Whole-body PET/CT reduces total scan time in patients with melanoma: Study

The findings, featured in the European Journal of Nuclear Medicine and Molecular Imaging, may have practical implications for the diagnostic work-up of melanoma patients, given the requirement for accurate whole-body imaging in this cancer type.

The latest introduction of the LAFOV PET/CT (positron emission tomography/computed tomography) scanner has given promising results concerning sensitivity and quality in cancer patients. Still, there need to be more studies beyond research purposes, with initial clinical experiences just beginning to be reported.

Considering the above, Christos Sachpekidis and colleagues from Germany aimed to determine a suitable acquisition time range for the new long axial field of view Biograph Vision Quadra PET/CT scanner from Siemens Healthcare by utilizing the activity of low dose [18F]FDG in a group of patients with melanoma.

The researchers enrolled forty-nine melanoma patients. All patients were given i.v. Injection of 2.0 MBq/kg [18F]FDG, they underwent total-body PET/CT from the head's top through the feet in two-bed positions. The PET images obtained of the first bed position from head to upper thigh were reconstructed and divided further into 2-min (PET-2), 4-min (PET-4), 5-min (PET-5), 6-min (PET-6), and 8-min (PET-8) duration groups.

The research team drew comparisons between the different reconstructed scan times concerning the visual assessment of the PET/CT scans utilizing PET-10 images as a reference. On the basis of SUV calculations of tumor lesions and background, they evaluated PET/CT image quality objectively, resulting in the computation of tumour-to-background ratio (TBR) and liver signal-to-noise ratio (SNR). Evaluation of a total of 60 scans was done.

The study led to the following findings:

• Regarding visual analysis, 81.7% of PET-10 scans were pathological, while the respective frequencies were 81.7% for PET-8, 81.7% for PET-6, 80% for PET-5, 76.7% for PET-4, and 75% for PET-2.
• The extent of metastatic involvement was vast in 18 PET-10 scans, depicting the accurate calculation of [18F]FDG-avid tumor lesions as very complicated.
• In the rest of the 42 PET-10 scans, for which the exact calculation of tumor lesions was workable, a total of 119 tumor lesions were counted.
• The lesion detection rates for shorter acquisitions were as follows: 97.5% for PET-8, 95.0% for PET-6, 89.9% for PET-5, 83.2% for PET-4, and 73.9% for PET-2.
• Regarding objective image quality evaluations, as a general trend, the trim of acquisition time was linked with decreased liver SNR and TBR. However, the change in tumor SUVmean values and TBR was insignificant up to 6 and 5 min acquisitions, respectively, in lesion-based analysis.

"Low-dose LAFOV PET/CT imaging is feasible in melanoma patients and can trim the total scan time from head to upper thigh up to 5 min providing similar diagnostic data to standard lengths of acquisition," the authors wrote.

"This may have considerable implications for the diagnostic work-up of melanoma patients, provided the need for true whole-body imaging in this cancer type."

Reference:

Sachpekidis, C., Pan, L., Kopp-Schneider, A. et al. Application of the long axial field-of-view PET/CT with low-dose [18F]FDG in melanoma. Eur J Nucl Med Mol Imaging (2022). https://doi.org/10.1007/s00259-022-06070-7