Current Status and Future Direction of Hepatic Radioembolisation.

Radioembolisation is a locoregional treatment modality for hepatic malignancies. It consists of several stages that are vital to its success, which include a pre-treatment angiographic simulation followed by nuclear medicine imaging, treatment activity choice, treatment procedure and post-treatment imaging. All these stages have seen much advancement over the past decade. Here we aim to provide an overview of the practice of radioembolisation, discuss the limitations of currently applied methods and explore promising developments

Calculation of lung mean dose and quantification of error for Y-90-microsphere radioembolization using Tc-99m-MAA SPECT/CT and diagnostic chest CT

Purpose: Current treatment planning for 90Y radioembolization estimates lung mean dose (LMD) by measuring the lung shunt fraction (LSF) from 99mTc-macroaggregated albumin (MAA) planar imaging and assuming a 1-kg lung mass. This methodology, however, overestimates LSF and LMD and could therefore unnecessarily limit the dose to target volume(s). We propose an improved LMD calculation that derives LSF from 99mTc-MAA SPECT/CT and the patient-specific lung mass from diagnostic chest CT. Furthermore, we investigated the errors in lung mass, LSF, and LMD arising from contour variability in patient data in order to estimate the precision of our proposed methodology. Methods: Our proposed LMD (LMDnew) calculation consisted of the following steps: (a) estimate liver counts from the MAA SPECT/CT liver contour; (b) estimate total lung counts by multiplying density (counts/g) from the MAA SPECT/CT left-lung contour by the total lung mass (g) from the diagnostic CT lung contours; (c) compute LSFnew from liver and lung counts; (d) calculate LMDnew using LSFnew and the total lung mass from the diagnostic CT (Mnew). LMDnew, LSFnew, and Mnew estimates were compared to standard model values (LMDclin, LSFclin, and 1 kg, respectively) in 52 consecutive patients with hepatocellular carcinoma who underwent radioembolization using 90Y glass microspheres. The precision of our methodology was quantified by varying lung and liver contours in the same patient population and calculating the resulting relative errors in the liver count, lung count, and lung mass measurements. Results: The median Mnew was 839 g (range, 550–1178 g) for men and 731 g (range, 548–869 g) for women. The median LSFnew was 0.02 (range, 0.01–0.11), while the median LMDnew was 4.9 Gy (range, 0.3–25.5 Gy). Mnew, LSFnew, and LMDnew were significantly lower than Mclin, LSFclin, and LMDclin, with respective relative mean (±SD) differences of −20% (±16%) for Mnew, −63% (±15%) for LSFnew, and −53% (±23%) for LMDnew. The estimated 1-sigma uncertainties in Mnew, LSFnew, and LMDnew were 9%, 10%, and 13%, respectively. Conclusions: We derived a method to calculate lung mass and LSF using routinely available diagnostic chest CT and 99mTc-MAA SPECT/CT. More importantly, we systematically quantified the errors in our measurements to establish the precision of the estimated lung dose (13%). The proposed methodology provides a more accurate LMD and an estimate of its precision, which will improve treatment and retreatment planning for 90Y radioembolizations

Imaging features of extranodal involvement in paediatric Hodgkin lymphoma

Detecting extranodal disease in paediatric Hodgkin lymphoma is of great importance for both treatment and prognosis. Different imaging techniques can be used to identify these extranodal sites. This pictorial essay provides an overview of imaging features of extranodal disease manifestation in paediatric Hodgkin lymphoma

The value of yttrium-90 PET/CT after hepatic radioembolization : a pictorial essay

Introduction: Distribution of microspheres after radioembolization can be accurately visualized using PET/CT. In this pictorial essay, we aim to demonstrate the value of 90Y-PET/CT after radioembolization. Methods: 90Y-PET/CT imaging was routinely performed after radioembolization at our institute. Patients were scanned the same day or the day after treatment, using a scanner with time-of-flight technology. We retrospectively reviewed all 90Y-PET/CTs from patients treated with radioembolization (both glass and resin microspheres) between January 2011 and January 2019. Five cases were selected that are illustrative of the added value of PET/CT after radioembolization. Results: 90Y-PET/CT allows for distribution assessment and dosimetry of 90Y-microspheres. It was used for the assessment of treatment success by visualization of tumor targeting, quantification of the absorbed dose, prediction of complications such as radioembolization-induced liver disease, and determining the required dosage for retreatment. Conclusion: PET/CT is an excellent modality for post-treatment imaging of 90Y-microspheres and could lead to improved dose planning and more personalized treatment

Hepatobiliary Imaging in Liver-directed Treatments

Hepatobiliary scintigraphy (HBS) is an emerging tool in the assessment of hepatic function. This nuclear imaging technique can be used to calculate both global and regional liver function. It has proven to be the most reliable way of assessing the distribution of liver function, especially in patients with impaired liver function due to, for example, cirrhosis or after chemotherapy. There are two types of tracers: Technetium-99m with a type of iminodiacetic acid and Technetium-99m galactosyl human serum albumin. The main indication for HBS is the assessment of the future liver remnant function in patients scheduled to undergo hemihepatectomy; to predict the risk of posthepatectomy liver failure. Another upcoming indication is the use of HBS in patients undergoing radioembolization

Fast and accurate quantitative determination of the lung shunt fraction in hepatic radioembolization

Radioembolization treatment is preceded by a 99mTc-MAA safety procedure, which is used to estimate the lung shunt fraction (LSF). Normally, the LSF is estimated by using the geometric mean of planar scintigraphy (PS-GM). However, concern has been raised about the potential overestimation of the LSF by PS-GM. Alternatively, SPECT/CT may be used for LSF estimation, but requires lengthy acquisitions, 3D segmentation, and has a limited field of view, which calls for extrapolation of the reconstructed lung counts, which introduces another source of error. We have developed a simplified SPECT/CT protocol for LSF estimation, called the quantitative orthogonal planar (QOP) method that requires only four projections to quantitatively reconstruct liver and lung activity. This mitigates the problems associated with LSF estimations from SPECT/CT. The purpose of this study was to introduce and evaluate QOP by comparing its performance to PS-GM and SPECT/CT in a retrospective patient study, and by supporting simulation experiments. Patients who received at least one 99mTc-MAA safety procedure in our center were included in this study. QOP and PS-GM were compared to SPECT/CT in Bland-Altman analyses. Supporting digital phantom experiments with a known ground-truth were performed to evaluate the performance of this method. Analysis of PS-GM versus SPECT/CT LSF estimates revealed both a larger imprecision and significant bias by PS-GM (limits of agreement: 8.1 percentage points (pp); bias: 2.7 pp). The QOP method agreed better with the SPECT/CT-based estimation (limits of agreement: 2.07 pp; bias: 0.52 pp). This observation was consistent with the digital phantom experiments. We have proposed and evaluated a novel method called QOP for LSF estimation that performs almost as accurate as SPECT/CT, but without the need for lung mass extrapolation, long scan duration, or extensive manual segmentation, making it as fast as current PS-GM

Standardized uptake values in FDG PET/CT for prosthetic heart valve endocarditis: a call for standardization

Background: The significance of and threshold values for the standardized uptake value (SUV) in FDG PET/CT to diagnose prosthetic heart valve (PHV) endocarditis (PVE) are unclear at present. Methods: A literature search was performed in the PubMed and EMBASE medical databases, comprising the following terms: (FDG OR *fluorode* OR *fluoro-de*) AND (endocarditis OR prosthetic heart valve OR valve replacement). Studies reporting SUVs correlated to the diagnosis of PVE were selected for analysis. Results