Maura C Cicci 1 2, Erin K Keenihan 2, Kate Bailey 2, Lynelle Graham 2, Stefan Sommer 3 4 5, Eli B Cohen 2 6
Background
CT is commonly used for detailed assessment of cortical bone due to its superior spatial resolution, though it lacks the soft tissue contrast provided by MRI. Standard MR sequences are often inadequate for bone imaging. This study aimed to evaluate whether short/ultra-short TE MR sequences (VIBE, PETRA, UTE) provide diagnostic image quality comparable to CT and superior to standard MR sequences (T1W, T2W, PD) in assessing canine skull anatomy.
Methods
A prospective method comparison study was conducted using eight healthy hound dogs. Each dog underwent CT and MRI imaging of the head. MRI sequences included standard T1W, T2W, PD and short/ultra-short TE sequences (VIBE, PETRA, UTE). Qualitative and quantitative assessments of cortical bone and foramina were performed using CT as the gold standard. Measurements focused on bone thickness, intracranial dimensions, and foramina. Statistical analyses included linear mixed-effects models, Levene’s test, folded F tests, and ordinal logistic mixed-effects models.
Results
Short/ultra-short TE MR sequences showed superior qualitative and quantitative assessment of cortical bone compared to standard MR sequences. PETRA and VIBE demonstrated the highest precision and closest approximation to CT measurements. PETRA, UTE, and VIBE matched CT in qualitative assessment of foramina. Standard MR sequences (particularly T2 and PD) had significant bias and greater variability in bone measurement. VIBE was uniquely unbiased for bone thickness measurements compared to CT. PETRA offered the best overall performance in qualitative assessments.
Limitations
The study involved only healthy adult dogs, limiting generalizability to pathological conditions. Imaging was not performed simultaneously; CT and MRI scans were conducted approximately two months apart. The UTE sequence used is not commercially available and was a research prototype.
Conclusions
Short/ultra-short TE MR sequences—particularly PETRA and VIBE—are viable alternatives to CT for imaging cortical bone of the canine skull. These sequences enhance MR protocols by reducing the need for CT, potentially decreasing anesthesia time, radiation exposure, and costs. However, certain anatomical regions like the tympanic bulla were less accurately assessed using UTE and VIBE due to bone-gas interface issues. Further studies in pathological cases and other anatomical regions are warranted.
Comparison of CT with ultra-short TE MR Sequences and standard MR images. A, Transverse CT image. B, Transverse VIBE MR image. C, UTE MR image. D, PETRA MR image. E, T2W MR image. F, PD MR image. G, T1W MR image.
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