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A 33-year-old female patient, who had sustained injuries following a fall, was presented to the emergency department. Upon arrival, she had altered consciousness with visible bleeding from the right ear and a superficial hematoma on the right side of the skull. A routine head CT scan, as a part of our institutional polytrauma protocol, was performed with a photon-counting detector (PCD) CT scanner (NAEOTOM Alpha.Prime) for further assessment.

Temporal bone trauma is commonly encountered in the emergency department. The tympanic cavity and tegmen, the ossicular chain, the bony labyrinth, the facial canal, the internal carotid artery, the jugular foramen and venous sinuses, as well as the intracranial contents are all potential injury sites. A specific and thorough reporting approach is needed due to the unique composition of these anatomical structures. A delayed or missed diagnosis of injuries to these structures can result in severe and permanent disabilities for the patient. [1] Ossicular luxation or fracture, disrupting the conductive chain, may cause conductive hearing loss (CHL). Six months after temporal bone trauma, persistent CHL occurs in 50% of the patients. The most common sites of ossicular dislocation are the incudostapedial and the incudomalleolar joints. [2] In the latter case, the joint dislocation is marked with displacement of the scoop (head of the malleus) from the cone (body and short process of the incus), disarticulating the normal “ice cream cone” in axial images and the typical “broken heart” sign in coronal MPR. [3] [4] CT is the imaging modality of choice in cases of temporal bone trauma. Traditionally, CT examination for head and for temporal bones are two separate scans, with the former focused on the low-contrast cerebrum and the latter, on high-contrast bony structures. This case is acquired with a newly developed single source PCD CT, NAEOTOM Alpha.Prime. The principle of PCD differs from that of conventional, energy-integrating detector (EID). With EID, X-ray photons are first converted into scintillation light and then into electrical signals, while with PCD, X-ray photons are converted directly into electrical signals. The detector elements in EID are separated by physical separators, while in PCD, they are separated by electric fields. The electronic circuit noise is also eliminated in PCD. These differences result in increased efficiency of X-ray photon utilization, and potentially, reduced image noise and radiation dose. Additionally, PCD has a smaller detector pixel size, which contributes to the decreased partial volume effects and blooming artifacts. This increases spatial resolution, which is especially important for imaging small, high-contrast structures, such as the ossicular chain. [5] Images acquired in routine head scan can be reconstructed both at 0.4 mm slice width with a sharp kernel (Hr76) for visualizing the temporal bones and at thicker slice width with a standard or smooth kernel for cerebrum imaging, obviating the necessity of having to do two separate scans. These high-resolution images can also be used to create three dimensional images, using cinematic rendering technique (cVRT), providing detailed, lifelike visualization. In trauma settings, PCD CT, with its increased spatial resolution in routine scans, may enable radiologists to reach diagnostic conclusions that were previously only possible with high resolution CT (HRCT) examinations.