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- Bobbio, Emanuele, et al.
(author)
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Incidental cardiac findings on somatostatin receptor PET/CT: What do they indicate and are they of clinical relevance?
- 2022
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In: Journal of nuclear cardiology : official publication of the American Society of Nuclear Cardiology. - : Springer Science and Business Media LLC. - 1532-6551. ; 29:3, s. 1159-1165
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Journal article (peer-reviewed)abstract
- We present the case of a 47-year-old man with a history of recurrent episodes of frontal headache, fever, and chest discomfort as well as longstanding, difficult to treat arterial hypertension. Clinical work-up revealed the unexpected finding of an underlying pheochromocytoma as well as recent "silent" myocardial infarction. Our case highlights the importance of paying attention to incidental cardiac findings on somatostatin receptor positron emission tomography/computed tomography, as routinely performed in patients with clinically suspected neuroendocrine tumors. These incidental cardiac findings cannot only indicate a primary or secondary (metastatic) neuroendocrine tumor, but also areas of myocardial inflammation, as somatostatin receptors cannot only be found on the majority of neuroendocrine tumors, but also among other tissues on the surface of activated macrophages and lymphocytes. The detection of myocardial inflammation is of clinical importance and its underlying etiology should be evaluated to prompt eventual necessary treatment, as it is a potential driving force for cardiac remodeling and poor prognosis.
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- Rydén, Tobias, et al.
(author)
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Deep learning generation of synthetic intermediate projections improves 177 Lu SPECT images reconstructed with sparsely acquired projections
- 2021
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In: Journal of Nuclear Medicine. - : Society of Nuclear Medicine. - 0161-5505 .- 2159-662X. ; 62:4, s. 528-534
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Journal article (peer-reviewed)abstract
- The aims were to decrease 177Lu-SPECT (single-photon emission computed tomography) acquisition time by reducing the number of projections and to circumvent image degradation by adding deep learning-generated synthesized projections. Methods: We constructed a deep convolutional U-structured network for generating synthetic intermediate projections (CUSIP). The number of SPECT investigations was 352 for training, 37 for validation, and 15 for testing. The input was every fourth projection of 120 acquired SPECT projections, i.e., 30 projections. The output was 30 synthetic intermediate projections (SIPs) per CUSIP. SPECT images were reconstructed with 120 or 30 projections, or 120 projections where 90 SIPs were generated from the 30 projections (30-120SIP); using 3 CUSIPs. The reconstructions were performed with two ordered subset expectation maximization (OSEM) algorithms: attenuation-corrected (AC)-OSEM, and attenuation, scatter, and collimator response-corrected (ASCC)-OSEM. Image quality of SIPs and SPECT images were quantitatively evaluated with root mean square error, peak signal-to-noise-ratio (PSNR), and structural similarity (SSIM) index metrics. From a Jaszczak SPECT Phantom, the recovery and signal-to-noise ratio (SNR) were determined. In addition, an experienced observer qualitatively assessed the SPECT image quality of the test set. Kidney activity concentrations, as determined from the different SPECT images, were compared. Results: The generated SIPs had a mean SSIM value of 0.926 (0.061). For AC-OSEM, the reconstruction with 30-120SIP had higher SSIM (0.993 vs. 0.989; p<0.001) and PSNR (49.5 vs. 47.2; p<0.001) values than the reconstruction with 30 projections. ASCC-OSEM had higher SSIM and PSNR values than AC-OSEM (p<0.001). There was a minor loss in recovery for the 30-120SIP set, but SNR was clearly improved compared to the 30-projection set. The observer assessed 27/30 of the images reconstructed with 30 projections as having unacceptable noise levels, whereas corresponding values were 2/60 for the 30-120SIP and 120 projection sets. Image quality did not differ significantly between the 30-120SIP and 120 projection reconstructions. The kidney activity concentration was similar between the different projection sets, excepting a minor reduction of 2.5% for the ASCC-OSEM 30-120SIP. Conclusion: Adopting synthetic intermediate projections for sparsely acquired projections considerably recovers image quality and could allow reduced SPECT acquisition time in clinical dosimetry protocols.
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