BackgroundThe purpose of this study is to identify a method for optimising the administered activity and acquisition time for 18F-FDG PET imaging, yielding images of consistent quality for patients with varying body sizes and compositions, while limiting radiation doses to patients and staff. Patients referred for FDG scans had bioimpedance measurements. They were injected with 3 MBq/kg of 18F up to 370 MBq and scanned on a Siemens Biograph mCT at 3 or 4 min per bed position. Data were rebinned to simulate 2- and 1-min acquisitions. Subjective assessments of image quality made by an experienced physician were compared with objective measurements based on signal-to-noise ratio and noise equivalent counts (NEC). A target objective measure of image quality was identified. The activity and acquisition time required to achieve this were calculated for each subject. Multiple regression analysis was used to identify expressions for the activity and acquisition time required in terms of easily measurable patient characteristics.ResultsOne hundred and eleven patients were recruited, and subjective and objective assessments of image quality were compared for 321 full and reduced time scans. NEC-per-metre was identified as the objective measure which best correlated with the subjective assessment (Spearman rank correlation coefficient 0.77) and the best discriminator for images with a subjective assessment of “definitely adequate” (area under the ROC curve 0.94). A target of 37 Mcount/m was identified. Expressions were identified in terms of patient sex, height and weight for the activity and acquisition time required to achieve this target. Including measurements of body composition in these expressions was not useful. Using these expressions would reduce the mean activity administered to this patient group by 66 MBq compared to the current protocol.ConclusionsExpressions have been identified for the activity and acquisition times required to achieve consistent image quality in FDG imaging with reduced patient and staff doses. These expressions might need to be adapted for other systems and reconstruction protocols.Electronic supplementary materialThe online version of this article (doi:10.1186/s13550-016-0250-3) contains supplementary material, which is available to authorized users.

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18 F-florbetapir is a promising tracer in amyloidosis. This study evaluates its use in patients with systemic AL amyloidosis (AL) before and after treatment, as well as its serial utility in monitoring. Fifteen AL patients with cardiac involvement underwent 18 F-florbetapir PET imaging. and t Three underwent repeat imaging post-chemotherapy. hree patients underwent repeat imaging after chemotherapy. All patients patients had demonstrable cardiac uptake with 18 F-florbetapir. Cardiac uptake appeared greater in chemotherapynaïve vs chemotherapy-established AL patients median ((mean left ventricular retention index 0.21 vs 0.14 min-1 , respectively) and greater in patients that had not achieved at least a partial haematological response (mean left ventricular retention index 0.2 vs 0.14 min-1 , respectively).. There was no interval difference in cardiac uptake, and no correlation in cardiac uptake with cardiac biomarkers or serum free light chains. This is the largest study of 18 F-florbetapir in patients with AL amyloidosis. It is the first study to include patients prior to starting before chemotherapy and uniquely includes patients who underwent repeat imaging after post-chemotherapy. All patients had cardiac uptake with 18 Fflorbetapir, regardless of haematological or NT-proBNP response to chemotherapy. There was a suggestion that treatment-naïve patients may have higher cardiac uptake. Larger studies are required to establish the role of this tracer in screening patients with amyloidosis for cardiac involvement, discriminating between ATTR and AL amyloidosis, and in disease monitoring.

Purpose18F-Florbetapir has been reported to show cardiac uptake in patients with systemic light-chain amyloidosis (AL). This study systematically assessed uptake of 18F-florbetapir in patients with proven systemic amyloidosis at sites outside the heart.MethodsSeventeen patients with proven cardiac amyloidosis underwent 18F-florbetapir PET/CT imaging, 15 with AL and 2 with transthyretin amyloidosis (ATTR). Three patients had repeat scans. All patients had protocolized assessment at the UK National Amyloidosis Centre including imaging with 123I-serum amyloid P component (SAP). 18F-Florbetapir images were assessed for areas of increased tracer accumulation and time–uptake curves in terms of standardized uptake values (SUVmean) were produced.ResultsAll 17 patients showed 18F-florbetapir uptake at one or more extracardiac sites. Uptake was seen in the spleen in 6 patients (35%; 6 of 9, 67%, with splenic involvement on 123I-SAP scintigraphy), in the fat in 11 (65%), in the tongue in 8 (47%), in the parotids in 8 (47%), in the masticatory muscles in 7 (41%), in the lungs in 3 (18%), and in the kidney in 2 (12%) on the late half-body images. The 18F-florbetapir spleen retention index (SRI) was calculated. SRI >0.045 had 100% sensitivity/sensitivity (in relation to 123I-SAP splenic uptake, the current standard) in detecting splenic amyloid on dynamic imaging and a sensitivity of 66.7% and a specificity of 100% on the late half-body images. Intense lung uptake was seen in three patients, one of whom had lung interstitial infiltration suggestive of amyloid deposition on previous high-resolution CT. Repeat imaging showed a stable appearance in all three patients suggesting no early impact of treatment response.Conclusion18F-Florbetapir PET/CT is a promising tool for the detection of extracardiac sites of amyloid deposition. The combination of uptake in the heart and uptake in the spleen on 18F-florbetapir PET/CT, a hallmark of AL, suggests that this tracer holds promise as a screening tool for AL.Electronic supplementary materialThe online version of this article (10.1007/s00259-018-3995-2) contains supplementary material, which is available to authorized users.

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