July 2021, Volume 71, Issue 7

IMAGING CORNER

“Superscan” on F18‑fluorodeoxyglucose Positron Emission Tomography — Computed Tomography [18‑F] FDG PET-CT

Myda Muzaffar  ( Department of Nuclear Medicine, Shaukat Khanum Memorial Cancer Hospital and Research Center Lahore, Pakistan )
Aamna Hassan  ( Department of Nuclear Medicine, Shaukat Khanum Memorial Cancer Hospital and Research Centre, Lahore, Pakistan )

Abstract

“Superscan” features have been described in 18F FDG PET-CT (F18 fluorodeoxyglucose Positron Emission Tomography‑Computed Tomography) scan; characterized by significantly increased uptake in one or more organ systems resulting in absent or decreased uptake in the organs which normally show physiological uptake. The importance of the awareness has evolved over the years in order to avoid false interpretation of scan findings as well as in determination of a high tumour burden. We present images of three patients who underwent 18F FDG PET-CT scan showing findings consistent with FDG PET-CT superscan.

Keywords: Superscan, F18‑fluorodeoxyglucose Positron Emission Tomography‑Computed Tomography, Hepatic, Hypermetabolic.

 

A 68-year-old female with hoarseness of voice, weight loss and neck swelling, diagnosed with diffuse large B-cell lymphoma was seen in the medical centre. Baseline PET-CT scan showed hepatic superscan (Figure-1).

A 12-year-old female with waxing waning fever and bilateral neck swelling was diagnosed with Hodgkin's lymphoma. Baseline PET-CT scan showed superscan (Figure-2). A 45-year-old female with known breast cancer; developed osseous metastases. PET-CT scan showed hepatic and skeletal superscan (Figure-3). All three cases show variations of FDG superscan with reduced FDG uptake in the brain, myocardium, kidneys, urinary bladder and soft tissue structures known as sink phenomenon.

The term “superscan” is well described on skeletal scintigraphy showing a characteristic pattern of increased skeletal radiotracer uptake with near-absent renal and soft tissue uptake.1 On 18‑F FDG PET-CT scan, superscan is characterized by markedly high uptake in one or more organs or organ systems with absent or diminished FDG uptake in organs that normally show physiological FDG uptake.2 Most of the reported FDG superscans have metastatic disease implying a heavy tumour burden represented by hypercellularity and hypermetabolism.3 A negative correlation has been seen between the tumour glycolytic volume and brain uptake. Superscan findings may reverse with effective treatment of disease.

Superscan has been described as metabolic skeletal superscan, hepatic superscan or both. A hepatic superscan is described by high hepatic FDG uptake with strikingly reduced or absent metabolic activity in the brain, mediastinum and the renal cortex.4-6

The knowledge of different patterns of superscan is necessary to avoid false negative interpretation and unnecessary neurological imaging or assessment.

 

References

 

1.      Buckley O, O’Keeffe S, Geoghegan T, Lyburn ID, Munk PL, Worsley D, et al. 99mTc bone scintigraphy superscans: A review. Nucl Med Commun 2007; 28:521‑7.

2.      Manov JJ, Roth PJ, Kuker R. Clinical pearls: Etiologies of superscan appearance on fluorine‑18‑fludeoxyglucose positron emission tomography‑computed tomography. Indian J Nucl Med 2017; 32:259-65.

3.      Kim DW, Kim CG, Park SA, Jung SA, Yang SH. Metabolic super scan in F‑FDG PET/CT imaging. J Korean Med Sci 2010; 25:1256‑7.

4.      Yang G, Nie P, Wang Z, Xing X. (18)F‑FDG hepatic superscan caused by a non‑germinal center subtype of diffuse large B‑cell lymphoma. Eur J Nucl Med Mol Imaging 2016; 43:1928.

5.      Mahajan S, Kalra S, Chawla M, Dougall P. Detection of diffuse infiltrative primary hepatic lymphoma on FDG PET‑CT: Hallmarks of hepatic superscan. World J Nucl Med 2016; 15:142‑4.

6.      Taneja S, Achong DM. Hepatic superscan on PET/CT due to Richter’s transformation of chronic lymphocytic leukemia. Clin Nucl Med 2010; 35:644‑5.

 

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