Peptide-receptor radionuclide therapy (PRRT) with radiolabeled somatostatin analogs such as octreotide is an effective therapy against neuroendocrine tumors. Other radiolabeled peptides and antibody fragments are under investigation. Most of these compounds are cleared through the kidneys and reabsorbed and partially retained in the proximal tubules, causing dose-limiting nephrotoxicity. An overview of renal handling of radiolabeled peptides and resulting nephrotoxicity is presented, and strategies to reduce nephrotoxicity are discussed. Modification of size, charge, or structure of radiolabeled peptides can alter glomerular filtration and tubular reabsorption. Coinfusion of competitive inhibitors of reabsorption also interferes with the interaction of peptides with renal endocytic receptors; coinfusion of basic amino acids is currently used for kidney protection in clinical PRRT. Furthermore, nephrotoxicity may be reduced by dose fractionation, use of radioprotectors, or use of mitigating agents. Decreasing the risk of nephrotoxicity allows for administration of higher radiation doses, increasing the effectiveness of PRRT.

Nuclear medicine imaging procedures play an important role in the assessment of inflammatory diseases. With the advent of 3-dimensional anatomic imaging, there has been a tendency to replace traditional planar scintigraphy by CT or MRI. Furthermore, scintigraphic techniques may have to be combined with other imaging modalities to achieve high sensitivity and specificity, and some may require time-consuming labeling procedures. On the other hand, new developments such as combined SPECT/CT increase the diagnostic power of scintigraphy. Also, the advent of PET had a considerable impact on the use of nuclear medicine imaging techniques. In this review, we aim to provide nuclear medicine specialists and clinicians with the relevant information on rational and efficient use of nuclear medicine imaging techniques in the assessment of patients with osteomyelitis, infected vascular prostheses, metastatic infectious disease, rheumatoid arthritis, vasculitis, inflammatory bowel disease, sarcoidosis, and fever of unknown origin.

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Aims/hypothesis A reliable method for in vivo quantification of pancreatic beta cell mass (BCM) could lead to further insight into the pathophysiology of diabetes. The glucagonlike peptide 1 receptor, abundantly expressed on beta cells, may be a suitable target for imaging. We investigated the potential of radiotracer imaging with the GLP-1 analogue exendin labelled with indium-111 for determination of BCM in vivo in a rodent model of beta cell loss and in patients with type 1 diabetes and healthy individuals. MethodsThe targeting of 111 In-labelled exendin was examined in a rat model of alloxan-induced beta cell loss. Rats were injected with 15 MBq 111 In-labelled exendin and single photon emission computed tomography (SPECT) acquisition was performed 1 h post injection, followed by dissection, biodistribution and ex vivo autoradiography studies of pancreatic sections. BCM was determined by morphometric analysis after staining with an anti-insulin antibody. For clinical evaluation SPECT was acquired 4, 24 and 48 h after injection of 150 MBq 111 In-labelled exendin in five patients with type 1 Maarten Brom and Wietske Woliner-van der Weg contributed equally to this study. Diabetologia (2014) 57:950-959 DOI 10.1007 diabetes and five healthy individuals. The tracer uptake was determined by quantitative analysis of the SPECT images. Results In rats, 111 In-labelled exendin specifically targets the beta cells and pancreatic uptake is highly correlated with BCM. In humans, the pancreas was visible in SPECT images and the pancreatic uptake showed high interindividual variation with a substantially lower uptake in patients with type 1 diabetes. Conclusions/interpretation These studies indicate that 111 Inlabelled exendin may be suitable for non-invasive quantification of BCM.

The Inveon small-animal PET scanner is characterized by a large, 127-mm axial length and a 161-mm crystal ring diameter. The associated high sensitivity is obtained by using all lines of response (LORs) up to the maximum ring difference (MRD) of 79, for which the most oblique LORs form acceptance angles of 38.3°with transaxial planes. The result is 2 phenomena that are normally not encountered in PET scanners: a parallax or depth-of-interaction effect in the axial direction and the breakdown of Fourier rebinning (FORE). Both effects cause a deterioration of axial spatial resolution. Limiting the MRD to smaller values reduces this axial blurring at the cost of sensitivity. Alternatively, 3-dimensional (3D) reconstruction techniques can be used in which the rebinning step is absent. The aim of this study was to experimentally determine the spatial resolution and sensitivity of the Inveon for its whole field of view (FOV). Methods: Spatial resolution and sensitivity were measured using filtered backprojection (FBP) with FORE, FBP with LOR angle-weighted adapted FORE (AFORE), and 3D ordered-subset expectation maximization followed by maximum a posteriori reconstruction (OSEM3D/ MAP). Results: Tangential and radial full width at half maximum (FWHM) showed almost no dependence on the MRD using FORE and FBP. Tangential FWHMs were 1.5 mm in the center of the FOV (CFOV) and 1.8 mm at the edge of the FOV (EFOV). Radial FWHMs were 1.5 and 3.0 mm in the CFOV and EFOV, respectively. In contrast, axial FWHMs increased with the MRD and ranged between 1.1 and 2.0 mm in the CFOV and between 1.5 and 2.7 mm in the EFOV for a MRD between 1 and 79. AFORE improved the axial resolution for a large part of the FOV, but image noise increased. OSEM3D/MAP yielded uniform spatial resolution in all directions, with an average FWHM of 1.65 6 0.06 mm. Sensitivity in the CFOV for the default energy and coincidence time window was 0.068; peak sensitivity was 0.111. Conclusion: The Inveon showed high spatial resolution and high sensitivity, both of which can be maintained using OSEM3D/MAP reconstruction instead of rebinning and 2D algorithms. The Inveon (Siemens) small-animal PET scanner differs from its predecessor, the microPET Focus 120 (F120; Siemens), by its larger lutetium orthosilicate (LSO) detector blocks, improved processing of high-speed events (1-4), and shorter, tapered light guides coupling the detector blocks to the photomultiplier tubes (5). The Inveon contains 4 rings of 16 blocks-20 · 20 detectors of 1.5 · 1.5 mm each, resulting in an axial length of 127 mm. The F120 consists of 4 rings of 24 blocks-12 · 12 detectors of the same size, leading to an axial length of 76 mm. Table 1 compares the geometric properties of the Inveon with several other commercial crystal-based small-animal PET scanners.The main advantage of the larger axial field of view (FOV) of the Inveon is the higher detection efficiency (or sensitivity), with a peak value as specified by the manufacturer of greater than 0.1 in the center of the FOV (CFOV) for the ...