Improved visualization of the inferior tympanic and mastoid canaliculi with photon counting detector CT

Purpose: To compare the performance of the photon-counting detector (PCD)-CT versus a state-of-the-art energy-integrating detector (EID)-CT to identify segments of the inferior tympanic canaliculus (Jacobsons nerve) and the mastoid canaliculus (Arnolds nerve).

Materials & methods: Patients were prospectively recruited to undergo temporal bone CT on both EID-CT (Siemens Somatom Force) and PCD-CT (Siemens NAEOTOM Alpha) scanners under an IRB-approved protocol. Three neuroradiologists reviewed cases by consensus comparing the ability to identify the proximal, mid, and distal segments of the inferior tympanic canaliculus/Jacobsons nerve and mastoid canaliculus/Arnolds nerve on each scanner using 5-point Likert scales (with 1 indicating EID is far superior to PCD, 3 indicating they are equivalent, and 5 indicating PCD is far superior to EID).

Results: Forty temporal bones were analyzed. Average Likert scores for the ability to evaluate the proximal, mid, and distal aspects of inferior tympanic canaliculus/Jacobsons nerve on the PCD compared to EID scanner were 4.5 (SD = 0.6), 4.2 (0.4), and 4.1 (0.3). The scores for the mastoid canaliculus/Arnolds nerve were 4.0 (0.4), 4.1 (0.4), and 4.0 (0.4). Overall, the PCD scanner performed better than EID for image quality (Median = 4.2, 95 % CI = [4.1, 5.0], p-value < 0.001).

Conclusion: PCD-CT provides superior visualization of the proximal, mid, and distal aspects of the inferior tympanic canaliculus/Jacobsons nerve and mastoid canaliculus/Arnolds nerve compared to EID-CT examinations. The improved visualization of these nerves could be important for characterization of subtle pathology involving these structures, such as tympanic paraganglioma or nodular perineural spread.