1048. Rubidium Uptake in Lung Lesions on Rb-82 Myocardial Perfusion PET/CT Scan: Clinical Importance and Correlation with FDG PET/CT
Authors * Denotes Presenting Author
  1. Soheil Kooraki *; University of California, Los Angeles
  2. Nandakumar Menon; University of California, Los Angeles
  3. Marigdalia Ramirez-fort; University of California, Los Angeles
  4. Mojtaba Olyaie; University of California, Los Angeles
  5. Rene Packard; University of California, Los Angeles
  6. Gholam Reza Berenji; Greater Los Angeles VA Healthcare; University of California, Los Angeles
Incidental or nonincidental lung nodules or masses are frequently encountered on 82-Rubidium myocardial perfusion PET/CT scan. The purpose of the present study was to measure the rubidium uptake in various lung lesions and evaluate if rubidium uptake in these lesions can predict malignancy. Furthermore, we aimed to examine if the rubidium uptake correlates with FDG activity in lung lesions.

Materials and Methods:
This IRB-approved, HIPAA-compliant, single-center, retrospective study was conducted on a veteran population who underwent Rubidium-82 myocardial perfusion imaging (Rb-82 MPI) for the evaluation of ischemic heart disease between October 2021 and July 2022. We found 27 patients with lung lesions (16 malignant, 11 benign) on Rb-82 MPI, who also had an FDG PET/CT completed within three months of acquiring MPI. On both rest and stress images of the Rb-82 MPI, the maximum standardized uptake value (SUVmax) of the lung lesion was measured and normalized relative to the SUV mean of the liver, background contralateral lung, and mediastinum. Similarly, on FDG PET/CT, the SUVmax of the same lesion was measured and normalized relative to SUV mean of the liver. Pearson correlation coefficient and area under the ROC curve were used for statistical analysis.

On either rest or stress Rb-82 MPI, the absolute SUVmax and normalized SUVmax values were not significantly different between benign and malignant lung lesions (p values >.05). Rubidium uptake of lung lesions on rest and stress images of Rb-82 MPI was consistent, however the correlation between normalized SUVmax values was not statistically significant. (SUV max normalized relative to contralateral lung; r = 0.75, p =.53). There was no significant correlation between normalized SUV measures of rest or stress rubidium and FDG uptake (p values >.05).

Rubidium uptake in lung lesions poorly correlates with FDG activity. The degree of Rb-82 uptake is not reliable for differentiation of benign from malignant lung lesions.