History
A 14-year-old girl presented herself to the emergency department due to a fall onto her outstretched right hand. A radiograph was performed with unremarkable findings. As, two weeks later, the pain and the movement limitations in the right wrist persisted, another radiograph was performed but this only revealed an equivocal result. A CT scan was requested for further evaluation, using an ultra-high resolution (UHR) mode on a photon-counting CT (PCCT) scanner (NAEOTOM Alpha).
Diagnosis
UHR CT images showed an oblique fracture line in the scaphoid. Neither dislocation nor distraction were seen. There were evident signs of increased density, or even sclerosis, in the fissure, suggesting partial healing. Based upon the CT findings, the patient was treated with an external splint fixation. Three weeks later, a follow-up radiograph was performed with evidence of advanced healing without complication.
Courtesy of Department of imaging methods, University Hospital Pilsen and Medical Faculty of Charles University, Pilsen, Czech Republic
Fig. 1: UHR CT images (Figs. 1a & 1b) and cVRT images (Figs. 1c & 1d) show an oblique fracture line (arrows) in the scaphoid without dislocation or distraction. Note that the input images for cVRT creation are reconstructed at 0.2 mm, with a very sharp kernel of Br84 and an image matrix of 1024 x 1024.
Courtesy of Department of imaging methods, University Hospital Pilsen and Medical Faculty of Charles University, Pilsen, Czech Republic
Fig. 2: cVRT images (Figs. 2a & 2c) and UHR CT images (Figs. 2b & 2c) show the fracture line in the scaphoid. Increased density is seen in the fissure (arrow) suggesting partial healing. Note that the input images for cVRT creation are reconstructed at 0.2 mm, with a very sharp kernel of Br84 and an image matrix of 1024 x 1024.
Comments
Scaphoid fractures are the most common amongst the carpal bones. Missed or inconclusive diagnoses on wrist radiographs may cause a delay of initial treatment. This can lead to nonunion, and ultimately, loss of wrist motion and eventual arthritis. CT imaging plays an important role for improved accuracy in the diagnosis, as well as in the follow-ups of a scaphoid fracture. It provides detailed information using multiplanar reformation (MPR) as well as 3D reconstructions such as cinematic volume rendering technique (cVRT). The traditional challenge with conventional CT scanners is to improve the spatial resolution without increasing radiation dose or accepting excessive image noise. This has become possible with the introduction of PCCT, especially when using the UHR mode. Images are acquired on a dual source PCCT (NAEOTOM Alpha) at 0.2 mm slice width and reconstructed with a very sharp kernel of Br84, using a large image matrix of 1024 x 1024. UHR scan data acquisition is feasible at full dose efficiency without additional combs or grids to reduce the detector aperture at the cost of reduced dose efficiency and increased radiation dose as in previous equipment. A model-based iterative reconstruction approach – Quantum Iterative Reconstruction (QIR) – is applied in the image reconstruction process for further image noise reduction, resulting in a sharp visualization of trabecular bone structures with low image noise. PCCT with UHR scan data acquisition can be very beneficial in minor injuries of peripheral bones, particularly when the radiograph is inconclusive, and the clinical symptoms are atypical. As shown in this case, the fracture line that is missed on the radiograph is clearly depicted on the UHR CT images. Because of their low image noise, these images are also used as input to create cVRT images for a lifelike 3D visualization of the scaphoid, helping the physicians to make an optimal treatment decision.
Examination Protocol