Alex A. Nagelschneider

MRI fails to localize a tumor in up to 40% of cases of ACTH dependent Cushing Disease (CD), impacting patient outcomes and creating uncertainty in the diagnosis. Photon-counting detector CT (PCD-CT) is a new CT technology with better imaging performance than conventional CT. PCD-CT is a novel imaging technique for CD, especially for MR-negative cases, however its application to CD remains unknown. We present a cohort of consecutive patients with a pre-operative PCD-CT undergoing transsphenoidal surgery for CD at a single institution from September 2023 to January 2025. All patients underwent gadolinium-enhanced pituitary MRI for baseline work-up and PCD-CT as part of their preoperative planning imaging. Both imaging modalities were used to localize the lesion and guide surgical planning. The accuracies of MRI and PCD-CT were based on confirmation of the lesion location by a combination of intraoperative visualization, pathologic confirmation, and postoperative biochemical remission, and were compared with each other via Fisher's exact test. Twenty-five patients with CD were included in this analysis. The cohort's median age was 50 years old, and 88% were female. At diagnosis, 88% had central obesity, 76% had hypertension, 48% had type II diabetes mellitus, and 20% had osteoporosis. Contrast-enhanced MRI accurately identified 56% of lesions, while it was negative in 24% and misleading in 20%. Dynamic contrast-enhanced PCD-CT was superior in localizing CD (p=0.01), accurately identifying 92% of lesions, while it was negative in 4% and misleading in 4% of cases. Early postoperative biochemical remission was achieved in 88% of cases, while 84% remained in remission at follow-up. PCD-CT had a high rate of adenoma localization confirmed intraoperatively, even among MR-negative cases, potentially leading to high remission and gland preservation rates. Its role in the clinical workflow of preoperative evaluation for CD requires further investigation, but current evidence supports its value in lesion localization, especially in MR-negative disease. CD＝ cushing disease; PCD＝ photon counting detector.

BACKGROUND AND PURPOSE: Photon-counting detector CT (PCD-CT) is now clinically available and offers ultra-high–resolution (UHR) imaging. Our purpose was to prospectively evaluate the relative image quality and impact on diagnostic confidence of head CTA images acquired by using a PCD-CT compared with an energy-integrating detector CT (EID-CT). MATERIALS AND METHODS: Adult patients undergoing head CTA on EID-CT also underwent a PCD-CT research examination. For both CT examinations, images were reconstructed at 0.6 mm by using a matched standard resolution (SR) kernel. Additionally, PCD-CT images were reconstructed at the thinnest section thickness of 0.2 mm (UHR) with the sharpest kernel, and denoised with a deep convolutional neural network (CNN) algorithm (PCD-UHR-CNN). Two readers (R1, R2) independently evaluated image quality in randomized, blinded fashion in 2 sessions, PCD-SR versus EID-SR and PCD-UHR-CNN versus EID-SR. The readers rated overall image quality (1 [worst] to 5 [best]) and provided a Likert comparison score (−2 [significantly inferior] to 2 [significantly superior]) for the 2 series when compared side-by-side for several image quality features, including visualization of specific arterial segments. Diagnostic confidence (0–100) was rated for PCD versus EID for specific arterial findings, if present. RESULTS: Twenty-eight adult patients were enrolled. The volume CT dose index was similar (EID: 37.1 ± 4.7 mGy; PCD: 36.1 ± 4.0 mGy). Overall image quality for PCD-SR and PCD-UHR-CNN was higher than EID-SR (eg, PCD-UHR-CNN versus EID-SR: 4.0 ± 0.0 versus 3.0 ± 0.0 (R1), 4.9 ± 0.3 versus 3.0 ± 0.0 (R2); all P values < .001). For depiction of arterial segments, PCD-SR was preferred over EID-SR (R1: 1.0–1.3; R2: 1.0–1.8), and PCD-UHR-CNN over EID-SR (R1: 0.9–1.4; R2: 1.9–2.0). Diagnostic confidence of arterial findings for PCD-SR and PCD-UHR-CNN was significantly higher than EID-SR: eg, PCD-UHR-CNN versus EID-SR: 93.0 ± 5.8 versus 78.2 ± 9.3 (R1), 88.6 ± 5.9 versus 70.4 ± 5.0 (R2); all P values < .001. CONCLUSIONS: PCD-CT provides improved image quality for head CTA images compared with EID-CT, both when PCD and EID reconstructions are matched, and to an even greater extent when PCD-UHR reconstruction is combined with a CNN denoising algorithm.

Historically, MRI has been unable to detect a pituitary adenoma in up to half of patients with Cushing disease. This is problematic, as the standard of care treatment is surgical resection, and its success is correlated with finding the tumor on imaging. Photon counting detector CT (PCD-CT) is a recent advancement that has multiple benefits over conventional energy integrating detector CT. We present the use of dynamic contrast enhanced imaging using PCD-CT for detection of pituitary adenoma in patients with Cushing disease. ABBREVIATIONS: PCD-CT ＝ Photon Counting Detector CT; EID ＝Energy-integrating detector; VMI = Virtual monochromatic imaging.