Can early phase cardiac [123I]mIBG images be used to diagnose Lewy body disease?

Abstract

Purpose Some studies have suggested that cardiac [123I]metaiodobenzylguanidine images obtained 15–20 min after tracer administration are as accurate for dementia with Lewy bodies (DLB) diagnosis as standard images acquired after a delay of 3–4 h; some suggest delayed imaging is preferable. We compare early and delayed heart-to-mediastinum ratios (HMR) in a well-characterised research dataset and make recommendations for clinical practice. Methods Images were acquired using a Siemens gamma camera with medium energy collimators. Early images were obtained at 20 min and delayed at 4 h (± 30) min. In total 167 pairs of images were reviewed: 30 controls, 39 people with dementia and 98 with mild cognitive impairment. HMR normal cutoff values derived from control data were ≥2.10 for early imaging and ≥1.85 for delayed. Results HMR tended to drop between early and delayed for abnormal images, but increase for normal images. Histograms of early and delayed HMR showed a slightly better separation of results into two groups for delayed imaging. Accuracy results were slightly higher for delayed imaging than early imaging (73 vs. 77%), sensitivity 63 vs. 65% and specificity 82 vs. 88%. However, this was not statistically significant – in total only 8/167 (5%) of scans changed designation between early and delayed imaging. Conclusion We suggest that a delayed image could be acquired only if the early result is borderline. This removes the need for delayed imaging in about 70% of patients. Adopting this protocol in clinical practice would reduce the time most patients have to wait and could free up scanner time.

Quantitative [123]I-Ioflupane DaTSCAN single-photon computed tomography-computed tomography in Parkinsonism

“…Firstly, our cohort is relatively small, with 26 patients; however, the previous papers on this subject have used similar sample sizes [20,35]. Therefore, a similar study using a larger sample size is warranted to confirm our findings with more statistical power.…”

“…Whilst the literature exploring the absolute quantification of DaTSCAN uptake in the brain is currently limited, our findings align with the results from Jreige et al . and Roberts in that a semiquantitative index can differentiate well between neurodegenerative Parkinsonian syndromes and SWEDD subjects [20,36]; however, Jreige et al . used SUVmax in their comparison with SBR, which can be miscalculated as the maximum concentration in the VOI can be subject to noise [37].…”

“…This is the most used quantitative index for evaluating DaTSCAN uptake [16,17]; however, a SPECT semiquantitative assessment often suffers from misalignment of the region of interest in borderline cases and inferior spatial resolution and sensitivity [18,19]. Therefore, an absolute, rather than relative, measure of the radioactivity in different regions of the brain is necessary [20]. This can be achieved by replacing the clinically used SPECT with SPECT-computed tomography (SPECT-CT), allowing the fusion of anatomical and functional information and positively impacting image interpretation and diagnostic accuracy [21].…”