The use of such an algorithm results in images characterized by increased spatial resolution and reduced noise. However, small sources of the order of 2-3 cm can be significantly overenhanced.

Background 99mTc-labelled bisphosphonates are used for imaging assessment of patients with transthyretin cardiac amyloidosis (ATTR). Present study evaluates whether quantitative SPECT/CT measurement of absolute myocardial 99mTc-labelled 3,3-diphosphono-1,2-propanodicarboxylic acid (Tc-DPD) uptake can diagnose patients with suspected ATTR. Methods Twenty-eight patients (25 male, age 80.03 ± 6.99 years) with suspected ATTR referred for Tc-DPD imaging had planar and SPECT/CT imaging of the chest. Three operators independently obtained Tc-DPD myocardial SUVmax and SUVmean above threshold (SMaT) (20, 40 and 60% of SUVmax), using a semi-automated threshold segmentation method. Results were compared to visual grading (0–3) of cardiac uptake. Results Twenty-two patients (78%) had cardiac uptake (2 grade 1, 15 grade 2, 5 grade 3). SUVmax and SMaT segmentation thresholds enabled separating grades 2/3 from 0/1 with excellent inter- and intra-reader correlation. Cut-off values 6.0, 2.5, 3 and 4 for SUVmax, SMaT20,40,60, respectively, separated between grades 2/3 and 0 /1 with PPV and NPV of 100%. SMaT20,40,60(cardiac)/SUVmean (liver) and SMaT20,40,60(cardiac)/SUVmean(liver/lung) separated grades 2 and 3. Conclusion Quantitative SPECT/CT parameters of cardiac Tc-DPD uptake are robust, enabling separation of patients with grades 2 and 3 cardiac uptake from grades 0 and 1. Larger patient cohorts will determine the incremental value of SPECT/CT quantification for ATTR management.

Introduction: This study aims to evaluate discrepant findings between positron emission tomography/magnetic resonance imaging (PET/MRI) and positron emission tomography/computed tomography (PET/CT) in a cohort of oncological patients and to undertake a phantom study to assess the potential for extended PET acquisitions to lead to false-positive findings on PET/MRI. Methods: Discrepant findings from a series of 106 patients undergoing sameday 18 F-fluorodeoxyglucose (FDG)-PET/CT and PET/MRI were reviewed. Phantom studies explored the potential for PET acquisition time to contribute to discrepancy.Results: There were 14 discrepant cases, 5 (35.7%) of which related to PET/ MRI acquisitions that had been extended to 10 min. Three of these five cases proved to be falsely positive. Phantom studies showed greater contrast recovery and signal to noise ratio for 10-min PET/MRI acquisitions compared to 2min acquisitions using PET/CT. There were no discrepancies when PET/CT showed disseminated disease (P = 0.036). Conclusions: Extended PET/MRI acquisitions used to accommodate multiple MRI sequences may be associated with false-positive findings compared to PET/CT. PET/MRI is more likely to have incremental value when the prior probability for disseminated disease is low.

We thank Panagi et al. [1] for their thoughtful approach to constructing a liver phantom for myocardial perfusion imaging (MPI). There are a number of sources within the gastrointestinal system which may be responsible for artefacts in MPI (in terms of motion, scatter and attenuation). The stomach and bowel are others [2]. Would they require similar principles of design?Stomach and bowel are also highly variable in position [3]. This would make sense particularly in viscera which are not anatomically fixed within peritoneum. Specifically, the study concentrated on cranio-caudal motion. Are other directions clinically significant in the authors' experience? How can the phantom be further enhanced to account adequately for intra-abdominal motion?Beyond that, how could we account for artefactual gastric radiotracer uptake exacerbated by medications such as proton pump inhibitors? This is an increasingly common problem as this therapy becomes more common. We have found it to increase the frequency of image re-acquisition [4].