the Japanese national structure survey of radiation oncology in 2010. Data were analyzed based on the institutional stratification by the annual number of new patients treated with radiotherapy per institution. The estimated annual numbers of new and total (new plus repeat) patients treated with radiation were 211 000 and 251 000, respectively. Additionally, the estimated cancer incidence was 805 236 cases, with ~26.2% of all newly diagnosed patients being treated with radiation. The types and numbers of treatment devices actually used included linear accelerator (LINAC; n = 829), telecobalt (n = 9), Gamma Knife (n = 46), 60Co remote afterloading system (RALS; n = 28), and 192Ir RALS (n = 131). The LINAC system used dual-energy functions in 586 units, three-dimensional conformal radiotherapy functions in 663, and intensity-modulated radiotherapy (IMRT) functions in 337. There were 564 JASTRO-certified radiation oncologists, 959.2 full-time equivalent (FTE) radiation oncologists, 1841.3 FTE radiotherapy technologists, 131.3 FTE medical physicists, 121.5 FTE radiotherapy quality managers, and 649.6 FTE nurses. The frequency of IMRT use significantly increased during this year. To conclude, although there was a shortage of personnel in 2010, the Japanese structure of radiation oncology has clearly improved in terms of equipment and utility.

Two-dimensional in vivo rectal dosimetry during high-dose-rate brachytherapy for cervical cancer: a phantom study

Background: The aim of the present study was to verify the dosimetric accuracy of two-dimensional (2D) in vivo rectal dosimetry using an endorectal balloon (ERB) with unfoldable EBT3 films for high-dose-rate (HDR) brachytherapy for cervical cancer. The clinical applicability of the technique was discussed.Material and methods: ERB inflation makes the EBT3 films unrolled, whereas its deflation makes them rolled. Patient-specific quality assurance (pQA) tests were performed in 20 patient plans using an Ir-192 remote afterloading system and a water-filled cervical phantom with the ERB. The dose distributions measured in ERBs were compared with those of the treatment plans.Results: The absolute dose profiles measured by the ERBs were in good agreement with those of treatment plans. The global gamma passing rates were 96–100% and 91–100% over 20 pQAs under the criteria of 3%/3 mm and 3%/2 mm, respectively, with a 30% low-dose threshold. Dose-volume histograms of the rectal wall were obtained from the measured dose distributions and showed small volume differences less than 2% on average from the patients’ plans over the entire dose interval. The positioning error of the applicator set was detectable with high sensitivity of 12% dose area variation per mm. Additionally, the clinical applicability of the ERB was evaluated in volunteers, and none of them felt any pain when the ERB was inserted or removed.Conclusions: The 2D in vivo rectal dosimetry using the ERB with EBT3 films was effective and might be clinically applicable for HDR brachytherapy for cervical and prostate cancers to monitor treatment accuracy and consistency as well as to predict rectal toxicity.

National survey of intracavitary brachytherapy for intact uterine cervical cancer in Japan.

To review the current status of, and labor expended for (in terms of time required), intracavitary brachytherapy (ICBT) in definitive radiotherapy/chemoradiotherapy for cervical cancer patients, two national surveys were performed. The first survey was conducted between July and August 2016 and consisted of a questionnaire of 12 items regarding ICBT procedures for cervical cancer, which was sent to 173 centers installed with high-dose-rate remote after-loading brachytherapy systems. Between November and December 2016, another survey was performed in 79 centers to evaluate labor required for ICBT procedures in terms of time spent and number of staff involved. In the first survey, the response rate was 77% of the 173 centers. ICBT was performed for cervical cancer in 118 (89%) centers. Imaging modalities used after applicator insertion were X-ray alone in 46 (40%), computed tomography in 69 (60%) and magnetic resonance imaging in 5 (4%) centers. Three-dimensional (3D) planning was performed in 55 centers (48%). Fifty-five (70%) centers responded to the second survey regarding ICBT-mandated labor. The median cumulative duration of the entire ICBT procedure was 330 min (the sum of the times spent by each staff member) and was longer in the 3D image–guided brachytherapy (3D-IGBT) (405 min) than in the X-ray group (230 min). This trend was significant for the specific processes of image acquisition and treatment planning, especially for radiation oncologists. In definitive radiotherapy/chemoradiotherapy for cervical cancer patients, 3D-IGBT use has been gradually spreading in Japan. The present survey revealed that ICBT, especially 3D-IGBT, requires substantial labor and time from staff.

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.

Temporo-spatial cell-cycle kinetics in HeLa cells irradiated by Ir-192 high dose-rate remote afterloading system (HDR-RALS).

BackgroundIntracavitary irradiation plays a pivotal role in definitive radiotherapy for cervical cancer, and the Ir-192 high dose-rate remote afterloading system (HDR-RALS) is often used for this purpose. Under this condition, tumor tissues receive remarkably different absorption doses, with a steep gradient, depending on distance from the radiation source. To obtain temporo-spatial information regarding cell-cycle kinetics in cervical cancer following irradiation by Ir-192 HDR-RALS, we examined HeLa cells expressing the fluorescence ubiquitination-based cell cycle indicator (Fucci), which allowed us to visualize cell-cycle progression.MethodsHeLa-Fucci cells, which emit red and green fluorescence in G1 and S/G2/M phases, respectively, were grown on 35-mm dishes and irradiated by Ir-192 HDR-RALS under normoxic and hypoxic conditions. A 6 French (Fr) catheter was used as an applicator. A radiation dose of 6 Gy was prescribed at hypothetical treatment point A, located 20 mm from the radiation source. Changes in Fucci fluorescence after irradiation were visualized for cells from 5 to 20 mm from the Ir-192 source. Several indices, including first green phase duration after irradiation (FGPD), were measured by analysis of time-lapse images.ResultsCells located 5 to 20 mm from the Ir-192 source became green, reflecting arrest in G2, in a similar manner up to 12 h after irradiation; at more distant positions, however, cells were gradually released from the G2 arrest and became red. This could be explained by the observation that the FGPD was longer for cells closer to the radiation source. Detailed observation revealed that FGPD was significantly longer in cells irradiated in the green phase than in the red phase at positions closer to the Ir-192 source. Unexpectedly, the FGPD was significantly longer after irradiation under hypoxia than normoxia, due in large part to the elongation of FGPD in cells irradiated in the red phase.ConclusionUsing HeLa-Fucci cells, we obtained the first temporo-spatial information about cell-cycle kinetics following irradiation by Ir-192 HDR-RALS. Our findings suggest that the potentially surviving hypoxic cells, especially those arising from positions around point A, exhibit different cell-cycle kinetics from normoxic cells destined to be eradicated.Electronic supplementary materialThe online version of this article (doi:10.1186/s13014-016-0669-8) contains supplementary material, which is available to authorized users.