Comparison of the Detection Rate of Simulated Microcalcifications in Full-Field Digital Mammography, Digital Breast Tomosynthesis, and Synthetically Reconstructed 2-Dimensional Images Performed With 2 Different Digital X-ray Mammography Systems.

OBJECTIVE: The aim of this study was to compare the microcalcification detectability in an anthropomorphic phantom model regarding number, size, and shape in full-field digital mammography (FFDM), synthetically reconstructed 2-dimensional (Synthetic-2D) images, and digital breast tomosynthesis (DBT) performed with 2 different x-ray mammography systems. MATERIALS AND METHODS: Simulated microcalcifications of different numbers (0 to >39), sizes (diameter, 100-800 µm), and shapes (round vs heterogeneous) were scattered by random distribution on 50 film phantoms each divided in 4 quadrants. The FFDM and DBT x-rays were taken from each of these 50 films with both x-ray mammography systems (SenoClaire; GE Healthcare, Selenia Dimensions, Hologic) using an anthropomorphic scattering body and automatic exposure control. The resulting exposure factors were similar to a clinical setting. The synthetically reconstructed 2D images were generated automatically on both systems. All FFDM, Synthetic-2D, and DBT images were interpreted in randomized order and independently of each other by 6 radiologists using a structured questionnaire. RESULTS: The number categories of simulated microcalcifications were correctly evaluated in 55.3% of instances (quadrant by reader) in FFDM, 50.9% in the Synthetic-2D views, and 59.5% in DBT, summarized for 200 quadrants per reader for each Device A and B, respectively. Full-field digital mammography was superior to Synthetic-2D (mean difference, 4%; 95% confidence interval [CI], 2%-7%; P < 0.001), and DBT was superior to both FFDM (mean difference, 4%; 95% CI, 2%-7%; P = 0.002) and Synthetic-2D (mean difference, 9%; 95% CI, 6%-11%; P < 0.001). This trend was consistent in all subgroup analyses. The number of the smallest microcalcifications (100-399 µm) was correctly evaluated in 25.2% of the FFDM, in 14.2% for Synthetic-2D, and in 28.3% of the DBT images. Underestimations of the number of simulated microcalcifications were more common than overestimations. Regarding the size categories of simulated microcalcifications, the rates of correct assessments were in 45.4% of instances in FFDM, 39.9% in the Synthetic-2D views, and 43.6% in DBT, summarized for 200 quadrants per reader and both imaging devices. CONCLUSIONS: In the presented in vitro environment using an anthropomorphic phantom model, standard full-field digital x-ray mammography was superior to synthetically reconstructed 2-dimensional images in the detection of simulated microcalcifications. In view of these results, it is questionable whether Synthetic-2D images can replace FFDM in clinical examinations at the present time. Further investigations are needed to assess the clinical impact of the in vitro results.

Reducing CT radiation dose with iterative reconstruction algorithms: the influence of scan and reconstruction parameters on image quality and CTDIvol.

OBJECTIVES: In this phantom CT study, we investigated whether images reconstructed using filtered back projection (FBP) and iterative reconstruction (IR) with reduced tube voltage and current have equivalent quality. We evaluated the effects of different acquisition and reconstruction parameter settings on image quality and radiation doses. Additionally, patient CT studies were evaluated to confirm our phantom results. METHODS: Helical and axial 256 multi-slice computed tomography scans of the phantom (Catphan(®)) were performed with varying tube voltages (80-140kV) and currents (30-200mAs). 198 phantom data sets were reconstructed applying FBP and IR with increasing iterations, and soft and sharp kernels. Further, 25 chest and abdomen CT scans, performed with high and low exposure per patient, were reconstructed with IR and FBP. Two independent observers evaluated image quality and radiation doses of both phantom and patient scans. RESULTS: In phantom scans, noise reduction was significantly improved using IR with increasing iterations, independent from tissue, scan-mode, tube-voltage, current, and kernel. IR did not affect high-contrast resolution. Low-contrast resolution was also not negatively affected, but improved in scans with doses <5mGy, although object detectability generally decreased with the lowering of exposure. At comparable image quality levels, CTDIvol was reduced by 26-50% using IR. In patients, applying IR vs. FBP resulted in good to excellent image quality, while tube voltage and current settings could be significantly decreased. CONCLUSIONS: Our phantom experiments demonstrate that image quality levels of FBP reconstructions can also be achieved at lower tube voltages and tube currents when applying IR. Our findings could be confirmed in patients revealing the potential of IR to significantly reduce CT radiation doses.

Supporting people with diabetes mellitus in applying for and participating effectively in paid work: validation of successful diabetes-related behaviors by experiential experts and professional care providers.

OBJECTIVE: To validate successful diabetes-related behaviors, proposed by a group of experiential experts, and to support people with diabetes in applying for and participating effectively in work. METHODS: In a survey among 77 experiential experts and 21 professional care providers, the behaviors were critically appraised regarding several key characteristics. RESULTS: Experiential experts (median scores: 91%, 86%, and 86%) and professionals (median scores: 76%, 76%, and 81%) mostly agreed with these behaviors in terms of clarity, content, and relevance, respectively. Feasibility was seen as somewhat problematic, with median scores by experiential experts and professionals of 65% and 52%, respectively. CONCLUSION: Both groups confirmed the validity of the proposed work-related behaviors that were expected to support people with diabetes. The challenge is to implement these behaviors in practice, by effective dissemination and incorporation in work-related self-management programs.

Harvesting experiential expertise to support safe driving for people with diabetes mellitus: a qualitative study evaluated by peers in a survey.

BACKGROUND: Hypoglycemia is a frequent phenomenon in people being treated for diabetes mellitus, which can acutely disrupt driving performance. For the benefit of personal and public traffic safety, we decided to identify successful diabetes-related (SDR) behaviors to support safe driving for people with diabetes, from the perspective of experiential experts with diabetes mellitus. Experiential experts are people who can manage their own illness and conditions by developing expertise relevant to maintaining health and countering illness, and who are able to use this expertise to the benefit of peers. OBJECTIVE: The aim of our study was to objectify and systematize experiential expertise in terms of SDR behaviors, based on reports by experiential experts, to support safe driving for people with type 1 and type 2 diabetes mellitus. The emphasis was on preventing hypoglycemia as a short-term complication during driving. METHODS: We performed a mixed-methods study involving (i) semi-structured in-depth interviews with 33 experiential experts with diabetes mellitus from the Dutch Diabetes Association (DVN; Diabetesvereniging Nederland), in order to identify SDR behaviors regarding safe driving, and (ii) a validation study by means of a survey among a panel of 98 experiential experts (peers) from the DVN, to determine the extent to which they agreed with the communicability, importance, and feasibility of these behaviors for drivers with diabetes mellitus. RESULTS: We identified a comprehensive set of 11 SDR behaviors, differentiated into seven general and four specific behaviors, to support safe driving. The general behaviors concern the following topics: (i) acquiring knowledge and information; (ii) acquiring and using self-measuring of blood glucose (SMBG) equipment; (iii) knowing one's physical response pattern; (iv) obtaining knowledge about the medication used; (v) preventing long-term eye complications; (vi) influencing factors that can affect blood glucose; and (vii) renewal procedure for driving license. The four specific behaviors refer to the following topics: (i) measures to be taken before driving; (ii) responding effectively to hypoglycemia while driving; (iii) informing and instructing passengers; and (iv) preventing hypoglycemia in drivers with type 2 diabetes mellitus not using SMBG equipment. Key factors for safe driving proved to be the ability of drivers to anticipate and respond effectively to hypoglycemia while driving and to inform and instruct fellow passengers. Participants of the validation survey agreed to a considerable degree with the communicability, importance, and feasibility of these behaviors to support safe driving for people with diabetes mellitus. CONCLUSIONS: This study resulted in the identification and description of SDR behaviors to support safe driving. It proved possible to operationalize experiential expertise in terms of such behaviors. The next step is to have these behaviors validated by professional care providers in the field of diabetes, followed by translation into recommendations in self-management programs.

Identifying experiential expertise to support people with diabetes mellitus in applying for and participating effectively in paid work: a qualitative study.

OBJECTIVE: Identifying and describing successful diabetes-related (SDR) behaviors from reports by experiential experts to support people with diabetes in applying for and participating effectively in paid work. METHODS: Data were collected by conducting in-depth interviews with experiential experts with diabetes (N = 47). RESULTS: A comprehensive set of SDR behaviors that can help people with diabetes apply for and participate in paid work. The most important factors were reported to be the ability to anticipate problems in job applications, effective self-management activities to prevent and/or respond to hypoglycemia and hyperglycemia at work, informing relevant others in the workplace, and successfully negotiating with employers about adjustments to work conditions. CONCLUSIONS: A set of work-related SDR behaviors was identified. After validation by experiential experts and professionals, these could be translated into recommendations and tested in experiments in self-management programs.

[Hypoglycaemia unawareness: judge driving ability prudently]. / Hypoglycemia unawareness: oordeel bewust over rijvaardigheid.

Several factors can influence the ability to drive by patients with diabetes mellitus. The most important factor would be hypoglycaemia. It seems logical that hypoglycaemia unawareness would be an important risk factor for accidents. However, in everyday practice, hypoglycaemia-related accidents are rare. Moreover, it seems that only a small subset of people with diabetes is responsible for the overall slightly elevated risk of car accidents. It appears that not hypoglycaemia unawareness itself is a risk factor, but primarily a history of previous hypoglycaemia-related accidents. Although ascertaining hypoglycaemia awareness currently seems the most suitable method for the assessment of driving ability, this may not be fair. In the future, we hope to have better methods of assessing the risk of accidents. Until that time, we should apply current law prudently, and mainly preclude from driving those diabetic patients who have experienced loss of consciousness or have needed outside help due to hypoglycaemia.

64-Slice spiral computed tomography of the coronary arteries: dose reduction using an optimized imaging protocol including individual weight-adaptation of voltage and current-time product.

Radiation dose and image quality were compared between a standard protocol (40 patients, group A) and a weight-adapted protocol of voltage and current-time product (44 patients, group B) using 64-slice coronary multidetector computed tomography (MDCT). Effective dose estimate was lower by 37% in all patients of group B (9.2 +/- 2.5 mSv) compared with group A (14.6 +/- 2.3 mSv, P < 0.0001). Group B patients with a small body mass index (BMI) benefited most with a dose reduction of 53% (6.7 +/- 1.5 mSv in group B versus 14.1 +/- 1.8 mSv in group A, P < 0.0001). Moderate reductions of 32% and 20% were achieved for patients with a medium and large BMI, respectively. Reduction in radiation dose did not affect the image quality as assessed by image noise, signal-to-noise ratios, and number of coronary segments with good diagnostic image quality. Individual weight-adaptation of voltage and current-time product significantly reduces the radiation dose without loss of image quality.

Automatic image-driven segmentation of the ventricles in cardiac cine MRI.

PURPOSE: To propose and to evaluate a novel method for the automatic segmentation of the heart's two ventricles from dynamic ("cine") short-axis "steady state free precession" (SSFP) MR images. This segmentation task is of significant clinical importance. Previously published automated methods have various disadvantages for routine clinical use. MATERIALS AND METHODS: The proposed method is primarily image-driven: it exploits the spatiotemporal information provided by modern 3D+time SSFP cardiac MRI, and makes only few and plausible assumptions about the image acquisition and about the imaged heart. Specifically, the method does not require previously trained statistical shape models or gray-level appearance models, as often used by other methods. RESULTS: The performance of the segmentation method was demonstrated through a qualitative visual validation on 32 clinical exams: no gross failures for the left-ventricle (right-ventricle) on 31 (29) of the exams were found. A validation of resulting quantitative cardiac functional parameters showed good agreement with a manual quantification of 19 clinical exams. CONCLUSION: The proposed method is feasible, fast, and robust against anatomical variability and image contrast variations.

Comparison of quantitative coronary angiography and first-pass perfusion magnetic resonance imaging for the detection of an impaired coronary perfusion in nonsevere coronary stenosis.

PURPOSE: To compare quantitative coronary angiography (QCA) and first-pass perfusion magnetic resonance imaging (FPP-MRI) in symptomatic patients with nonsevere coronary stenosis to detect a reduced coronary flow velocity reserve (CFVR). MATERIALS AND METHODS: In 35 patients, FPP-MRI and CFVR measurements were performed in 40 coronary arteries with a diameter stenosis (DS) <70% by QCA. From FPP-MRI a myocardial perfusion reserve index (MPRI) was calculated. CFVR was calculated as the ratio of the average peak flow velocity during infusion of adenosine and at rest and was considered reduced if <2. Diagnostic performance of MPRI and DS to detect a reduced CFVR was compared by receiver operating characteristic (ROC) curve analysis. RESULTS: CFVR was reduced in 16 coronary arteries (40%). Mean DS did not differ in coronary arteries with a reduced CFVR (41.0% +/- 13.3) and a normal CFVR (36.5% +/- 12.3; P = 0.281). Mean MPRI was lower in coronary arteries with a reduced CFVR (1.12 +/- 0.12) compared to a normal CFVR (1.33 +/- 0.2; P < 0.001). Sensitivity, specificity, and area under the ROC curve (AUC) were higher for MPRI (81%, 79%, 0.84) than for DS (56%, 58%, 0.60). CONCLUSION: FPP-MRI detects impaired CFVR in symptomatic patients with nonsevere coronary stenosis more accurately than QCA and can identify patients with symptomatic ischemia.

Detection of mechanical ventricular asynchrony by high temporal resolution cine MRI.

The purpose was to assess the feasibility of high temporal resolution cine MRI (HTRC-MRI) to detect and to quantify mechanical ventricular asynchrony in patients with left bundle branch block (LBBB). Inter- and intraventricular delays were quantified by HTRC-MRI in 32 patients with (n=17) and without (n=15) LBBB. In patients with LBBB, delays by HTRC-MRI were correlated with echocardiographic parameters using pulsed wave Doppler echocardiography (PW-Echo) and tissue Doppler imaging (TDI-Echo). The interventricular delay by HTRC-MRI was 110+/-50 ms in patients with and -1+/-18 ms in patients without LBBB (P<0.0001). The intraventricular delay was 336+/-86 ms in patients with compared to 40+/-49 ms in patients without LBBB (P<0.0001). A strong correlation (r=0.78, P=0.0002) and good agreement (mean difference: 39+/-36 ms) was found for the interventricular delay between HTRC-MRI and PW-Echo. A good correlation (r=0.66, P=0.0042), but a large discrepancy (mean difference: 257+/-64 ms) was found for the intraventricular delay between HTRC-MRI and TDI-Echo. Detection and quantification of mechanical ventricular asynchrony using HTRC-MRI is feasible. However, further comparison with other imaging modalities is required.

Myocardial contractile response to increasing doses of dobutamine in patients with reperfused acute myocardial infarction by cardiac magnetic resonance imaging.

BACKGROUND: Cardiac magnetic resonance imaging uses contractile response to dobutamine (DCMR) and delayed contrast enhancement (DE) to assess myocardial viability. However, early after acute myocardial infarction (AMI) the optimal dose of dobutamine is unclear. METHODS: In patients early after reperfused AMI, DCMR at 5, 10 and 20 microg*kg(-1)*min(-1) and measurement of DE was performed. On three short-axis slices 18 segments were graded as no DE, DE <50% and DE >or=50%. Thickening (systolic-diastolic wall thickness) and contractile reserve (max. thickening - rest) were determined. Segments were classified dysfunctional if thickening was >2 SD below normal or <2 mm. RESULTS: Forty-nine patients participated. In segments with no DE, thickening increased continuously but contractile reserve was low (0.9 +/- 3.2 mm) and dysfunctional segments were unchanged (rest: 13.1% vs. 20 microg: 14.8%). In segments with DE, contractile reserve was high (1.4 +/- 3.0 mm and 1.5 +/- 3.0 mm) and dysfunctional segments decreased from rest to 20 microg (50 vs. 24.8% and 79.9 vs. 43.2%). Between 5 and 10 microg no change of thickening and of dysfunctional segments occurred. CONCLUSION: Early after AMI, DCMR demonstrated no diagnostic benefit in segments with no DE. In segments with DE, higher dose of dobutamine can provide additional information on contractile reserve and dysfunctional segments.

Prediction of myocardial recovery by dobutamine magnetic resonance imaging and delayed enhancement early after reperfused acute myocardial infarction.

The purpose was to study dobutamine magnetic resonance cine imaging (DOB-MRI) and delayed myocardial contrast enhancement (DE) early after reperfused acute myocardial infarction (AMI) for the predicion of segmental myocardial recovery and to find the optimal dose of dobutamine. Fifty patients (56+/-12 years, 42 males) with reperfused AMI underwent DOB-MRI and DE studies 3.5 (1-19) days after reperfusion. In DOB-MRI systolic wall thickening (SWT) was measured in 18 segments at rest and during dobutamine at 5, 10 and 20 microg*kg(-1)*min(-1). Dysfunctional segments were identified and the extent of DE was measured for each segment. Segmental recovery was examined after 8 (5-15) months. Two hundred-forty-eight segments were dysfunctional with presence of DE in 193. DOB-MRI showed the best prediction of recovery at 10 microg*kg(-1)*min(-1) of dobutamine with sensitivity of 67%, specificity of 63% and accuracy of 66% using a cut-off value for SWT of 2.0 mm. DE revealed a sensitivity of 68%, specificity of 65% and accuracy of 67% using a cut-off value of 46%. Combined analysis of DOB-MRI and DE did not improve diagnostic performance. Early prediction of segmental myocardial recovery after AMI is possible with DOB-MRI and DE. No improvement is achieved by dobutamine >10 microg*kg(-1)*min(-1) or a combination of DOB-MRI and DE.

The fate of osteochondral grafts after autologous osteochondral transplantation: a one-year follow-up study in a minipig model.

INTRODUCTION: Because articular cartilage shows little intrinsic capacity of spontaneous regeneration, a variety of treatment options are currently at use to repair cartilage damage. One of these is the autologous osteochondral transplantation (AOT). The aim of the present work was to study the histological changes during the progress of 1 year after AOT in the knee joint. MATERIALS AND METHODS: Twelve Minipigs underwent an AOT on the medial femoral condyles of both knees using cooled diamond studded trephines with a diameter of the grafts of 4.6 mm. Three animals were sacrificed at each 2, 8, 26 and 52 weeks after the operation. The condyles were analyzed histologically and immunohistologically for collagen types I and II. RESULTS: A successful bony incorporation was observed in all specimens. The transplant demonstrated an increasingly stable integration of the chondral matrix into the cartilage of the surrounding femoral condyle. At 52 weeks after the operations 5 of 6 condyles showed a chondral integration at least at one side of the graft. Immunohistologically all specimens showed physiological staining characteristics up to 52 weeks after operation. The quality of the chondral part of the graft showed a wide range of variations, ranging from vital tissue resembling native cartilage after 52 weeks, to severe degenerative signs beginning 2 weeks after operation and ending at 52 weeks with deep fissures fragmenting the cartilage and the complete loss of vital cells. CONCLUSION: The press-fit technique allows a stable bony incorporation. A chondral integration of the graft seems to occur, provided that a close contact between the interfaces can be achieved. Present results demonstrate a vital cartilagenous transplant for up to 52 weeks. However, some specimens showed in part severe degenerative signs. A possible explanation is an insufficient cooling of the trephines in relation to the small diameter of the grafts used in the minipig model. The collagen network seems not to be affected for up to 52 weeks.

Prediction of left ventricular remodeling and analysis of infarct resorption in patients with reperfused myocardial infarcts by using contrast-enhanced MR imaging.

PURPOSE: To prospectively evaluate the accuracy of clinical and cardiac magnetic resonance (MR) imaging parameters for predicting left ventricular (LV) remodeling by using follow-up imaging as reference standard, and to prospectively evaluate infarct resorption in patients with reperfused first myocardial infarcts. MATERIALS AND METHODS: The study was approved by the institutional ethics committee and all patients gave written informed consent. In 55 patients (48 men, seven women; mean age+/-standard deviation, 56 years+/-13), contrast material-enhanced and cine MR imaging were performed 5 days+/-3 and 8 months+/-3 after myocardial infarction (MI). Microvascular obstruction (MO) and infarct size were estimated at first-pass enhancement (FPE) and delayed enhancement (DE) MR, respectively. Remodeling was defined as an increase in LV end-diastolic volume index of 20% or higher at follow-up. Differences in continuous and categorical data were analyzed by using Student t test and Fischer exact test as appropriate. RESULTS: Patients with remodeling (n=13, 24%) had higher creatine kinase MB (P<.05), more anterior infarcts (P<.05), more often a reduced Thrombolysis in Myocardial Infarction flow (P<.05), larger infarct size at DE MR (P<.001), a greater extent of MO at FPE MR (P<.01), lower ejection fraction (P<.001) and higher LV end-systolic volume index (P<.01). Infarct size at DE MR was a powerful predictor for remodeling (odds ratio: 1.18, P<.001), demonstrating that the risk for remodeling increased 2.8-fold with each 10% increase in infarct size. Infarct size of 24% or more of LV area predicted remodeling with high sensitivity (92%), specificity (93%), and accuracy (93%). Infarct resorption was larger in patients with remodeling (P<.01). CONCLUSION: Infarct size 24% or more of the LV area constitutes an important threshold to predict remodeling. Patients with remodeling develop disproportionate infarct resorption.

The decision not to drive during hypoglycemia in patients with type 1 and type 2 diabetes according to hypoglycemia awareness.

OBJECTIVE: In recent years, there has been an ongoing discussion on the relationship between diabetes and driving. As driving performance will inevitably decline at lower levels of glycemia, patients' decisions concerning driving or taking corrective action when hypoglycemia occurs immediately before or during driving seems paramount. RESEARCH DESIGN AND METHODS: Twenty-four type 1 diabetic patients with normal awareness of hypoglycemia (T1Norm group), 21 type 1 diabetic patients with impaired awareness of hypoglycemia (T1Imp group), and 20 type 2 diabetic patients with normal awareness of hypoglycemia (T2 group) were studied. They were asked whether they felt hypoglycemic and whether they would currently drive during experimental euglycemia (5.0 mmol/l) and hypoglycemia (2.7 mmol/l). RESULTS: In the T1Norm group, 1 patient (4.2%) decided to drive during hypoglycemia. In the T1Imp group, 9 patients (42.9%) said they would drive in the hypoglycemic condition. In the T2 group, 5 patients (25%) would drive. This was more frequently the case for patients on oral hypoglycemic agents (chi2 = 4.44; P = 0.04). No effect of sex (chi2 = 0.78; P = 0.38) or age (chi2 = 0.22; P = 0.64) was noted. CONCLUSIONS: Patients with type 1 diabetes and impaired awareness of hypoglycemia frequently decided to drive while hypoglycemic, whereas patients with type 1 diabetes and normal awareness of hypoglycemia appeared to make safe decisions concerning hypoglycemia and driving. Strikingly, patients with type 2 diabetes and normal hypoglycemia awareness frequently made potentially dangerous decisions as well, particularly when using oral hypoglycemic agents. Therefore, early, clear, and consistent education is imperative.

Contrast-enhanced cardiac MR imaging in the detection of reduced coronary flow velocity reserve.

PURPOSE: To prospectively evaluate the accuracy of contrast material-enhanced cardiac magnetic resonance (MR) imaging for determining impaired coronary flow velocity reserve (CFR) by using Doppler flow measurement as the reference standard. MATERIALS AND METHODS: The study was approved by the institutional ethics committee, and all patients gave written informed consent. Eligible patients underwent contrast-enhanced cardiac MR imaging and invasive measurement of CFR. For contrast-enhanced MR imaging, a three-section single-shot saturation recovery gradient-recalled echo sequence with steady-state free precession was used. Sections were divided into six segments. For each segment, a transmural and subendocardial myocardial perfusion reserve index (MPRI) was calculated by using the upslope of the signal intensity-time curve during the first pass of contrast material at rest and during adenosine infusion (140 microg per kilogram body weight per minute). MPRIs of vascular regions were compared with the corresponding CFR. Receiver operating characteristic (ROC) analysis was performed to find the number of segments needed for best diagnostic accuracy of MPRI and to find a cutoff value for MPRI in the detection of a reduced CFR. RESULTS: Thirty-five patients were evaluated (male-to-female ratio, 27:8; mean age +/- standard deviation, 63.5 years +/- 8.2; mean body mass index, 28.8 kg/m(2) +/- 3.8), and 43 vascular regions were analyzed. A linear correlation was found between the MPRI and CFR (r = 0.44, P < .05). The MPRI was significantly lower in vascular regions with a CFR of less than 2.00 than in regions with a CFR of 2.00 or greater (P < .05). Detection of a CFR of less than 2.00 was more accurate with subendocardial MPRI measurements than with transmural measurements. The mean subendocardial MPRI of the segments with the three lowest MPRIs of a vascular region showed the best diagnostic performance in the detection of a CFR of less than 2.00 (area under the ROC curve, 0.85; sensitivity, 84%; specificity, 75%) by using a cutoff value of 1.21. CONCLUSION: The diagnostic accuracy of subendocardial perfusion analysis in contrast-enhanced cardiac MR imaging is higher than that of transmural analysis.

Multidetector CT urography: experimental analysis of radiation dose reduction in an animal model.

The purpose of this study was to evaluate the possibility of reducing X-ray exposure during multidetector CT urography (MDCTU) considering image quality using a porcine model. MDCTU was performed in eight healthy pigs. Scanning was conducted using a gradual reduction of the tube current-time product at 120 kV [200-20 mAs (eff.) in ten steps]. Three blinded observers independently evaluated the image data for anatomic detail, subjective image quality, and subjective image noise. Overall image quality was compared to milliampere-second settings and radiation dose. Objective noise measurements were assessed. Noise measurements in patients were also performed to verify the comparabilty of the animal model. Adequate image quality allowing for detailed visualization of the upper urinary tract was obtained when the tube current-time product was decreased to 70 eff. mAs at 120 kV. Image noise did not impair image quality to a relevant degree using these parameters. There was high agreement among the observers (ICC = 0.95). In the animal experiments, reduced-dose MDCTU produced good image quality. A maximum current-time product reduction to 70 eff. mAs at 120 kV (CTDI(vol) = 5.3 mGy) proved to be feasible, thereby offering an advantageous dosage reduction. The study provides a basis for the development of reduced-dose MDCTU protocols in humans.

Multicontrast-weighted magnetic resonance imaging of atherosclerotic plaques at 3.0 and 1.5 Tesla: ex-vivo comparison with histopathologic correlation.

The purpose was to analyze magnetic resonance (MR) plaque imaging at 3.0 Tesla and 1.5 Tesla in correlation with histopathology. MR imaging (MRI) of the abdominal aorta and femoral artery was performed on seven corpses using T1-weighted, T2-weighted, and PD-weighted sequences at 3.0 and 1.5 Tesla. Cross-sectional images at the branching of the inferior mesenteric artery and the profunda femoris were rated with respect to image quality. Corresponding cross sections of the imaged vessels were obtained at autopsy. The atherosclerotic plaques in the histological slides and MR images were classified according to the American Heart Association (AHA) and analyzed for differences. MRI at 3.0 Tesla offered superior depiction of arterial wall composition in all contrast weightings, rated best for T2-weighted images. Comparing for field strength, the highest differences were observed in T1-weighted and T2-weighted techniques (both P< or =0.001), with still significant differences in PD-weighted sequence (P< or =0.005). The majority of plaques were histologically classified as calcified plaques. In up to 21% of the cases, MRI at both field strengths detected signal loss characteristic of calcification although calcified plaque was absent in histology. MRI at 3.0 Tesla offers superior plaque imaging quality compared with 1.5 Tesla, but further work is necessary to determine whether this translates in superior diagnostic accuracy.