The effect of a novel Bayesian penalised likelihood PET reconstruction algorithm on the assessment of malignancy risk in solitary pulmonary nodules according to the British Thoracic Society guidelines

PURPOSE

British Thoracic Society (BTS) guidelines advocate using FDG PET-CT with the Herder model to estimate malignancy risk in solitary pulmonary nodules (SPNs). Qualitative and semi-quantitative assessment of SPN uptake is based upon analysis of Ordered Subset Expected Maximisation (OSEM) PET images. Our aim was to assess the effect of a Bayesian Penalised Likelihood (BPL) PET reconstruction on the assessment of SPN FDG uptake and estimation of malignancy risk (Herder score).

METHODS

Subjects with SPNs who underwent FDG PET-CT between 2014-2017, with histological confirmation of malignancy or histological/imaging follow-up confirmation of benignity were included. Two blinded readers independently classified SPN uptake on both OSEM and BPL (BTS score; 1 = none; 2 = ≤ mediastinal blood pool (MBP); 3 = >MBP but ≤ 2x liver; 4 = >2x liver), with resultant calculation of the Herder score (%) for both reconstructions.

RESULTS

97 subjects with 75 (77%) malignant SPNs were included. BPL increased the BTS score in 25 (26%) SPNs; 9 SPNs (7 malignant) increased from BTS score 2 to 3, 16 (13 malignant) from BTS score 3 to 4, with a mean Herder score increase of 18 ± 22%. The mean Herder score for all SPNs with BPL was higher than OSEM (73 ± 29 vs 68 ± 32%, p = 0.001). There was no difference in Herder model diagnostic performance between BPL and OSEM, with similar areas under the curve (0.84 vs 0.83, p = 0.39).

CONCLUSION

BPL increases the Herder score in 26% of SPNs compared to OSEM but does not alter the diagnostic performance of the Herder model.

Diabetes and bone: advantages and limitations of radiological, radionuclide and hybrid techniques in the assessment of diabetic foot

A common cause of morbidity and mortality in diabetic patients are foot infection/complications often leading to amputation of lower extremities. Various radiological and radionuclide techniques are available for the assessment of diabetic patients with bone or soft tissue infections. However, there are several advantages and limitations. The major limitation of all these techniques is their inability to accurately differentiate osteomyelitis from charcot's/neuropathic joints. Radiologically, magnetic resonance imaging (MRI) is the technique of choice and a radiolobeled white cell scan is a useful nuclear medicine technique in the evaluation of diabetic patients with suspected foot infection. In this review we discuss the efficacy of radiological and radionuclide techniques in the assessment of diabetic foot infection.