PET-CT Teaching Case

Let's go through key learning points:

Summary of PET CT report should include these all relevant findings: Increased metabolic activity is noted in the irregular spiculated lesion in the apicoposterior segment of the left upper lobe. No evidence of active lesion in other segments of the lungs or elsewhere in the given images. No significantly enlarged or metabolically active mediastinal or axillary lymphnodes seen. No pleural lesions / effusion. Most likely cause for such lesion is malignancy such as non small cell carcinoma of the lung. An aggressive infection or lymphoma can give a similar appearance. Should biopsy show this to be due to a primary lung tumour then PET staging would be T2,N0,M0. Note: At another institute this case was reported as the left upper lobe carcinoma of the bronchus. No other D/D was considered! Biopsy showed Marginal Zone Lymphoma. This case and write up is contributed by Dr Sanjay Gandhi, MBBS, MD, DNB, FRCR, FHEA, Consultant Radiologist, Frenchay Hospital, North Bristol NHS Trust. Honorary Senior Clinical Lecturer, University of Bristol and Visiting Senior Lecturer, University of West of England

Further PET learning points: Cardiac activity is physiological on PET. Low grade gastro-intestinal activity especially in stomach and large bowel is also physiological. Kidneys and bladder show normal FDG excretion. Ovaries can show increased activity near ovulation (correlate with size). Trainees should read all information given with the images. This case was known to have an extra renal pelvis, therefore at the very start residents were told to ignore the left kidney. BROWN FAT UPTAKE: A potential source of false-positive FDG PET interpretations in oncologic imaging. commonly seen in neck, medaistinum. Sometimes, also in abdomen. No abnormal soft tissue lesion would be seen in the areas of increased activity.