Application of the steepest slope model reveals different perfusion territories within the mouse placenta.

OBJECTIVES: The steepest slope model is a numerically robust and fast method for perfusion quantification. The purpose of this study was to evaluate if the steepest slope model can be used for quantifying placental perfusion in mice based on dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) datasets. MATERIAL AND METHODS: T1-weighted DCE MRI was performed in 5 pregnant BALB/c mice on gestation day (gd) 14.5 and in 5 mice on gd 16.5 using a 7T small animal MRI scanner. The placentas were manually delineated in the DCE datasets and the arterial input function (AIF) was selected from the kidney hilus. Placental perfusion was determined on a voxel-by-voxel basis using the steepest slope model. Perfusion was averaged over the entire placenta as well as separately calculated for the high-flow compartment within the central labyrinth zone and for the remaining low-flow placenta tissue. The AIF selection was independently performed by two observers for assessment of inter-observer differences. RESULTS: Mean perfusion on gd 14.5 was 135 ml/min/100 ml (standard deviation SD: 29 ml/min/100 ml placenta) and 112 ml/min/100 ml on gd 16.5 for the whole placenta (SD: 32 ml/min/100 ml). Perfusion in the high flow compartment in the central labyrinth was significantly higher (p ≤ 0.002) than in the low-flow compartment including the remaining placenta tissue: 184 ml/min/100 ml (SD: 39 ml/min/100 ml) vs. 119 ml/min/100 ml (SD 28 ml/min/100 ml) on gd 14.5 and 158 ml/min/100 ml (SD: 58 ml/min/100 ml) vs. 114 ml/min/100 ml (SD: 52 ml/min/100 ml of placenta) on gd 16.5. The mean relative inter-rater observer difference was 6%. CONCLUSION: The steepest slope model is a computationally simple method, which allows perfusion quantification in the mouse placenta. Furthermore, the results of this work indicate that the different placental compartments should be analyzed separately to prevent biased results due to averaging.

Fractures of the thoracic spine in patients with minor trauma: comparison of diagnostic accuracy and dose of biplane radiography and MDCT.

OBJECTIVES: To investigate the accuracy of biplane radiography in the detection of fractures of the thoracic spine in patients with minor trauma using multidetector computed tomography (MDCT) as the reference and to compare the dose of both techniques. METHODS: 107 consecutive trauma patients with suspected fractures of the thoracic spine on physical examination were included. All had undergone biplane radiography first, followed by a MDCT scan between October 2008 and October 2012. A fourfold table was used for the classification of the screening test results. Both the Chi-square test (χ(2)) and the mean dose-length product (DLP) were used to compare the diagnostic methods. RESULTS: MDCT revealed 77 fractures in 65/107 patients (60.7%). Biplane radiography was true positive in 32/107 patients (29.9%), false positive in 19/107 patients (17.8%), true negative in 23/107 (21.5%) and false negative in 33/107 patients (30.8%), showing a sensitivity of 49.2%, a specificity of 54.7%, a positive predictive value (PPV) of 62.7%, a negative predictive value (NPV) of 41.1%, and an accuracy of 51.4%. The presence of a fracture on biplane radiography was highly statistical significant, if this was simultaneously proven by MDCT (χ(2)=7.6; p=0.01). None of the fractures missed on biplane radiography was unstable. The mean DLP on biplane radiography was 14.5mGycm (range 1.9-97.8) and on MDCT 374.6mGycm (range 80.2-871). CONCLUSIONS: The sensitivity and the specificity of biplane radiography in the diagnosis of fractures of the thoracic spine in patients with minor trauma are low. Considering the wide availability of MDCT that is usually necessary for taking significant therapeutic steps, the indication for biplane radiography should be very restrictive.

Magnetic resonance cholangiopancreatography in the diagnosis of primary sclerosing cholangitis.

BACKGROUND AND STUDY AIMS: Magnetic resonance cholangiopancreatography (MRCP) is a less-invasive alternative to endoscopic retrograde cholangiopancreatography (ERCP) for the diagnosis of primary sclerosing cholangitis (PSC). This study evaluated the diagnostic accuracy of MRCP in PSC compared with ERCP, and assessed the diagnostic accuracy of different T2w sequences. PATIENTS AND METHODS: 95 patients (69 PSC, 26 controls) were evaluated using both ERCP and MRCP. Exclusion criteria included secondary sclerosing cholangitis and contraindications to MRCP. The diagnosis of PSC was confirmed in 69 patients based on ERCP as the reference gold standard. MRCP was performed using a 1.5 Tesla MR unit, using breath hold, coronal and transverse half-Fourier acquisition single-shot turbo spin-echo (HASTE), coronal-oblique, fat-suppressed half-Fourier rapid acquisition with relaxation enhancement (RARE), and coronal-oblique, fat-suppressed, multisection, thin-section HASTE (TS-HASTE) sequences. The MRCP morphological criteria of PSC were evaluated and compared with ERCP. RESULTS: The sensitivity, specificity, and diagnostic accuracy were 86%, 77%, and 83%, respectively, using the MRCP-RARE sequence, and increased further to 93%, 77%, and 88%, respectively, by the inclusion of follow-up MRCP in 52 patients, performed at 6-12-month intervals. HASTE and TS-HASTE sequences showed significantly lower diagnostic accuracy but provided additional morphologic information. CONCLUSIONS: MRCP can diagnose PSC but has difficulties in early PSC and in cirrhosis, and in the differentiation of cholangiocarcinoma, Caroli's disease, and secondary sclerosing cholangitis. A positive MRCP would negate some diagnostic ERCP studies but a negative MRCP would not obviate the need for ERCP.