Evaluating Calcification in Below-the-Knee Lesions Using Adjusted Computed Tomography Window Settings

Full-moon calcified plaque is difficult to treat in coronary arteries. Computed tomography (CT) is used to evaluate calcification, but severe plaque can be difficult to assess due to artifacts. Adjusting noncontrast CT window settings may improve plaque evaluation. This study aimed to assess true full-moon calcifications and their impact on procedural success in below-the-knee (BTK) endovascular therapy (EVT) and antegrade guidewire success in chronic total occlusion (CTO) cases.

This retrospective, single-center study analyzed full-moon calcifications in the tibial and peroneal arteries using noncontrast CT. In total, 103 vessels from 58 patients, including 37 CTO cases, were analyzed. The primary endpoints were procedural success in all cases and antegrade guidewire success in CTO cases. Plaques occupying >80% of the cross-sectional area were defined as full-moon calcifications. Those retaining a full-moon shape after artifact reduction were classified as true full-moon calcifications. The proportion of full-moon calcified slices was compared between successful and unsuccessful groups. In addition, a subgroup analysis was conducted for stenotic lesions to evaluate the association between true full-moon calcification and device passage failure or balloon under-expansion.

Procedural success was achieved in 68 cases (66.0%). True full-moon calcifications were significantly higher in the procedural failure group than in the success group (22.81% [interquartile range, IQR: 5.96-33.75] vs 1.87% [IQR: 0.00-10.57], p<0.001). In CTO cases, antegrade guidewire success was achieved in 13 cases (35.1%), with true full-moon calcifications significantly higher in unsuccessful cases (13.95% [IQR: 2.06-31.29] vs 0.00% [IQR: 0.00-1.89], p=0.0012). In multivariate analysis, diabetes mellitus (p=0.0115), lesion length (p=0.00488), CTO presence (p<0.001), and true full-moon calcifications (p<0.001) were independent predictors negatively associated with procedural success. Hemodialysis was significantly associated with an increased full-moon calcification burden (β=6.66, 95% confidence interval [CI]=0.10-13.22, p=0.047). True full-moon calcification was significantly higher in stenotic lesions with device passage failure or balloon under-expansion (21.68% vs 0.00%, p=0.0117).

True full-moon calcifications predict procedural failure in BTK EVT and unsuccessful antegrade guidewire passage in CTO cases. Noncontrast CT evaluation with artifact reduction may aid in procedural planning and treatment strategy.Clinical ImpactThis study clarifies the clinical significance of true full-moon calcifications in below-the-knee endovascular therapy (EVT). Applying artifact reduction techniques in noncontrast CT allows for more accurate assessment of severely calcified plaques. Identifying high-risk lesions preoperatively may help anticipate wire crossing or device delivery difficulties and guide strategy optimization. These findings may support improving procedural success in EVT for patients with critical limb-threatening ischemia (CLTI) who have complex lesions, including severe calcification and chronic total occlusion (CTO). This study demonstrates the clinical value of noncontrast CT in preprocedural lesion assessment and treatment planning in peripheral interventions.