Early time-related course of image findings in postmortem MRI: Typical findings and observer agreement in a porcine model.

PURPOSE: To assess early time-related image findings in postmortem magnetic resonance imaging (MRI) and to evaluate observer agreement in a porcine model. MATERIAL AND METHODS: Three pigs were examined by MRI at 15 different time points in the first 36h after death. Two observers independently recorded the postmortem interval (PMI) to the appearance of fluid collection (pleural space, interlobar and interlobular pulmonary fissures and hepatic interlobar fissures), gas accumulation (intrahepatic and intracardial) and blood clotting (aorta and intrahepatic venous vessels). Cohen's Kappa statistics and intraclass correlation coefficient (ICC) were used to evaluate intra- and interobserver agreement. RESULTS: Intrahepatic gas was evident after 12, 17 and 30h. Also, intracardiac gas was present in all animals. However, no chronological appearance has been observed. Blood clotting in the hepatic vein was observed within 3min, aortic clotting with a delay of 2-12h after death. Interlobular pulmonary fluid (median PMI: 2h, range 2-2h), pleural effusion (median PMI: 10.5h, range 9-12h) and hepatic interlobar fissure fluid (median PMI: 11.5h, range 11-12h) displayed a chronological appearance pattern. Qualitative and quantitative detection of most postmortem findings showed excellent intra- and interobserver agreement with Kappa values>0.8 or ICC>0.75. CONCLUSION: Pulmonary and hepatic fissural fluid collection as well as intravasal gas accumulation are early time-related image findings in postmortem MRI. The chronological appearance of these findings can be assessed with excellent observer agreement in a porcine model.

Intraindividual comparison of image quality using retrospective and prospective respiratory gating for the acquisition of thin sliced four dimensional multidetector CT of the thorax in a porcine model.

PURPOSE: To intraindividually compare image quality and anatomical depiction of the lung and mediastinum using retrospective and prospective respiratory gating techniques for the acquisition of 4D-multidetector computed tomography (MDCT) of the chest in a porcine model. MATERIALS AND METHODS: Twelve trachealy intubated domestic pigs underwent 64-row MDCT of the thorax. For retrospective and prospective gating the automated respiratory frequency was adjusted to 10, 14, 18, and 22 respiratory cycles per minute. Further, free breathing MDCT scans of the lung were performed at the same respiratory settings. A breathhold scan was acquired which served as the reference standard. Three reviewers independently analyzed the MDCT data applying a 4-point-grading scale regarding the degree of artifacts observed and anatomical depiction (1, excellent, no artifacts; 4, nondiagnostic due to severe artifacts). For statistical analysis the Wilcoxon matched pairs and Chi-square test were used. RESULTS: Breathhold imaging allowed for the highest image quality (mean value: trachea, 1.00; bronchi, 1.10; lung parenchyma, 1.08; diaphragm, 1.00; pericardium, 1.80). Retrospective gating proved to be of superior image quality compared to prospective gating for all respiratory frequencies. With the respiratory frequency set to 14/min retrospective gating even enabled an identical image quality score as at breathhold. Performing image acquisition during continuous breathing lead to a severe decrease in image quality. CONCLUSIONS: High image quality can be acquired using respiratory gating techniques for 4D-MDCT of the thorax. Retrospective is superior to prospective gating and can be of an equivalent image quality as standard breathhold imaging, but at the cost of a significantly higher radiation dose.

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.

Accelerating image acquisition in 64-MDCT: the influence of scan parameters on image resolution and quality in a phantom study.

Computed tomographic (CT) image resolution and quality were evaluated utilizing varying scan protocols with accelerated image acquisition. A resolution phantom with hole diameters from 0.2 to 1.0 mm was scanned in axial, coronal, and sagittal plane using a 64-slice multidetector CT with varying scan parameters. No relevant differences in image resolution and quality were detected between the fastest scan protocol, with the shortest rotation time and highest pitch, and the slowest protocol. Accelerated CT protocols resulted in diagnostic images with adequate resolution and quality.

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.

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). METHODS: Twenty patients with disseminated cancer disease in which MDCT had assured the presence of at least one pulmonary nodule were examined using a respiratory-gated DWI MR-sequence. Grey scale inverted source images and coronal maximum intensity projection (MIP) images were consensually analysed by two experienced radiologists. Size and location of any nodule detected were assessed. Additionally, the readers evaluated each hemithorax for the presence of at least one nodule and applied a four-point conspicuity scale (1-hemithorax definitely affected; 4-hemithorax definitely not affected). MDCT data served as reference. RESULTS: At MDCT, a total of 71 pulmonary noduIes was found (size 3-5mm, n=16; 6-9mm, n=22; ≥10mm, n=33). For the DWI MR-sequence, a sensitivity of 86.4% was calculated for nodules ranging 6-9mm and 97% for nodules ≥10mm. In contrast, only 43.8% of lesions ≤5mm was detected. The separate analysis of each hemithorax for the presence of at least one pulmonary nodule revealed a specificity rate, PPV and NPV of DWI-MR of 92.3%, 96% and 80%, respectively. CONCLUSIONS: The presented study is the first to confirm the diagnostic potential of DWI-MR in the detection of solid lung nodules. This technique allows for the detection of nodules ≥6mm with reasonably high sensitivity rates (>86%). The observation of false positive findings decreases the accuracy of this approach compared with MDCT.

Computer-assisted surgery and intraoperative three-dimensional imaging for screw placement in different pelvic regions.

BACKGROUND: The purpose of this study was to assess the feasibility and accuracy of computer-assisted surgery (CAS) for screw placement in different pelvic regions using intraoperative three-dimensional (3D) imaging and to evaluate the influence of surgeons' experience with such a system on procedure time, radiation time, radiation dose, and misplacement rate. METHODS: Experimental study in a human cadaveric model (n=5) for percutaneous screw placement in the anterior column of the acetabulum, the posterior pelvic ring (S1, S2), and the superior pubic ramus via 3D fluoroscopic navigated procedure. Accuracy of screw placement was assessed by 3D image intensifier, including the reconstruction of multiplanar images and by computer tomography (CT) scan. Influence of surgeons' experience was assessed by direct comparison of a low- and high-volume surgeon using the same technical setting. RESULTS: In 100% of all procedures, intraoperative Iso-C3D image analysis was sufficient to confirm a correct screw placement. The postoperative CT scan revealed no further screw misplacement. However, for a correct supraacetabular screw placement, the intraoperative 3D scan was essential. In this group, the 3D scan showed screw misplacement in three cases. Procedure time for all indications and screw failure rate were significantly lower for the higher experienced surgeon. CONCLUSION: The 3D fluoroscopic navigated procedure in pelvic surgery seems to be a useful tool for all surgeons and especially for less experienced ones. Furthermore, the intraoperative reconstruction of multiplanar 3D images allows a secure control of implant positioning.

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.

Anatomical variations of the right coronary artery may be a source of difficult block and conduction recurrence in catheter ablation of common-type atrial flutter.

AIMS: Although Eustachian valves and recesses have been related to resistance to block, the effect of convective cooling by the right coronary artery (RCA) has not been evaluated in the clinical setting. METHODS AND RESULTS: The distance and course of the RCA in relation to the cavotricuspid isthmus (CTI) in addition to variants of CTI anatomy and the presence of Eustachian valves were analysed from computed tomography scans of 54 patients. Ablation power was titrated using a step-up protocol. Invasive follow-up was available for 34 patients. The RCA came closest to the CTI inferiorly separated by a mean of 5.3 ± 2.5 mm compared with 7.3 ± 3.3 mm septally and 5.7 ± 2.3 mm anteriorly (P < 0.01). The maximum power required for CTI block correlated inversely with the distance of the RCA to the CTI, whereas the cumulative energy was highest in the presence of recesses. Neither failure of acute block nor a higher rate of conduction recurrence could be attributed to variants of CTI anatomy or the presence of a Eustachian valve. Using multivariate analysis, a position of the RCA underneath the central part of the CTI was the only significant predictor for late conduction recurrence. These patients showed a 2.7 mm larger distance of the RCA to the tricuspid valve plane (P = 0.05). CONCLUSION: The RCA affects CTI ablation as higher power settings are required at closer distances to the ablation site. Late conduction recurrences were observed in patients with a variation of the RCA, leaving the atrioventricular groove towards the atrial aspect.

Prospective respiratory-triggered 64-slice CT pulmonary angiography for detection of pulmonary embolism--a feasibility study in a porcine model.

The objective of this study is to investigate the feasibility of prospectively respiratory-triggered CT pulmonary angiography (CTPA) for detection of pulmonary embolism (PE) in a porcine model. A free-breathing respiratory-triggered multislice CTPA (120 kV, 140 mAs(eff), 2.5-mm slice thickness) and two CTPA in breath-hold technique (120 kV, 140 mAs(eff.) and 250mAs(eff), 1-mm and 3-mm image reconstruction) were performed in six pigs with pulmonary embolism. Diagnostic accuracy was computed, and differences in detection rates between both techniques were assessed on a per-embolus basis with the Wilcoxon test. Thin-sliced 1-mm images, acquired with 250mAs(eff), served as the standard of reference. Respiratory-triggered CTPA reached high diagnostic accuracy in detection of lobar and segmental PE equal to the results with the breath-hold technique (p > 0.05). For detection of subsegmental emboli, standard breath-hold techniques performed significantly better than respiratory-gated CTPA (sensitivity, 68.3% versus 24.4%; p < 0.05). Free-breathing respiratory-triggered CTPA is feasible for detection of lobar and segmental PE, with diagnostic accuracy equivalent to that of a standard CTPA in breath-hold. Although this technique is not recommended for assessment of emboli in the subsegmental vasculature, prospective respiratory-triggered CTPA may be of added value in patients who cannot hold their breath appropriately for CTPA scanning.

Feasibility of 18F-sodium fluoride PET/CT for imaging of atherosclerotic plaque.

UNLABELLED: The aim of this study was to examine the prevalence, distribution, and topographic relationship of vascular (18)F-sodium fluoride uptake and arterial calcification in major arteries. METHODS: Image data obtained from 75 patients undergoing whole-body (18)F-sodium fluoride PET/CT were evaluated retrospectively. Arterial radiotracer uptake and calcification were analyzed qualitatively and semiquantitatively. RESULTS: (18)F-sodium fluoride uptake was observed at 254 sites in 57 (76%) of the 75 study patients, and calcification was observed at 1,930 sites in 63 (84%) of the patients. Colocalization of radiotracer accumulation and calcification could be observed in 223 areas of uptake (88%). However, only 12% of all arterial calcification sites showed increased radiotracer uptake. CONCLUSION: Our data indicate the feasibility of (18)F-sodium fluoride PET/CT for the imaging of mineral deposition in arterial wall alterations. (18)F-sodium fluoride PET/CT may provide relevant information about the morphologic and functional properties of calcified plaque.

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.

Intraoperative cone-beam computed tomography in oral and maxillofacial surgery using a C-arm prototype: first clinical experiences after treatment of zygomaticomaxillary complex fractures.

PURPOSE: To describe the first clinical applications of intraoperative cone-beam computed tomography with an integrated flat-panel detector in oral and maxillofacial surgery after surgical treatment of zygomaticomaxillary complex fractures PATIENTS AND METHODS: Nine cone-beam computed tomography datasets of patients with zygomaticomaxillary complex fractures were intraoperatively acquired using a mobile isocentric C-arm (PowerMobil; Siemens Medical Solutions, Erlangen, Germany), including a flat-panel detector. Datasets based on 400, 200, and 100 fluoroscopic images were performed with different tube currents (4.6 mA, 3.3 mA, 2.3 mA, 1.2 mA, and 0.5 mA) and a current tube voltage of 100 kV. Postprocessing resulted in 15 different datasets available for comparison with corresponding preoperative computed tomography datasets. Four oral and maxillofacial surgeons and 2 experienced radiologists evaluated each dataset regarding noise, transition, and the delimitation of landmarks. RESULTS: All examinations were successfully performed. Reconstructed datasets showed high-resolution images of all midfacial osseous structures in near-computed tomography quality. Regarding high-contrast structures, detailed analyses of datasets acquired in this study suggest that the parameters 400 projections, 1.2 mA, and 100 kV are sufficient. In terms of soft-tissue visualization, a higher level of mA seems preferable. CONCLUSIONS: The tested prototype predicts a new era in cone-beam computed tomography imaging. The integration of a flat-panel detector will overcome the limitations of current available systems. The size of the field of view is increased allowing regularly the visualization of the whole facial skeleton. Particularly in cases of open reduction of unilateral fractures, the assessment of symmetry is of clinical value.

3D C-arm as an alternative modality to CT in postmortem imaging: technical feasibility.

OBJECT: The aim of our study was to demonstrate the image quality of the new device using human cadavers, extending the horizon of available imaging modalities in forensic medicine. MATERIALS AND METHODS: Six human cadavers were examined, revealing C-arm data sets of the head, neck thorax, abdomen and pelvis. High-resolution mode was performed with 500 fluoroscopy shots during a 190 degrees orbital movement with a constant tube voltage of 100 kV and a current of 4.6 mA. Based on these data sets subsequent three-dimensional reconstructions were generated. RESULTS: Reconstructed data sets revealed high-resolution images of all skeletal structures in a near-CT quality. The same image quality was available in all reconstruction planes. Artefacts caused by restorative dental materials are less accentuated in CBCT data sets. The system configuration was not powerful enough to generate sufficient images of intracranial structures. CONCLUSION: After the here-demonstrated encouraging preliminary results, the forensic indications that would be suitable for imaging with a 3D C-arm have to be defined. Promising seems the visualization local limited region of interest as the cervical spine or the facial skeleton.

Cervical soft tissue imaging using a mobile CBCT scanner with a flat panel detector in comparison with corresponding CT and MRI data sets.

OBJECTIVE: The aim of this study was to evaluate soft tissue image quality of a mobile cone-beam computed tomography (CBCT) scanner with an integrated flat-panel detector. STUDY DESIGN: Eight fresh human cadavers were used in this study. For evaluation of soft tissue visualization, CBCT data sets and corresponding computed tomography (CT) and magnetic resonance imaging (MRI) data sets were acquired. Evaluation was performed with the help of 10 defined cervical anatomical structures. RESULTS: The statistical analysis of the scoring results of 3 examiners revealed the CBCT images to be of inferior quality regarding the visualization of most of the predefined structures. Visualization without a significant difference was found regarding the demarcation of the vertebral bodies and the pyramidal cartilages, the arteriosclerosis of the carotids (compared with CT), and the laryngeal skeleton (compared with MRI). Regarding arteriosclerosis of the carotids compared with MRI, CBCT proved to be superior. CONCLUSIONS: The integration of a flat-panel detector improves soft tissue visualization using a mobile CBCT scanner.

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.

Evaluation of the influence of acquisition and reconstruction parameters for 16-row multidetector CT on coronary calcium scoring using a stationary and dynamic cardiac phantom.

A calcium-scoring phantom with hydroxyapatite-filled cylindrical holes (0.5 to 4 mm) was used. High-resolution scans were performed for an accuracy baseline. The phantom was mounted to a moving heart phantom. Non-moving data with the implementation of an ECG-signal were acquired for different pitches (0.2/0.3), heart rates (60/80/95 bpm) and collimations (16 x 0.75/16 x 1.5 mm). Images were reconstructed with a cone-beam multi-cycle algorithm at a standard thickness/increment of 3 mm/1.5 mm and the thinnest possible thickness (0.8/0.4 and 2/1). Subsequently, ECG-gated moving calcium-scoring phantom data were acquired. The calcium volume and Agatston score were measured. The temporal resolution and reconstruction cycles were calculated. High-resolution scans determine the calcium volume with a high accuracy (mean overestimation, 0.8%). In the non-moving measurements, the volume underestimation ranged from about 6% (16 x 0.75 mm; 0.8/0.4 mm) to nearly 25% (16 x 1.5 mm; 3/1.5 mm). Moving scans showed increased measurement errors depending on the reconstructed RR interval, collimation, pitch, heart rate and gantry rotation time. Also, a correlation with the temporal resolution could be found. The reliability of calcium-scoring results can be improved with the use of a narrower collimation, a lower pitch and the reconstruction of thinner images, resulting in higher patient doses. The choice of the correct cardiac phase within the RR interval is essential to minimize measurement errors.

Characterization of the peri-infarction zone using T2-weighted MRI and delayed-enhancement MRI in patients with acute myocardial infarction.

To characterize the peri-infarction zone using T2-weighted (T2w) magnetic resonance imaging (MRI) and infarct size on delayed enhancement (DE) MRI in patients with acute myocardial infarction (AMI). In 65 patients, short-axis T2w and DE MRI images were acquired 5 +/- 3 d after AMI. The MRI was analyzed using a threshold method defining infarct size on DE MRI and edema on T2w MRI as areas with signal intensity larger than +2 SD above remote normal myocardium. The peri-infarction zone was calculated as the difference between the size of edema and the infarct size. The size of edema on T2w MRI (31.3 +/- 13.4% of LV area) was larger than the infarct size on DE MRI (20.3 +/- 10.4% of LV area, p< 0.0001). The size of the peri-infarction zone was 11.0 +/- 10.0% of the LV area. Good correlation was found between infarct size on DE MRI and peak creatine kinase (CK) isoenzyme MB (r = 0.65, p< 0.0001), but there was no correlation between the size of the peri-infarction zone and CK MB (r = 0.05, p = 0.67). The peri-infarction zone was larger in patients with an infarct size <28% of the LV area (12.6 +/- 10.0% LV area) compared with patients with an infarct size > or =28% of the LV area (6.7 +/- 9.0% of the LV area, p< 0.05). The peri-infarction zone does not correlate with enzymatic parameters of infarct size and is substantially larger in small infarcts, indicating viable myocardium.

Multislice computed tomography-urography: intraindividual comparison of different preparation techniques for optimized depiction of the upper urinary tract in an animal model.

OBJECTIVES: We sought to evaluate intraindividually 3 different preparation protocols for achieving improved opacification and anatomic depiction of the upper urinary tract in multisclice computed tomography urography (MSCTU) using a porcine model. MATERIAL AND METHODS: MSCTU was performed in 8 healthy pigs. Each animal underwent 3 MSCT urographies using 3 different preparations before the injection of contrast material: A, intravenous (iv) saline (250 mL); B, iv low-dose furosemide (0.1 mg/kg); and C, iv saline (250 mL) plus iv low-dose furosemide (0.1 mg/kg). Image analysis was performed blinded to the applied protocols and included the evaluation of the opacification and anatomic depiction of the upper urinary tract by means of graded scales. Ureteral distension was determined and density was measured within the collecting system. RESULTS: Furosemide significantly improved both mean opacification scores and mean scores of anatomic depiction compared with the exclusive infusion of saline for MSCTU. There was no significant difference between the application of furosemide and the combination of furosemide plus saline. A significant increase of 25-26% for ureteral distension was found when furosemide was applied. Significant lower mean attenuation values (Hounsfield units) and standard deviation were found within the opacified urine for diuretic-enhanced MSCTU. CONCLUSIONS: Low-dose furosemide injection is superior to saline infusion for achieving optimal enhancement in MSCTU. It is not necessary to combine furosemide and saline infusion. In MSCTU, low-dose furosemide is a simple add-on simplifying image acquisition timing and removing the need for abdominal compression devices.

Value of multiplanar reformations (MPR) in multidetector CT (MDCT) of acute vertebral fractures: do we still have to read the transverse images?

OBJECTIVE: To determine the value of multiplanar reformations (MPRs) in multidetector computed tomography (MDCT) diagnosis of acute vertebral fractures and to assess the necessity to read the whole set of transverse images. METHODS: Retrospectively, 56 MDCT of 55 patients with acute vertebral fractures were included. The images were analyzed by two radiologists in a consensus procedure. First, the diagnosis was made exclusively from sagittal and coronal MPRs; secondly, the transverse images were analyzed with knowledge of the MPRs. Diagnostic accuracy is given as percentage. Image amounts were compared using the Wilcoxon test. RESULTS: In 244 vertebral bodies, all 70 fractured vertebrae were diagnosed on reviewing MPRs only. There were no false positive cases. In 2/70 fractures, the anatomically exact diagnosis was complemented by reading the transverse images. Forty-two of 43 unstable fractures were diagnosed correctly on MPRs only. With preference of MPR reading, the total number of images to be analyzed could be reduced significantly (P < 0.01). CONCLUSION: Reading of MPRs alone is a feasible approach for correct assessment of vertebral fractures and classifying them into stable/unstable, if MPRs are done properly. Transverse images must be analyzed in complex fractures or uncertain findings.