Blood pool SPECT: rheumatological and orthopedic focus, a pictorial essay.

Single photon emission computed tomography (SPECT) has revolutionized delayed bone scan acquisitions and promises to bring the same benefits to early acquisitions, especially in areas of complex anatomy. To date, however, only a few studies have been published about the utility of blood pool SPECT. The accurate assessment of inflammatory processes can be an indisputable added value to the diagnosis. We present here a series of clinical cases illustrating the utility of blood pool SPECT in various clinical situations in rheumatology and orthopedics. We grouped the cases according to three patterns that facilitate clinical reasoning: inflammatory osseous pathology (pattern A), inflammatory para-osseous pathology (pattern B) and inflammatory extra-osseous pathology (pattern C). A total of seventeen clinical cases are presented. This new semiology requires time and effort to be mastered but expands the diagnostic range offered by bone scintigraphy. More prospective studies on blood pool SPECT will be needed, especially those aiming to clarify its role.

Added diagnostic value of respiratory-gated 4D 18F-FDG PET/CT in the detection of liver lesions: a multicenter study.

PURPOSE: The aim of the present study was to evaluate the added diagnostic value of respiratory-gated 4D18F-FDG PET/CT in liver lesion detection and characterization in a European multicenter retrospective study. METHODS: Fifty-six oncological patients (29 males and 27 females, mean age, 61.2 ± 11.2 years) from five European centers, submitted to standard 3D-PET/CT and liver 4D-PET/CT were retrospectively evaluated. Based on visual analysis, liver PET/CT findings were scored as positive, negative, or equivocal both in 3D and 4D PET/CT. The impact of 4D-PET/CT on the confidence in classifying liver lesions was assessed. PET/CT findings were compared to histology and clinical follow-up as standard reference and diagnostic accuracy was calculated for both techniques. At semi-quantitative analysis, SUVmax was calculated for each detected lesion in 3D and 4D-PET/CT. RESULTS: Overall, 72 liver lesions were considered for the analysis. Based on visual analysis in 3D-PET/CT, 32/72 (44.4%) lesions were considered positive, 21/72 (29.2%) negative, and 19/72 (26.4%) equivocal, while in 4D-PET/CT 48/72 (66.7%) lesions were defined positive, 23/72 (31.9%) negative, and 1/72 (1.4%) equivocal. 4D-PET/CT findings increased the confidence in lesion definition in 37/72 lesions (51.4%). Considering 3D equivocal lesions as positive, sensitivity, specificity, and accuracy were 88.9, 70.0, and 83.1%, respectively, while the same figures were 67.7, 90.0, and 73.8% if 3D equivocal findings were included as negative. 4D-PET/CT sensitivity, specificity, and accuracy were 97.8, 90.0, and 95.4%, respectively, considering equivocal lesions as positive and 95.6, 90.0, and 93.8% considering equivocal lesions as negative. The SUVmax of the liver lesions in 4D-PET (mean ± SD, 6.9 ± 3.2) was significantly higher (p < 0.001) than SUVmax in 3D-PET (mean ± SD, 5.2 ± 2.3). CONCLUSIONS: Respiratory-gated PET/CT technique is a valuable clinical tool in diagnosing liver lesions, reducing 3D undetermined findings, improving diagnostic accuracy, and confidence in reporting. 4D-PET/CT also improved the quantification of SUVmax of liver lesions.

Respiratory gated PET/CT in a European multicentre retrospective study: added diagnostic value in detection and characterization of lung lesions.

PURPOSE: The aim of our work is to evaluate the added diagnostic value of respiratory gated (4-D) positron emission tomography/computed tomography (PET/CT) in lung lesion detection/characterization in a large patient population of a multicentre retrospective study. METHODS: The data of 155 patients (89 men, 66 women, mean age 63.9 ± 11.1 years) from 5 European centres and submitted to standard (3-D) and 4-D PET/CT were retrospectively analysed. Overall, 206 lung lesions were considered for the analysis (mean ± SD lesions dimension 14.7 ± 11.8 mm). Maximum standardized uptake values (SUV(max)) and lesion detectability were assessed for both 3-D and 4-D PET/CT studies; 3-D and 4-D PET/CT findings were compared to clinical follow-up as standard reference. RESULTS: Mean ± SD 3-D and 4-D SUV(max) values were 5.2 ± 5.1 and 6.8 ± 6.1 (p < 0.0001), respectively, with an average percentage increase of 30.8 %. In 3-D PET/CT, 86 of 206 (41.7 %) lesions were considered positive, 70 of 206 (34 %) negative and 50 of 206 (24.3 %) equivocal, while in 4-D PET/CT 117 of 206 (56.8 %) lesions were defined as positive, 80 of 206 (38.8 %) negative and 9 of 206 (4.4 %) equivocal. In 34 of 50 (68 %) 3-D equivocal lesions follow-up data were available and the presence of malignancy was confirmed in 21 of 34 (61.8 %) lesions, while in 13 of 34 (38.2 %) was excluded. In 31 of these 34 controlled lesions, 20 of 34 (58.8 %) and 11 of 34 (32.4 %) were correctly classified by 4-D PET/CT as positive and negative, respectively; 3 of 34 (8.8 %) remained equivocal. With equivocal lesions classified as positive, the overall accuracy of 3-D and 4-D was 85.7 and 92.8 %, respectively, while the same figures were 80.5 and 94.2 % when equivocal lesions were classified as negative. CONCLUSION: The respiratory gated PET/CT technique is a valuable clinical tool in diagnosing lung lesions, improving quantification and confidence in reporting, reducing 3-D undetermined findings and increasing the overall accuracy in lung lesion detection and characterization.