Incidence of Radiation-induced Nausea and Vomiting: A Prospective Single-institution Pilot Study.

Radiation-induced nausea and vomiting (RINV) is a frequent adverse event that occurs in patients undergoing radiotherapy. However, research on RINV is underrepresented. This prospective single-institution exploratory pilot study investigated the incidence of RINV according to the irradiation site and observed the efficacy of symptomatic antiemetic treatment in controlling symptoms of RINV. The primary outcomes were the proportions of emesis-free days and nausea-free days. The secondary endpoints included the time to the first episode of RINV, frequency of vomiting, and severity of nausea, including its impact on eating habits and weight loss. Fifteen patients were enrolled in each group (minimal, low, and moderate emetogenic risk). All patients received greater than 20 Gy in five fractions. Evaluation was based on weekly questionnaires completed by patients during routine clinic visits. Nausea and vomiting occurred in 11 and 0 patients, respectively. Six of 15 patients in the minimal-risk group, 1 in the low-risk group, and 4 in the moderate-risk group experienced nausea. Although all 11 symptomatic patients were offered antiemetics, only 3 used them, who reported satisfactory control of nausea. The percentage of emesis-free days for all patients was 100% and the percentage of nausea-free days for the 11 patients who developed RINV was 38%. An unexpectedly high percentage of patients in the minimal-risk group experienced nausea; all had breast cancer. Future studies should investigate factors beyond the irradiation site, including the characteristics of the patient and the treatment, to better predict an individual's risk of RINV.

Current status and issues with the dosimetric assay of iodine-125 seed sources at medical facilities in Japan: a questionnaire-based survey†.

In conducting dosimetric assays of seed sources containing iodine-125 (125I), several major guidelines require the medical physicist to verify the source strength before patient treatment. Japanese guidelines do not mandate dosimetric assays at medical facilities, but since 2017, three incidents have occurred in Japan wherein seeds with incorrect strengths were delivered to medical facilities. Therefore, this study aimed to survey the current situation and any barriers to conducting the dosimetric assay of iodine-125 seeds at medical facilities in Japan. We conducted a questionnaire-based survey from December 2020 to April 2021, to examine whether seed assay and verification of the number of seeds delivered were being performed. We found that only 9 facilities (16%) performed seed assay and 28 (52%) verified the number of seeds. None of the facilities used an assay method that ensured traceability. The reasons for not performing an assay were divided into two categories: lack of resources and legal issues. Lack of resources included lack of instruments, lack of knowledge of assay methods, shorthand, or all of the above, whereas legal issues included the inability to resterilize iodine-125 seeds distributed in Japan and/or purchase seeds dedicated to the assay. Dosimetric assays, including simple methods, are effective in detecting calibration date errors and non-radioactive seeds. The study findings suggest that familiarization of medical personnel with these assay methods and investigation of the associated costs of labor and equipment should be recommended, as these measures will lead to medical reimbursement for quality assurance.

Evaluation of dose perturbations around iodine-125 seed sources in supplemental external beam prostate radiotherapy.

We investigated dose perturbations caused by 125I seeds in patients undergoing supplemental external beam radiotherapy (EBRT) for prostate cancer. We examined two types of nonradioactive seed models: model 6711 and model STM1251. All experiments were performed using a water-equivalent phantom. Radiochromic film was used to measure the dose distributions adjacent to the seeds upstream and downstream of the external beam source. Single and clusters of multiple seeds were placed in slots in a solid water (SW) slab to measure dose perturbations with separate versus dense seed placement at beam energies of 6 or 10 MV. Monte Carlo simulations (MCSs) were also performed to include the theoretical basis against film dosimetry. Distinct patterns of dose enhancement (buildup [BU]) were upstream, and dose reduction (builddown [BD]) were downstream of the radiation source. Model 6711 with lower photon beam energies produced larger dose perturbations of BU and BD than the model STM1251. The results showed the same tendency with different seed placements and beam energies. However, these differences were not observed in the rotational irradiation measurement, which replicated a clinical plan. Dose perturbations around seeds result in dose enhancement and dose reduction with varying impact depending on the photon beam energy and seed type. This has the potential to cancel out these perturbations using multiple beam direction fields.

[Technical Report: Quality Assurance for 125I Seed Sources in Permanent Prostate Brachytherapy].

This technical report provides useful information on the current status and issues of quality control in 125I seed source strength measurement for Permanent Prostate Brachytherapy in Japan.With the spread of 125I seed brachytherapy, the traceability of source strength measurements with the single-seed assay was established in Japan. This allows medical facilities to measure reference air kerma rate of 125I seeds with their own well-type of ionization chamber. However, it is difficult to maintain the traceability chain because the 125I reference air kerma rate standards have been hardly utilized by medical facilities so far. Meanwhile, some serious incidents of contamination of the different source strengths and dead seeds were reported in Japan.To address the specific issues in Japan, JASTRO Brachytherapy Subcommittee established a working group (WG) in 2021. The goal of this WG is to investigate the management methods of source strength measurement used in medical facilities, and to discuss the ideal and practicable methods of source management such as verifying the number of seeds and source strength. Initially, a questionnaire survey was conducted to facilities offering 125I seed brachytherapy in Japan. Sixty-seven out of 95 facilities responded (response rate 70.5%). This survey revealed that 41% of facilities did not perform either confirmation of the number of seeds or measurement of source strength. There are several reasons why the source strength was not measured in those facilities. For example, 125I seeds are provided under the sterilized conditions; quality assurance by source suppliers is reliable; and there is not sufficient staff.The single-seed assay is regarded as an internationally standardized and the most reliable measurement method. Therefore, it is an essential measurement technique to ensure traceability of source strength measurements. However, our survey found that most Japanese facilities do not perform single-seed assays. Meanwhile, some facilities have performed batch assay as an alternative method, in which all of the multiple sources in a batch are measured while loaded into sterilized cartridges. Although the measurement by the batch assay is less accurate than the one by the single-seeded assay, the batch assay does not require re-sterilization of the source and can be performed quickly. It might be useful to detect unexpected errors such as differences in the number of sources and abnormalities in source strength.In this report, we will introduce several methods of source strength measurement that have been implemented in medical facilities. The quality assurance of 125I seed sources in prostate interstitial brachytherapy should be provided not only by the source suppliers but also by the medical facilities that use sources to treat patients. We hope that medical facilities will refer to this technical report and use it as an aid to quality assurance in their own facilities.

Multi-Institutional Study of End-to-End Dose Delivery Quality Assurance Testing for Image-Guided Brachytherapy Using a Gel Dosimeter.

PURPOSE: To quantify dose delivery errors for high-dose-rate image-guided brachytherapy (HDR-IGBT) using an independent end-to-end dose delivery quality assurance test at multiple institutions. The novelty of our study is that this is the first multi-institutional end-to-end dose delivery study in the world. MATERIALS AND METHODS: The postal audit used a polymer gel dosimeter in a cylindrical acrylic container for the afterloading system. Image acquisition using computed tomography, treatment planning, and irradiation were performed at each institution. Dose distribution comparison between the plan and gel measurement was performed. The percentage of pixels satisfying the absolute-dose gamma criterion was reviewed. RESULTS: Thirty-five institutions participated in this study. The dose uncertainty was 3.6% ± 2.3% (mean ± 1.96σ). The geometric uncertainty with a coverage factor of k = 2 was 3.5 mm. The tolerance level was set to the gamma passing rate of 95% with the agreement criterion of 5% (global)/3 mm, which was determined from the uncertainty estimation. The percentage of pixels satisfying the gamma criterion was 90.4% ± 32.2% (mean ± 1.96σ). Sixty-six percent (23/35) of the institutions passed the verification. Of the institutions that failed the verification, 75% (9/12) had incorrect inputs of the offset between the catheter tip and indexer length in treatment planning and 17% (2/12) had incorrect catheter reconstruction in treatment planning. CONCLUSIONS: The methodology should be useful for comprehensively checking the accuracy of HDR-IGBT dose delivery and credentialing clinical studies. The results of our study highlight the high risk of large source positional errors while delivering dose for HDR-IGBT in clinical practices.

Temperature Characteristics of Resonance Frequency for Double-Layered Thickness-Shear Resonator.

The effect of the difference in the thickness ratio of the double-layered thickness-shear resonator on the temperature characteristics of the resonance frequency was investigated using a Ca3TaGa3Si2O14 (CTGS) single crystal. Three specimens with thickness ratios of x = 0.25 , 0.33, and 0.50 were prepared using 122° Y - and 171° Y -cut CTGS substrates. For the specimens with x = 0.25 and 0.33, the temperature characteristics varied depending on the order of the resonance mode. For the specimen with x = 0.50 , on the other hand, almost the same temperature characteristics were observed regardless of the order of the resonance mode. To interpret this phenomenon, a new equation for predicting the temperature characteristics of the fundamental mode (first mode) for the double-layered resonator was created using the electric flux density ratio generated in the two substrates. The expected values using this equation were in good agreement with the result of the first mode temperature characteristics.

Radiation dose rate variations in different measurement scenarios after prostate 125I brachytherapy.

PURPOSE: This study aimed to directly compare different measurement scenarios using a supplemental radiation exposure measurement data set. MATERIALS AND METHODS: Two sets of measurement scenarios comparing different body postures, such as standing and chair sitting positions, and different measurement directions, such as anterior and posterior directions, were assessed for radiation dose rate variations in this study at the Tokyo Medical Center, Japan. The estimated precaution time for holding children in the spoon position while sitting was also calculated. RESULTS: Different radiation dose rate measurement scenarios showed different variation tendencies. Radiation dose rate measurement showed higher mean values of measured radiation dose tendency in the standing position than in the sitting positions. The measurement from the anterior direction showed a slightly lower tendency than that from the posterior direction. Assuming a dose limit of 1 mSv, the precaution time calculated for children being held in the spoon position for a certain duration every day was 51.5 (range, 12.5-152.2) minutes. CONCLUSIONS: Our study presented a supplemental radiation exposure measurement data set and directly compared different measurement scenarios. Several trends in radiation exposure variations were found in the measurement scenarios at different body postures and different measurement directions. Our study data set could be a useful source of concrete information regarding radiation safety and contribute to the review and revision of public guidance in the future.

Newly formulated GROWJECT® is bioequivalent to the prior GROWJECT® formulation and causes less injection-associated pain.

Daily treatment with subcutaneous injections of recombinant human GH can be physically and emotionally stressful for children and their caregivers owing to the pain caused by injection. In this study, 52 healthy male subjects were randomized to investigate the bioequivalence and compare the safety and injection-associated pain between the prior GROWJECT® sc formulation and the new formulation, which contains less phosphate buffer. Single subcutaneous doses of each formulation were administered in a crossover manner. Adverse events were monitored throughout the study and subjects rated injection site pain on a 5-point scale. The 90% confidence intervals of the geometric least square means ratio for the area under the human GH concentration-time curve from 0 to 24 h and maximum concentration were 1.002-1.049 and 0.971-1.075 following 6 mg and 0.992-1.038 and 0.973-1.058 following 12 mg, respectively. No severe adverse events were observed. The mean pain score was significantly higher (i.e., less painful) with the new formulation than with the prior formulation regardless of the order of treatment. The new GROWJECT® sc formulation was bioequivalent to the prior formulation and associated with less injection site pain.

Time to achieve a prostate-specific antigen nadir of ≤0.2 ng/mL and related factors after permanent prostate brachytherapy.

PURPOSE: The purpose of this study was to identify the time to achieve a prostate-specific antigen (PSA) nadir of ≤0.2 ng/mL and the related factors to achieve this goal. MATERIALS AND METHODS: We retrospectively reviewed 2218 Japanese prostate cancer patients who received 125I brachytherapy with or without external beam radiotherapy between 2003 and 2013 at one institution. Among them, patients followed up for ≥72 months and without luteinizing hormone-releasing hormone (LH-RH) agonist/antagonist were included (total of 1089 patients). The time to a PSA nadir of ≤0.2 ng/mL (months) was defined as the time between the date of implantation and the first time the lowest PSA value reached ≤0.2 ng/mL. Biochemical recurrence (BCR) was determined using the Phoenix definition. Multivariate linear regression analysis was performed to detect the related factors to achieve this nadir. RESULTS: We assigned 409, 592, and 88 patients to the low-, intermediate-risk, and high-risk groups, respectively. The median followup time was 9.5 years. The median time to achieve a PSA nadir of ≤0.2 ng/mL was 44.0 (95% confidence interval: 42.3-45.7) months. The percentage of patients that achieved the nadir was 89.1%. BCR was noted in 107 (9.8%) patients. In the multivariate analysis of patients without BCR, younger age, larger prostate volume at implantation, higher initial PSA level, and monotherapy were significantly associated with longer time to achieve the PSA nadir. CONCLUSION: The median time to achieve a PSA nadir of ≤0.2 ng/mL was 44.0 months. Some patients, however, may require a lengthy period of time to do so.

Comparison of prostate verification with implanted gold markers in tissue surrounding the prostate and pelvic bony anatomy for external beam radiation therapy following low-dose-rate brachytherapy: a prospective clinical trial.

We aimed to investigate whether gold marker implantation in the tissue surrounding the prostate could accurately monitor setup errors during external beam radiation therapy (EBRT) following low-dose-rate (LDR) brachytherapy. Thirty-eight patients had confirmed intermediate- or high-risk prostate cancer and received EBRT following LDR brachytherapy. In >175 computed tomography imaging sessions, the average values of the weekly setup error during EBRT to the prostate centroid at the time of gold marker matching in the surrounding tissue of the prostate and pelvic bone matching were measured and then compared using the Wilcoxon signed-rank test. Gold marker matching in the surrounding tissue of the prostate estimated setup errors better than those estimated by bone matching (3D displacement = 2.7 ± 2.0 vs 3.8 ± 2.6 mm, P < 0.01). Overall, the standard deviation of systematic (Σ) and random (σ) setup error was lower with gold marker matching than with bone matching (3D displacement = 1.8 and 1.1 mm vs 2.1 and 1.6 mm, respectively). With gold marker matching, the setup error of the position of the prostate centroid was smaller, and the optimal setup margin was lower than that with bone matching (2Σ + 0.7σ and 2.5Σ + 0.7σ of 3D displacement = 4.3 and 5.2 mm vs 5.3 and 6.4 mm, respectively). This high-precision radiotherapy approach placing gold markers in the surrounding tissue of the prostate can allow more accurate setup during EBRT following LDR brachytherapy.

Plan reproducibility of intraoperatively custom-built linked seeds compared to loose seeds for prostate brachytherapy.

PURPOSE: Few studies have compared the implant quality of linked and loose seeds for prostate brachytherapy. This study aimed to evaluate and compare plan reproducibility of intraoperatively built custom linked seeds and loose seeds for prostate brachytherapy. MATERIAL AND METHODS: Between December 2010 and March 2014, 76 localized prostate cancer patients received Iodine-125 brachytherapy with external beam radiotherapy. Linked and loose seeds were implanted in 39 and 37 patients, respectively. The primary endpoint was the mean (± standard deviation) of the absolute change in the minimum dose received by 90% of the prostate volume between intraoperative and post-operative planning (ΔD90) to confirm plan reproducibility. Comparisons between the groups were evaluated using 2-sample t tests. RESULTS: The ΔD90 values were 6.95 ± 11.6% and -0.41 ± 8.5% for the loose and linked seed groups, respectively (p < 0.01). The linked seed group showed decreased post-operative D90 (118.8% vs. 127.2%), V150 (51.7% vs. 66.7%), and RV100 (0.44 ml vs. 0.61 ml) compared to the loose seed group (p < 0.01), whereas lung migration tended to be reduced (0% vs. 8%). CONCLUSIONS: The plan reproducibility of the linked seed group was better than that of the loose seed group. Moreover, the linked seed group showed less migration and lower rectal dose.

Predictive factors of long-term rectal toxicity following permanent iodine-125 prostate brachytherapy with or without supplemental external beam radiation therapy in 2216 patients.

PURPOSE: We analyzed factors associated with rectal toxicity after iodine-125 prostate brachytherapy (BT) with or without external beam radiation therapy (EBRT). METHODS AND MATERIALS: In total, 2216 prostate cancer patients underwent iodine-125 BT with or without EBRT between 2003 and 2013. The median followup was 6.9 years. Cox proportional hazards modeling was used for univariate and multivariate analyses to assess clinical and dosimetric factors associated with rectal toxicity. Dosimetric parameters from 1 day after implantation (Day 1) and 1 month after implantation (Day 30) were included in the analyses. RESULTS: The 7-year cumulative incidence of Grade 2 or higher rectal toxicity was 5.7% in all patients. The multivariate analysis revealed that antiplatelet or anticoagulant therapy, neoadjuvant androgen deprivation therapy, treatment modality, Day 1 rectal volume receiving 100% of the prescribed dose (RV100), and the Day 30 minimal percent of the prescribed dose delivered to 30% of the rectum (RD30) were associated with rectal toxicity. Day 1 RV100 was a common predictor in both BT-alone and the BT + EBRT groups. The 5-year cumulative incidence of Grade 2 or higher rectal toxicity was 12.6%, 5.9%, and 1.7% for BT + 3-dimensional conformal radiation therapy, BT + intensity-modulated radiation therapy, and the BT-alone groups, respectively (p < 0.001). CONCLUSIONS: Rectal dosimetric parameters in BT were associated with late rectal toxicity. Although the risk of rectal toxicity was higher when EBRT was combined with BT, with proper and achievable rectal dose constraints intensity-modulated radiation therapy yielded less toxicity than 3-dimensional conformal radiation therapy.

Single-energy metal artifact reduction in postimplant computed tomography for I-125 prostate brachytherapy: Impact on seed identification.

PURPOSE: To evaluate the effectiveness of the single-energy metal artifact reduction (SEMAR) technique for improving the accuracy of I-125 seed identification in postimplant computed tomography (CT) after prostate brachytherapy. METHODS AND MATERIALS: Postimplant CT images of 40 patients treated with I-125 prostate brachytherapy were acquired. For all patients, 2 data sets were reconstructed, 1 with SEMAR algorithms (SEMAR image), and the other without SEMAR algorithms (non-SEMAR image). Seed locations are automatically detected by the automatic seed finder tool, and their locations were compared between the SEMAR and non-SEMAR images. Dosimetric parameters using seed locations as detected were compared. RESULTS: The true-positive fraction of properly detected seeds on the SEMAR image as determined from a reference seed distribution defined by one investigator was significantly higher than the true-positive fraction on the non-SEMAR image (p = 0.011). The variabilities in D90 (p = 0.001), V100 (p = 0.007), and V150 (p = 0.007) were significantly reduced for seed location on the SEMAR image as compared with non-SEMAR image. CONCLUSIONS: Prostate postimplant CT with SEMAR improved the accuracy of seed localization and postimplant dosimetric parameters.

Prospective study of direct radiation exposure measurements for family members living with patients with prostate (125)I seed implantation: Evidence of radiation safety.

PURPOSE: To broaden the current understanding of radiation exposure and risk and to provide concrete evidence of radiation safety related to (125)I seed implantation. METHODS AND MATERIALS: Direct radiation exposure measurements were obtained from dosimeters provided to 25 patients who underwent (125)I seed implantation, along with their family members. The estimated lifetime exposure dose and the precaution time for holding children near the patient's chest were calculated in two study periods. RESULTS: During the first and second study period, the mean estimated lifetime exposure doses were, respectively, 7.61 (range: 0.45, 20.21) mSv and 6.84 (range: 0.41, 19.20) mSv for patients, and 0.19 (range: 0.02, 0.54) mSv and 0.25 (range: 0.04, 1.00) mSv for family members. The mean ratios of first and second period measurements were 1.05 (range: 0.44, 3.18) for patients and 1.82 (range: 0.21, 7.04) for family members. The corresponding absolute differences between first and second period measurements were -0.77 (range: -11.40, 7.63) mSv and 0.06 (range: -0.26, 0.79) mSv, respectively. Assuming a dose limit of 1 mSv, the precaution times for holding a child every day of the first and second periods were 250.9 (range: 71.3, 849.4) min and 275.2 (range: 75.0, 883.4) min, respectively. Assuming a dose limit of 0.5 mSv, the corresponding precaution times were 179.0 (range: 35.6, 811.5) min and 178.9 (range: 37.5, 1131.8) min, respectively. CONCLUSIONS: Our study demonstrated low radiation exposures to family members of patients undergoing (125)I prostate implantation. It was clear that (125)I seed implantation did not pose a threat to the safety of family members.

Predictive factors for urinary toxicity after iodine-125 prostate brachytherapy with or without supplemental external beam radiotherapy.

PURPOSE: We examined the factors associated with urinary toxicities because of brachytherapy with iodine-125 with or without supplemental external beam radiotherapy (EBRT) for prostate cancer. METHODS AND MATERIALS: We investigated 1313 patients with localized prostate cancer treated with iodine-125 brachytherapy with or without supplemental EBRT between 2003 and 2009. The International Prostate Symptom Score (IPSS) and Common Terminology Criteria for Adverse Events data were prospectively determined. Patients, treatment, and implant factors were investigated for their association with urinary toxicity or symptoms. RESULTS: IPSS resolution was not associated with biologically effective dose (BED). Baseline IPSS, total needles, and the minimal dose received by 30% of the urethra had the greatest effect according to multivariate analysis (MVA). Urinary symptom flare was associated with baseline IPSS, age, BED, and EBRT on MVA. Urinary symptom flare and urinary Grade 2 or higher (G2+) toxicity occurred in 51%, 58%, and 67% (p = 0.025) and 16%, 22%, and 20% (p = 0.497) of the <180, 180-220, and >220 Gy BED groups, respectively. Urinary G2+ toxicity was associated with baseline IPSS, neoadjuvant androgen deprivation therapy (NADT), and seed density on MVA. When we divided patients into four groups according to prostate volume (<30 cc or ≥30 cc) and NADT use, urinary G2+ toxicity was most commonly observed in those patients with larger prostates who received NADT, and least in the patients with smaller prostates and no NADT. CONCLUSIONS: NADT was associated with urinary G2+ toxicity. Higher dose and supplemental EBRT did not appear to increase moderate to severe urinary toxicities or time to IPSS resolution; however, it influenced urinary symptom flare.

Comparison of genitourinary and gastrointestinal toxicity among four radiotherapy modalities for prostate cancer: Conventional radiotherapy, intensity-modulated radiotherapy, and permanent iodine-125 implantation with or without external beam radiotherapy.

PURPOSE: To compare late genitourinary (GU) and gastrointestinal (GI) toxicity following different prostate cancer treatment modalities. MATERIALS AND METHODS: This study included 1084 consecutive prostate cancer patients treated with conventional radiotherapy, intensity-modulated radiotherapy (IMRT), permanent iodine-125 implantation (PI) alone, and PI combined with external beam radiotherapy (PI+EBRT). The effects of treatment- and patient-related factors on late grade ⩾ 2 (G2+) GU/GI toxicity risk were assessed. RESULTS: The median follow-up was 43 months (range, 12-97 months). Compared to the PI+EBRT, there was significantly less G2+ GU toxicity in the conventional radiotherapy (hazard ratio [HR] = 0.39; 95% CI, 0.20-0.77) and the IMRT (HR=0.45, 95% CI, 0.27-0.73). Compared to the PI+EBRT, there was significantly more G2+ GI toxicity in the IMRT (HR = 2.38; 95% CI, 1.16-4.87). In PI-related groups, prostate equivalent dose in 2 Gy fractions was a significant predictor of G2+ GU toxicity (p = 0.001), and the rectal volume receiving more than 100% of the prescribed dose was a significant predictor of G2+ GI toxicity (p = 0.001). CONCLUSION: The differences in the late G2+ GU/GI risk cannot be explained by the differences in treatment modalities themselves, but by the total radiation dose to the GU/GI tract, which had a causal role in the development of late G2+ GU/GI toxicity across all treatment modality groups.

Microfocus X-ray imaging of the internal geometry of brachytherapy seeds.

Precise and reliable geometrical data on the internal structure of seeds are indispensable for dosimetric calculation in brachytherapy. We used a novel microfocus X-ray imaging technique for observing the internal structure of brachytherapy seeds. Two popular (125)I seed models were evaluated. Obtained high precision images enabled us to observe the internal structure of seeds qualitatively. Geometrical size parameters were evaluated quantitatively with uncertainty of 0.01-0.04 mm (k=2).

Assessing protection against radiation exposure after prostate (125)I brachytherapy.

PURPOSE: To expand the radiation dose rate measurement data set by measuring radiation under various prostate (125)I brachytherapy situations. METHODS AND MATERIALS: Measurements were obtained from 63 consecutive unselected patients at Tokyo Medical Center, Japan. Differences in factors during measurements, such as body postures, distances from the skin surface, and measurement directions were considered. Furthermore, shielding effects of lead-lined underwear, consisting mainly of 0.1-mm thickness of lead, were also assessed. RESULTS: Radiation exposure varies according to the patient's body posture, with results differing as much as approximately 40.0% in measured radiation dose rates at 30cm from the anterior skin surface. Weight, body mass index, and tissue thickness showed good correlations with measured radiation dose rates. The magnitude of radiation exposure attenuation by shielding was approximately 95.8%, similar to the attenuation ratio based on tissue measurements made in the lateral direction. The respective mean times required to reach 1mSv were 1.2, 7.6, and 65.4 days in the standing position and 0.6, 4.6, and 40.4 days in the supine position at the site of contact, and at 30 and 100cm from the anterior skin surface. CONCLUSIONS: This study obtained supplemental information pertaining to radiological protection and confirmed that shielding can be an effective tool for reducing exposures.

Dosimetric effects of prone and supine positions on post-implant assessments for prostate brachytherapy.

PURPOSE: Post-implant dosimetric assessment is essential for optimal care of patients receiving prostate brachytherapy. In most institutions, post-implant computed tomography (CT) is performed in the supine position. This study aimed to assess variability in dosimetric parameters with postural changes during acquisition of post-implant CT scans. MATERIAL AND METHODS: In total, 85 consecutive patients were enrolled in this study. Fifty-three patients underwent seed implantation alone, and the remaining 32 received a combination of seed implantation and external beam radiotherapy. For post-implant analyses, CT scans were obtained in two patient positions, supine and prone. To evaluate differences in dosimetric parameters associated with postural change, the dosimetric data obtained in the supine position were defined as the standard. RESULTS: The median prostate volume was 22.4 ml in the supine and 22.5 ml in the prone position (p = 0.51). The median prostate D90 was 120.1% in the supine and 120.3% in the prone position, not significantly different. The mean prostate V100 was 97.1% in the supine and 97.0% in the prone position, again not significantly different. Median rectal V100 in supine and prone positions were 0.42 ml and 0.33 ml, respectively (p < 0.01). Rectal D2cc was also significantly decreased in the prone as compared with the supine position (median, 59.1% vs. 63.6%; p < 0.01). A larger post-implant prostate volume was associated with decreased rectal doses in the prone position. CONCLUSIONS: Though there were no significant differences among prostate D90 assessments according to postural changes, our results suggest that post-implant rectal doses decreased in the prone position.

Symptomatic pericardial effusion after chemoradiation therapy in esophageal cancer patients.

PURPOSE: We investigated clinical and treatment-related factors as predictors of symptomatic pericardial effusion in esophageal cancer patients after concurrent chemoradiation therapy. METHODS AND MATERIALS: We reviewed 214 consecutive primary esophageal cancer patients treated with concurrent chemoradiation therapy between 2001 and 2010 in our institute. Pericardial effusion was detected on follow-up computed tomography. Symptomatic effusion was defined as effusion ≥grade 3 according to Common Terminology Criteria for Adverse Events v4.0 criteria. Percent volume irradiated with 5 to 65 Gy (V5-V65) and mean dose to the pericardium were evaluated employing dose-volume histograms. To evaluate dosimetry for patients treated with two-dimensional planning in the earlier period (2001-2005), computed tomography data at diagnosis were transferred to a treatment planning system to reconstruct three-dimensional plans without modification. Optimal dosimetric thresholds for symptomatic pericardial effusion were calculated by receiver operating characteristic curves. Associating clinical and treatment-related risk factors for symptomatic pericardial effusion were detected by univariate and multivariate analyses. RESULTS: The median follow-up was 29 (range, 6-121) months for eligible 167 patients. Symptomatic pericardial effusion was observed in 14 (8.4%) patients. Dosimetric analyses revealed average values of V30 to V45 for the pericardium and mean pericardial doses were significantly higher in patients with symptomatic pericardial effusion than in those with asymptomatic pericardial effusion (P<.05). Pericardial V5 to V55 and mean pericardial doses were significantly higher in patients with symptomatic pericardial effusion than in those without pericardial effusion (P<.001). Mean pericardial doses of 36.5 Gy and V45 of 58% were selected as optimal cutoff values for predicting symptomatic pericardial effusion. Multivariate analysis identified mean pericardial dose as the strongest risk factor for symptomatic pericardial effusion. CONCLUSIONS: Dose-volume thresholds for the pericardium facilitate predicting symptomatic pericardial effusion. Mean pericardial dose was selected based not only on the optimal dose-volume threshold but also on the most significant risk factor for symptomatic pericardial effusion.