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Distinguishing enhancing from non-enhancing hyperdense adnexal lesions with spectral reconstructions at photon
Danielle Rigau1, Daniel Parrott2, Bhavik Bansal3
1Department of Radiology, New York University Langone Health, New York City, USA. danielle.rigau@nyulangone.org.
Purpose:
Hyperdense adnexal lesions on conventional CT often necessitate follow-up imaging. Photon counting CT (PCCT) allows for the generation of virtual unenhanced (VUE) and iodine map images. The purpose was to investigate the utility of PCCT spectral reconstructions to distinguish enhancing from nonenhancing hyperdense adnexal lesions.
Methods:
A retrospective Picture Archiving and Communication System (PACS) search identified adult women with adnexal lesions on contrast-enhanced PCCT and with pelvic MRI or ultrasound within 180 days characterizing the lesion, the reference standard. Patients with adnexal lesions > 1 cm and > 20 Hounsfield Units (HU) on 70 keV PCCT images were included. Two radiologists drew region-of-interest measurements independently on adnexal lesions on thin-client software. Attenuation on VUE and 70 keV images, iodine density (ID), and iodine density normalized to aortic enhancement (NID) were recorded from the same region-of-interest. Attenuation change (ΔHU) from VUE to 70 keV was computed. Wilcoxon rank-sum test was used to compare ID, NID, and ΔHU for enhancing versus nonenhancing lesions. Receiver-operating characteristic (ROC) curves were used to determine optimal thresholds for enhancement. Inter-reader agreement was assessed with intraclass correlation coefficients (ICC).
Results:
38 women (median [Interquartile Range (IQR)] age: 44[37,48]) were included. 22 had nonenhancing and 16 had enhancing lesions. ΔHU for enhancing and nonenhancing lesions was 27[24,37]HU and 2[-1,5]HU, respectively (p<.001). ID of enhancing and nonenhancing lesions was 1.15[0.98,1.60] mg/ml and 0.05[-0.08,0.18] mg/ml, respectively (p<.001). NID of enhancing and nonenhancing lesions was 22[14,29]% and 1.0[-1.0,3.0]%, respectively (p<.001). The optimal ΔHU for detecting enhancement at 70 keV was 12.0HU with 100% sensitivity and 95% specificity (Area Under the Curve (AUROC) = 0.99[95% Confidence Interval (CI): 0.97,1.00]). 0.4 mg/mL ID and 8% NID both had 100% sensitivity and 95% specificity (AUROC = 0.99[95%CI: 0.97,1.00]; AUROC = 0.99[95% CI: 0.96,1.00]; respectively). ICC[95% CI] was 0.74[0.56,0.86].
Conclusion:
Attenuation change utilizing VUE images and iodine quantification can differentiate enhancing from nonenhancing hyperdense adnexal lesions at PCCT with excellent diagnostic performance. Accurate assessment of hyperdense adnexal lesion enhancement on PCCT may negate the need for follow-up imaging.
