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

Abstract

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.