Quantitative Evaluation of Scintillation Camera Imaging Characteristics of Isotopes Used in Liver Radioembolization

Scintillation camera imaging is used for treatment planning and post-treatment dosimetry in liver radioembolization (RE). In yttrium-90 (90Y) RE, scintigraphic images of technetium-99m (99mTc) are used for treatment planning, while 90Y Bremsstrahlung images are used for post-treatment dosimetry. In holmium-166 (166Ho) RE, scintigraphic images of 166Ho can be used for both treatment planning and post-treatment dosimetry. The aim of this study is to quantitatively evaluate and compare the imaging characteristics of these three isotopes, in order that imaging protocols can be optimized and RE studies with varying isotopes can be compared.Phantom experiments were performed in line with NEMA guidelines to assess the spatial resolution, sensitivity, count rate linearity, and contrast recovery of 99mTc, 90Y and 166Ho. In addition, Monte Carlo simulations were performed to obtain detailed information about the history of detected photons. The results showed that the use of a broad energy window and the high-energy collimator gave optimal combination of sensitivity, spatial resolution, and primary photon fraction for 90Y Bremsstrahlung imaging, although differences with the medium-energy collimator were small. For 166Ho, the high-energy collimator also slightly outperformed the medium-energy collimator. In comparison with 99mTc, the image quality of both 90Y and 166Ho is degraded by a lower spatial resolution, a lower sensitivity, and larger scatter and collimator penetration fractions.The quantitative evaluation of the scintillation camera characteristics presented in this study helps to optimize acquisition parameters and supports future analysis of clinical comparisons between RE studies

Abdo-Man: a 3D-printed anthropomorphic phantom for validating quantitative SIRT

BACKGROUND: The use of selective internal radiation therapy (SIRT) is rapidly increasing, and the need for quantification and dosimetry is becoming more widespread to facilitate treatment planning and verification. The aim of this project was to develop an anthropomorphic phantom that can be used as a validation tool for post-SIRT imaging and its application to dosimetry. METHOD: The phantom design was based on anatomical data obtained from a T1-weighted volume-interpolated breath-hold examination (VIBE) on a Siemens Aera 1.5 T MRI scanner. The liver, lungs and abdominal trunk were segmented using the Hermes image processing workstation. Organ volumes were then uploaded to the Delft Visualization and Image processing Development Environment for smoothing and surface rendering. Triangular meshes defining the iso-surfaces were saved as stereo lithography (STL) files and imported into the Autodesk® Meshmixer software. Organ volumes were subtracted from the abdomen and a removable base designed to allow access to the liver cavity. Connection points for placing lesion inserts and filling holes were also included. The phantom was manufactured using a Stratasys Connex3 PolyJet 3D printer. The printer uses stereolithography technology combined with ink jet printing. Print material is a solid acrylic plastic, with similar properties to polymethylmethacrylate (PMMA). RESULTS: Measured Hounsfield units and calculated attenuation coefficients of the material were shown to also be similar to PMMA. Total print time for the phantom was approximately 5 days. Initial scans of the phantom have been performed with Y-90 bremsstrahlung SPECT/CT, Y-90 PET/CT and Tc-99m SPECT/CT. The CT component of these images compared well with the original anatomical reference, and measurements of volume agreed to within 9 %. Quantitative analysis of the phantom was performed using all three imaging techniques. Lesion and normal liver absorbed doses were calculated from the quantitative images in three dimensions using the local deposition method. CONCLUSIONS: 3D printing is a flexible and cost-efficient technology for manufacture of anthropomorphic phantom. Application of such phantoms will enable quantitative imaging and dosimetry methodologies to be evaluated, which with optimisation could help improve outcome for patients

High FDG uptake on FDG-PET scan in HIV-1 infected patient with advanced disease

We report the case of a 48-year-old Caucasian male positive for HIV-1 who was admitted in our clinic for a fever of unknown origin with weight loss. The CD4 cell count was 99/mm3 and the viral load (VL) was 836500 copies/ml. A first FDG-PET-CT showed abnormal hypermetabolism of multiple lymp nodes, of the bone marrow and of the spleen. Tuberculosis and lymphoma were excluded by a lymph node biopsy and a culture. Six months after the start of a highly active anti-retroviral therapy (HAART) containing lamuvidine, tenofovir, atazanavir boosted by ritonavir, a new FDG-PET-CT showed a complete normalisation of the metabolism in the regions previously described as having a high FDG uptake. The VL was < 37 copies/ml and his CD4 cell count was 399/mm3. In conclusion: in patients with advanced HIV infections presenting with FUO, high uptake in 18FDG-PET-CT can be the marker of advanced disease reflecting the areas of viral replication

Bremsstrahlung SPECT/CT

The first bremsstrahlung imaging was performed early 1966 by Simon et al. [1, 2] using a rectilinear scanner following a liver radioembolisation via the hepatic artery with 90Y loaded 15 μm diameter microspheres. Although of very low quality, this imaging already provided the main information: the carcinoid tumours were well preferentially targeted (Fig. 13.1)