Background: MRI fails to localize up to 40 to 60% of corticotroph microadenomas, impacting cure
rates and forcing surgeons to explore the whole gland. Photon-counting detector CT
(PCD-CT) is a newly introduced modified CT with a lower radiation dose than conventional
CT. PCD-CT is a promising imaging modality for Cushing’s disease (CD), especially
for MR-negative cases, due to its high tissue discrimination capacity and minimal
artifact by sinus pneumatization, but its accuracy remains to be studied.
Methods: We present a prospective cohort of consecutive patients undergoing endoscopic transnasal
surgery (ETS) for CD at a single institution from September 2023 to June 2024. All
patients underwent gadolinium-enhanced dynamic pituitary MRI for baseline work-up
and CT angiography with PCD-CT as part of their preoperative planning imaging for
carotid visualization. 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 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.
Results: Fifteen patients with CD were included in this analysis. The cohort’s median age
was 54 years old (interquartile range: 44–63), and 87% of the patients were females.
At diagnosis, 93% had central obesity, 73% had hypertension, 53% had type II diabetes
mellitus, and 27% had osteoporosis. A potential lesion was identified on MRI in 12
patients and on PCD-CT in all 15. True adenoma location was confirmed via intraoperative
visualization and pathologic confirmation in 12 cases, and by intraoperative visualization
and biochemical remission in 3 cases. MRI failed to accurately identify the tumor
in 33% of cases—including 3 cases where it was unable to localize a lesion and 2 cases
where it was misleading; PCD-CT identified the lesion accurately in all 15 cases (67
vs. 100%, p = 0.04). Immediate postoperative biochemical remission was achieved in 87% of cases,
and additional ETS for resection of residual was required for one patient. All 12
patients with more than one month of follow-up achieved biochemical remission, and
no cases of panhypopituitarism were noted.
Conclusion: PCD-CT achieves high rates of adenoma localization in Cushing’s disease, even among
MR-negative cases, leading to high remission rates and avoidance of blind pituitary
exploration. Its role in the clinical workflow of preoperative evaluation for CD remains
to be determined, but current evidence supports its value in lesion localization,
especially in MR-negative disease.
Fig. 1 Left posterior pituitary adenoma in a 66-year-old patient with Cushing’s disease.
The tumor is not visualized with gadolinium-enhanced MRI (left), but is accurately
identified via PCD-CT (gray-scale middle; color-scale right). Lesion location was
confirmed intraoperatively in combination with histopathological diagnosis.
