Optimization of a Photon-counting Detector Computed TomographyCT Protocol for Determining Disease Activity in Peripheral Inflammatory Arthritides

Purpose or Learning Objective: Inflammatory arthritides are characterized by chronic inflammation of synovial and peritendon structures. Photon-counting detector computed tomography CT (PCD-CT) allows for semiquantitative iodine mapping of inflamed tissues, thatwhich could provide valuable data for assessing disease activity and facilitate early diagnosis, as well as support therapeutic decision- making. However, due to the novelty of this technique, currently there are no accepted postcontrast musculoskeletal protocol recommendations are currently in place. Our aim was to determine the ideal timing of scan acquisition after intravenous contrast administration.

Methods or Background: We obtained 0.4- mm slice thickness CT scans of bilateral wrist-hand regions of 13 peripheral arthritis patients (69.23% female; age [mean ± standard deviation]: 58.08 ± 21.31 years) were obtained. Native and postcontrast (1 mL/kg; flow rate: 2.5 mL/sec) 120-, 180-, and 240- second measurements were performed. Spectral images were postprocessed to obtain data required for iodine mapping. Density and iodine concentration values were measured at multiple locations in enhancing synovial and peritendon soft tissues (n = 276), as well as in fat (n = 100), muscle (n = 100), and vessell structures (n = 100) structures as controls in both pre-, and postcontrast phases. Synovitis and tenosynovitis detected on CT images were verified by ultrasonography und measurements. We used a mixed-effects linear regression model was used to analyze the relation between the concentration and density values of the different phases. We assessed descriptive statistics were utilized to assess dose values and patient characteristics with descriptive statistics.

Results or Findings: Inflamed tissues on all postcontrast phases presented significantly different density and iodine concentration values (P < 0.001) compared with adipose tissue and vessel structures. However, no significant differences (P > 0.05) were detected in concentration and density values among between the three different postcontrast phases. The average effective dose value for both phases was 0.056 mSv ± 0.011 mSv ([mean ± standard deviation)].

Conclusion: One postcontrast PCD-CT scan would be sufficient to detect for accurate detection of disease activity accurately. A 120- second phase protocol may be the most optimal due to its short duration.

Publication History

Article published online:
22 May 2024