Diagnostic Imaging of Patellofemoral Instability. / Bildgebende Diagnostik der patellofemoralen Instabilität.

BACKGROUND: Throughout the literature, patellofemoral instability (PI) is defined as an increased risk of re-/luxation of the patella within the patellofemoral joint (PFJ). In most patients it is caused by traumatic patella luxation or the existence of a range of predisposing anatomic risk factors leading to an unphysiological movement sequence within the PFJ also known as patellofemoral maltracking. In order to provide an individualized therapy approach, clinical and radiological evaluation of those risk factors of variable magnitude becomes essential. Diagnostic imaging such as magnetic resonance imaging (MRI), plain radiography, and computed tomography (CT) are straightforward diagnostic tools in terms of evaluation and treatment of PI. METHOD: In this review we performed a precise analysis of today's literature concerning the radiological evaluation of anatomic risk factors leading to PI. The purpose of the review is to present a logical compilation of the different anatomical risk factors causing PI and provide a straight overview of valuable radiological imaging techniques. RESULTS AND CONCLUSION: PI is frequently based on a multifactorial disposition. The most relevant predisposing risk factors are trochlea dysplasia, rupture of the medial patellofemoral ligament (MPFL), patella alta, abnormal tibial tubercle to trochlea groove distance (TT-TG), femoral torsion deformities, and genu valgum. Although plain X-rays may provide basic diagnostic value, cross-sectional imaging (MRI, CT) is the standard radiological tool in terms of evaluation and detection of severity of predisposing anatomic variants leading to PI. KEY POINTS: · Based on today's literature, PI is characterized as an increased risk of patella re-/luxation within the PFJ.. · Underlying anatomic risk factors of variable magnitude mark the pathological cause of PI.. · Modern diagnostic imaging (MRI and CT) permits straightforward diagnosis of the typical features in terms of PI.. · To provide an individualized therapy approach, precise radiological evaluation and determination of the severity of predisposing anatomic anomalies are essential.. CITATION FORMAT: · Maas KJ, Warncke ML, Leiderer M et al. Diagnostic Imaging of Patellofemoral Instability. Fortschr Röntgenstr 2021; 193: 1019 - 1033.

Diagnostic Yield of Multidetector Computed Tomography in Patients with Acute Spondylodiscitis.

Purpose To determine the value of multidetector computed tomography (MDCT) in patients with acute spondylodiscitis. Methods and Materials For data acquisition, we searched our radiological database for all patients who had undergone magnetic resonance imaging (MRI) for suspected spondylodiscitis between 2007 and 2015 (n = 325). For further analyses, we included all patients (n = 67) who initially underwent MDCT prior to MRI. Overall accuracy, sensitivity, specificity and positive and negative predictive values were calculated for MDCT and, separately, for contrast-enhanced CT (CECT, n = 36) and for non-enhanced CT (NECT, n = 31). MRI together with clinical evaluation served as the standard of reference. RESULTS: In 34 of 43 patients with acute spondylodiscitis on MRI, correct diagnosis was already made by the initial MDCT scan. The specificity and positive predictive value were 100 % for MDCT. The sensitivity was 79 % and the negative predictive value was 72 %. The overall accuracy was 87 %. Accuracy was higher for CECT (89 %) than for NECT (84 %), however without statistical significance (p = 0.55). MDCT detected 90 % of paravertebral abscesses (34/38), but only 6 % of epidural abscesses (2/36). Conclusion MDCT has moderate sensitivity, but high specificity for acute spondylodiscitis. Thus, if MDCT is positive for spondylodiscitis, treatment can be started without further delay. However, MRI should be added to both MDCT negative and positive cases to rule out complications such as epidural abscesses that cannot reliably be detected by MDCT. Key Points: · Patients with acute spondylodiscitis are often initially suspected of having other differential diagnosis because of nonspecific symptoms.. · Therefore, MDCT is frequently performed prior to MRI in patients with acute spondylodiscitis.. · MDCT proved moderate sensitivity but high specificity for the diagnosis of acute spondylodiscitis.. · Paravertebral abscess is a strong indicator for the presence of spondylodiscitis on MDCT.. · However, MRI is crucial to rule out epidural abscesses, an important complication.. Citation Format · Rausch VH, Bannas P, Schoen G et al. Diagnostic Yield of Multidetector Computed Tomography in Patients with Acute Spondylodiscitis. Fortschr Röntgenstr 2017; 189: 339 - 346.

Impact of tube current-time and tube voltage reduction in 64-detector-row computed tomography pulmonary angiography for pulmonary embolism in a porcine model.

PURPOSE: To evaluate the impact of dose reduction in multidetector computed tomography pulmonary angiography (CTPA) for detection of pulmonary embolism (PE). MATERIALS AND METHODS: After induction of PE in 6 anesthetized pigs, a 64-detector-row CTPA was performed at 3 different dose protocols: A (120 kV/120 mAseff.), B (120 kV/80 mAseff.), and C (80 kV/80 mAseff.). Images were evaluated by 2 radiologists independently. A high-dose CTPA (120 kV/250 mAseff.) served as a reference standard. Sensitivity, specificity, and positive and negative predictive values were calculated and compared using the Wilcoxon test. Interobserver agreement was determined by calculation of κ values. Radiation exposure and objective image parameters were assessed and compared with a 2-sided t test. RESULTS: In the reference scan, a total of 94 emboli were detected: 17 in the main and lobar pulmonary level (category A), 47 in the segmental level (category B), and 30 in the subsegmental level (category C). All protocols reached high diagnostic accuracy in the detection of PE in category A. No significant difference was observed between protocols A and B in the detection rate of segmental and subsegmental PE (sensitivity: 93.6% and 91.5% vs 85.1% and 87.2%; positive predictive value: 100% and 97.7% vs 97.5% and 95.3%). Interobserver agreement was excellent at the segmental (κ=0.97 and 0.94) and subsegmental levels (κ=0.94 and 0.92). Using protocol C, the detection rate of segmental and subsegmental emboli was significantly impaired and interobserver agreement was significantly inferior (sensitivity: 46.8% and 44.6% at segmental and 56.7% and 50.0% at subsegmental level; κ=0.70 and 0.60, respectively; P<0.05). Vessel attenuation was significantly higher in protocol C, [710.3 Hounsfield units (HU) ±200.6 SD] than in protocols A (414.4 HU±82.5 SD) and B (428.8 HU±78.9 SD) (P<0.001). Signal-to-noise and contrast-to-noise ratios were significantly decreased in protocols B (55.6; 45.8) and C (44.3; 39.4) compared with protocol A (62.1; 52.3) (P<0.05). Radiation dose was significantly reduced between protocols A and B and protocols B and C [volume CT dose index (CTDIvol): 7.1 vs 4.7 vs 1.4 mGy; dose-length product: 199.5 vs 132.1 vs 39.4 mGy·cm and E: 3.39 vs 2.25 vs 0.6 mSv; P<0.05]. CONCLUSION: This animal study proves the diagnostic use of a low-dose CTPA protocol with 80 mAseff. at 120 kV for PE evaluation without significant loss of diagnostic accuracy compared with a standard protocol with 120 mAseff. Using an "ultra-low"-dose CTPA protocol (80 kV; 80 mAseff.), emboli detection at the segmental and subsegmental level is significantly impaired, whereas evaluation of central emboli is still feasible with high diagnostic accuracy.

Intraindividual comparison of gadolinium- and iodine-enhanced 64-slice multidetector CT pulmonary angiography for the detection of pulmonary embolism in a porcine model.

This study is an evaluation of the diagnostic accuracy of gadolinium-enhanced computed tomography pulmonary angiography (CTPA) for the detection of pulmonary embolism (PE) in comparison with iodine-enhanced CTPA. PE was induced in five anesthetized pigs by administration of blood clots through an 11-F catheter inside the jugular vein. Animals underwent CTPA in breathhold with i.v. bolus injection of 50 ml gadopentetate dimeglumine (0.4 mmol/kg, 4 ml/s). Subsequently, CTPA was performed using the same imaging parameters but under administration of 70 ml nonionic iodinated contrast material (400 mg/ml, 4 ml/s). All images were reconstructed with 1 mm slice thickness. A consensus readout of the iodium-enhanced CTPAs by both radiologists served as reference standard. Gadolinium-enhanced CTPAs were evaluated independently by two experienced radiologists, and differences in detection rate between both contrast agents were assessed on a per embolus basis using the Wilcoxon signed-rank test. Interobserver agreement was determined by calculation of қ values. PE was diagnosed independently by both readers in all five pigs by the use of gadolinium-enhanced CTPA. Out of 60 pulmonary emboli detected in the iodine-enhanced scans, 47 (78.3%; reader 1) and 44 (62.8%; reader 2) emboli were detected by the use of gadolinium. All 13 (100%) emboli in lobar arteries (by both readers) and 26 (reader 1) and 25 (reader 2) out of 27 emboli (96.3% and 92.6%) in segmental arteries were detected by the use of the gadolinium-enhanced CTPA. In subsegmental arteries, only 8 (40%; reader 1) and 6 (30%; reader 2) out of 20 emboli were detected by the gadolinium-enhanced CTPA. By comparing both scans on a per vessel basis (Wilcoxon test), Gd-enhanced CTPA was significantly inferior in emboli detection on subsegmental level (P < 0.0001). The interobserver agreement was excellent on lobar and segmental level (қ = 1.0 and 0.93, respectively), whereas readers only reached moderate agreement for PE evaluation on subsegmental level (қ = 0.56). Compared to conventional CTPA with iodinated contrast media, gadolinium-based contrast agents achieve an equivalent diagnostic accuracy in detection of PE down to segmental level. Gadolinium-enhanced CTPA may be considered as an alternative for the diagnostic workup of acute pulmonary embolism in patients with contraindications to iodinated contrast agents.