Incidence
and Intensity of ¹⁸FDG Uptake on Whole Body PET/CT in Patients with
Polymyalgia Rheumatica

C.E. Owen^1,2,
A.M.T. Poon^2,3, S.T. Lee^2,3,4, K. Pathmakaj³,
C. McMenamin¹, A.M. Scott^2,3,4, R.R.C. Buchanan^1,2

¹Department of Rheumatology, Austin
Health, Heidelberg VIC ²Department of Medicine, University of
Melbourne, Parkville VIC ³Department of Molecular Imaging and
Therapy, Austin Health, Heidelberg VIC ⁴Olivia Newton-John Cancer
Research Institute, Heidelberg VIC

Background/Purpose:
To characterise the incidence
and intensity of ¹⁸Fluorodeoxyglucose (¹⁸FDG) uptake on
whole body PET/CT in untreated patients with newly diagnosed Polymyalgia
Rheumatica (PMR).

Methods: Patients with newly diagnosed PMR according
to the 2012 EULAR/ACR Classification Criteria[1]
were prospectively recruited. A whole body scan from skull vertex to toes
(including dedicated hand views) was performed at baseline using a Phillips TF
PET/CT machine in all untreated patients. A range of demographic, clinical and
laboratory data were collected. Images were reviewed with Medview software by
an experienced Nuclear Medicine Physician. Both qualitative and
semi-quantitative (standardised uptake value maximum [SUV_max])
analysis of joint and vascular ¹⁸FDG uptake were performed. Statistical
analyses were undertaken using Stata 13.0 (Statcorp, College Station, TX, USA). 

Results: Thirteen patients with PMR were
recruited. Mean age was 68.47 years, there was a slight male predominance (53.85%)
and all were Caucasian. All patients reported bilateral shoulder pain at presentation,
but hip symptoms were less common (69.23%). Disease activity was high (mean
PMR-AS 80.29) and the median HAQ-DI score was 2.125. In addition to involvement
of the shoulder capsule (11/13, 84.62%), hip capsule (11/13, 84.62%),
trochanteric bursae (12/13, 92.31%) and interspinous bursae (10/13, 76.92%), a
high incidence of ¹⁸FDG uptake at the ischial tuberosities (12/13, 92.31%)
and knee capsule (9/13, 69.23%) was seen. Involvement of the palmar aspect of
the hands/wrists and feet was also observed in 5/13 (38.46%) and 2/13 (15.38%)
cases respectively. With respect to SUV_max at sites of ¹⁸FDG
uptake, the highest mean result occurred at the ischial tuberosities (4.38)
followed by the shoulder capsule (3.94), interspinous bursae (3.62) and knee
capsule (3.48).

Conclusion:
Patients with newly
diagnosed, untreated PMR exhibit most intense ¹⁸FDG uptake at the
ischial tuberosities on whole body PET/CT. Frequent involvement of peripheral
joints, especially the knee capsule, is also observed.       

Figure 1: Intense ¹⁸FDG uptake at
the ischial tuberosities in a patient with newly diagnosed, untreated PMR.