# 18F-NaF PET/CT identifies muscular and subcutaneous calcifications in both dermatomyositis- and systemic sclerosis-related calcinosis

## TL;DR

18F-NaF PET/CT can detect and quantify calcinosis in dermatomyositis and systemic sclerosis better than clinical exams or CT scans.

## Contribution

18F-NaF PET/CT is shown to detect calcinosis in muscles and subcutaneous tissue, offering new insights into disease mechanisms.

## Key findings

- 18F-NaF PET/CT detected calcinosis in all patients, including subcutaneous and muscle deposits.
- 18F-NaF PET/CT scores were higher than clinical exam scores, indicating better sensitivity.
- 18F-NaF uptake occurred in calcinosis deposits without corresponding CT calcifications.

## Abstract

Calcinosis is a morbid complication of dermatomyositis (DM) and systemic sclerosis (SSc) with no effective pharmacologic treatment or validated whole-body assessment modality. 18F-NaF PET/CT may help to quantify and characterize calcinosis.

In this pilot study, we enrolled three adults with DM and three with SSc, all with new calcinosis deposits. Each underwent 18F-NaF PET/CT and clinical examination with semi-quantitative scoring of calcinosis. We described the 18F-NaF PET/CT findings and compared these to CT imaging alone as well as to clinical examination.

Calcinosis was noted on 18F-NaF PET/CT in the subcutaneous tissue in all patients and the muscle in three patients, including two with SSc. The average semi-quantitative score was 23.5 by 18F-NaF PET/CT and 20 by clinical exam. Wilcoxon signed rank test indicated greater scores by 18F-NaF PET/CT than by clinical exam (p = 0.0264). 18F-NaF uptake varied among calcinosis deposits and occurred without corresponding calcifications on CT.

18F-NaF PET/CT appears to be a sensitive method of detecting and characterizing calcinosis that provides both quantitative and qualitative data beyond what can be obtained by physical examination or CT alone. 18F-NaF uptake occurs in muscle in both SSc and DM, suggesting the possibility that myositis may be driving calcinosis in a subset of patients with SSc.