Image-guided personalized predictive dosimetry by artery-specific SPECT/CT partition modeling for safe and effective 90Y radioembolization.

UNLABELLED: Compliance with radiobiologic principles of radionuclide internal dosimetry is fundamental to the success of (90)Y radioembolization. The artery-specific SPECT/CT partition model is an image-guided personalized predictive dosimetric technique developed by our institution, integrating catheter-directed CT hepatic angiography (CTHA), (99m)Tc-macroaggregated albumin SPECT/CT, and partition modeling for unified dosimetry. Catheter-directed CTHA accurately delineates planning target volumes. SPECT/CT tomographically evaluates (99m)Tc-macroaggregated albumin hepatic biodistribution. The partition model is validated for (90)Y resin microspheres based on MIRD macrodosimetry. METHODS: This was a retrospective analysis of our early clinical outcomes for inoperable hepatocellular carcinoma. Mapping hepatic angiography was performed according to standard technique with the addition of catheter-directed CTHA. (99m)Tc-MAA planar scintigraphy was used for liver-to-lung shunt estimation, and SPECT/CT was used for liver dosimetry. Artery-specific SPECT/CT partition modeling was planned by experienced nuclear medicine physicians. RESULTS: From January to May 2011, 20 arterial territories were treated in 10 hepatocellular carcinoma patients. Median follow-up was 21 wk (95% confidence interval [CI], 12-50 wk). When analyzed strictly as brachytherapy, (90)Y radioembolization planned by predictive dosimetry achieved index tumor regression in 8 of 8 patients, with a median size decrease of 58% (95% CI, 40%-72%). Tumor thrombosis regressed or remained stable in 3 of 4 patients with baseline involvement. The best α-fetoprotein reduction ranged from 32% to 95%. Clinical success was achieved in 7 of 8 patients, including 2 by sublesional dosimetry, in 1 of whom there was radioembolization lobectomy intent. Median predicted mean radiation absorbed doses were 106 Gy (95% CI, 105-146 Gy) to tumor, 27 Gy (95% CI, 22-33 Gy) to nontumorous liver, and 2 Gy (95% CI, 1.3-7.3 Gy) to lungs. Across all patients, tumor, nontumorous liver, and lungs received predicted ≥91 Gy, ≤51 Gy, and ≤16 Gy, respectively, via at least 1 target arterial territory. No patients developed significant toxicities within 3 mo after radioembolization. The median time to best imaging response was 76 d (95% CI, 55-114 d). Median time to progression and overall survival were not reached. SPECT/CT-derived mean tumor-to-normal liver ratios varied widely across all planning target volumes (median, 5.4; 95% CI, 4.1-6.7), even within the same patient. CONCLUSION: Image-guided personalized predictive dosimetry by artery-specific SPECT/CT partition modeling achieves high clinical success rates for safe and effective (90)Y radioembolization.

Traumatic perilymphatic fistula secondary to stapes luxation into the vestibule: a case report.

A penetrating ear injury with a perilymphatic fistula is not an uncommon occurrence in otolaryngologic practice, but stapes luxation is rare. We report the case of an 11-year-old boy who developed a traumatic perilymphatic fistula secondary to an atypical stapes luxation into the vestibule. After sustaining a penetrating injury to the right ear, the patient presented with otalgia, vertigo, vomiting, gait unsteadiness, and hearing loss. High-resolution computed tomography (HRCT) of the temporal bone detected pneumolabyrinth, indicating a perilymphatic fistula. The stapes had pivoted on the footplate at the oval window, and then it made an unusual 180° flip and luxated deeply into the vestibule, with the capitulum stapedis pointing medially. Conservative management was chosen in view of the high surgical risks posed by the deeply luxated stapes and the likelihood of a fracture of the stapes footplate. This case illustrates the importance of an accurate diagnosis and interpretation of a traumatic perilymphatic fistula and stapes luxation as seen on HRCT of the temporal bone.

Hepatic falciform ligament Tc-99m-macroaggregated albumin activity on SPECT/CT prior to Yttrium-90 microsphere radioembolization: prophylactic measures to prevent non-target microsphere localization via patent hepatic falciform arteries.

Yttrium-90 (Y-90) selective internal radiation therapy (SIRT) is increasingly used to treat inoperable hepatocellular carcinoma. We describe two patients where hepatic falciform ligament Technetium-99m-macroaggregated albumin (Tc-99m-MAA) activity was identified on single photon emission computed tomography with integrated low-dose CT (SPECT/CT) scan during pre-therapy planning, and the steps taken to prevent radiation dermatitis. The first patient underwent prophylactic coil embolization of the patent hepatic falciform artery; the second patient underwent super-selective infusion of Y-90 resin microspheres to avoid the patent hepatic falciform artery. The incidence of falciform ligament Tc-99m-MAA activity detected on SPECT/CT at our institution is 10%. Tc-99m-MAA SPECT/CT scan provides valuable diagnostic information for treatment planning prior to Y-90 SIRT.