Non-Target Activity Detection by Post-Radioembolization Yttrium-90 PET/CT: Image Assessment Technique and Case Examples.

High resolution yttrium-90 ((90)Y) imaging of post-radioembolization microsphere biodistribution may be achieved by conventional positron emission tomography with integrated computed tomography (PET/CT) scanners that have time-of-flight capability. However, reconstructed (90)Y PET/CT images have high background noise, making non-target activity detection technically challenging. This educational article describes our image assessment technique for non-target activity detection by (90)Y PET/CT, which qualitatively overcomes the problem of background noise. We present selected case examples of non-target activity in untargeted liver, stomach, gallbladder, chest wall, and kidney, supported by angiography and (90)Y bremsstrahlung single-photon emission computed tomography with integrated computed tomography (SPECT/CT) or technetium-99m macroaggregated albumin SPECT/CT.

Intra-arterial CT angiography visualization of arterial supply to inferior vena cava tumor thrombus prior to radioembolization of hepatocellular carcinoma.

Unresectable hepatocellular carcinoma has a high frequency of vascular invasion and arterial parasitization. Trans-arterial radioembolization using yttrium-90 (Y90) microspheres is a possible treatment option. Paramount to its success is the meticulous angiographic interrogation of tumor feeding arteries and extra-hepatic supply. We describe a patient with tumor invasion of the inferior vena cava with arterial supply from the right inferior phrenic artery, which was exquisitely visualized using intra-arterial computed tomographic angiography (IACTA) during the planning technetium-99m macro aggregated albumin phase. This technique was useful in planning which artery to administer Y90 microspheres into for maximal brachytherapy. Although patient outcome was poor due to significant arterio-portal shunting, we believe that IACTA is a useful adjunct to conventional digital subtraction angiography in planning radioembolization therapy.

Fluorine-18-fluorodeoxyglucose PET/CT for the evaluation of suspected recurrent uterine leiomyosarcomas.

BACKGROUND: Uterine leiomyosarcomas are rare and aggressive malignancies of the uterine corpus with high recurrence rates and poor prognoses. The current recommendation for detection of recurrent uterine leiomyosarcoma involves periodic physical examination and conventional imaging such as CT or MRI. The role of fluorine-18-fluorodeoxyglucose positron emission tomography with integrated computed tomography (FDG-PET/CT) in the detection of recurrent uterine leiomyosarcomas is not yet established. PURPOSE: To evaluate the use of FDG-PET/CT as a single integrated modality for the evaluation of suspected recurrent uterine leiomyosarcomas. MATERIAL AND METHODS: A retrospective study was performed on patients who underwent FDG-PET/CT scans for suspected recurrent uterine leiomyosarcoma. Only patients with follow-up data were included in the study. FDG-PET/CT was evaluated as a single integrated imaging modality. A positive lesion on FDG-PET/CT was defined as a focal abnormality detected on either the PET or CT components, or both. RESULTS: Sixteen consecutive patients over 5 years underwent FDG-PET/CT for suspected recurrent uterine leiomyosarcoma. Five patients were excluded due to incomplete follow-up data. The remaining 11 patients were aged 36-58 years (mean age 48). FDG-PET/CT had a sensitivity of 100% (95% CI 63-100) and specificity of 100% (95% CI 20-100) for the detection of recurrent uterine leiomyosarcomas. Sites of metastases include lungs, peritoneum, liver, pancreas and breast, of which lungs and peritoneum were the most common. Two (18%) patients had discordant findings: FDG-PET negative metastatic nodules in the breast and lung detected on the CT component. The maximum standardized uptake value (SUVmax) of metastatic lesions ranged from 2.0 to 16.0 (mean 7.6). CONCLUSION: FDG-PET/CT as a single integrated modality may be a useful for the evaluation of suspected recurrent uterine leiomyosarcomas. FDG-PET negative discordant nodules detected on the CT component may represent metastases and should be followed up closely.

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.