Quantitative Measurement of Pulmonary Iodine Deposition on DECT as a Novel Marker of Amiodarone-Induced Pulmonary Toxicity

Background: Amiodarone-induced lung disease (AILD) is a serious adverse effect of amiodarone therapy that is difficult to diagnose, since its symptoms, clinical findings, and test results are nonspecific. Because amiodarone contains iodine, pulmonary iodine deposition is a putative marker of AILD, and dual-energy CT (DECT) is sensitive for iodine detection.

Aim: To quantify pulmonary iodine deposition in patients with high and low clinical probability of AILD and in controls.

Methods: This retrospective observational study included patients who underwent non-contrast DECT for suspected AILD. Pulmonologists classified patients as low clinical probability (n=31, 21 males; mean age 75 years) or high clinical probability (n=13, 6 males; mean age 83 years). Fifteen age- and sex-matched controls underwent non-contrast DECT after trauma and had no history of amiodarone treatment. A dedicated software application segmented the lung into normally aerated lung, ground-glass opacity (GGO), and consolidation, and quantified iodine deposition (mg/ml per voxel). Measurements were validated by phantom iodine calibration.

Results: Overall lung air content was 84.04% in controls, 82.87% in the low-probability group, and 80.24% in the high-probability group. Iodine deposition was significantly higher in the high-probability group than in the low-probability group in normal lung (P=.014), GGO (P=.002), and consolidation (P=.052). Iodine was not detected in controls (mean 0.0048 mg/ml).

Conclusion: Quantitative iodine deposition on DECT is a diagnostic marker of amiodarone-induced pulmonary toxicity and may help differentiate patients who should discontinue amiodarone from those whose lung disease is unrelated to amiodarone exposure