Apex Dose Research Articles

Ruthenium-106 (106Ru) plaque brachytherapy for treatment of circumscribed choroidal hemangioma.

To describe the clinical and imaging features of circumscribed choroidal hemangiomas (CCH) and their treatment outcomes with Ruthenium-106 (106Ru) plaque brachytherapy. Retrospective study of 24 patients (24 eyes) diagnosed with CCH and treated with 106Ru plaque between 2017 and 2022. Analysis included pre- and post-treatment clinical and imaging features such as tumor regression, reduction in height, subretinal fluid (SRF) resolution, and change in best-corrected visual acuity (BCVA). The mean age at presentation was 36 years (range, 16-57). The most common tumor location was the temporal quadrant (n = 19) with macular involvement (n = 13). Associated features were macular SRF (n = 22) and inferior exudative retinal detachment (n = 10). Nineteen of the 24 patients underwent primary treatment, whereas 5 patients underwent plaque as a salvage treatment. The mean tumor apex dose was 40 Gy. At a median follow-up of 7.5 months (range 3-65 months), 18 eyes showed complete regression, whereas 6 eyes showed partial regression. The mean height decreased from 4.8 (SD 1.28) mm at presentation to 2.5 (SD 1.63) mm. Median BCVA improved from logMAR 1.2 (IQR 0.4-2) at baseline to logMAR 1.05 (IQR 0.1-1.95) (p = 0.4). Complete resolution of the macula and tumor SRF was observed in 15 (68%) and 13 (57%) eyes, respectively. The radiation-related complications observed were radiation maculopathy (4 eyes), retinopathy (1 eye), and vitreous hemorrhage (1 eye). Ruthenium-106 plaque brachytherapy is effective for CCH (> 3 mm height) as a primary and salvage treatment for tumors unresponsive to other modalities.

Apical dose versus volume dose of Ruthenium-106 brachytherapy for uveal melanoma

ObjectiveRuthenium-106 brachytherapy is commonly used to treat uveal melanomas. Most centres prescribe a radiation dose to the tumour apex that is calculated with the tumour located in the centre of the plaque. Recent work suggests that D99%—the minimum radiation dose delivered to 99% of tumour volume—may be a better predictor of tumour control than apex dose. Both dosing regimens may be affected by tumour and treatment variables differently. We explored the effect of differences in these variables on volume and apex dose using a 3-dimensional planning model. MethodsThe time required to deliver 100 Gy to the tumour apices of representative tumours ranging from 2- to 6-mm thickness with central plaque positioning was calculated in Plaque Simulator™. This treatment time was used for further calculations, including D99% with central plaque placement, and apical and tumour volume doses when tumour and plaque characteristics were altered, including eccentric plaque placement, either away from (tilt) or along (offset) scleral surface, tumour shape, and plaque type. ResultsD99% was always greater than the apex dose when plaques were placed centrally, and the difference increased with tumour thickness. Increasing degrees of tumour offset reduced apical dose and D99%, with a greater effect on apical dose for thicker and D99% for thinner tumours, respectively. Differences in tumour shape and plaque type had idiosyncratic effects on apical and volume dosing. ConclusionD99% and apex dose are affected by tumour and treatment characteristics in different ways, highlighting the complexity of radiation delivery to uveal tumours.

Deep-learning-driven dose prediction and verification for stereotactic radiosurgical treatment of isolated brain metastases

PurposeWhile deep learning has shown promise for automated radiotherapy planning, its application to the specific scenario of stereotactic radiosurgery (SRS) for brain metastases using fixed-field intensity modulated radiation therapy (IMRT) on a linear accelerator remains limited. This work aimed to develop and verify a deep learning-guided automated planning protocol tailored for this scenario.MethodsWe collected 70 SRS plans for solitary brain metastases, of which 36 cases were for training and 34 for testing. Test cases were derived from two distinct clinical institutions. The envisioned automated planning process comprised (1): clinical dose prediction facilitated by deep-learning algorithms (2); transformation of the forecasted dose into executable plans via voxel-centric dose emulation (3); validation of the envisaged plan employing a precise dosimeter in conjunction with a linear accelerator. Dose prediction paradigms were established by engineering and refining two three-dimensional UNet architectures (UNet and AttUNet). Input parameters encompassed computed tomography scans from clinical plans and demarcations of the focal point alongside organs at potential risk (OARs); the ensuing output manifested as a 3D dose matrix tailored for each case under scrutiny.ResultsDose estimations rendered by both models mirrored the manual plans and adhered to clinical stipulations. As projected by the dual models, the apex and average doses for OARs did not deviate appreciably from those delineated in the manual plan (P-value≥0.05). AttUNet showed promising results compared to the foundational UNet. Predicted doses showcased a pronounced dose gradient, with peak concentrations localized within the target vicinity. The executable plans conformed to clinical dosimetric benchmarks and aligned with their associated verification assessments (100% gamma approval rate at 3 mm/3%).ConclusionThis study demonstrates an automated planning technique for fixed-field IMRT-based SRS for brain metastases. The envisaged plans met clinical requirements, were reproducible across centers, and achievable in deliveries. This represents progress toward automated paradigms for this specific scenario.

Brachytherapy With 15- Versus 20-mm Ruthenium 106 Plaques Without Verification of Plaque Position Is Associated With Local Tumor Recurrence and Death in Posterior Uveal Melanoma

Brachytherapy with episcleral plaques is the most common primary tumor treatment for uveal melanoma. This study aims to compare the risk of tumor recurrence and metastatic death between two frequently used ruthenium-106 plaque designs: CCB (20.2 mm) and CCA (15.3 mm). Data were obtained from 1387 consecutive patients treated at XXX between 1981 and 2022 (439 with CCA and 948 with CCB plaques). During the period, scleral transillumination was performed to delineate tumor margins before plaque insertion, but no minimum scleral dose was used, and accurate plaque positioning was not verified after scleral attachment. Patients treated with CCA plaques had smaller tumors than those treated with CCB plaques (mean diameter 8.6 vs. 10.5 mm, P<0.001). There were no differences in patient sex, age, tumor distance to the optic disc, tumor apex dose, dose rate, or in rates of ciliary body involvement, eccentric plaque placement, or adjunct transpupillary thermotherapy. The average difference between plaque and tumor diameter was greater with the CCB plaque, and a smaller difference was an independent predictor of tumor recurrence. The 15-year incidence of tumor recurrence was 28% and 15% after treatment with CCA and CCB plaques, respectively (competing risk analysis, P<0.001). Multivariate Cox regression analysis revealed a lower risk for tumor recurrence with CCB plaques (HR 0.50). Similarly, patients treated with CCB plaques had a lower risk for uveal melanoma-related mortality (HR 0.77). Adjunct transpupillary thermotherapy did not reduce these risks. Uni- and multivariate time-dependent Cox regressions demonstrated that tumor recurrence was associated with uveal melanoma-related and all-cause mortality. Compared to 20 mm plaques, brachytherapy with 15 mm ruthenium plaques is associated with a higher risk for tumor recurrence and death. These adverse outcomes may be avoided by increasing safety margins and implementing effective methods to verify accurate plaque positioning.

Brachytherapy for Peripheral Retinal Capillary Haemangioblastoma in von Hippel-Lindau Disease.

To report our experience with 106ruthenium-brachytherapy of peripheral capillary haemangioblastomas in patients with von Hippel-Lindau disease. Retrospective case series. A total of 53 haemangioblastomas, treated with 106ruthenium-brachytherapy, were included in our study. The applied radiation dose, visual outcome, angioma activity, need for vitreoretinal surgery and incidence of secondary complications such as macular oedema, secondary glaucoma, vitreous haemorrhage, and epiretinal gliosis were assessed. All treated eyes could be preserved. In 11 patients (20.8%), single brachytherapy did not achieve complete inactivation of the tumour. 31% developed macular oedema postoperatively. Tractional retinal detachment developed in 23.8%, and epiretinal gliosis was observed in 2.4% of patients. Vitreoretinal surgery was necessary in 50% of all treated eyes. At the end of the follow-up, 40.5% of all treated eyes achieved visual acuity (VA) of 0.6 or better, and one third reached a VA of less than 0.1. Mean irradiation dose to the tumour apex was 144 Gy. Higher apex doses correlated with better tumour control of irradiated haemanigoblastomas and lower complication rates. Brachytherapy of peripheral retinal capillary haemangioblastomas is an effective treatment modality. Higher irradiation doses seem to lead to more successful treatment.

Low Dose 125I Brachytherapy And Transpupillary Thermal Therapy (TTT) For Small To Medium Size Choroidal Melanoma

To evaluate our institutional outcomes after treatment of small to medium size choroidal melanoma with low dose COMS brachytherapy. Single center, retrospective review of small to medium size choroidal melanoma < 5 mm in apical height managed from 2005-2019 with 125I brachytherapy at prescribed dose < 80 Gy, using a homogeneous dose calculation methodology. Ocular outcomes included visual acuity, presence of ocular radiation side effects, and local tumor recurrence. The Kaplan-Meier method was used to estimate overall survival, and metastasis rates were reported using cumulative incidence with death as a competing risk. Univariable associations were analyzed using Cox proportional hazards regression. Radiation statistics were calculated using Monte Carlo dosimetry. There were 146 patients included. Patient demographics and presenting tumor features are described in Table 1. Patients were treated with 125I plaque radiotherapy at median dose 65 Gy (IQR: 65-65 Gy) to depth of 5 mm, with additional transpupillary thermotherapy (TTT) at the time of plaque removal in 140 (95.9%) cases. Median follow-up was 6.7 years (IQR: 2.7-9.3 years). At final follow-up, median logMAR visual acuity was 1.1 (IQR: 0.4-2.0) with Snellen acuity 20/15-20/40 (20%), 20/50-20/160 (26%), and 20/200 or worse (54%). Radiation complications were as follows: cystoid macular edema in 54 (38%), radiation maculopathy in 71 (50%), non-proliferative radiation retinopathy in 53 (38%), proliferative radiation retinopathy in 20 (14%), and radiation papillopathy in 53 (38%). There were 11 patients who required subsequent pan-retinal laser photocoagulation (8%). Radiation dose did not appear to impact radiation maculopathy or retinopathy, but radiation papillopathy was significantly associated with point dose, maximum dose, and mean dose to the optic disc (p < 0.05). Local tumor control was achieved in 145 (99.3%) patients with recurrence in 1 (0.7%) patient 6.5 years after plaque. The 5-year cumulative incidence of distant metastasis was 7.2% with 5-year overall survival of 96.2%. Low dose 125I plaque radiotherapy with TTT provided high rates of local tumor control. Radiation maculopathy, retinopathy, and papillopathy were still observed even with reduced radiation apex dose. Future studies are warranted to determine rates of tumor control and ocular toxicity in low dose brachytherapy without TTT.Abstract 3687; TablePatient CharacteristicsMedian age61 years (IQR: 51-68 years)SexFemale 58%ComorbiditiesAtherosclerotic disease 44%Diabetes 18%Hyperlipidemia 45%Hypertension 49%Tumor CharacteristicsMedian logMAR visual acuity0.18 (IQR: 0.0-0.4)Snellen acuity20/15-20/40 68%20/50-20/160 29%20/200 or worse 3%Tumor dimensionsLargest basal diameter (IQR) 8.0 mm (IQR: 6.7-10.0 mm)Thickness (IQR) 2.0 mm (IQR: 2.0-2.0 mm)Secondary retinal detachment18%Subfoveal/subretinal fluid88% Open table in a new tab

Effect of plaque brachytherapy dose and dose rate on risk for disease-related mortality in 1238 patients with choroidal melanoma

BackgroundEpiscleral brachytherapy is the most common treatment for medium-sized choroidal melanomas. Although controversial, inadequate brachytherapy dose and dose rates have at least a hypothetical implication on patient survival.MethodsAll patients who...

Ru-106 plaque radiotherapy for vasoproliferative tumors of retina: a 15-year single-center experience.

This study evaluates the outcomes of ruthenium-106 (Ru-106) plaque brachytherapy for vasoproliferative tumors (VPTs) of the ocular fundus in a single referral ocular oncology center. The clinical charts of all patients diagnosed with VPT who underwent plaque radiotherapy from 2002 to 2017 were reviewed. Clinical features, types of treatment, outcomes and complications were evaluated. Of 46 patients with VPT diagnosis in our ocular oncology clinic, 25 (54.34%) cases were treated with Ru-106 plaque brachytherapy. Eleven patients (44%) were male, and the mean age at the time of diagnosis was 40.92 ± 13.11years. The mean follow-up time was 47.56 ± 36.87months. Inferotemporal quadrant was the most common site of the tumor (64.00%). The mean delivered apex and scleral dose was 101.56 ± 6.51 and 412.26 ± 113.66 Gray (Gy), respectively. Initial tumor length, width and thickness were 10.26 ± 3.42, 8.05 ± 2.83 and 4.27 ± 1.10mm, respectively. The mean tumor thickness decreased to 2.60 ± 0.63mm, postoperatively. Complete resolution of subretinal fluid around the tumor was achieved in 81.80% of cases. Visual acuity was more than 20/400 in 64% of patients before treatment and 60% of patients at last follow-up. Our study showed that Ru-106 plaque radiotherapy is an effective and safe method of treatment in VPTs.

Ruthenium-106 plaque brachytherapy for the treatment of diffuse choroidal hemangioma in Sturge-Weber syndrome.

To evaluate the efficacy of ruthenium-106 plaque brachytherapy for the treatment of diffuse choroidal hemangioma (DCH) in Sturge-Weber syndrome (SWS). A total of 8 patients with DCH in SWS managed with plaque brachytherapy were retrospectively included. Patients were treated with ruthenium-106 plaque therapy (median apex dose: 83 Gy) at the thickest tumor region. On follow-up, we recorded the tumor thickness, the best-corrected visual acuity (BCVA), subretinal fluid (SRF) status, and complications following treatment. At a median follow-up of 43mo, tumor regression was observed in all cases, with a complete resolution of SRF and reduction in tumor-thickness. No radiation complications were recorded during the follow up time. Ruthenium-106 plaque therapy to the thickest portion of the tumor seems to be a useful treatment in patients with DCH in SWS.

High-dose ruthenium-106 plaque therapy for circumscribed choroidal hemangioma: a retrospective study of 25 Chinese patients.

To evaluate the efficacy and safety of ruthenium-106 (106Ru) plaque radiotherapy at a dose (>50 Gy) higher than recommended (29-50 Gy) for treatment of circumscribed choroidal hemangioma (CCH) in Chinese patients. This retrospective study included 25 symptomatic CCH patients undergoing 106Ru plaque brachytherapy involving 25 eyes between January 2005 and August 2016. Ophthalmic examination was performed at the baseline and at each post-treatment follow-up visit, using best-corrected visual acuity (BCVA), dilated fundus examination, and B-scan ultrasonography. The primary efficacy outcome measures included the changes in BCVA and hemangioma dimensions at the last followup visit from the baseline. The mean follow-up duration was 28.0±26.6 (range, 12-110)mo. All the hemangiomas were located in the posterior pole except for two involving the fovea. The mean apex dose of 106Ru plaque radiotherapy was 84.4±19.7 Gy. The mean BCVA improved from 41.4±29.3 (0-97) at the baseline to 53.0±33.8 (0-97) ETDRS letters at the last visit (P=0.01). The mean hemangioma height declined from 3.98±0.88 (2.40-5.50) mm to 0.84±1.63 (0-6.47) mm (P≤0.001), and the greatest linear diameter (GLD) reduced from 9.36±2.23 (6.80-15.00) to 7.40±2.45 (0-13.00) mm (P≤0.001). Hemangioma size increased in one (4%) eye with a worsened vision, and subretinal fluid completely resolved in all but one patient (4%). Radiation-related retinopathy was observed in two patients at post-treatment 9 and 11mo, respectively. 106Ru plaque brachytherapy at a dose (>50 Gy) higher than recommended (29-50 Gy) is an effective treatment regimen for symptomatic CCH associated with significantly improved visual acuity and a favorable safety profile in Chinese patients.

Does the apex optimization line matter for single-channel vaginal cylinder brachytherapy planning?

The objective of this study is to test the impact of the use of the apex optimization line for new vaginal cylinder (VC) applicators. New single channel VC applicators (Varian) that have different top thicknesses but the same diameters as the old VC applicators (2.0 cm diameter, 2.3, 2.6, 3.0, and 3.5 cm) were compared using phantom studies. Old VC applicator plans without the apex optimization line were also compared to the plans with an apex optimization line. The apex doses were monitored at 5 mm depth doses (eight points) where a prescription dose (Rx) of 6 Gy was prescribed. VC surface doses (eight points) were also analyzed. The new VC applicator plans without apex optimization line presented significantly lower 5‐mm depth doses over the Rx (on average −31 ± 7%, P < 0.00001) due to thicker VC tops (3.4 ± 1.1 mm thicker with the range of 1.2–4.4 mm) than the old VC applicators. Old VC applicator plans also showed a statistically significant reduction (P < 0.00001) due to the Ir‐192 source anisotropic effect at the apex region, but the percent reduction over the Rx was only −7 ± 9%. However, by adding the apex optimization line to the new VC applicator plans, the plans improved 5‐mm depth doses (−7 ± 9% over Rx) that were not statistically different from old VC applicator plans (P = 0.923), along with apex VC surface doses (−22 ± 10% over old VC vs −46 ± 7% without using apex optimization line). The use of the apex optimization line is important in order to avoid significant additional cold doses (−24 ± 2%) at the prescription depth (5 mm) of the apex, specifically for the new VC applicators that have thicker tops. A template‐based vaginal cylinder planning reduced the intra‐ and inter‐planner variations of manual generation of apex optimization line, along with treatment time.

Comparison of dosimetric and clinical outcomes between short- and long-channel cylinder applicators for vaginal brachytherapy in intermediate- and high-risk endometrial cancer

PurposeVaginal brachytherapy (VBT) using a cylinder applicator is a standard treatment of intermediate- and high-risk endometrial cancer. We conducted a retrospective study of the dosimetric and clinical outcomes at our institution with 2 single-channel applicators in patients receiving VBT. Methods and MaterialsOne hundred thirty-six patients with endometrial cancer treated from 2006 to 2016 receiving VBT after definitive surgery were evaluated. Two cylinders were used with the distal dwell position 7.1–12.8 mm from the apex varying by diameter (short channel), and 3.2 mm from the apex (long channel). We prescribed 18–26 Gy in 3–4 fractions at 0.5 cm depth. Measurements of the distance from the apex to the prescription isodose line were taken from CT imaging. Student's t test and the Wilcoxon rank-sum test were used with corrections for multiple comparisons. ResultsPatients had International Federation of Gynecology and Obstetrics 2009 Stage I-II disease (70 Stage IA, 58 Stage IB, 9 Stage II). Mean cylinder apex dose was 95.2% and 154.7% of prescription (p < 0.001), and mean distance from apex to the prescription isodose line was 0.54 mm and 3.5 mm (p < 0.001) for the short- and long-channel cylinders, respectively. There were no significant differences in any toxicity between cylinders. Four patients (2.9%) had vaginal recurrence, all of whom were treated with the short-channel cylinder. Cylinder type was not associated with vaginal recurrence (p = 0.27). ConclusionsA cylinder applicator with a distal dwell position closer to the apex results in higher doses to the vaginal cuff and increased D2cc to the bladder. All four recurrences were in the short-channel cylinder. Additional investigation into applicator design and impact on patient outcomes in larger cohorts with sufficient followup is warranted.

Efficacy and Safety of Low-Dose Iodine Plaque Brachytherapy for Juxtapapillary Choroidal Melanoma

To evaluate low- vs high-dose plaque brachytherapy for juxtapapillary choroidal melanoma. Retrospective interventional case series. Setting: Single institution. Forty-seven patients with juxtapapillary choroidal melanoma. Iodine-125 plaque brachytherapy. Eyes were divided into apex low-dose (LD) and high-dose (HD) groups (≤ or > median apex dose 84.35 Gy). Main outcome measures were time to distant failure, local failure, death, enucleation, radiation retinopathy, optic neuropathy, and best-corrected visual acuity (BCVA). Freedom from distant failure rates were 96%and 95% in apex LD and HD groups at 5 years and 77% and 95% at 10 years, respectively (P= .84). Freedom from local failure rates were 90% in the apex LD group vs 89% in the HD group at 5 and 10 years (P= .96). Apex LD and HD groups did not differ for time to death or enucleation. Five- and 10-year freedom from radiation retinopathy and optic neuropathy rates were higher in the apex LD than HD group. Loss of ≥3BCVA lines, final BCVA 20/40 or better, and final BCVA 20/200 or worse were more favorable in the 5mm LD compared to HD group. Visual acuity outcomes did not differ between apex LD and HD groups. Low-dose iodine-125 plaque brachytherapy (67.5-81Gy at tumor apex) provides safe and effective tumor control for juxtapapillary choroidal melanoma and may be associated with reduced radiation toxicity. Larger trials are needed to determine the optimaltherapeutic dose for juxtapapillary choroidal melanoma.

Permanent prostate brachytherapy postimplant magnetic resonance imaging dosimetry using positive contrast magnetic resonance imaging markers

PurposePermanent prostate brachytherapy dosimetry using computed tomography-magnetic resonance imaging (CT-MRI) fusion combines the anatomic detail of MRI with seed localization on CT but requires multimodality imaging acquisition and fusion. The purpose of this study was to compare the utility of MRI only postimplant dosimetry to standard CT-MRI fusion-based dosimetry. Methods and MaterialsTwenty-three patients undergoing permanent prostate brachytherapy with use of positive contrast MRI markers were included in this study. Dose calculation to the whole prostate, apex, mid-gland, and base was performed via standard CT-MRI fusion and MRI only dosimetry with prostate delineated on the same T2 MRI sequence. The 3-dimensional (3D) distances between seed positions of these two methods were also evaluated. Wilcoxon-matched-pair signed-rank test compared the D90 and V100 of the prostate and its sectors between methods. ResultsThe day 0 D90 and V100 for the prostate were 98% versus 94% and 88% versus 86% for CT-MRI fusion and MRI only dosimetry. There were no differences in the D90 or V100 of the whole prostate, mid-gland, or base between dosimetric methods (p > 0.19), but prostate apex D90 was high by 13% with MRI dosimetry (p = 0.034). The average distance between seeds on CT-MRI fusion and MRI alone was 5.5 mm. After additional automated rigid registration of 3D seed positions, the average distance between seeds was 0.3 mm, and the previously observed differences in apex dose between methods was eliminated (p > 0.11). ConclusionsPermanent prostate brachytherapy dosimetry based only on MRI using positive contrast MRI markers is feasible, accurate, and reduces the uncertainties arising from CT-MRI fusion abating the need for postimplant multimodality imaging.

PREDICTORS OF TREATMENT RESPONSE OF VASOPROLIFERATIVE RETINAL TUMORS TO RUTHENIUM-106 BRACHYTHERAPY.

To identify predictors of treatment response by evaluating long-term outcomes of vasoproliferative retinal tumors after ruthenium-106 brachytherapy. In a retrospective case series, 39 eyes of 38 patients with vasoproliferative retinal tumors received ruthenium-106 brachytherapy between 2001 and 2013. Baseline clinical and morphologic parameters were analyzed regarding posttreatment tumor activity status. Within a median follow-up period of 2.9 ± 2.9 years, overall, a tumor inactivation was achieved in 72% of cases and visual acuity remained stable in 69%. The mean apex dose was 90 ± 23 Gy (range, 51-140 Gy). Mean tumor thickness decreased significantly, from 2.9 ± 0.9 mm to 1.5 ± 1.0 mm (P < 0.001; paired t-test). Persistence or recurrence of tumor activity occurred in 28% of cases, requiring secondary intervention with intravitreal drug injections, vitrectomy, cryotherapy, or repeated brachytherapy. Comparison of inactive and active vasoproliferative retinal tumors revealed significant correlation between both initial basal tumour diameter and area and subsequent tumour activity status. In particular, a diameter >7.5 mm was associated with an 8-fold risk of persistent or recurrent activity, whereas basal area >40 mm demonstrated a 6-fold risk (P = 0.009 and 0.021, respectively; Fisher's exact-test). In contrast, tumor thickness was not found to be of prognostic relevance. Ruthenium-106 brachytherapy is an effective and safe therapeutic option for vasoproliferative retinal tumors. Additionally, tumor diameter and area are efficient predictors of persistence or recurrence of tumor activity.

SU-F-P-61: Does It Matter Not to Use Optimization Points at the Apex for Vaginal Cylinder HDR Brachytherapy Planning?

Purpose: To test the impact of the use of apex optimization points for new vaginal cylinder (VC) applicators. Methods: New “ClickFit” single channel VC applicators (Varian) that have a different top thicknesses but the same diameters as the old VC applicators (2.3 cm diameter, 2.6 cm, 3.0 cm, and 3.5 cm) were compared using phantom studies. Old VC applicator plans without apex optimization points were also compared to the plans with the optimization points. The apex doses were monitored at 5 mm depth doses (8 points) where a prescription dose (Rx) of 6Gy was prescribed. VC surface doses (8 points) were also analyzed. Results: The new VC applicator plans without apex optimization points presented significantly lower 5mm depth doses than Rx (on average −31 ± 7%, p <0.00001) due to their thicker VC tops (3.4 ± 1.1 mm thicker with the range of 1.2 to 4.4 mm) than the old VC applicators. Old VC applicator plans also showed a statistically significant reduction (p <0.00001) due to Ir-192 source anisotropic effect at the apex region but the % reduction over Rx was only −7 ± 9%. However, by adding apex optimization points to the new VC applicator plans, the plans improved 5 mm depth doses (−7 ± 9% over Rx) that were not statistically different from old VC plans (p = 0.923), along with apex VC surface doses (−22 ± 10% over old VC versus −46 ± 7% without using apex optimization points). Conclusion: The use of apex optimization points are important in order to avoid significant additional cold doses (−24 ± 2%) at the prescription depth (5 mm) of apex, especially for the new VC applicators that have thicker tops.

Ruthenium-106 brachytherapy for thick uveal melanoma: reappraisal of apex and base dose radiation and dose rate.

PurposeTo evaluate the outcomes of ruthenium-106 (106Ru) brachytherapy in terms of radiation parameters in patients with thick uveal melanomas.Material and methodsMedical records of 51 patients with thick (thickness ≥ 7 mm and < 11 mm) uveal melanoma treated with 106Ru brachytherapy during a ten-year period were reviewed. Radiation parameters, tumor regression, best corrected visual acuity (BCVA), and treatment-related complications were assessed.ResultsFifty one eyes of 51 consecutive patients including 25 men and 26 women with a mean age of 50.5 ± 15.2 years were enrolled. Patients were followed for 36.1 ± 26.5 months (mean ± SD). Mean radiation dose to tumor apex and to sclera were 71 (± 19.2) Gy and 1269 (± 168.2) Gy. Radiation dose rates to tumor apex and to sclera were 0.37 (± 0.14) Gy/h and 6.44 (± 1.50) Gy/h. Globe preservation was achieved in 82.4%. Preoperative mean tumor thickness of 8.1 (± 0.9) mm decreased to 4.5 (± 1.6) mm, 3.4 (± 1.4) mm, and 3.0 (± 1.46) mm at 12, 24, and 48 months after brachytherapy (p = 0.03). Four eyes that did not show regression after 6 months of brachytherapy were enucleated. Secondary enucleation was performed in 5 eyes because of tumor recurrence or neovascular glaucoma. Tumor recurrence was evident in 6 (11.8%) patients. Mean Log MAR (magnification requirement) visual acuity declined from 0.75 (± 0.63) to 0.94 (± 0.5) (p = 0.04). Best corrected visual acuity of 20/200 or worse was recorded in 37% of the patients at the time of diagnosis and 61.7% of the patients at last exam (p = 0.04). Non-proliferative and proliferative radiation-induced retinopathy was observed in 20 and 7 eyes.ConclusionsThick uveal melanomas are amenable to 106Ru brachytherapy with less than recommended apex radiation dose and dose rates.

Suspected vitreous seeding of uveal melanoma: relevance of diagnostic vitrectomy

AimTo review all cases of suspected vitreous seeding of treated or untreated uveal melanoma at our clinic and to compare clinical, cytological and histological findings with patients’ survival.MethodsRetrospective non-randomised study...

SU‐E‐T‐16: A Comparison of Expected Dwell Times and Dose Variations for NAMD Patients Treated with An Episcleral Brachytherapy Device

Purpose:To evaluate the variations in dwell times and doses expected when using an episcleral brachytherapy device for treatment of neovascular agerelated macular degeneration (n‐AMD) based on accurate imaging modalitiesMethods:Data from 40 eyes from 40 subjects with known n‐ AMD acquired through the Distance of Choroid Study (DOCS) conducted at Moorfields Eye Hospital was used to determine the target depth; the distance from the outer scleral surface of the eye, through the choroid, to the apex of the choroidal neovascularization (CNV). Each subject underwent, in triplicate, enhanced‐depth Spectral Domain Optical Coherence Tomography (SD‐OCT), Swept Source Optical Coherence Tomography, (SS‐OCT) and Ocular Ultrasound (O‐US). These data are the most comprehensive and accurate measurements of the dimensions of the CNV and adjacent layers of the eye for this cohort of patients. During treatment of n‐AMD, patients receive a dose of 24Gy to the apex at the target depth. Using the percentage depth dose for a Sr‐90 episcleral brachytherapy device, dwell times and doses to the apex were computed to determine the expected variations.Results:The mean target depth and the 95% confidence interval (CI) determined by combining O‐US with SD‐OCT were 1326 (956,1696)µm and with SS‐OCT were 1332 (970,1693)µm. The calculated corresponding mean dwell times and 95% (CI) were 334 (223,445)s and 335 (226,445)s for SD‐OCT and SS‐OCT determined depths, respectively. The corresponding mean apex dose and 95% (CI) were 24 (35.9,18.0)Gy (SD‐OCT) and 24 (35.6,18.1)Gy (SS‐OCT).Conclusion:For episcleral brachytherapy treatment of n‐AMD, using a patient population average target depth for treatment planning is inadequate, resulting in dose variations of a factor of approximately two over the 95% CI and larger variations for a nontrivial segment of the population. Each patient should have individualized imaging studies to determine the target depth for use in the dwell time calculation.Study was sponsored by Salutaris Medical Devices, Ltd., a subsidiary of Salutaris Medical Devices, Inc. Hamilton and Marsteller are founders of Salutaris Medical Devices, Inc. Drew, McGovern and Vitali are minor equity holders in Salutaris Medical Devices, Inc.

SU‐E‐T‐448: Heightened Apical Positivity of 2‐Year Post‐Radiotherapy Biopsies Is Not Related to Suboptimal Dosimetry

Purpose:Previous research has demonstrated that following radiation therapy for prostate cancer, there is a relative increase in positive biopsies in the apex versus the rest of the prostate. The increase could be due to: 1) Inter‐fraction apex motion or deformation, 2) Intra‐fraction apex motion or deformation, 3) Suboptimal dose coverage in the apex, 4) Tissue composition in the apex and/or 5) Prostate size. In this initial study, the potential for suboptimal dose coverage in the apex was assessed by splitting the prostate planning target volume into the apex (inferior third) and remainder.Methods:69 patients were selected from 303 patients treated on a clinical radiotherapy trial for prostate cancer. These patients were selected as they had both a localized (sextant template) 2‐year post‐treatment biopsy and 3D dose information. Of these patients, 10 had positive biopsies in the apex, 8 in the remainder and 11 in both locations. For all patients, the following dosimetric data was acquired from the apex dose volume histogram: Dmean, Dmax, Dmin, D95% and V100%. Unpaired, one‐tailed t‐tests were used to test for statistical significance (p &lt; 0.05) between all dosimetric parameters for patients with positive versus negative apical biopsies. Additionally, D95% for the apex was plotted against D95% of the remainder.Results:There was no statistical difference for the selected apical dosimetric parameters for patients with positive versus negative biopsies (p‐values &gt; 0.05). No correlation was found between D95% (normalized to the prescription dose) for the apex and remainder (R2 = 0.0116).Conclusion:No correlation was found between positive apical biopsy and suboptimal dosimetric coverage. Current research is looking into inter‐fraction apex motion and deformation as a potential source of the increased apical failure using daily CBCT images.