Single Photon Emission Tomography in the Diagnostic Assessment of Cardiac and Vascular Infectious Diseases.

Cardiac and vascular infection is an arising cause of mortality and morbidity in the adult population. Diagnosis based on culture and anatomic imaging are frequently inconclusive. Radiolabeled leucocyte scintigraphy plays a useful role in the diagnosis and management of these serious infectious conditions. In this paper, we present an update on the diagnostic performance of single- photon emission tomographic (SPECT) techniques using different radionuclides in the management of patients with cardiac and vascular infections. We performed a thorough search of recent literature on the topic. We present a discussion on the clinical utility of different SPECT tracers in cardiac and vascular infections, including infective endocarditis, cardiac implantable electronic device (CIED) infections, left ventricular assist device infection, and vascular graft infection. Radionuclide technique using SPECT tracers is a useful imaging modality in the diagnosis of cardiac infection. Among the different SPECT tracers for infection imaging, radiolabeled leucocyte scintigraphy is currently the most useful tool in the diagnosis and management of patients with suspected cardiac and vascular infection. Radiolabeled leucocyte scintigraphy has a high specificity, a result of the ability of the leucocytes to accumulate as sites of pyogenic infection but not at sites of sterile inflammation such as seen in the early post-operative period or in response to the presence of a prosthetic cardiac or vascular material. Limited experience with radiotracers for in vivo labelling of leucocytes such as 99mTc-sulesomab and 99mTc-besilesomab show acceptable diagnostic performance without the need for the tedious process of ex-vivo labeling. 67Ga scintigraphy used to be popular for cardiac and vascular infection imaging. Its use has run out of favor following the availability of more effective molecular imaging methods. SPECT techniques with radiolabeled leucocyte scintigraphy has a high diagnostic performance in the evaluation of patients with suspected cardiac or vascular infection. It is able to confirm or reject the presence of infection when results of anatomic imaging or culture remain inconclusive. Its diagnostic performance is not compromised by sterile inflammation occurring in the early post-operative period or in response to implanted prosthetic materials.

18F-FDG-PET metabolic metrics and International Prognostic Score for risk assessment in HIV-infected patients with Hodgkin lymphoma.

OBJECTIVES: Baseline metabolic metrics on fluorine-18-fluorodeoxyglucose PET (F-FDG PET) have prognostic value in Hodgkin lymphoma. International Prognostic Score (IPS) is used in the risk stratification of Hodgkin lymphoma. We compared the metabolic indices in HIV-infected and the IPS in HIV-infected and uninfected patients with Hodgkin lymphoma. PATIENTS AND METHODS: We retrospectively reviewed the data of HIV-infected and HIV-uninfected patients with classic Hodgkin lymphoma who had F-FDG PET for staging and compared the maximum standardized uptake value, mean standardized uptake value, metabolic tumor volume, and total lesion glycolysis between the two groups. We also compared the IPS and other prognostic indicators and correlated them with the metabolic indices in the two groups. RESULTS: We studied 160 patients, which included 57 patients who were infected with HIV. The mean age was 33.84±11.88 years, with 38% (n=61) being female. The median cluster of differentiation 4 count and HIV viral load were 259 cells/mm and 4837.50 copies/ml, respectively. No significant difference in maximum standardized uptake value, mean standardized uptake value, metabolic tumor volume, and total lesion glycolysis between the two groups was found. Among the seven parameters of the IPS, only male sex (HIV-uninfected group higher, P=0.005) and serum albumin less than 4 g/dl were significantly different. The other parameters were not significantly different between the two groups. Other prognostic indicators including bulky disease, extranodal involvement, and the number of nodal groups involved were not significantly different between the two groups. CONCLUSION: There was no significant difference in F-FDG metabolic parameters, IPS, and other risk indicators between HIV-infected and HIV-uninfected patients with Hodgkin lymphoma.

Synthesis, 68Ga-radiolabeling, and preliminary in vivo assessment of a depsipeptide-derived compound as a potential PET/CT infection imaging agent.

Noninvasive imaging is a powerful tool for early diagnosis and monitoring of various disease processes, such as infections. An alarming shortage of infection-selective radiopharmaceuticals exists for overcoming the diagnostic limitations with unspecific tracers such as (67/68)Ga-citrate or (18)F-FDG. We report here TBIA101, an antimicrobial peptide derivative that was conjugated to DOTA and radiolabeled with (68)Ga for a subsequent in vitro assessment and in vivo infection imaging using Escherichia coli-bearing mice by targeting bacterial lipopolysaccharides with PET/CT. Following DOTA-conjugation, the compound was verified for its cytotoxic and bacterial binding behaviour and compound stability, followed by (68)Gallium-radiolabeling. µPET/CT using (68)Ga-DOTA-TBIA101 was employed to detect muscular E. coli-infection in BALB/c mice, as warranted by the in vitro results. (68)Ga-DOTA-TBIA101-PET detected E. coli-infected muscle tissue (SUV = 1.3-2.4) > noninfected thighs (P = 0.322) > forearm muscles (P = 0.092) > background (P = 0.021) in the same animal. Normalization of the infected thigh muscle to reference tissue showed a ratio of 3.0 ± 0.8 and a ratio of 2.3 ± 0.6 compared to the identical healthy tissue. The majority of the activity was cleared by renal excretion. The latter findings warrant further preclinical imaging studies of greater depth, as the DOTA-conjugation did not compromise the TBIA101's capacity as targeting vector.