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PurposeTo study the dosimetric differences of various channel combinations of the Capri vaginal applicator.Methods and materialsThe Capri consists of a single central channel (R1), an inner array of 6 channels (R2), and an outer array of 6 channels (R3). Three-dimensional plans were simulated for 6 channel arrangements (R1, R2, R12, R13, R23, and R123). Treatment plans were optimized to the applicator surface or 5-mm depth while minimizing dose to organs at risk (OARs: bladder, rectum, sigmoid, and urethra). The clinical target volume (CTV) was defined as a 5-mm circumferential shell extending 4 cm in length around the applicator. Clinical target volume coverage (Dmean, D90, V100, and V150) and OAR doses (D0.1 cm3, D1 cm3, D2 cm3, and Dmean) were compared. A comparison between the Capri (R123) and a conventional single-channel applicator was also done. Statistical significance (P value<.05) was evaluated with a 2-tailed t test.ResultsWhen prescribing to 5-mm depth, CTV coverage using all 13 channels (R123) versus a single channel (R1) was similar; however, when prescribing to the surface there were differences (P<.0001) in all CTV metrics except for the V150. The R1 plans had higher doses to all OARs compared with R123 plans (P<.007). Doses to OARs were not significantly different between R23 and R123 plans (P=.05-.95), and CTV coverage differences were on the order of 1%. Capri R123 plans provided slightly lower CTV D90 and Dmean but equivalent OAR doses with smaller standard deviations compared with conventional cylinder plans for both prescriptions.ConclusionsThe Capri multichannel applicator provides equivalent target coverage at 5-mm depth, with significantly reduced dose to OARs relative to using a single channel. Optimal plans can be achieved using R12 (lowest V150) or R123 or R23 (lowest OAR doses).

PurposeTo study the dosimetric differences of various channel combinations of the Capri vaginal applicator.Methods and materialsThe Capri consists of a single central channel (R1), an inner array of 6 channels (R2), and an outer array of 6 channels (R3). Three-dimensional plans were simulated for 6 channel arrangements (R1, R2, R12, R13, R23, and R123). Treatment plans were optimized to the applicator surface or 5-mm depth while minimizing dose to organs at risk (OARs: bladder, rectum, sigmoid, and urethra). The clinical target volume (CTV) was defined as a 5-mm circumferential shell extending 4 cm in length around the applicator. Clinical target volume coverage (Dmean, D90, V100, and V150) and OAR doses (D0.1 cm3, D1 cm3, D2 cm3, and Dmean) were compared. A comparison between the Capri (R123) and a conventional single-channel applicator was also done. Statistical significance (P value<.05) was evaluated with a 2-tailed t test.ResultsWhen prescribing to 5-mm depth, CTV coverage using all 13 channels (R123) versus a single channel (R1) was similar; however, when prescribing to the surface there were differences (P<.0001) in all CTV metrics except for the V150. The R1 plans had higher doses to all OARs compared with R123 plans (P<.007). Doses to OARs were not significantly different between R23 and R123 plans (P=.05-.95), and CTV coverage differences were on the order of 1%. Capri R123 plans provided slightly lower CTV D90 and Dmean but equivalent OAR doses with smaller standard deviations compared with conventional cylinder plans for both prescriptions.ConclusionsThe Capri multichannel applicator provides equivalent target coverage at 5-mm depth, with significantly reduced dose to OARs relative to using a single channel. Optimal plans can be achieved using R12 (lowest V150) or R123 or R23 (lowest OAR doses).

PurposeTo determine the ability of image-guided high-dose-rate brachytherapy (IG-HDR) to provide local control (LC) of lesions in non-traditional locations for patients with heavily pre-treated malignancies.Material and methodsThis retrospective series included 18 patients treated between 2012 and 2014 with IG-HDR, either in combination with external beam radiotherapy (EBRT; n = 9) or as monotherapy (n = 9). Lesions were located in the pelvis (n = 5), extremity (n = 2), abdomen/retroperitoneum (n = 9), and head/neck (n = 2). All cases were performed in conjunction between interventional radiology and radiation oncology. Toxicity was graded based on CTCAE v4.0 and local failure was determined by RECIST criteria. Kaplan-Meier analysis was performed for LC and overall survival.ResultsThe median follow-up was 11.9 months. Two patients had localized disease at presentation; the remainder had recurrent and/or metastatic disease. Seven patients had prior EBRT, with a median equivalent dose in 2 Gy fractions (EQD2) of 47.0 Gy. The median total EQD2s were 34 Gy and 60.9 Gy for patients treated with monotherapy or combination therapy, respectively. Image-guided high-dose rate brachytherapy was delivered in one to six fractions. Six patients had local failures at a median interval of 5.27 months with a one-year LC rate of 59.3% and a one-year overall survival of 40.7%. Six patients died from their disease at a median interval of 6.85 months from the end of treatment. There were no grade ≥ 3 acute toxicities but two patients had serious long term toxicities.ConclusionsWe demonstrate a good one year LC rate of nearly 60%, and a favorable toxicity profile when utilizing IG-HDR to deliver high doses of radiation with high precision into targets not readily accessible by other forms of local therapy. These preliminary results suggest that further studies utilizing this approach may be considered for patients with difficult to access lesions that require LC.

PurposeTo assess the magnitude of dosimetric reductions of a focal and ultra-focal high-dose-rate (HDR) prostate brachytherapy treatment strategy relative to standard whole gland (WG) treatment.Methods and materialsHDR brachytherapy plans for five patients treated with WG HDR monotherapy were optimized to assess different treatment strategies. Plans were generated to treat the hemigland (HG), one-third gland (1/3G), and one-sixth gland (1/6G), as well as to assess treating the WG with a boost to one of those sub-volumes (WG + HG, WG + 1/3G, WG + 1/6G). Dosimetric parameters analyzed included Target D90%, V100%, V150%, Bladder (B), Rectal (R), Urethral (U) D0.1, 1 and 2cc, Urethral V75%, and the V50% to the contralateral HG. Two-tailed t tests were used for comparison of means, and p-values less than 0.05 were considered statistically significant.ResultsTarget objectives (D90 > 100% and V100 > 97%) were met in all cases. Significant organs at risk dose reductions were achieved for all approaches compared with WG plans. 1/6G vs WG plans resulted in the greatest reduction in dose with a mean bladder D2cc 24.7 vs 64.8%, rectal D2cc 32.8 vs 65.3%, urethral D1cc 52.1 vs 103.8%, and V75 14.5 vs 75% (p < 0.05 for all comparisons).ConclusionSignificant dose reductions to organs at risk can be achieved using HDR focal brachytherapy. The magnitude of the reductions achievable with treating progressively smaller sub-volumes suggests the potential to reduce morbidity, but the clinical impact on morbidity and tumor control remain to be investigated.

PurposeTo report early clinical outcomes of high-dose-rate interstitial image-guided brachytherapy (BT) in the definitive management of locally advanced cervical cancer.MethodsWe retrospectively analyzed 31 locally advanced cervical cancer patients treated at our institution between January 2010 and April 2013. About 88% had advanced disease based on the International Federation of Gynecology and Obstetrics guidelines, and 87% received concurrent chemotherapy. All patients were treated with external beam radiation therapy to a median dose of 45 Gy (range, 39.6-58 Gy) before receiving BT. High-dose-rate BT was delivered in a single implant to a median dose of 6 Gy × five fractions to a CT-defined volume. Median total equivalent 2-Gy dose, dose covered by 90% of the high-risk clinical target volume (HR-CTV D90), and HR-CTV were 84, 87.4, and 49.9 cc, respectively. Kaplan-Meier method was used for actuarial survival analysis, and toxicity was graded using Common Terminology Criteria for Adverse Events, version 4.0.ResultsMedian followup was 19.3 months. Two-year actuarial local control, regional control, and distant metastasis (DM) were 90%, 93%, and 23.6%, respectively. Two-year disease-free survival was 55%. Genitourinary, gastrointestinal, or gynecologic Grade 3 toxicity was seen in 5 patients (3 T4a and 2 T3b) for crude rates of 13%, 7%, and 3%, respectively. Stratifying HR-CTV by <30 and >30 cc and then by HR-CTV D90 of <85, 85-90, and >90 Gy showed that 100% of the local failures, regional failures, DM, and G3 toxicity occurred in >30 cc group. The rate of DM was also significantly higher in the >30 cc group (p = 0.036).ConclusionsAn interstitial approach can achieve excellent outcomes in cases where intracavitary and/or hybrid approaches are either not suitable or not available.

PurposeWe compared the dosimetry of brachyablation (BA) and stereotactic ablative radiotherapy (SABR) in the treatment of liver metastases.Methods and materialsTreatment plans for 10 consecutive liver metastasis patients, treated with SABR, were replanned for BA. BA treatment was planned using five 12 Gy fractions to the same planning target volume (PTV) used for SABR. Dosimetric parameters were compared using a Student's paired t test.Results and conclusionsBA and SABR plans had similar mean volume receiving 100% of the prescribed dose (94.1% vs. 93.9% of PTV, p = 0.8). Mean volume receiving 150% of the prescribed dose for BA was 63.6%, whereas for SABR it was 0. The minimum dose to the PTV was 65.8% for BA, whereas for SABR it was 87.4% (p = 0.0002). Liver volume receiving ≥15 Gy was similar for BA and SABR (278 vs. 256 cc, p = 0.3). Small bowel mean dose, as percent prescription dose, was higher for BA (10.8% vs. 7.1%, p = 0.006). Stomach mean dose was similar (4.9% vs. 4.8% of prescription dose, p = 0.98). Right kidney mean dose was greater for BA (6.7% vs. 4.2%, p = 0.07). BA leads to a higher target dose, similar dose to organs at risk, but potentially with lower target coverage compared with SABR. Further work is needed to determine ideal suitability for mono vs. combination therapy with this approach.

PurposeTo assess the magnitude of dosimetric reductions of a focal and ultra-focal high-dose-rate (HDR) prostate brachytherapy treatment strategy relative to standard whole gland (WG) treatment.Methods and materialsHDR brachytherapy plans for five patients treated with WG HDR monotherapy were optimized to assess different treatment strategies. Plans were generated to treat the hemigland (HG), one-third gland (1/3G), and one-sixth gland (1/6G), as well as to assess treating the WG with a boost to one of those sub-volumes (WG + HG, WG + 1/3G, WG + 1/6G). Dosimetric parameters analyzed included Target D90%, V100%, V150%, Bladder (B), Rectal (R), Urethral (U) D0.1, 1 and 2cc, Urethral V75%, and the V50% to the contralateral HG. Two-tailed t tests were used for comparison of means, and p-values less than 0.05 were considered statistically significant.ResultsTarget objectives (D90 > 100% and V100 > 97%) were met in all cases. Significant organs at risk dose reductions were achieved for all approaches compared with WG plans. 1/6G vs WG plans resulted in the greatest reduction in dose with a mean bladder D2cc 24.7 vs 64.8%, rectal D2cc 32.8 vs 65.3%, urethral D1cc 52.1 vs 103.8%, and V75 14.5 vs 75% (p < 0.05 for all comparisons).ConclusionSignificant dose reductions to organs at risk can be achieved using HDR focal brachytherapy. The magnitude of the reductions achievable with treating progressively smaller sub-volumes suggests the potential to reduce morbidity, but the clinical impact on morbidity and tumor control remain to be investigated.

PurposeTo determine the ability of image-guided high-dose-rate brachytherapy (IG-HDR) to provide local control (LC) of lesions in non-traditional locations for patients with heavily pre-treated malignancies.Material and methodsThis retrospective series included 18 patients treated between 2012 and 2014 with IG-HDR, either in combination with external beam radiotherapy (EBRT; n = 9) or as monotherapy (n = 9). Lesions were located in the pelvis (n = 5), extremity (n = 2), abdomen/retroperitoneum (n = 9), and head/neck (n = 2). All cases were performed in conjunction between interventional radiology and radiation oncology. Toxicity was graded based on CTCAE v4.0 and local failure was determined by RECIST criteria. Kaplan-Meier analysis was performed for LC and overall survival.ResultsThe median follow-up was 11.9 months. Two patients had localized disease at presentation; the remainder had recurrent and/or metastatic disease. Seven patients had prior EBRT, with a median equivalent dose in 2 Gy fractions (EQD2) of 47.0 Gy. The median total EQD2s were 34 Gy and 60.9 Gy for patients treated with monotherapy or combination therapy, respectively. Image-guided high-dose rate brachytherapy was delivered in one to six fractions. Six patients had local failures at a median interval of 5.27 months with a one-year LC rate of 59.3% and a one-year overall survival of 40.7%. Six patients died from their disease at a median interval of 6.85 months from the end of treatment. There were no grade ≥ 3 acute toxicities but two patients had serious long term toxicities.ConclusionsWe demonstrate a good one year LC rate of nearly 60%, and a favorable toxicity profile when utilizing IG-HDR to deliver high doses of radiation with high precision into targets not readily accessible by other forms of local therapy. These preliminary results suggest that further studies utilizing this approach may be considered for patients with difficult to access lesions that require LC.

PurposeWe compared the dosimetry of brachyablation (BA) and stereotactic ablative radiotherapy (SABR) in the treatment of liver metastases.Methods and materialsTreatment plans for 10 consecutive liver metastasis patients, treated with SABR, were replanned for BA. BA treatment was planned using five 12 Gy fractions to the same planning target volume (PTV) used for SABR. Dosimetric parameters were compared using a Student's paired t test.Results and conclusionsBA and SABR plans had similar mean volume receiving 100% of the prescribed dose (94.1% vs. 93.9% of PTV, p = 0.8). Mean volume receiving 150% of the prescribed dose for BA was 63.6%, whereas for SABR it was 0. The minimum dose to the PTV was 65.8% for BA, whereas for SABR it was 87.4% (p = 0.0002). Liver volume receiving ≥15 Gy was similar for BA and SABR (278 vs. 256 cc, p = 0.3). Small bowel mean dose, as percent prescription dose, was higher for BA (10.8% vs. 7.1%, p = 0.006). Stomach mean dose was similar (4.9% vs. 4.8% of prescription dose, p = 0.98). Right kidney mean dose was greater for BA (6.7% vs. 4.2%, p = 0.07). BA leads to a higher target dose, similar dose to organs at risk, but potentially with lower target coverage compared with SABR. Further work is needed to determine ideal suitability for mono vs. combination therapy with this approach.

PurposeTo report early clinical outcomes of high-dose-rate interstitial image-guided brachytherapy (BT) in the definitive management of locally advanced cervical cancer.MethodsWe retrospectively analyzed 31 locally advanced cervical cancer patients treated at our institution between January 2010 and April 2013. About 88% had advanced disease based on the International Federation of Gynecology and Obstetrics guidelines, and 87% received concurrent chemotherapy. All patients were treated with external beam radiation therapy to a median dose of 45 Gy (range, 39.6-58 Gy) before receiving BT. High-dose-rate BT was delivered in a single implant to a median dose of 6 Gy × five fractions to a CT-defined volume. Median total equivalent 2-Gy dose, dose covered by 90% of the high-risk clinical target volume (HR-CTV D90), and HR-CTV were 84, 87.4, and 49.9 cc, respectively. Kaplan-Meier method was used for actuarial survival analysis, and toxicity was graded using Common Terminology Criteria for Adverse Events, version 4.0.ResultsMedian followup was 19.3 months. Two-year actuarial local control, regional control, and distant metastasis (DM) were 90%, 93%, and 23.6%, respectively. Two-year disease-free survival was 55%. Genitourinary, gastrointestinal, or gynecologic Grade 3 toxicity was seen in 5 patients (3 T4a and 2 T3b) for crude rates of 13%, 7%, and 3%, respectively. Stratifying HR-CTV by <30 and >30 cc and then by HR-CTV D90 of <85, 85-90, and >90 Gy showed that 100% of the local failures, regional failures, DM, and G3 toxicity occurred in >30 cc group. The rate of DM was also significantly higher in the >30 cc group (p = 0.036).ConclusionsAn interstitial approach can achieve excellent outcomes in cases where intracavitary and/or hybrid approaches are either not suitable or not available.

PurposeTo determine the utility of focal high-dose-rate brachytherapy for localized prostate cancer, we investigated the impact on target coverage and dose to organs at risk (OARs) with hemigland (HG) compared with whole-gland (WG) treatment.Methods and materialsA total of 10 WG implants were used to generate 10 WG and 20 HG (left and right) treatment plans optimized with the inverse planning simulation annealing algorithm using Oncentra MasterPlan (Nucletron B.V., Veenendaal, The Netherlands). The standard distribution of 17-18 catheters designed for WG was used to generate HG plans. The same OARs namely bladder, rectum, and urethra contours and dose constraints were applied for HG and WG plans. The HG contour was a modification of the WG contour whereby the urethra divided the prostate into HGs. The prescription dose was 7.25 Gy×6. Evaluated dose parameters were target dose D90, V100, and V150 and D0.1 cc, D1 cc, and D2 cc to OARs.ResultsThe HG plans had a D90, V100, and V150 to the HG target of 112%, 97.6%, and 33.8%, respectively. The WG plans had a D90, V100, and V150 to the WG target of 108%, 98.8%, and 26.5%, respectively. The OAR D2 cc doses were significantly lower in HG vs. WG plans: rectum (53.1% vs. 64.1%, p<0.0001), bladder (55.9% vs. 67.5%, p<0.0001), and urethra (69.3% vs. 95.2%, p<0.0001).ConclusionsIn the present model, HG plans yielded a statistically significant decreased radiation dose to OARs and provided complete target coverage with a catheter array designed for WG coverage. The good dosimetry results obtained in this study support the feasibility of HG brachytherapy by using a subset of the WG catheter array. Catheter distribution and dosimetry refinements tailored to subtotal prostate brachytherapy should be explored to see if further improvements in dosimetry can be achieved.

PurposeTo determine the utility of focal high-dose-rate brachytherapy for localized prostate cancer, we investigated the impact on target coverage and dose to organs at risk (OARs) with hemigland (HG) compared with whole-gland (WG) treatment.Methods and materialsA total of 10 WG implants were used to generate 10 WG and 20 HG (left and right) treatment plans optimized with the inverse planning simulation annealing algorithm using Oncentra MasterPlan (Nucletron B.V., Veenendaal, The Netherlands). The standard distribution of 17-18 catheters designed for WG was used to generate HG plans. The same OARs namely bladder, rectum, and urethra contours and dose constraints were applied for HG and WG plans. The HG contour was a modification of the WG contour whereby the urethra divided the prostate into HGs. The prescription dose was 7.25 Gy×6. Evaluated dose parameters were target dose D90, V100, and V150 and D0.1 cc, D1 cc, and D2 cc to OARs.ResultsThe HG plans had a D90, V100, and V150 to the HG target of 112%, 97.6%, and 33.8%, respectively. The WG plans had a D90, V100, and V150 to the WG target of 108%, 98.8%, and 26.5%, respectively. The OAR D2 cc doses were significantly lower in HG vs. WG plans: rectum (53.1% vs. 64.1%, p<0.0001), bladder (55.9% vs. 67.5%, p<0.0001), and urethra (69.3% vs. 95.2%, p<0.0001).ConclusionsIn the present model, HG plans yielded a statistically significant decreased radiation dose to OARs and provided complete target coverage with a catheter array designed for WG coverage. The good dosimetry results obtained in this study support the feasibility of HG brachytherapy by using a subset of the WG catheter array. Catheter distribution and dosimetry refinements tailored to subtotal prostate brachytherapy should be explored to see if further improvements in dosimetry can be achieved.

A low loss 4-6 GMz 3-bit tunable filter was designed and fabricated on a quarz substrate. A high-Q 3-bit orthogonal RF-MEMS capacitance network is presented and its significance on the filter Q is discussed. Detailed design equations for the capacitively-loaded coupled open-loop,=2 resonators and realization of capacitive external coupling with source-load impedance loading are discussed. The measured filter shows an unloaded-Q of 85-170, an insertion loss of 1.5-2.8 dB (including connector loss), and the measured 1-dB bandwidth is 4.35 +- 0.35% over the 4-6 GMz tuning range. The measured IIP3 and 1-dB power compression point at 5.91 GMz are > 40 dBm and 27.5 dBm, respectively. The unloaded Q and insertion loss can be improved to 125-210 and 1.8-1.1 dB with the use of a thicker bottom electrode. To our knowledge, this is the highest Q tunable planar filter to-date at this frequency range., The original document contains color images. Published IEEE Transactions on Microwave Theory and Techniques, v10 n20 p1-8, Jan 2008.