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To assess the effect of tumor size and tumor-to-liver contrast of simulated hypovascular liver tumors on the diagnostic accuracy of hepatic computed tomography (CT).This retrospective study was approved by the institutional review board, and informed consent was waived. A total of 153 simulated hypovascular liver tumors were embedded in 70 hepatic CT data sets that were acquired during the portal venous phase. The simulated tumors had 3 different diameters (6, 10, and 14 mm) and 3 different tumor-to-liver contrast values (20, 35, and 50 HU). There were also 30 hepatic CT data sets without liver tumors. Three radiologists independently performed tumor detection on the randomized 100 hepatic CT data sets.The lowest sensitivity was obtained for the 6-mm tumors with a tumor-to-liver contrast of 20 HU (4.1%), and the highest sensitivity was obtained for the 10- and 14-mm tumors with a tumor-to-liver contrast of 50 HU (100%). Increasing the contrast from 20 to 35 to 50 HU in the 6-mm tumors yielded a significant increase in sensitivity (4.1%, 48.8%, and 92.4%, respectively; P0.0001). The sensitivity for the 10- and 14-mm tumors also increased significantly as the tumor-to-liver contrast value increased from 20 to 35 HU (P0.01). However, no significant increase in sensitivity was seen for the 10- and 14-mm tumors as the tumor-to-liver contrast values increased from 35 to 50 HU (P = 0.733 and P = 1.0, respectively).Increasing the tumor-to-liver contrast from 20 to 35 HU results in a significant increase in the detection of hypovascular liver tumors ranging from 6 to 14 mm in diameter. Optimization of the tumor-to-liver contrast is necessary for improved detection of hypovascular liver tumors.

X-ray computed tomography (CT) using phase contrast can provide images with greatly enhanced soft-tissue contrast in comparison to conventional attenuation-based CT. We report on the first scan of a human specimen recorded with a phase-contrast CT system based on an x-ray grating interferometer and a conventional x-ray tube source. Feasibility and potential applications of preclinical and clinical phase-contrast CT are discussed.A hand of an infant was scanned ex vivo at 40 kVp tube voltage. The simultaneously recorded attenuation and phase-contrast CT images were quantitatively compared with each other, by introducing a specific Hounsfield unit for phase-contrast imaging.We observe significantly enhanced soft-tissue contrast in the phase images, when compared with the attenuation data. Particularly, tendons and ligaments appear with strongly increased contrast-to-noise ratio.Our results demonstrate the huge potential of phase-contrast CT for clinical investigations of human specimens and, potentially, of humans. Because the applied technique works efficiently with conventional x-ray tubes and detectors, it is suitable for the realization of preclinical and clinical phase-contrast CT systems.

The aim of the study was to determine the sensitivity and specificity for typical abdominal injuries after major blunt trauma in postmortem multislice computed tomography (MSCT) and magnetic resonance imaging (MRI).Thirty-four cases of accidental death underwent postmortem pre-autopsy MSCT and MRI. The imaging findings were correlated with the autopsy findings.Sensitivity and specificity for liver injury in computed tomography (CT) alone were 53% and 84%. In MRI, a sensitivity of 58% and a specificity of 46% were found. CT and MRI together (when either one was positive, liver-injury was considered) had a sensitivity of 73% and a specificity of 63%. For major liver lacerations (grades II-VI) a slightly higher sensitivity of 81% and a better specificity of 100% were noted. CT and MRI together showed a sensitivity of 50% for injuries of the spleen, specificity was 89%. CT and MRI together had a sensitivity of only 25% for trauma of the kidney, but a specificity of 100%.A lot of cases with small organ injuries (such as superficial liver-laceration) seemed that could not be found by MSCT or by MRI, leading to a rather low sensitivity. Nevertheless, most of the life-threatening liver injuries could be detected, which is essential in forensic pathology.

OBJECTIVE: Postmortem examination of chest trauma is an important domain in forensic medicine, which is today performed using autopsy. Since the implementation of cross-sectional imaging methods in forensic medicine such as computed tomography (CT) and magnetic resonance imaging (MRI), a number of advantages in comparison with autopsy have been described. Within the scope of validation of cross-sectional radiology in forensic medicine, the comparison of findings of postmortem imaging and autopsy in chest trauma was performed. METHODS: This retrospective study includes 24 cases with chest trauma that underwent postmortem CT, MRI, and autopsy. Two board-certified radiologists, blind to the autopsy findings, evaluated the radiologic data independently. Each radiologist interpreted postmortem CT and MRI data together for every case. The comparison of the results of the radiologic assessment with the autopsy and a calculation of interobserver discrepancy was performed. RESULTS: Using combined CT and MRI, between 75% and 100% of the investigated findings, except for hemomediastinum (70%), diaphragmatic ruptures (50%; n=2) and heart injury (38%), were discovered. Although the sensitivity and specificity regarding pneumomediastinum, pneumopericardium, and pericardial effusion were not calculated, as these findings were not mentioned at the autopsy, these findings were clearly seen radiologically. The averaged interobserver concordance was 90%. CONCLUSION: The sensitivity and specificity of our results demonstrate that postmortem CT and MRI are useful diagnostic methods for assessing chest trauma in forensic medicine as a supplement to autopsy. Further radiologic-pathologic case studies are necessary to define the role of postmortem CT and MRI as a single examination modality.

BACKGROUND: Until August 2004 there were 106 forensic cases examined with postmortem multislice computed tomography (MSCT) and magnetic resonance (MR) imaging before traditional autopsy within the Virtopsy project. Intrahepatic gas (IHG) was a frequent finding in postmortem MSCT examinations. The aim of this study was to investigate its cause and significance. METHODS: There were 84 virtopsy cases retrospectively investigated concerning the occurrence, location, and volume of IHG in postmortem MSCT imaging (1.25 mm collimation, 1.25 mm thickness). We assessed and noted the occurrence of intestinal distention, putrefaction, and systemic gas embolisms and the cause of death, possible open trauma, possible artificial respiration, and the postmortem interval. We investigated the relations between the findings using the contingency table (chi2 test) and the comparison of the postmortem intervals in both groups was performed using the t test in 79 nonputrefied corpses. RESULTS: IHG was found in 47 cases (59.5%). In five of the cases, the IHG was caused or influenced by putrefaction. Gas distribution within the liver of the remaining 42 cases was as follows: hepatic arteries in 21 cases, hepatic veins in 35 cases, and portal vein branches in 13 cases; among which combinations also occurred in 20 cases. The presence of IHG was strongly related to open trauma with systemic gas. Pulmonary barotrauma as occurring under artificial respiration or in drowning also caused IHG. Putrefaction did not seem to influence the occurrence of IHG until macroscopic signs of putrefaction were noticeable. CONCLUSIONS: IHG is a frequent finding in traumatic causes of death and requires a systemic gas embolism. Exceptions are putrefied or burned corpses. Common clinical causes such as necrotic bowel diseases appear rarely as a cause of IHG in our forensic case material.

We evaluated the incidence and clinical relevance of alternate or additional findings on unenhanced CT in patients with acute flank pain and suspected urinary calculi.A consecutive series of 1,500 patients underwent unenhanced CT due to acute flank pain. The absence or presence of urinary tract calculi and their localization were recorded. Alternate or additional CT findings were classified according to whether they required immediate or deferred treatment, or were of little or no clinical importance.Of the 1,500 patients 1,035 (69%) had urinary tract calculi, including 309 (30%) with nephrolithiasis, 377 (36%) with ureterolithiasis and 349 (34%) with the 2 conditions. Urolithiasis alone was found in 331 of these patients (32%) and additional pathological conditions were noted in 704 (68%). Of all patients 1,064 (71%) had other or additional CT findings. Of all patients 207 (14%) had nonstone related CT findings requiring immediate or deferred treatment, 464 (31%) had pathological conditions of little clinical importance and 393 (26%) had pathological conditions of no clinical relevance. CT was normal in 105 of all patients (7%).Unenhanced CT in patients with acute flank pain allows the accurate diagnosis of urinary stone disease and it can also provide further important information leading to emergency or deferred treatment in a substantial number of patients.

The goal of this study was the full-body documentation of a gunshot wound victim with multislice helical computed tomography for subsequent comparison with the findings of the standard forensic autopsy. Complete volume data of the head, neck, and trunk were acquired by use of two acquisitions of less than 1 minute of total scanning time. Subsequent two-dimensional multiplanar reformations and three-dimensional shaded surface display reconstructions helped document the gunshot-created skull fractures and brain injuries, including the wound track, and the intracerebral bone fragments. Computed tomography also demonstrated intracardiac air embolism and pulmonary aspiration of blood resulting from bullet wound-related trauma. The "digital autopsy," even when postprocessing time was added, was more rapid than the classic forensic autopsy and, based on the nondestructive approach, offered certain advantages in comparison with the forensic autopsy.

Purpose: We determine long-term morphological changes of the upper urinary tract following ileal orthotopic bladder substitution with an afferent tubular segment without a flap-valve type antireflux procedure.Materials and Methods: A consecutive series of long-term survivors (5 years or greater) following ileal orthotopic bladder substitution underwent regular radiological followup with excretory urography. Preoperative and postoperative renal size, parenchymal thickness, pelvicaliceal dilatation and upper urinary tract obstruction were assessed by 2 radiologists.Results: A total of 76 patients with a median followup of 84 months (range 60 to 155) were evaluable. Four patients (2.6%) underwent unilateral nephroureterectomy during followup. Of the remaining 148 renoureteral units 141 (95%) revealed no significant changes in size or parenchymal thickness during followup. Renal size decreased in 6 (4%) and parenchymal thickness in 7 (5%) renoureteral units, 5 of which already had renal pathologies (d...

Objective To test the clinical value of magnetic resonance imaging (MRI) pelvimetry for the diagnosis of cephalopelvic disproportion. Methods All deliveries from January 1993 through December 1994 were reviewed to identify 42 nulliparas at term with vertex presentation and cesarean delivery due to dystocia. Complete data were available for 41 women, and subjects were divided into the following two subgroups, according to clinical data: “cephalopelvic disproportion” ( n = 28) and “failure to progress” ( n = 13). Ten nulliparous women with uncomplicated vaginal delivery served as controls. Pelvimetry data from postpartum MRI were correlated with fetal and neonatal dimensions to evaluate various criteria for the diagnosis of cephalopelvic disproportion. Results Comparing both the fetal head volume derived from antepartum ultrasound assessment and the neonatal head volume (postpartum measurement) with maternal pelvic capacity determined by MRI, cephalopelvic disproportion (head volume exceeding pelvic capacity) indicated that 25 and 27, respectively, of the 28 women had been clinically diagnosed correctly with cephalopelvic disproportion, corresponding to sensitivities of 89% and 96%, respectively. Fetal head volume was not larger than pelvic capacity in any of the women in the control group. In seven of the 13 women diagnosed as “failure to progress,” the fetal head volume exceeded the pelvic capacity. Conclusion A fetal head volume estimate exceeding MRI-measured pelvic capacity is a frequent rinding in nulliparas with cesarean birth due to cephalopelvic disproportion. An appropriate prospective study to determine the benefits of an antepartum diagnosis of cephalopelvic disproportion in high-risk nulliparas is warranted.

Conventional computed tomography (CT) processes the raw data of a single rotation at any given level to produce the image at that level. Scan collimation and interspacing are determined prospectively. Spiral CT combines longitudinal patient transport with continuous data acquisition. Interpolated projections are used for reconstructing any level inside the scanned volume. Therefore, spiral CT allows any number of images, their spacing, position, and field of view to be determined retrospectively. Technically, the only limiting factors of spiral CT are the load of the x-ray tube and the computation power of the scanner. Spiral CT is superior to conventional CT in detecting lung nodules, in imaging the representative slice of a small nodule by retrospective selection, and in its ability to reformat the image in any plane. It also allows rapid scanning and three-dimensional re-formation of images. It may reduce the dose of contrast agent required for optimal enhancement of the vascular structures, reduce the radiation dose, and eliminate motion artifacts.

Quantitative liver function tests are based on the clearance concept and measure the plasma disappearance of a test compound such as galactose. Metabolism is inferred to be predominantly hepatic, and usually no knowledge is obtained of the true time course of metabolite formation. Dynamic 31phosphorus magnetic resonance spectroscopy after intravenous administration of fructose directly measures hepatic sugar metabolism. To determine the feasibility and the utility of 31P magnetic resonance spectroscopy, we studied the responses of six healthy subjects and nine patients with nonalcoholic cirrhosis to a fructose load. Results were related to the impairment of hepatic function assessed by the galactose-elimination capacity test. Liver spectra were acquired in a 1.5 T whole-body nuclear magnetic resonance unit with a surface coil (9-cm diameter) placed ventrally on the liver; the one-dimensional chemical-shift imaging technique was used to obtain spectra from tissue slices parallel to the surface coil. After a basal spectrum had been obtained, fructose (250 mg/kg) was injected intravenously, and further spectra were collected sequentially every 6 min for 1 hr. Formation of monophosphate esters (9% +/- 5% vs. 20% +/- 8% of total area; p less than 0.01) and utilization of inorganic phosphate (5% +/- 4% vs. 11% +/- 3% of total area; p less than 0.005) were markedly decreased in cirrhotic patients. These measures correlated with the severity of the impairment of liver function measured by the galactose-elimination capacity (r = 0.53 to 0.69; p less than 0.05). We conclude that dynamic 31P magnetic resonance spectroscopy is a safe, clinically feasible test that allows detailed insights into biochemical events in liver disease.

Protocols for two- and three-dimensional phase contrast magnetic resonance angiography of the major vessels in the abdomen were developed and demonstrated in healthy volunteers. Phase contrast imaging provides excellent suppression of stationary tissue signal and can be used to quantify the speed and direction of flow in a given vessel. The two-dimensional protocols provide rapid breath-held images, which proved useful for anatomical localization. The three-dimensional studies required longer acquisition times but provided superior image quality. Artifacts from bowel and respiratory motion were not significant with either protocol. Vasculature detected includes the renal, splenic, hepatic, and mesenteric systems as well as the aorta and inferior vena cava.

The effects of patient age, anatomic level, anteroposterior location, and phase of respiration on pulmonary density were analyzed retrospectively in 33 children and prospectively in 13 children. Density standards were positioned on the chest wall for correction of scanner performance changes. The subgroup of 32 children over 7 years of age, ie, with respiratory cooperation, was analyzed separately using moderate inspiration; its mean lung density (MLD) of three levels was -792 HU (95% range, -702-882 HU). Although MLD decreased with increasing age, a significant linear regression was found only in the prospective subgroup. Densities of the apical, subcarinal, and basal levels of the lung were not different. From maximal expiration to maximal inspiration, MLD decreased by 158 HU in the subgroup studied prospectively. Anteroposterior density gradients averaged 56 HU at the subcarinal level and increased with maximal expiration.

Breathing motion severely degrades the quality of magnetic resonance images (MRI) of the thorax and upper abdomen and interferes with the acquisition of quantitative data. To minimize these motion effects, we built an MRI compatible ventilator for use in animal studies. Solid state circuitry is used for controlling ventilation parameters. The ventilator can be triggered internally at frequencies of 0.1 to 30 Hz or it can be triggered externally such as by the MRI pulse sequence. When triggered by the scanner, ventilation is synchronized to occur between image data acquisitions. Thus, image data are obtained when there is no breathing motion and at a minimum lung volume when hydrogen density is maximum. Since the ventilator can be adjusted to operate at virtually any frequency from conventional to high frequency, ventilation can be synchronized to all commonly used repetition times (100 ms to 2000 ms or more; 600 to 30 breaths/min). Scan synchronous ventilation eliminates breathing motion artifacts from most imaging sequences (single and multiple spin echo and inversion recovery). Best image quality is obtained when scan synchronous ventilation is combined with cardiac gating. These methods are also useful for quantitative research studies of thoracic and abdominal organs.

As a pilot study, 31-P-spectra of the quadriceps femoris muscle (1.5T) and proton images of the right thigh (.5T) were performed in two cyclists (T) and two untrained (UT) subjects. During ischemia, while MRI did not show any change, phosphocreatine (PCr) concentration decreased and inorganic phosphate (Pi) increased. Recovery occurred within 3 minutes. Ergometric bicycle tests were performed outside the magnet. Submaximal workload (UT 150W/T 260W, 3.5 minutes) caused transient minimal changes in phosphorus metabolites. Supramaximal, partially anaerobic exercise (UT 320W/T 350W, 3.5 minutes) induced similar changes in heart rate, oxygen uptake rate, and plasma lactate in both groups. Decrease of the PCr/Pi ratio, however, was more pronounced in UT subjects and clearly lasted longer. If methodical problems can be resolved, combined MRS and MRI in whole body magnets may become a standard noninvasive modality, adding unique information on morphology (organ volume) and local metabolism to classic mechanical and global physiologic data.

To test the potential of 1.5 Tesla magnetic resonance imaging (MRI) for assessing the protein concentration of pleural effusions, five pleural fluid analogs (saline + 0, 2, 4, 6, 8 g albumin/100 mL) and, for comparison, four saline dilutions of whole blood were evaluated in vitro. The relaxation rates (1/T1, 1/T2) of albumin solutions were determined by 1.5 T spectroscopy (MRS) and correlated with albumin concentration (1/T1:slope 0.02, r + 0.89, P less than .05; 1/T2: slope 0.16, r = 0.997, P less than .001). MRI studies of these solutions showed no significant correlation with 1/T1, but 1/T2 showed a positive correlation with albumin concentration (r = 0.98, P less than .01). Both MRI relaxation rates were significantly correlated with blood concentration, and slopes were greater than for albumin solutions. These preliminary studies, demonstrating differences in correlation between relaxation rates and the concentration of albumin and blood, suggest that MRI has the potential for differentiating pleural effusions of different chemical composition.

Previously, we reported that oleic acid infusion in dogs produced a patchy and predominantly peripheral increase in lung density. The present study examines in more detail the morphology of the early stages of development of the oleic acid lesion using computed tomography (CT), specimen radiography, and conventional histology. Dogs were sacrificed 10, 30, 60, and 240 minutes after infusion of oleic acid (.05 ml/kg). After freezing in dry-ice, the thorax was scanned and cut into 1-cm thick sections. Frozen sections were then contact radiographed and sampled for histology. Within 10 minutes of infusion, subtle increases in peripheral lung density were visible on the contact radiographs. Patchy areas of peripheral density, resembling secondary lobules, were especially prominent 60 and 240 minutes after infusion. These lesions were often clearly associated with the distal bronchovascular structures. Histologic signs of edema were present in all animals sacrificed 30 or more minutes after receiving oleic acid. These correlative studies provide additional insight into the early subgross development of oleic acid-induced injury by showing the relationship between the developing edema and the bronchovascular structure of the lung.