Rapid multi-catheter segmentation for magnetic resonance image-guided catheter-based interventions.

BACKGROUND: Magnetic resonance imaging (MRI) is the gold standard for delineating cancerous lesions in soft tissue. Catheter-based interventions require the accurate placement of multiple long, flexible catheters at the target site. The manual segmentation of catheters in MR images is a challenging and time-consuming task. There is a need for automated catheter segmentation to improve the efficiency of MR-guided procedures. PURPOSE: To develop and assess a machine learning algorithm for the detection of multiple catheters in magnetic resonance images used during catheter-based interventions. METHODS: In this work, a 3D U-Net was trained to retrospectively segment catheters in scans acquired during clinical MR-guided high dose rate (HDR) prostate brachytherapy cases. To assess confidence in segmentation, multiple AI models were trained. On clinical test cases, average segmentation results were used to plan the brachytherapy delivery. Dosimetric parameters were compared to the original clinical plan. Data was obtained from 35 patients who underwent HDR prostate brachytherapy for focal disease with a total of 214 image volumes. 185 image volumes from 30 patients were used for training using a five-fold cross validation split to divide the data for training and validation. To generate confidence measures of segmentation accuracy, five trained models were generated. The remaining five patients (29 volumes) were used to test the performance of the trained model by comparison to manual segmentations of three independent observers and assessment of dosimetric impact on the final clinical brachytherapy plans. RESULTS: The network successfully identified 95% of catheters in the test set at a rate of 0.89 s per volume. The multi-model method identified the small number of cases where AI segmentation of individual catheters was poor, flagging the need for user input. AI-based segmentation performed as well as segmentations by independent observers. Plan dosimetry using AI-segmented catheters was comparable to the original plan. CONCLUSION: The vast majority of catheters were accurately identified by AI segmentation, with minimal impact on plan outcomes. The use of multiple AI models provided confidence in the segmentation accuracy and identified catheter segmentations that required further manual assessment. Real-time AI catheter segmentation can be used during MR-guided insertions to assess deflections and for rapid planning of prostate brachytherapy.

Dosimetric Investigation of Six Ru-106 Eye Plaques by EBT3 Radiochromic Films and Monte Carlo Simulation.

Background: Ophthalmic brachytherapy using radioactive plaques is an effective technique for the treatment of uveal melanoma. Ru-106 eye plaques are considered as interesting issue due to their steep gradient dose. The pre-planning evaluation of dosimetric parameters is essential for the treatment planning system. Objective: The current study aims at providing dose distributions of six Ru-106 eye plaques (CCA, CCB, CGD, CIB, COB and COD) using radiochromic EBT3 film, Geant4 Monte Carlo toolkit and the treatment planning software (Plaque Simulator). Material and Methods: In this experimental study, an in-house phantom was employed for depth dose measurements with EBT3 films. Also, Geant4.10.5 scoring mesh was implemented to obtain the 2D dose distribution of the plaques. The results were compared with Plaque Simulator software and the manufacturer's (BEBIG) data. The gamma index criterion (3%/3 mm) was used to evaluate dose distributions obtained by the film measurements and Geant4 simulation. Results: A good agreement was achieved between simulation and experimental results. Gamma index passing rate was 94.2%, 89.3%, 88.2%, 82.2%, 92.2% and 90.1% for CCA, CCB, CGD, CIB, COB and COD plaques, respectively. Absolute dose rate (mGy/min) obtained by EBT3 film at the depth of 2 mm was 79.4 mGy/min, 81.0 mGy/min, 78.6 mGy/min, 62.2 mGy/min, 75.2 mGy/min and 81.2 mGy/min for CCA, CCB, CGD, CIB, COB and COD plaques, respectively. Conclusion: The measured dose distributions and lateral dose profiles may be utilized in the treatment planning system to cover clinical volumes such as the clinical target volume and the gross tumor volume.

Comparing dosimetry of locally advanced cervical cancer patients treated with 3 versus 4 fractions of MRI-guided brachytherapy.

PURPOSE: To demonstrate the feasibility of treating cervical cancer patients with MRI-guided brachytherapy (MRgBT) using 24 Gy in 3 fractions (F) versus a standard, more resource-intensive regimen of 28 Gy in 4F, and its ability to meet EMBRACE II planning aims. METHODS AND MATERIALS: A retrospective review of 224 patients with FIGO Stage IB-IVA cervical cancer treated with 28 Gy/4F (n = 91) and 24 Gy/3F (n = 133) MRgBT between 2016-2021 was conducted. Multivariable linear regression models were fitted to compare dosimetric parameters between the two groups, adjusting for CTVHR and T stage. RESULTS: Most patients had squamous cell carcinoma, T2b disease, and were treated with intracavitary applicator plus interstitial needles (96%). The 28 Gy/4F group had higher CTVHR (median 28 vs. 26 cm3, p = 0.04), CTVIR D98% (mean 65.5 vs. 64.5 Gy, p = 0.03), rectum D2cm3 (mean 61.7 vs. 59.2 Gy, p = 0.04) and bladder D2cm3 (81.3 vs. 77.9 Gy, p = 0.03). There were no significant differences in the proportion of patients meeting the EMBRACE II OAR dose constraints and planning aims, except fewer patients treated with 28 Gy/4F met rectum D2cm3 < 65 Gy (73 vs. 85%, p = 0.027) and ICRU rectovaginal point < 65 Gy (65 vs. 84%, p = 0.005). CONCLUSIONS: Cervical cancer patients treated with 24 Gy/3F MRgBT had comparable target doses and lower OAR doses compared to those treated with 28 Gy/4F. A less-resource intense fractionation schedule of 24 Gy/3F is an alternative to 28 Gy/4F in cervix MRgBT.

Acute toxicity and health-related quality of life outcomes of localized prostate cancer patients treated with magnetic resonance imaging-guided high-dose-rate brachytherapy: A prospective phase II trial.

PURPOSE: To report acute toxicity and health-related quality of life (HRQoL) outcomes of a phase II clinical trial of magnetic resonance imaging (MRI)-guided prostate high-dose-rate brachytherapy (HDR-BT) combined with external beam radiotherapy. METHODS AND MATERIALS: Patients with intermediate- and high-risk prostate cancer (PCa) were eligible. Treatment consisted of a single 15 Gy MRI-guided HDR-BT followed by external beam radiotherapy (37.5-46 Gy depending on their risk category). Dosimetry, toxicity and HRQoL outcomes were collected prospectively at baseline, 1 and 3 months using Common Terminology Criteria for Adverse Events Version 4.0 and the expanded PCa index composite, respectively. General linear mixed modeling was conducted to assess the changes in expanded PCa index composite domain scores over time. A minimally important difference was defined as a deterioration of HRQoL scores at 3 months compared to baseline ≥ 0.5 standard deviation. A p value ≤ 0.05 was considered statistically significant. RESULTS: Sixty-one patients were included. Acute grade (G)2 urinary toxicity was observed in 18 (30%) patients while 1 (2%) patient had G3 toxicity, and none had G4 toxicity. Two patients had an acute urinary retention. G2 gastrointestinal toxicity was reported by 5 (8%) patients with no G3-4. Compared to baseline, urinary HRQoL scores significantly declined at 1 month (p < 0.001) but recovered at 3 months (p > 0.05). Bowel (p < 0.001) and sexual (p < 0.001) domain scores showed a significant decline over the 3-month follow-up period. At 3 months, 44%, 49% and 57% of patients reported a minimally important difference respectively in the urinary bowel and sexual domains. CONCLUSION: MRI-guided HDR-BT boost is a safe and well tolerated treatment of intermediate- and high-risk PCa in the acute setting. A longer follow-up and a comparison to ultrasound-based HDR-BT are needed to assess the potential benefit of MRI-guided prostate HDR-BT.

Comparison of Iodide-125 and Ruthenium-106 Brachytherapy in the Treatment of Choroidal Melanomas.

BACKGROUND: To compare iodine-125 (125I) with ruthenium-106 (106Ru) episcleral plaque radiation therapy in terms of the effectiveness and non-inferiority for choroidal melanoma treatment. OBJECTIVE: To report the non-inferiority of new made iodine-125 (125I) compared with ruthenium-106 (106Ru) episcleral plaque radiation. PATIENTS AND METHODS: A retrospective, non-randomized comparative case series. In this series the patients treated with 125I and 106Ru episcleral plaques for choroidal melanoma between September 2013 and August 2017 at Farabi Hospital are compared. Local control of choroidal melanomas after 125I and 106Ru plaques implantation and vision changes are the main outcome measures. RESULTS: A total of 35 patients were identified (125I = 15, 106Ru = 20). No significant difference between two groups in visual acuity, diameter and thickness changes were observed after treatment. Multivariate linear regression (MLR) analysis showed that final diameter was only, independently and significantly, correlated with the pre-treatment diameter of the tumor (ß = 0.59, 95% confidence interval [CI]: 0.29, 1.34, P = 0.003). The same MLR analysis for the final thickness and visual acuity, after adjusting for age and sex showed no significant difference between two groups. A single patient treated with 106Ru had local tumor recurrence with no one in the 125I group. No statistical difference in the rate of ocular complications was observed. CONCLUSION: The treatment with our 125I plaques is as effective as 106Ru plaques in controlling choroidal melanoma tumor and preserving the vision during the two and half year of follow-up. The complication rates are alike. It means that the effectiveness of 125I is not only comparable to 106Ru but also superior when the outcome of the interest is the thickness of the tumors.

Patient-reported sexual adjustment after definitive chemoradiation and MR-guided brachytherapy for cervical cancer.

PURPOSE: The treatment of locally advanced cervical cancer with definitive chemoradiation (CRT) is associated with vaginal toxicity and altered sexual satisfaction. This prospective study assessed patient-reported sexual adjustment, vaginal dosimetry, and physician-reported vaginal toxicity in patients with cervical cancer treated with CRT and MR-guided brachytherapy (BT). MATERIALS AND METHODS: Between 2008 and 2010, International Federation of Gynecologists and Obstetricians stage IB-IVA patients with cervical cancer receiving definitive CRT were enrolled in a feasibility study assessing MR-guided BT. Patients completed the validated sexual adjustment questionnaire (SAQ) before BT (baseline) and during followup. Physician-reported vaginal toxicity was recorded. The International Commission on Radiation Units and Measurements rectovaginal point, mean vaginal dose, and D2cm3 were calculated. Mean SAQ scores at baseline and followup assessments were calculated. Mean time effects were estimated using a linear mixed-effects model. A multivariable linear mixed-effects model was used to examine the association between total and individual scores (repeated measures) and covariates. RESULTS: Sixty patients were approached to participate: 29 consented and 27 completed the SAQ at baseline and followup. The diagnosis of cervical cancer and treatment negatively impacted sexual relationships in 61% and 39%, respectively. There were no significant changes in sexual adjustment over time (p = 0.599). There were no associations between sexual adjustment and the International Commission on Radiation Units and Measurements rectovaginal point dose or clinical vaginal involvement. Patients with higher International Federation of Gynecologists and Obstetricians stages (≥IIB) had significantly worse sexual adjustment (p = 0.005). CONCLUSION: CRT and MR-guided BT negatively impacted sexual relationships in patients with cervix cancer; however, there were no significant longitudinal changes in patient-reported sexual adjustment. Worse sexual adjustment may be associated with more advanced disease presentations.

Magnetic Resonance Imaging-guided Brachytherapy Re-irradiation for Isolated Local Recurrence of Soft Tissue Sarcoma.

Management options for locally recurrent sarcoma of the pelvis in patients previously treated with external beam radiation and surgery are limited. Pelvic exenteration is often the only viable but unattractive option. We present a patient with recurrent myxoid round cell liposarcoma of the ischiorectal fossa treated in 2013 with preoperative radiation (50 Gy in 25 fractions) and subsequent wide local resection. Four years later, a follow-up magnetic resonance imaging (MRI) scan demonstrated a 1 x 1 cm T2 hypointense soft tissue pre-sacral nodule consistent with local recurrence (LR). The patient declined posterior pelvic exenteration and was treated with 12 Gy using high dose rate brachytherapy (BT) under MRI-guidance followed by a further external beam radiation to a dose of 30 Gy in 15 fractions.

Comparison of dosimetric parameters derived from whole organ and wall contours for bladder and rectum in cervical cancer patients treated with intracavitary and interstitial brachytherapy.

For volumes up to 2 cm3 of the bladder and possibly up to 5 cm3 of the rectum, doses computed from the whole organ were good estimates of the doses in the wall in cervix brachytherapy, and there were no significant differences between patients treated with or without interstitial needles.

Technique adaptation, strategic replanning, and team learning during implementation of MR-guided brachytherapy for cervical cancer.

PURPOSE: MR-guided brachytherapy (MRgBT) with interstitial needles is associated with improved outcomes in cervical cancer patients. However, there are implementation barriers, including magnetic resonance (MR) access, practitioner familiarity/comfort, and efficiency. This study explores a graded MRgBT implementation strategy that included the adaptive use of needles, strategic use of MR imaging/planning, and team learning. METHODS AND MATERIALS: Twenty patients with cervical cancer were treated with high-dose-rate MRgBT (28 Gy in four fractions, two insertions, daily MR imaging/planning). A tandem/ring applicator alone was used for the first insertion in most patients. Needles were added for the second insertion based on evaluation of the initial dosimetry. An interdisciplinary expert team reviewed and discussed the MR images and treatment plans. RESULTS: Dosimetry-trigger technique adaptation with the addition of needles for the second insertion improved target coverage in all patients with suboptimal dosimetry initially without compromising organ-at-risk (OAR) sparing. Target and OAR planning objectives were achieved in most patients. There were small or no systematic differences in tumor or OAR dosimetry between imaging/planning once per insertion vs. daily and only small random variations. Peer review and discussion of images, contours, and plans promoted learning and process development. CONCLUSIONS: Technique adaptation based on the initial dosimetry is an efficient approach to implementing MRgBT while gaining comfort with the use of needles. MR imaging and planning once per insertion is safe in most patients as long as applicator shifts, and large anatomical changes are excluded. Team learning is essential to building individual and programmatic competencies.

Intermediate dose-volume parameters and the development of late rectal toxicity after MRI-guided brachytherapy for locally advanced cervix cancer.

PURPOSE: The dose delivered to the most exposed 2 cm3 [Formula: see text] of the rectum and bladder is predictive of late rectal and bladder toxicity in cervix cancer patients. We investigated the predictive value of intermediate doses to the rectum and bladder for late rectal/bladder toxicity after MRI-guided brachytherapy for patients with locally advanced cervix cancer. METHODS AND MATERIALS: Toxicity was prospectively graded using Common Toxicity Criteria for Adverse Events v4.0 and retrospectively verified for women with Stage IB-IVA cervix cancer treated consecutively with MRI-guided brachytherapy between 2008 and 2013. The minimum equivalent dose in 2 Gy fractions delivered to 0.1, 1, 2, 5, and 10 cm3 of the rectum and bladder and the absolute volume of the rectum receiving 55, 60, 65, 70, and 75 Gy3 (V55-75) were collected. The association between dose-volume parameters and Grade 2+ rectal/bladder toxicity was examined using logistic regression. RESULTS: With a median followup of 44 months, cumulative incidences of Grade 2+ rectal and bladder toxicity among the 106 patients were 29% and 15% at 3 years, respectively. All the dose-volume parameters were significantly associated with late Grade 2+ rectal and bladder toxicity (p < 0.05), except for bladder [Formula: see text] . On multivariable logistic regression, both [Formula: see text]  > 70 Gy3 and V55 > 11 cm3 (p < 0.05) were predictive of late Grade 2+ rectal toxicity, with improved model fitting and higher area under the curve compared with the model with [Formula: see text]  > 70 Gy3 alone. CONCLUSIONS: In this study, V55 was predictive of late Grade 2+ rectal toxicity. Adding V55 to  [Formula: see text] improved prediction accuracy.

A prospective study of DWI, DCE-MRI and FDG PET imaging for target delineation in brachytherapy for cervical cancer.

BACKGROUND AND PURPOSE: We examined the utility of dynamic contrast-enhanced MRI (DCE-MRI), diffusion-weighted MRI (DWI), and FDG-PET imaging for brachytherapy target delineation in patients with locally advanced cervical cancer. MATERIALS AND METHODS: Twenty-two patients had DWI, DCE-MRI, and FDG-PET/CT scans after brachytherapy applicator insertion, in addition to standard T2-weighted (T2w) 3T MRI. Gross tumor volume (GTVB) and high-risk clinical target volume (HRCTV) were contoured first on T2w images, and then modified if indicated upon review of DWI/DCE-MRI/FDG-PET images by two observers. The primary endpoint was utility, determined by the number of patients whose volumes were modified, and interobserver variability. RESULTS: Eleven patients' T2w-GTVB were modified based on DWI/DCE-MRI/FDG-PET by observer 1, due to clearer demarcation (7) and residual disease not well visualized on T2w MRI (4). GTVB was modified in 17 patients by observer 2 (11 and 6, respectively). Incorporation of functional imaging improved the conformity index (CI) for GTVB from 0.54 (T2w alone) to 0.65 (P=0.003). HRCTV was modified in 3 and 8 patients by observers 1 and 2, respectively, with a trend toward higher CI using functional imaging (0.71 to 0.76, P=0.06). CONCLUSIONS: DWI/DCE-MRI/FDG-PET imaging as a supplement to T2w MRI decreased interobserver variability in GTVB delineation.

Dosimetric and late radiation toxicity comparison between iodine-125 brachytherapy and stereotactic radiation therapy for juxtapapillary choroidal melanoma.

PURPOSE: To compare the dose distributions and late radiation toxicities for (125)I brachytherapy (IBT) and stereotactic radiation therapy (SRT) in the treatment of juxtapapillary choroidal melanoma. METHODS: Ninety-four consecutive patients with juxtapapillary melanoma were reviewed: 30 have been treated with IBT and 64 with SRT. Iodine-125 brachytherapy cases were modeled with plaque simulator software for dosimetric analysis. The SRT dosimetric data were obtained from the Radionics XKnife RT3 software. Mean doses at predetermined intraocular points were calculated. Kaplan-Meier estimates determined the actuarial rates of late toxicities, and the log-rank test compared the estimates. RESULTS: The median follow-up was 46 months in both cohorts. The 2 cohorts were balanced with respect to pretreatment clinical and tumor characteristics. Comparisons of radiation toxicity rates between the IBT and SRT cohorts yielded actuarial rates at 50 months for cataracts of 62% and 75% (P=.1), for neovascular glaucoma 8% and 47% (P=.002), for radiation retinopathy 59% and 89% (P=.0001), and for radiation papillopathy 39% and 74% (P=.003), respectively. Dosimetric comparisons between the IBT and SRT cohorts yielded mean doses of 12.8 and 14.1 Gy (P=.56) for the lens center, 17.6 and 19.7 Gy (P=.44) for the lens posterior pole, 13.9 and 10.8 Gy (P=.30) for the ciliary body, 61.9 and 69.7 Gy (P=.03) for optic disc center, and 48.9 and 60.1 Gy (P<.0001) for retina at 5-mm distance from tumor margin, respectively. CONCLUSIONS: Late radiation-induced toxicities were greater with SRT, which is secondary to the high-dose exposure inherent to the technique as compared with IBT. When technically feasible, IBT is preferred to treat juxtapapillary choroidal melanoma.

A comparison between ¹²5Iodine brachytherapy and stereotactic radiotherapy in the management of juxtapapillary choroidal melanoma.

AIMS: To compare the treatment efficacy and radiation complications between (125)Iodine brachytherapy and stereotactic radiotherapy in the management of juxtapapillary choroidal melanoma. METHODS: Consecutive juxtapapillary melanoma patients treated with radiotherapy were included. Patients were divided into two cohorts: patients treated with (125)Iodine brachytherapy and patients with stereotactic radiotherapy. Comparison included the rates postradiotherapy local recurrence, secondary enucleation, metastasis and radiotherapy complications. Kaplan-Meier estimates were used to determine the actuarial rates, and logrank test to compare between the estimates. RESULTS: We included 94 patients with juxtapapillary melanoma treated with radiotherapy. The brachytherapy cohort included 30 patients and stereotactic radiotherapy was 64. The median follow-up was 46 months in both cohorts. No statistically significant differences existed between the two cohorts on comparing pretreatment clinical data and tumour characteristics. On comparing treatment efficacy, the actuarial rates at 50 months for tumour recurrence were 11% and 7% (p=0.61), secondary enucleation was 11% and 21% (p=0.30) and for metastasis were 4% and 16% (p=0.11), respectively. On comparing treatment complications, the actuarial rates at 50 months for cataracts were 62% and 75% (p=0.1), for neovascular glaucoma 8% and 47% (p=0.002), for radiation retinopathy 59% and 89% (p=0.0001), and for radiation papillopathy 39% and 74% (p=0.003), respectively. CONCLUSIONS: Both (125)Iodine brachytherapy and stereotactic radiotherapy demonstrate comparable efficacy in the management of juxtapapillary choroidal melanoma. However, stereotactic radiotherapy shows statistically significant higher radiation-induced ocular morbidities at 4 years postradiotherapy.

Improving quality assurance for assembled COMS eye plaques using a pinhole gamma camera.

A quality assurance system has been designed to verify the location and strength of seeds loaded in a brachytherapy eye plaque. This system consists of (1) a pinhole camera in conjunction with a Lumisys ACR-2000i computed radiography (CR) unit to image the location and measure the relative strength of the seeds with autoradiography, and (2) a source strength jig with a survey meter to estimate the total activity of the seeds in the plaque. Five holders of different sizes were made for fixation of the COMS (Collaborative Ocular Melanoma Study) plaques (12, 14, 16, 18, and 20 mm) in the camera. The plaque-to-pinhole distance (dpp) has been optimized to be 30 mm to give approximately uniform intensity on the CR image for uniformly loaded COMS plaques. The pinhole-to-detector distance (dpd) can be kept at either 30 mm for 1:1 scale, or at larger distances for higher magnification. For a 1:1 scaling and pinhole diameter of 0.345 mm, useful images are obtained with time-activity product (mCi sec) ranging from 5 to 250 mCi sec. Within this range, the pinhole system is able to differentiate seed activities of >10%. The resulting pinhole autoradiograph is able to (1) confirm the correct number of seeds loaded in the plaque, (2) verify the proper sitting of the seeds in the silastic carrier and the plaque, (3) verify the relative activity distribution of the seeds loaded in the plaque, and (4) potentially evaluate the integrity of the seed. The source strength measurement system is able to measure the total strength of seeds in the plaque ranging from 10 to 80 mCi with an uncertainty of 5%.

EDR2 film dosimetry for IMRT verification using low-energy photon filters.

Recently the EDR2 (extended dose range) film has been introduced commercially for applications in radiation therapy dosimetry. In addition to characterizing the wide dynamic range, several authors have reported a reduced energy dependence of this film compared to that of X-Omatic Verification (XV) films for megavoltage photon beams. However, those investigations were performed under limited geometrical conditions. We have investigated the dosimetric performance of EDR2 film for the verification of IMRT fields at more clinically relevant conditions by comparing the film doses with the doses measured with an ion chamber and XV films. The effects of using a low energy scattered photon filter on EDR2 film dosimetry was also studied. In contrast to previous reports our results show that EDR2 film still exhibits considerable energy dependence (a maximum discrepancy of 9%, compared with an ion chamber) at clinically relevant conditions (10 cm depth for IMRT fields). However, by using the low-energy filters the discrepancy is reduced to within 3%. Therefore, EDR2 film, in combination with the filters, is found to be a promising two-dimensional dosimeter for verification of IMRT treatment fields.