Interstitial Prostate Brachytherapy Research Articles

A power Doppler ultrasound method for improving intraoperative tip localization for visually obstructed needles in interstitial prostate brachytherapy.

High-dose-rate (HDR) interstitial brachytherapy (BT) is a common treatment technique for localized intermediate to high-risk prostate cancer. Transrectal ultrasound (US) imaging is typically used for guiding needle insertion, including localization of the needle tip which is critical for treatment planning. However, image artifacts can limit needle tip visibility in standard brightness (B)-mode US, potentially leading to dose delivery that deviates from the planned dose. To improve intraoperative tip visualization in visually obstructed needles, we propose a power Doppler (PD) US method which utilizes a novel wireless mechanical oscillator, validated in phantom experiments and clinical HDR-BT cases as part of a feasibility clinical trial. Our wireless oscillator contains a DC motor housed in a 3D printed case and is powered by rechargeable battery allowing the device to be operated by one person with no additional equipment required in the operating room. The oscillator end-piece features a cylindrical shape designed for BT applications to fit on top of the commonly used cylindrical needle mandrins. Phantom validation was completed using tissue-equivalent agar phantoms with the clinical US system and both plastic and metal needles. Our PD method was tested using a needle implant pattern matching a standard HDR-BT procedure as well as an implant pattern designed to maximize needle shadowing artifacts. Needle tip localization accuracy was assessed using the clinical method based on ideal reference needles as well as a comparison to computed tomography (CT) as a gold standard. Clinical validation was completed in five patients who underwent standard HDR-BT as part of a feasibility clinical trial. Needle tips positions were identified using B-mode US and PD US with perturbation from our wireless oscillator. Absolute mean±standard deviation tip error for B-mode alone, PD alone, and B-mode combined with PD was respectively: 0.3±0.3mm, 0.6±0.5mm, and 0.4±0.2mm for the mock HDR-BT needle implant; 0.8±1.7mm, 0.4±0.6mm, and 0.3±0.5mm for the explicit shadowing implant with plastic needles; and 0.5±0.2mm, 0.5±0.3mm, and 0.6±0.2mm for the explicit shadowing implant with metal needles. The total mean absolute tip error for all five patients in the feasibility clinical trial was 0.9±0.7mm using B-mode US alone and 0.8±0.5mm when including PD US, with increased benefit observed for needles classified as visually obstructed. Our proposed PD needle tip localization method is easy to implement and requires no modifications or additions to the standard clinical equipment or workflow. We have demonstrated decreased tip localization error and variation for visually obstructed needles in both phantom and clinical cases, including providing the ability to visualize needles previously not visible using B-mode US alone. This method has the potential to improve needle visualization in challenging cases without burdening the clinical workflow, potentially improving treatment accuracy in HDR-BT and more broadly in any minimally invasive needle-based procedure.

Validation of a surface-based deformable MRI-3D ultrasound image registration algorithm toward clinical implementation for interstitial prostate brachytherapy

PURPOSEThe purpose of this study was to evaluate and clinically implement a deformable surface-based magnetic resonance imaging (MRI) to three-dimensional ultrasound (US) image registration algorithm for prostate brachytherapy (BT) with the aim to reduce operator dependence and facilitate dose escalation to an MRI-defined target. METHODS AND MATERIALSOur surface-based deformable image registration (DIR) algorithm first translates and scales to align the US- and MR-defined prostate surfaces, followed by deformation of the MR-defined prostate surface to match the US-defined prostate surface. The algorithm performance was assessed in a phantom using three deformation levels, followed by validation in three retrospective high-dose-rate BT clinical cases. For comparison, manual rigid registration and cognitive fusion by physician were also employed. Registration accuracy was assessed using the Dice similarity coefficient (DSC) and target registration error (TRE) for embedded spherical landmarks. The algorithm was then implemented intraoperatively in a prospective clinical case. RESULTSIn the phantom, our DIR algorithm demonstrated a mean DSC and TRE of 0.74 ± 0.08 and 0.94 ± 0.49 mm, respectively, significantly improving the performance compared to manual rigid registration with 0.64 ± 0.16 and 1.88 ± 1.24 mm, respectively. Clinical results demonstrated reduced variability compared to the current standard of cognitive fusion by physicians. CONCLUSIONSWe successfully validated a DIR algorithm allowing for translation of MR-defined target and organ-at-risk contours into the intraoperative environment. Prospective clinical implementation demonstrated the intraoperative feasibility of our algorithm, facilitating targeted biopsies and dose escalation to the MR-defined lesion. This method provides the potential to standardize the registration procedure between physicians, reducing operator dependence.

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.

GEC-ESTRO ACROP prostate brachytherapy guidelines

This is an evidence-based guideline for prostate brachytherapy. Throughout levels of evidence quoted are those from the Oxford Centre for Evidence based Medicine (https://www.cebm.ox.ac.uk/resources/levels-of-evidence/oxford-centre-for-evidence-based-medicine-levels-of-evidence-march-2009).Prostate interstitial brachytherapy using either permanent or temporary implantation is an established and evolving treatment technique for non-metastatic prostate cancer.Permanent brachytherapy uses Low Dose Rate (LDR) sources, most commonly I-125, emitting photon radiation over months. Temporary brachytherapy involves first placing catheters within the prostate and, on confirmation of accurate positioning, temporarily introducing the radioactive source, generally High Dose Rate (HDR) radioactive sources of Ir-192 or less commonly Co-60. Pulsed dose rate (PDR) brachytherapy has also been used for prostate cancer [1] but few centres have adopted this approach. Previous GEC ESTRO recommendations have considered LDR and HDR separately [2–4] but as there is considerable overlap, this paper provides updated guidance for both treatment techniques.Prostate brachytherapy allows safe radiation dose escalation beyond that achieved using external beam radiotherapy alone as it has greater conformity around the prostate, sparing surrounding rectum, bladder, and penile bulb. In addition there are fewer issues with changes in prostate position during treatment delivery. Systematic review and randomised trials using both techniques as boost treatments demonstrate improved PSA control when compared to external beam radiotherapy alone [5–7].

Low-cost 3D print–based phantom fabrication to facilitate interstitial prostate brachytherapy training program

PurposeThe purpose of this study was to manufacture a realistic and inexpensive prostate phantom to support training programs for ultrasound-based interstitial prostate brachytherapy. Methods and MaterialsFive phantom material combinations were tested and evaluated for material characteristics; Ecoflex 00–30 silicone, emulsion silicone with 20% or 50% mineral oil, and regular or supersoft polyvinyl chloride (PVC). A prostate phantom which includes an anatomic simulated prostate, urethra, seminal vesicles, rectum, and normal surrounding tissue was created with 3D-printed molds using 20% emulsion silicone and regular and supersoft PVC materials based on speed of sound testing. Needle artifact retention was evaluated at weekly intervals. ResultsSpeed of sound testing demonstrated PVC to have the closest ultrasound characteristics of the materials tested to that of soft tissue. Several molds were created with 3D-printed PLA directly or cast on 3D-printed PLA with high heat resistant silicone. The prostate phantom fabrication workflow was developed, including a method to produce dummy seeds for low-dose-rate brachytherapy practice. A complete phantom may be fabricated in 1.5–2 h, and the material cost for each phantom was approximated at $23.98. ConclusionsA low-cost and reusable phantom was developed based on 3D-printed molds for casting. The proposed educational prostate phantom is an ideal cost-effective platform to develop and build confidence in fundamental brachytherapy procedural skills in addition to actual patient caseloads.

Declining Resident Exposure to Interstitial Prostate Brachytherapy: An Analysis of ACGME Case Logs from 2007-2018

Declining Resident Exposure to Interstitial Prostate Brachytherapy: An Analysis of ACGME Case Logs from 2007-2018

A Plan Quality Assurance (QA) Method for HDR Breast Brachytherapy with Multi-Lumen Balloon Applicator and HDR Interstitial Prostate Brachytherapy

A challenge facing the physics community has been quick plan quality checks for high-dose-rate (HDR) brachytherapy treatment planning. This study aims to develop a QA method of manually verifying the planned treatment time from treatment planning system (TPS) for HDR breast brachytherapy using multi-lumen balloon applicators and HDR interstitial prostate brachytherapy.

Impact of Prostate Gland Size ≥60 cc on Physician and Patient-Reported Toxicity after High Dose Rate Prostate Brachytherapy

Prostate volume of ≥60 cubic centimeters (cc) has been a relative contraindication to treatment with interstitial prostate brachytherapy (BT), with some studies showing associations between large prostate size and increased acute toxicity. These studies primarily used low dose rate BT. Few studies have explored toxicity in men with large glands undergoing high dose rate (HDR) BT. We compared the acute patient and physician reported toxicity between men undergoing HDR BT with gland size <60 cc and those with gland size ≥60 cc. We performed a retrospective cohort study of men undergoing prostate HDR BT as part of a prospectively maintained database. The 13.5 Gy x 2 was used for monotherapy and 13.5-15 Gy x 1 for boost to supplement EBRT. Gland size was determined using pre-treatment MRI or TRUS. The International Prostate Symptom Score (IPSS) and Expanded Prostate Cancer Index Composite Short Form (EPIC-26) were used to assess urinary, bowel, and sexual function at baseline and in follow-up. The Common Terminology Criteria for Adverse Events (CTCAE) v4.0 criteria were used to assess genitourinary (GU) and gastrointestinal (GI) toxicity. Baseline demographic and clinical characteristic data were compared between men with gland size <60 cc and those with gland size ≥60 cc using Fisher’s exact and non-parametric Wilcoxon Rank Sum tests. Patient-reported toxicities were compared using Generalized estimating equations (GEE) with an independent weight matrix to account for the correlation between multiple observations. Physician reported toxicities were assessed using a generalized linear mixed effects model. One hundred nineteen men were included in this analysis. Median follow-up was 7.6 months. Median prostate size was 36 cc (range: 13.9-91.9 cc). Thirteen men (10.9%) had a gland size ≥60 cc. There were no differences in baseline urinary medication use, baseline IPSS, or baseline EPIC-26 domain scores between the two groups. There were no differences in mean IPSS over time between the two groups (p=0.9). Men with gland size ≥60 cc had a greater decline in the EPIC-26 urinary incontinence domain score at 1 month (p<0.01) that met criteria for minimal clinically important difference (MCID), but no difference at 3 or 6 months. Men with gland size ≥60 cc had higher urinary irritative/obstructive domain scores at 3 months (p=0.03) that met criteria for MCID, but no difference at 1 or 6 months. There was no difference between groups in bowel or sexual domains. There was a trend towards higher acute urinary retention (AUR) in the ≥ 60 cc group (p=0.06). There was no difference in grade ≥2 GU toxicity and grade ≥2 GI toxicity. Men with prostate gland size of ≥60 cc have no difference in acute physician-reported toxicity, but a trend towards worse AUR and worse urinary incontinence at one month, yet better urinary irritative/obstructive scores at 3 months. Further investigation is needed to limit the impact of therapy on urinary function in men with gland size ≥60 cc.

A cold spot compensation technique using a combination of trans-rectal ultrasonography and intraoperative computed tomography for interstitial permanent prostate brachytherapy: a single-arm prospective trial.

PurposeTo evaluate the efficacy of a cold spot compensation technique using a combination of trans-rectal ultrasonography (TRUS) and computed tomography (CT) for permanent interstitial prostate brachytherapy.Material and methodsSixty-five patients were treated with the cold spot compensation technique using TRUS-CT fusion. The prescribed dose was set at 145 Gy. The dose to 90% of prostate volume (D90) was planned to be within 195 Gy (134%) and 205 Gy (141%). After implantation using the conventional technique, additional seeds were implanted if cold spots were detected on TRUS-CT fusion images.ResultsCold spots were detected in 32 of 65 patients (49%) and were compensated by additional seeds. Median number of additional seeds was 3 (range, 1-5). A CT scan 1 month later revealed that the percentage of patients receiving an undesirably low D90 (160-180 Gy) was significantly reduced in the examination arm compared to historical controls. However, mean operation time was significantly longer in the examination arm (64 min) than in historical controls (49 min, p < 0.001). With median follow-up of 18 months (range, 9-24 months), no grade 3 or worse toxicity was encountered.ConclusionThe cold spot compensation technique using TRUS-CT fusion appears effective for patients receiving permanent interstitial prostate brachytherapy.

Evaluation of I-125 Seed Migration After Prostate Brachytherapy

One of the risks of transperineal interstitial prostate brachytherapy is seed migration after treatment. Sometimes, seed migration cause serious side effects such as seed embolization which may cause organ ischemia. The purpose of this study is to evaluate the seed migration after brachytherapy at our facility and report on finding new predictors of seed migration. From May 2006 to April 2016, 320 patients were treated with permanent I-125 seed implantation, 202 patients were treated with brachytherapy alone and 118 patients were treated with brachytherapy combined with external beam radiotherapy. We used free seeds in all cases. We planned the prescription dose of brachytherapy alone was 145 Gy and that of brachytherapy combined with external beam radiotherapy was 104 Gy and 40 Gy (20 fraction / 4 weeks). The average age of patients was 66.2 years old (median 66 y, range 50 – 78 y). The average volume of prostate was 25.4 cc (median 24.5 cc, range 11.3 – 54.5 cc). The chest, abdominal, and pelvic radiographs were performed at 1st and 30th days after implantation (Day 1 and Day 30), and also pelvic CT was performed at Day 1 and Day 30 in each case. We investigated not only the location, the number, and the frequency of the migration, but as a new indicator of seed migration, we calculated “seed density” that was defined by the following formula: seed density = the number of Implanted seeds / prostate volume (cc). Seed migration was observed in 92 cases (28.8%) in 320 cases. The number of migration seeds was 144 out of 21876 (0.66%). In 16 cases (5.0%), seed migration was observed on day 1, and further seed dislocation was observed at Day 30. The numbers of migrated seeds located at lung region, abdominal/pelvic region, and other regions were 47 (32.6%), 89 (61.8%), and 8 (5.6%). Other sites included thigh, obturator muscle, spinal canal, kidney, and atrium. The average seed density was 2.8 (median 2.7, range 1.5 – 4.8). There was no significant difference in migration ratio by comparison for every 50 cases ( #1 – 50: 26% (13 of 50 cases), #51 – 100: 38% (19 of 50 cases), #101 – 150: 22% (11 of 50 cases), #151 – 200: 28% (14 of 50 cases), #201 – 251: 30% (15 of 50 cases), #251 – 300: 34% (17 of 50 cases), #301 – 320: 15% (3 of 20 cases)). And, there was no significant difference in migration ratio between high prostate volume group (≥ 25 cc, 34.0% (52 of 153 cases)) and low prostate volume group (< 25 cc, 24% (40 of 167 cases)). The migration ratio of high seed density group (≥ 3, 41.6% (37 of 89 cases)) was significantly higher than that of low seed density group (< 3, 23.8% (55 of 231 cases)) (p= 0.0073). The seed migration ratio after prostate brachytherapy at our institution was 28.8% (92 of 320 cases), which was comparable to previous reports. The migration ratio of high seed density group (density ≥ 3) was significantly higher than that of low seed density group (density < 3). This study showed that the seed density could be a new indicator of seed migration after prostate brachytherapy.

PO-0926: Interstitial HDR prostate brachytherapy: comparison of pre- and post-implant dose distribution

PO-0926: Interstitial HDR prostate brachytherapy: comparison of pre- and post-implant dose distribution

Dosimetric comparison between treatment plans of patients treated with low-dose-rate vs. high-dose-rate interstitial prostate brachytherapy as monotherapy: Initial findings of a randomized clinical trial

PurposeThe aim of this study was to compare the dosimetry of intraoperative dose plans of prostate cancer patients treated with low-dose–rate (LDR) and high-dose–rate (HDR) interstitial brachytherapy (BT). Methods and MaterialsA randomized clinical trial was initiated at our institution to compare the results and side effects of LDR and HDR BT as monotherapy in the treatment of early, organ-confined prostate cancer patients. Eighty-seven patients were randomly assigned to receive HDR afterloading BT with one fraction of 19 Gy or permanent LDR 125I seed BT with 145 Gy. Inverse optimization algorithms were used for planning. Stranded seeds were implanted using live ultrasound imaging after preimplant treatment planning. Final dosimetry of HDR treatments was based on updated needle and contour positions. Statistical comparisons with nonparametric test were performed between the corresponding dose–volume parameters. ResultsThe V100 and V150 were 99% and 61%, respectively, for LDR, whereas 98% and 32% for HDR treatments. The D90 was less for HDR (122% vs. 110%). The dose distributions were more homogeneous and conformal with HDR technique (dose homogeneity index, 0.39 vs. 0.67; conformal index, 0.65 vs. 0.80). The urethra and rectum received significantly less dose with HDR. The D10 and D30 for urethra were 133% and 128%, respectively, for LDR and 114% and 111% for HDR treatments. The D2cm3 for rectum was 68% and 55% for LDR and HDR technique, respectively. ConclusionsBoth techniques provided acceptable target volume coverage with a slightly higher value with the LDR technique. The dose distributions were more homogeneous and conformal, and both urethra and rectum were better protected with the HDR technique.

Comparison of prostate contours between conventional stepping transverse imaging and Twister-based sagittal imaging in permanent interstitial prostate brachytherapy.

PurposeTo compare prostate contours on conventional stepping transverse image acquisitions with those on twister-based sagittal image acquisitions.Material and methodsTwenty prostate cancer patients who were planned to have permanent interstitial prostate brachytherapy were prospectively accrued. A transrectal ultrasonography probe was inserted, with the patient in lithotomy position. Transverse images were obtained with stepping movement of the transverse transducer. In the same patient, sagittal images were also obtained through rotation of the sagittal transducer using the “Twister” mode. The differences of prostate size among the two types of image acquisitions were compared. The relationships among the difference of the two types of image acquisitions, dose-volume histogram (DVH) parameters on the post-implant computed tomography (CT) analysis, as well as other factors were analyzed.ResultsThe sagittal image acquisitions showed a larger prostate size compared to the transverse image acquisitions especially in the anterior-posterior (AP) direction (p < 0.05). Interestingly, relative size of prostate apex in AP direction in sagittal image acquisitions compared to that in transverse image acquisitions was correlated to DVH parameters such as D90 (R = 0.518, p = 0.019), and V100 (R = 0.598, p = 0.005).ConclusionsThere were small but significant differences in the prostate contours between the transverse and the sagittal planning image acquisitions. Furthermore, our study suggested that the differences between the two types of image acquisitions might correlated to dosimetric results on CT analysis.

Development of a three dimensional printed MRI compatible template for high dose rate prostate brachytherapy implants

Introduction The significance of the delineation of prostate gland and its main surrounding organs in contemporary HDR prostate brachytherapy requires the use of highly sophisticated imaging techniques, such as MRI. Therefore, implant related equipment should meet MRI compatibility standards. Purpose This work presents the construction and testing of an inexpensive MR-compatible prostate-template for HDR brachytherapy which took place in Metropolitan hospital, Greece Materials and methods A free CAD designer and a 3D printer system were utilised for template production. The template was tested under clinical conditions, using the imaging, operating and sterilization equipment of our department along with a home-made prostate phantom. Results The template was printed according to the original design and fitted well in the equipment currently in use. MRI field does not interfere with the item, while the needle arrangement is consistent in several depths in the phantom. Among the contemporary commercially available templates for HDR interstitial prostate brachytherapy, the 3D printed template constructed in our clinic offers a reusable, cost-effective solution. Conclusion The functionality of the presented prototype template exploits the possibilities of employing 3D printing technology in clinical practice of brachytherapy which will allow the configuration of patient-specific equipment. Disclosure No conflict of interest, financial or other, exists.

Urinary Incontinence Following Prostate Brachytherapy

To define the incidence, time course, and risk factors associated with the development of urinary incontinence (UI) following prostate brachytherapy. A total of 2461 men were identified who underwent permanent interstitial prostate brachytherapy with or without external beam radiation therapy. We examined the relationship between clinical- and treatment-related variables with the onset of UI, defined as leakage requiring pad usage, and further classified as stress (SUI) or urge (UUI) predominant, using univariate and Cox proportional hazards regression models. The changes in International Prostate Symptom Score and quality of life domains were assessed from baseline to last follow, and examined by UI status. Patients were followed for a median of 6.4 years (interquartile range 4.1-9.3). UI was reported in 108 individuals (4.4%), at a median of 1.8 years (interquartile range 5 months-4.4 years): 30 with SUI and 78 with UUI. Seventy-two men (66.7%) reported using 1, 24 (22.2%) using 2, and 12 (11%) using ≥3 pads per day. On multivariate analysis, post-implantation transurethral resection of the prostate, urinary retention, external beam radiation therapy, and higher pretreatment International Prostate Symptom Score were significantly associated with the development of SUI, although transurethral resection of the prostate was the only significant risk factor associated with SUI. Men experiencing UI reported greater declines in urinary quality of life; however, no significant difference was observed between SUI and UUI. UI occurred in 4.4% of patients following prostate brachytherapy and is more commonly urge-predominant in character. Distinct risk factors exist for the development of UUI vs SUI. Urinary leakage requiring pad usage was associated with declines in urinary QOL.

Dosimetric Comparison between Treatment Plans of Patients Treated with Low-Dose-Rate Versus High-Dose-Rate Interstitial Prostate Brachytherapy as Monotherapy: Initial Findings of a Randomized Clinical Trial

To assess and compare the dosimetry of intraoperative dose plans of prostate cancer patients treated with low-dose rate and high-dose rate interstitial brachytherapy. A randomized clinical trial was initiated at our institution to compare the results and side effects of low-dose-rate (LDR) and high-dose-rate (HDR) brachytherapy (BT) as monotherapy in the treatment of early, organ confined prostate cancer patients. Fifty patients with low and selected intermediate risk prostate cancer were randomly assigned to receive HDR afterloading BT with one fraction of 19 Gy or permanent LDR I-125 seed BT with 145 Gy. In both techniques the implantation was performed with transrectal ultrasound guidance in spinal anesthesia, and intraoperative dose plans were made on ultrasound images using inverse optimization algorithms (IPSA for LDR and HIPO for HDR). Dose-volume constraints for prostate, urethra and rectum were applied during optimization. Stranded seeds were implanted into the prostate using live ultrasound imaging following preimplant treatment planning. The HDR treatments were performed after preimplant planning, but final dosimetry was based on updated needle and contour positions. Treatment plans were compared using dose-volume histograms, dose coverage metrics including V100, V150, conformal index (COIN) and dose homogeneity index (DHI) for prostate. Dose to urethra was characterized by D10, D30, D0.1cc and D0.01cc. Dose to rectum was described by D2cc, D1cc, D0.1cc, D0.01cc and D10. Statistical comparisons with non-parametric test were performed between the corresponding parameters. The median needle number was 20 and 18 for LDR and HDR treatments, respectively. The mean seed number was 46.The total seed activity was 26.8 mCi with individual median seed activity of 0.562 mCi. The target coverage by the prescribed dose was larger than 95% for both patient groups, and the V100 was higher for LDR patients. The other parameters are shown in the table.To make the comparison more easy dose parameters are given in relative values, in percentages related to prescribed dose. Except for volume of the prostate the difference between the means of all other parameters for the two patient groups was statistically significant (p<0.05). Both techniques provided acceptable target volume coverage, but higher percentage of target volume was irradiated by the prescribed dose with LDR technique. The dose distributions were more homogeneous with HDR technique, and both urethra and rectum received less relative dose in patients treated with HDR technique. To assess whether these dosimetric data translate in differences in clinical outcomes more patient data and longer follow-up are needed.Tabled 1ProstateV (ccm)V100V150DHICOINLDR32.299620.370.64HDR35.497300.700.80UrethraV (cc)D10D30D0.1ccD0.01ccLDR1.4135129136.0146.9HDR1.6113110113.1115.3RectumD2ccD1ccD0.1ccD0.01ccD10LDR67.179.098.4111.288HDR54.762.875.781.067 Open table in a new tab

Comparison of Prostate Contours between Conventional Stepping Transverse Imaging and Twister Based Sagittal Imaging in Permanent Interstitial Prostate Brachytherapy

Comparison of Prostate Contours between Conventional Stepping Transverse Imaging and Twister Based Sagittal Imaging in Permanent Interstitial Prostate Brachytherapy

A comparison study on various low energy sources in interstitial prostate brachytherapy.

PurposeLow energy sources are routinely used in prostate brachytherapy. 125I is one of the most commonly used sources. Low energy 131Cs source was introduced recently as a brachytherapy source. The aim of this study is to compare dose distributions of 125I, 103Pd, and 131Cs sources in interstitial brachytherapy of prostate.Material and methodsProstaSeed 125I brachytherapy source was simulated using MCNPX Monte Carlo code. Additionally, two hypothetical sources of 103Pd and 131Cs were simulated with the same geometry as the ProstaSeed 125I source, while having their specific emitted gamma spectra. These brachytherapy sources were simulated with distribution of forty-eight seeds in a phantom including prostate. The prostate was considered as a sphere with radius of 1.5 cm. Absolute and relative dose rates were obtained in various distances from the source along the transverse and longitudinal axes inside and outside the tumor. Furthermore, isodose curves were plotted around the sources.ResultsAnalyzing the initial dose profiles for various sources indicated that with the same time duration and air kerma strength, 131Cs delivers higher dose to tumor. However, relative dose rate inside the tumor is higher and outside the tumor is lower for the 103Pd source.ConclusionsThe higher initial absolute dose in cGy/(h.U) of 131Cs brachytherapy source is an advantage of this source over the others. The higher relative dose inside the tumor and lower relative dose outside the tumor for the 103Pd source are advantages of this later brachytherapy source. Based on the total dose the 125I source has advantage over the others due to its longer half-life.

Dosimetry of permanent interstitial prostate brachytherapy for an interoperative procedure, using O-arm based CT and TRUS

PurposeThe aim of this report is dosimetric evaluation for an intraoperative fusion computed tomography (CT) as a superior predictor of 1-month CT based dosimetry in comparison to transrectal ultrasound (TRUS) in permanent interstitial prostate brachytherapy.Material and methodsData of 65 patients treated with seed implantation were analyzed. All procedures has been performed with patients in the lithotomy position inside the O-arm system. An end-fine probe is used as a landmark to fuse TRUS and O-arm-based CT images. There was no difference in the patient's position, probe position, and timing of image acquisition between the two imaging modalities. Dose-volume histogram (DVH) parameters such as the dose to 90% of prostate volume (D90) has been analyzed.ResultsThe area under the curve of the receiver operating characteristic tended to be larger on fusion CT than on TRUS for most DVH parameters (71.85% vs. 59.59% for D90; p = 0.07). Significant relationships between fusion CT and 1-month CT were confirmed using Pearson's correlation coefficients for most DVH parameters (R = 0.48, p < 0.01 for D90), although the relationship between TRUS and 1-month CT was poor. Large dose reduction (35 Gy for D90) was seen from TRUS to fusion CT, especially in patients with high body weight and small prostate volume.ConclusionsIntraoperative fusion CT appears to have higher predictive power for 1-month CT-based dosimetry than TRUS. A prospective trial using fusion CT-based planning is warranted.

Seed migration after transperineal interstitial prostate brachytherapy by using loose seeds: Japanese prostate cancer outcome study of permanent iodine-125 seed implantation (J-POPS) multi-institutional cohort study

BackgroundThe incidence and associated factors of loose seed migration were investigated in cohort 1 of the Japanese Prostate Cancer Outcome Study of Permanent Iodine-125 Seed Implantation (J-POPS).MethodsThe study subjects were 2160 patients, consisting of 1641 patients who underwent permanent iodine-125 seed implantation (PI) and 519 patients who underwent PI combined with external beam radiation therapy (PI + EBRT). The presence or absence of seed migration to the chest and abdominal/pelvic region was determined.ResultsSeed migration was observed in 22.7 % of PI group patients and 18.1 % of PI + EBRT group patients (p = 0.0276). Migration to the lungs and abdominal/pelvic region was observed in 14.6 % and 11.1 % of the patients in the PI group, and 11.2 % and 8.5 % of the patients in the PI + EBRT group, respectively. In the PI group, the number of implanted seeds was associated with the seed migration incidence. Neither the PI nor the PI + EBRT group showed any difference in the volume of the prostate receiving 100 % of the prescribed dose (V100 [%]) or the minimal dose received by 90 % of the prostate volume (D90 [Gy]) between the patients with and without seed migration.ConclusionsThis prospective cohort study investigating the largest number of past cases showed no difference in D90 (Gy) or V100 (%) between seed migration or the absence thereof in both the PI group and PI + EBRT group.Trial registrationClinicalTrials.gov: NCT00534196