Objectives To assess the reliability of judging the spatial relation between the inferior alveolar nerve (IAN) and mandibular third molar (MTM) based on MRI or CT/CBCT images. Methods Altogether, CT/CBCT and MRI images of 87 MTMs were examined twice by 3 examiners with different degrees of experience. The course of the IAN in relation to the MTM, the presence/absence of a direct contact between IAN and MTM, and the presence of accessory IAN were determined. Results The IAN was in > 40% of the cases judged as inferior, while an interradicular position was diagnosed in < 5% of the cases. The overall agreement was good (κ = 0.72) and any disagreement between the imaging modalities was primarily among the adjacent regions, i.e., buccal/lingual/interradicular vs. inferior. CT/CBCT judgements presented a very good agreement for the inter- and intrarater comparison (κ > 0.80), while MRI judgements showed a slightly lower, but good agreement (κ = 0.74). A direct contact between IAN and MTM was diagnosed in about 65%, but in almost 20% a disagreement between the judgements based on MRI and CT/CBCT was present resulting in a moderate overall agreement (κ = 0.60). The agreement between the judgements based on MRI and CT/CBCT appeared independent of the examiner’s experience and accessory IAN were described in 10 cases in MRI compared to 3 cases in CT/CBCT images. Conclusions A good inter- and intrarater agreement has been observed for the assessment of the spatial relation between the IAN and MTM based on MRI images. Further, MRI images might provide advantages in the detection of accessory IAN compared to CT/CBCT. Clinical relevance MRI appears as viable alternative to CT/CBCT for preoperative assessment of the IAN in relation to the MTM.

ZUSAMMENFASSUNGZiel Ziel der Studie war den Einfluss einer intravenösen Kontrastmittelgabe auf phantomlos gemessene volumetrische Knochendichtewerte im Routine-MDCT zu evaluieren. Zusätz-lich sollte eine Formel zur Berechnung der wahrheitsgetreuen Knochendichte aus arteriell und venös gemessenen Werten aufgestellt werden. Material und Methodik 112 postmenopausale Frauen imAlter von 40 bis 77 Jahren (mittleres Alter 57,31; SD 9,61), die ein triphasisches MDCT (nativ, arteriell und venös) ABSTR AC TAim To evaluate the differences in phantom-less bone mineral density (BMD) measurements in contrast-enhanced routine MDCT scans at different contrast phases, and to develop an algorithm for calculating a reliable BMD value.Materials and Methods 112 postmenopausal women from the age of 40 to 77 years (mean age: 57.31 years; SD 9.61) who underwent a clinically indicated MDCT scan, consisting of an unenhanced, an arterial, and a venous phase, were included. A retrospective analysis of the BMD values of the Th12 to L4 vertebrae in each phase was performed using a commercially available phantom-less measurement tool.Results The mean BMD value in the unenhanced MDCT scans was 79.76 mg/cm³ (SD 31.20), in the arterial phase it was 85.09 mg/cm³ (SD 31.61), and in the venous phase it was 86.18 mg/cm³ (SD 31.30). A significant difference (p < 0.001) was found between BMD values on unenhanced and contrastenhanced MDCT scans. There was no significant difference between BMD values in the arterial and venous phases (p = 0.228). The following conversion formulas were calculated using linear regression: unenhanced BMD = -2.287 + 0.964 * . The intrarater agreement of BMD measurements was calculated with an intraclass correlation (ICC) of 0.984 and the interobserver reliability was calculated with an ICC of 0.991.Conclusion Phantom-less BMD measurements in contrastenhanced MDCT scans result in increased mean BMD values, but, with the formulas applied in our study, a reliable BMD value can be calculated. However, the mean BMD values did not differ significantly between the arterial and venous phases. Key points▪ BMD can be assessed on routine CT scans using a phantom-less tool.

As alterations in the lungs often result in similar imaging appearances and a differentiation between transudates, exsudates, blood and cells is not feasible by chest X‑ray or CT, a systematic approach is essential to make an appropriate diagnosis. Hence, consideration of the temporal course, predominant pattern, distribution of findings, additional findings and clinical presentation are indispensable.