Frank Oliver Henes

Diffusion‐weighted MR‐imaging for the detection of pulmonary nodules at 1.5 Tesla: Intraindividual comparison with multidetector computed tomography

Introduction: To investigate the feasibility of diffusion‐weighted imaging (DWI) MRI for detecting pulmonary nodules at 1.5 Tesla in comparison with standard multidetector computed tomography (MDCT).

Diffusion weighted MRI and 18F-FDG PET/CT in non-small cell lung cancer (NSCLC): Does the apparent diffusion coefficient (ADC) correlate with tracer uptake (SUV)?

INTRODUCTION To investigate the potential correlation of the apparent diffusion coefficient assessed by diffusion-weighted MRI (DWI) and glucose metabolism determined by the standardized uptake value (SUV) at 18F-FDG PET/CT in non-small cell lung cancer (NSCLC). MATERIALS AND METHODS 18F-FDG PET/CT and DWI (TR/TE, 2000/66 ms; b-values, 0 and 500 s/mm(2)) were performed in 41 consecutive patients with histologically verified NSCLC. Analysing the PET-CT data calculation of the mean (SUV(mean)) and maximum (SUV(max)) SUV was performed. By placing a region-of-interest (ROI) encovering the entire tumor mean (ADC(mean)) and minimum ADC (ADC(min)) were determined by two independent radiologists. Results of 18F-FDG PET-CT and DWI were compared on a per-patient basis. For statistical analysis Pearsons correlation coefficient, Bland-Altman and regression analysis were assessed. RESULTS Data analysis revealed a significant inverse correlation of the ADC(min) and SUV(max) (r=-0.46; p=0.032). Testing the correlation of the ADC(min) and SUV(max) for each histological subtype separately revealed that the inverse correlation was good for both adenocarcinomas (r=-0.47; p=0.03) and squamouscell carcinomas (r=-0.71; p=0.002), respectively. No significant correlation was found for the comparison of ADC(min) and SUV(mean) (r=-0.29; p=0.27), ADC(mean) vs. SUV(mean) (r=-0.28; p=0.31) or ADC(mean) vs. SUV(max) (r=-0.33; p=0.23). The κ-value of 0.88 indicated a good agreement between both observers. CONCLUSION This preliminary study is the first to verify the relation between the SUV and the ADC in NSCLC. The significant inverse correlation of these two quantitative imaging approaches points out the association of metabolic activity and tumor cellularity. Therefore, DWI with ADC measurement might represent a new prognostic marker in NSCLC.

Comparison of diagnostic accuracy of Magnetic Resonance Imaging and Multidetector Computed Tomography in the detection of pelvic fractures.

OBJECTIVE To compare diagnostic accuracy and interobserver reliability of Magnetic Resonance Imaging (MRI) and Multidetector Computed Tomography (MDCT) in the detection of acute pelvic fractures. MATERIALS AND METHODS In 38 consecutive patients (mean age 74.7 years) with a positive finding of anterior pelvis fracture in the conventional X-rays, pelvic MRI and MDCT were performed for further evaluation of pelvic ring fractures. Two radiologists independently read all data sets. Sensitivity and specificity were calculated based on mean scores for each method. Sensitivities of CT and MRI were compared using a paired proportion test (McNemar). Diagnostic validity of both methods was assessed by the interobserver variability using kappa statistics. Combined clinical data and findings from all imaging studies served as the reference standard. RESULTS 122 fractures were identified in the reference standard (37 sacral, 58 pubic, 22 acetabular, 1 ischial, 4 ilial). On average, MRI detected 96.3% whereas CT detected 77% of all fractures. With regard to sensitivity, MRI proved to be significantly better compared to MDCT (observer 1, p=0.0009; observer 2, p=0.0003 by observer 2). In particular, MRI performed better in the depiction of sacral fractures, reaching a sensitivity of 98.6% compared to 66.1% at CT. The interobserver variability was determined to be very good (k=0.955 for MRI and 0.902 for MDCT). CONCLUSION MRI reaches a significantly higher sensitivity than CT in the detection of acute pelvic fractures, particularly of the sacrum. Especially in elderly patients with suspicion of a sacral fracture and negative results at MDCT, MRI may be considered as the next step in diagnostic workup.

Impact of a 4th generation iterative reconstruction technique on image quality in low-dose computed tomography of the chest in immunocompromised patients

PURPOSE To determine the image quality of an iterative reconstruction (IR) technique in low-dose MDCT (LDCT) of the chest of immunocompromised patients in an intraindividual comparison to filtered back projection (FBP) and to evaluate the dose reduction capability. MATERIALS AND METHODS 30 chest LDCT scans were performed in immunocompromised patients (Brilliance iCT; 20-40 mAs; mean CTDIvol: 1.7 mGy). The raw data were reconstructed using FBP and the IR technique (iDose4™, Philips, Best, The Netherlands) set to seven iteration levels. 30 routine-dose MDCT (RDCT) reconstructed with FBP served as controls (mean exposure: 116 mAs; mean CDTIvol: 7.6 mGy). Three blinded radiologists scored subjective image quality and lesion conspicuity. Quantitative parameters including CT attenuation and objective image noise (OIN) were determined. RESULTS In LDCT high iDose4™ levels lead to a significant decrease in OIN (FBP vs. iDose7: subscapular muscle 139.4 vs. 40.6 HU). The high iDose4™ levels provided significant improvements in image quality and artifact and noise reduction compared to LDCT FBP images. The conspicuity of subtle lesions was limited in LDCT FBP images. It significantly improved with high iDose4™ levels (> iDose4). LDCT with iDose4™ level 6 was determined to be of equivalent image quality as RDCT with FBP. CONCLUSION iDose4™ substantially improves image quality and lesion conspicuity and reduces noise in low-dose chest CT. Compared to RDCT, high iDose4™ levels provide equivalent image quality in LDCT, hence suggesting a potential dose reduction of almost 80%.

Accuracy of thoracic aortic measurements assessed by contrast enhanced and unenhanced magnetic resonance imaging

AIM To assess, whether unenhanced balanced steady-state-free precession sequences provide axial thoracic aortic measurements comparable to contrast enhanced magnetic resonance angiography with good intra- and interobserver agreement. MATERIALS AND METHODS Enhanced and unenhanced sequences of the thoracic aorta in 23 consecutive patients were evaluated. Axial thoracic aortic diameters were measured at predefined levels by two independent readers. Pearsons correlation coefficient and Bland-Altman analysis were used to compare enhanced and unenhanced sequences. t-Test was used to determine possible significant differences between the measurements obtained by enhanced and unenhanced sequences. A p-value of less than .05 indicated statistical significance. Intraclass correlation coefficient and Bland-Altman were used for inter- and intraobserver correlation and agreement. RESULTS There was no significant difference in diameter measurements between enhanced and unenhanced sequences (ascending aorta, p=0.98; descending aorta, p=0.52). Bland-Altman revealed good agreement between enhanced and unenhanced sequences for ascending (mean bias, -0.01cm; with 95% limits of agreement, ±0.30cm) and descending aortic diameters (mean bias, 0.05cm; with 95% limits of agreement, ±0.30cm). Inter- and intraobserver agreement (mean bias, less than ±0.15; with 95% limits of agreement, less than ±0.42cm for all measurements) as well as correlation (r>0.8 for all measurements) were excellent. CONCLUSION Unenhanced balanced steady-state-free precession sequences enable rapid and accurate determination of axial thoracic aortic diameters with excellent inter- and intraobserver agreement, but without the risk of contrast media associated side-effects.

Clinical presentation and long-term outcome of 144 patients with microscopic polyangiitis in a monocentric German cohort

OBJECTIVE To evaluate the clinical presentation and long-term outcome of a vasculitis centre cohort of patients with microscopic polyangiitis (MPA) with respect to organ manifestations, treatment, chronic damage and mortality. METHODS We performed a retrospective chart review at our vasculitis referral centre. MPA patients admitted between 1991 and 2013 classified by a modified European Medicines Agency algorithm were diagnosed and treated according to a standardized interdisciplinary approach. RESULTS Comprehensive data from standardized interdisciplinary workups was available for 144 patients (median follow-up 72 months). The overall standardized mortality ratio was 1.40 (95% CI 0.91, 2.07; P = 0.13). We observed a higher mortality [hazard ratio (HR) 4.04 (95% CI 1.21, 13.45), P = 0.02] in 17 patients with MPA-associated fibrosing interstitial lung disease (ILD) and 56 patients with peripheral nervous system involvement [HR 5.26 (95% CI 1.10, 25.14), P = 0.04] at disease onset. One hundred and fifteen patients (79.9%) responded to the initial treatment. Sixty-one (42.3%) achieved complete remission and 54 (37.5%) achieved partial remission. Twenty (13.9%) showed a refractory disease course. CONCLUSION MPA patients at our tertiary rheumatology referral centre seemed to have a less severe phenotype resulting in a less severe disease course and better outcome than reported in other cohorts. Fibrosing ILD was significantly associated with mortality in this cohort.

Significance of clinical examination, CT and MRI scan in the diagnosis of posterior pelvic ring fractures

INTRODUCTION Patients with a fracture in the anterior pelvic ring often simultaneously demonstrate pain in the posterior pelvic ring. The aim of the present prospective study was to assess the sensitivity of CT, MRI and clinical examination in the detection of fractures in the posterior pelvic ring in patients with fractures of the anterior pelvic ring diagnosed in conventional radiographs. METHODS Sixty patients with radiographic signs of an anterior pelvic ring injury were included in this prospective analysis. Following a focused clinical examination of the posterior pelvis, all patients underwent both a CT and then a MRI scan of their pelvis. Two board certified radiologists evaluated the CT and MRI scans independently. To estimate the presence of osteoporosis the Hounsfield units of the vertebral body of L5 were measured in each case. RESULTS Fifty-three women and seven men, with a mean age of 74.7+/-15.6 years were included into the study. A fracture of the posterior pelvic ring was found in fourty-eight patients (80%) patients using MRI. Fractures of the posterior pelvic ring would have been missed in eight cases (17%), if only CT had been used. Eighty-five percent of the patients with a posterior fracture had an osteoporosis. The majority of the cases suffered from a low energy trauma. Thirty-eight patients (83%) with positive clinical signs at the posterior pelvic ring actually had a fracture of the posterior pelvic ring in the MRI. The clinical examination proved to be equally effective to CT in detecting posterior pelvic ring fractures. CONCLUSION The significance of both, clinical examination and CT was confirmed in the detection of fractures in the posterior pelvic ring. MRI examination of the pelvis however, was found to be superior in detecting undislocated fractures in a cohort of patients with a high incidence of osteoporosis. Using MRI may be beneficial in select cases, especially when reduced bone density is suspected.

Intraindividual comparison of contrast-enhanced MRI and unenhanced SSFP sequences of stenotic and non-stenotic pulmonary artery diameters.

PURPOSE To evaluate the agreement of pulmonary artery diameters assessed with 3D contrast-enhanced MR angiography (CE-MRA) and a 2D balanced steady-state-free precession sequence (bSSFP) in non-stenotic and stenotic pulmonary arteries (PA). METHODS AND MATERIALS 44 right and left PAs (30 non-stenotic and 14 stenotic) were examined in 23 consecutive patients by performing CE-MRA as well as bSSFP. Two independent readers determined the transverse diameters of the PA. RESULTS No significant difference in diameter measurements was found between CE-MRA and bSSFP (p = 0.8608 for the stenotic and p = 0.6208 for the non-stenotic PA). Bland-Altman analysis revealed good agreement between CE-MRA and bSSFP for both the non-stenotic (mean bias, 0.07 cm; with 95 % limits of agreement, ± 0.34 cm) and the stenotic (mean bias, 0.05 cm; with 95 % limits of agreement, ± 0.30 cm) PA. CONCLUSION bSSFP allows rapid and accurate determination of PA diameters without the use of ionizing radiation and the risk of contrast media-associated side-effects.

Correlation of right ventricular dysfunction parameters and pulmonary vascular obstruction score in acute pulmonary embolism in a porcine model

This paper aims to non-invasively determine right ventricular dysfunction parameters (RVDP) in acute pulmonary embolism (APE) and to correlate these parameters with a computed tomography (CT)-based pulmonary artery obstruction score (OS). In seven domestic pigs, magnetic resonance imaging (MRI) was performed before (n = 7) and after (n = 5) APE was induced. Analysis of relative changes in right ventricular stroke volume (RVSV%), output (RVO%), end-systolic (RVESV%), end-diastolic volume (RVEDV%), and heart rate (HR%) was performed. Additionally, for the determination of the OS, all animals underwent contrast-enhanced CT–pulmonary angiography. The CT-based OS correlated strongly with RVSV% (r = 0.9576; p = 0.0104) and RVO% (r = 0.9703; p = 0.0061). Contrarily, almost no correlation could be demonstrated for the OS and the increase of RVESV % (r = 0.3850; p = 0.5222), RVEDV% (r = 0.1830; p = 0.7683), and HR% (r = 0.5494; p = 0.3375). The results of this experimental study underline that the CT-based OS correlates with RVDP as determined by cardiac MRI and might be a helpful tool for the severity assessment in APE.

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 &kgr; 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 (&kgr;=0.97 and 0.94) and subsegmental levels (&kgr;=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; &kgr;=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.