Comparison of sliced and whole lung sets for the LLNL and JAERI torso phantoms using GE detectors

The performance characteristics of sliced lung sets were compared to lung sets with activity homogeneously distributed throughout the lung tissue substitute material. The activity estimate from planar sources differs from the estimate from homogeneous sources by a factor of 0.88 to 1.09 depending on the photon energy. This error is small compared to other uncertainties commonly encountered in lung counting, i.e., activity deposition in the lung, detector placement, size difference between individuals, etc. Sliced lung sets could be used instead of homogeneous lung sets to test or provide an interim calibration for a lung counting system.

Peri-anhepatic phase oxygen kinetics in porcine liver transplantation

BACKGROUND

We applied a liver transplantation animal model to examine the relationship between oxygen delivery and consumption. The presence of pathologic flow-dependent oxygen consumption was investigated during and after the anhepatic phase. The effect of venous-to-venous bypass on oxygen kinetics was evaluated.

METHODS

Twelve pigs were randomly divided into two groups. The non-bypass group consisted of six pigs that were subjected to clamping of the hepatic artery, portal vein, and the superior and inferior vena cava to produce an anhepatic phase. The bypass group consisted of six pigs that underwent vascular clamping and liver transplantation with venous bypass. Hemodynamics, oxygen delivery index (DO2) and oxygen consumption index (VO2) were recorded during the peri-anhepatic phase. Best-fit regression lines were calculated for DO2 vs VO2.

RESULTS

In the pigs without venous bypass, the blood pressure, cardiac index and VO2 dropped significantly after vascular clamping and lactic acidosis developed. In pigs with venous bypass, vascular clamping induced a significant decline of cardiac output and DO2 but VO2 was maintained by a compensatory increase in oxygen extraction ratio. DO2 and VO2 after the release of vascular clamping increased significantly higher than that before vascular clamping. The O2 supply-dependent regression line was drawn from the points below critical oxygen delivery with a slope of 0.232 (95% CI = 0.110-0.354, r2 = 0.50, p = 0.010). The pathologic supply-dependent line was drawn from the points with supranormal DO2 and VO2 with a slope of 0.185 (95% CI = 0.050-0.333, r2 = 0.510, p = 0.029). The slope of the supply-independent line was 0.0089 (95% CI = -0.030-0.050, r2 < 0.009, p = 0.12).

CONCLUSIONS

Oxygen delivery dropped below the critical level and flow-dependent oxygen consumption developed during the anhepatic phase without venous bypass. Venous-to-venous bypass is necessary to maintain a critical DO2 and stable hemodynamics during porcine liver transplantation. Pathologic flow-dependent oxygen consumption developed after the anhepatic phase.

Adult ovarian granulosa cell tumors: spectrum of sonographic and CT findings with pathologic correlation

OBJECTIVE

The objective of this study was to evaluate the spectrum of sonographic and CT findings in adult ovarian granulosa cell tumors with pathologic correlation.

MATERIALS AND METHODS

Transabdominal sonograms and CT scans in 13 patients with pathologically proven adult ovarian granulosa cell tumors were retrospectively reviewed. Morphologic characteristics of the lesions shown on sonography and CT were correlated with the histopathologic findings.

RESULTS

On the basis of sonographic and CT findings, 13 cases of adult ovarian granulosa cell tumor were categorized into five morphologic patterns: multilocular cystic (n = 6), thick-walled unilocular cystic (n = 2), thin-walled unilocular cystic (n = 1), homogeneously solid (n = 2), and heterogeneously solid (n = 2) masses. Histopathologically, the multilocular cystic masses were characterized by a predominately macrofollicular pattern of granulosa cells and multiple cystic spaces with watery fluid or hemorrhage. Unilocular central cystic masses seen on CT correlated pathologically with confluence and expansion of the cystic spaces. Homogeneously solid masses seen on sonography and CT were correlated with evenly distributed trabecular or diffuse patterns in the tumor cells. Intratumoral bleeding, infarcts, fibrous degeneration, and irregularly arranged tumor cells yielded heterogeneously solid tumors.

CONCLUSION

Adult ovarian granulosa cell tumors have a varied histologic appearance and a varied arrangement of tumor cells, both of which can create a spectrum of imaging manifestations. Appreciation of these manifestations is helpful in the diagnosis of this tumor.

Fatal pulmonary embolism in a child undergoing extra-ventricular drainage surgery--a case report

Thromboembolism is rather common in neurological patients and patients with brain tumor, who are bed-ridden or with partial immobile limb. In serious instances morbidity and mortality are inevitable. We present a case report on a fatal pulmonary embolism in a 2-year-old girl who underwent extra-ventricular drainage procedure under general anesthesia for occipital subdural effusion, a sequela of the former surgery undertaken to remove the choroid plexus papilloma 13 days ago. Sudden cardiac arrest occurred during induction of anesthesia and she finally succumbed in spite of vigorous cardiopulmonary resuscitation. Transthoracic and transesophageal echocardiography performed in the course of resuscitation disclosed thrombi of various sizes scattering in right atrium, the right ventricle, main pulmonary trunk, and the left pulmonary artery. The cause of death was thought to be severe obstruction of right ventricular outflow tract by large thrombi. The etiological factors which possibly led to the thrombosis were discussed, and the methods of diagnosis and treatment were also explored.

Genetics of metalaxyl resistance in Phytophthora infestans

Several sexual crosses involving isolates of Phytophthora infestans of diverse sensitivities to metalaxyl were studied. Metalaxyl sensitivity was determined by comparing the growth of an isolate on metalaxyl-amended agar medium (5 microg/ml) with growth on medium containing no metalaxyl. When both parents had the same phenotype for metalaxyl sensitivity (both resistant or both sensitive), all F1 progeny had the parental phenotype. In two crosses (75 and 76) each involving one sensitive and one resistant parent, however, the progeny segregated 1:1, suggesting that the common resistant parent (Bg8) was heterozygous for metalaxyl sensitivity. When an F2 progeny was constructed from resistant F1 isolates in cross 76, the progeny segregated 1:3 (sensitive:resistant), indicating that metalaxyl resistance in Bg8 is conferred by a single dominant gene. Variation in the progeny sensitivity appears to involve minor genes. A correlation study between metalaxyl resistance and fitness components did not reveal any association.

Cerebral blood volume measurements using dynamic contrast-enhanced x-ray computed tomography: application to isoflurane anaesthetic studies

A convenient and simple method of measuring cerebral blood volume (CBV) will aid in the clinical management of patients with cerebrovascular diseases and head trauma. Using a two-compartment model to characterize the distribution of x-ray contrast agent in the brain, we have developed a non-equilibrium (dynamic) x-ray CT method to measure CBV and have applied this method to study the effects of isoflurane. CBV and cerebral blood flow (CBF, ex vivo) measurements were made in two groups of New Zealand White rabbits at varying (study group) and constant (control group) arterial CO2 concentration. ANOVA for repeated measures was used on the control data to determine the precision of our two-compartment CT-CBV method. The results showed that the precision of our CT-CBV measurement was 9.8%. In addition a paired t-test analysis of the control data revealed that the duration of isoflurane anaesthesia had no effect on the repeated measurements of CBV or CBF. The rate of change in CBV (0.049 ml/100 g/mmHg) and CBF (6.2 ml/min/100 g/mmHg) with respect to changes in arterial CO2 concentration under the influence of isoflurane anaesthesia was similar to those reported in previous studies, thus validating our experimental CT-CBV and CBF measurements. Our CT-CBV method will lead to more information on the relationship between CBV and CBF under different pharmacological interventions in both normal and disease conditions.

Immunolocalization of high-density lipoproteins in arterial walls of rats

The inverse correlation between serum high-density lipoprotein (HDL) levels and coronary heart disease in humans suggests that HDL has a protective effect against the development of atherosclerosis. However, there is a lack of data concerning its distribution across the arterial wall. In order to detect this lipoprotein, we performed immunogold labeling on ultrathin sections of L.R. White embedded rat arterial tissue. Electron microscopic examination revealed that HDL was localized in the cytoplasm of the endothelial cells and the smooth muscle cells, but not in the nucleus or other organelles. The HDL was also present in the subendothelial space, the extracellular matrix as well as the intercellular clefts between the endothelial cells. Quantitative study revealed that rats on a high cholesterol diet for one month have more immunogold labeling (P < 0.05) in the subendothelial space, the smooth muscle cells and the extracellular matrix as compared to rats on a normal diet. After 12 months of normal diet, the intracellular labeling was significantly increased (P < 0.05) in the endothelial cells and the smooth muscle cells as compared to 1 month on the normal diet. The increase was greater (P < 0.05) for the high-cholesterol diet than for the normal diet treatment.

Dynamic CT measurement of cerebral blood flow: a validation study

BACKGROUND AND PURPOSE

Our objective was to develop a method to correct for the effect of partial volume averaging (PVA) in the CT measurement of contrast enhancement in small arteries, and to validate a dynamic contrast-enhanced CT method for the measurement of regional cerebral blood flow (rCBF).

METHODS

Contrast-enhanced CT scans of tubes of known inner diameters were obtained to estimate the size-dependent scaling factors (PVSF) due to PVA. The background-subtracted image profiles of the contrast-filled tubes were fitted to gaussian curves, and the standard deviations (SDs) of these curves were correlated with the PVSF of each tube. In the second part of this investigation, 13 studies were performed in six New Zealand white rabbits under normal conditions. Dynamic CT measurements of rCBF, regional cerebral blood volume (rCBV), and regional mean transit time (rMTT) were calculated in the left and right parietal lobes and the basal ganglia. The CT rCBF values were compared with those obtained by the microsphere method, which is the standard of reference.

RESULTS

We found strong correlations for the SDs of the gaussian curves to the known inner diameters of the tubes and to their size-related PVSF. These correlations demonstrated that the error from PVA in the measurement of arterial enhancement can be corrected without knowledge of the actual size of the artery. The animal studies revealed a mean (+/- SD) rCBF of 73.3 +/- 31.5 mL/100 g per minute, a mean rCBV of 1.93 +/- 0.74 mL/100 g, and a mean rMTT of 1.81 +/- 1.02 seconds. A strong correlation was found between rCBF values derived by the CT and the microsphere methods.

CONCLUSION

We have validated a new dynamic CT method for measuring rCBF. The accuracy of this technique suggests that it can be used as an alternative diagnostic tool to assess the cerebral hemodynamics in experimental and clinical situations.

Inhibition of apoptosis-associated DNA fragmentation activity in nonapoptotic cells: the role of DNA fragmentation factor-45 (DFF45/ICAD)

We have investigated the mechanism whereby nuclear DNA fragmentation activity emerging during early apoptosis is inhibited during normal cell life. In a cell-free system, cytosol fractions from diverse nonapoptotic human cell lines (Jurkat T-cell leukemia, HeLa carcinoma, SK-N-MC neuroblastoma, and WI-38 embryonic lung fibroblast) potently neutralized the nuclear DNA fragmentation activity of cytosol from apoptotic anti-Fas treated Jurkat cells. Recombinant human DNA fragmentation factor 45 kDa subunit (DFF45/ICAD), an inhibitor of the caspase-activated DNase DFF40/CAD, substituted for healthy cytosol in inhibiting DNA fragmentation. An antiserum against human DFF45 detected 44 and 34 kDa proteins (major and minor, respectively) in the cytosols but not in the nuclear or membrane fractions of various cultured human cells. Cytosols depleted of DFF45/ICAD by immunoadsorption had little or no inhibitor of nuclear DNA fragmentation activity and no caspase-activated DNA fragmentation activity. We conclude that immunoreactive DFF45/ICAD is the principal inhibitor of apoptotic DNase activity in the cytosol of healthy cells.

An adiabatic approximation to the tissue homogeneity model for water exchange in the brain: II. Experimental validation

A frequently reported limitation to using water as a tracer for measuring CBF has been the dependence of the CBF estimate on the experimental time (referred to as the falling flow phenomenon, FFP). To eliminate the FFP, we have developed the adiabatic solution of the tissue homogeneity model to replace the solution of the single-compartment Kety model. In Part I, the derivation of the adiabatic solution was presented. In this second part, the adiabatic solution was applied to measure CBF in rabbits using nuclear magnetic resonance spectroscopy and the tracer deuterium oxide. It was shown that the FFP, observable when the 2H clearance data were analyzed with the Kety equation, was significantly reduced when the same data were analyzed with the adiabatic solution of the tissue homogeneity model. By concurrently measuring CBF with radioactive microspheres, it was determined that the CBF estimates from the adiabatic solution were accurate for true blood flow values less than 60 mL x 100 g(-1) x min(-1). Above this value the CBF estimate was progressively underestimated, which was attributed to the diffusion limitation of water in the brain.

Spatial localization combining projection presaturation with a two-dimensional excitation pulse

Single-shot spatial localization of short T1 nuclei was achieved by outer volume suppression with projection presaturation followed by selective excitation of the desired volume with a two-dimensional (2D) pulse. After the projection, presaturation with a 2D pulse avoided signal contamination from magnetization regrowth in the outer volume, whereas preceding the 2D pulse with projection presaturation reduced any unwanted excitation in the outer volume caused by the 2D pulse. The improvement in outer volume suppression achieved by combining these two techniques was demonstrated by images collected after the application of projection presaturation alone, a 2D pulse alone, and the two combined.

An adiabatic approximation to the tissue homogeneity model for water exchange in the brain: I. Theoretical derivation

Using the adiabatic approximation, which assumes that the tracer concentration in parenchymal tissue changes slowly relative to that in capillaries, we derived a time-domain, closed-form solution of the tissue homogeneity model. This solution, which is called the adiabatic solution, is similar in form to those of two-compartment models. Owing to its simplicity, the adiabatic solution can be used in CBF experiments in which kinetic data with only limited time resolution or signal-to-noise ratio, or both, are obtained. Using computer simulations, we investigated the accuracy and the precision of the parameters in the adiabatic solution for values that reflect 2H-labeled water (D2O) clearance from the brain (see Part II). It was determined that of the three model parameters, (1) the vascular volume (Vi), (2) the product of extraction fraction and blood flow (EF), and (3) the clearance rate constant (kadb), only the last one could be determined accurately, and therefore CBF must be determined from this parameter only. From the error analysis of the adiabatic solution, it was concluded that for the D2O clearance experiments described in Part II, the coefficient of variation of CBF was approximately 7% in gray matter and 22% in white matter.

Congenital Ewing's sarcoma of the humerus

We report an extremely rare case of Ewing's sarcoma (ES) of the humerus in a Chinese neonate. Plain radiography and magnetic resonance imaging showed extensive neoplastic involvement of the humeral diaphysis and adjacent soft tissues, confirmed on histology and immunohistochemistry as being due to ES. This is the first report of congenital ES in a long bone. Since ultrasound at 20 weeks gestation showed a normal fetal skeleton, the ES may have begun to develop in the late middle or third trimester.

Temporal sampling requirements for the tracer kinetics modeling of breast disease

The physiological parameters measured in the tracer kinetics modeling of data from a dynamic contrast-enhanced magnetic resonance (MR) breast exam (blood flow-extraction fraction product [FE], volume of the extracellular extravascular space [Ve], and blood volume [Vb]) may enable non-invasive diagnosis of breast cancer. One of the factors that compromises the accuracy and precision of the parameter estimates, and therefore their diagnostic potential, is the temporal resolution of the MR scans used to measure contrast agent (gadolinium-diethylenetriamine pentaacetic acid [Gd-DTPA]) concentration in an artery (arterial input function [AIF]) and in the tissue (tissue residue function [TRF]). Using computer simulations, we have examined, for several AIF widths, the errors introduced into estimates of tracer kinetic parameters in breast tissue due to insufficient temporal sampling. Temporal sampling errors can be viewed as uncertainties and biases in the parameter estimates introduced by the uncertainty in the relative alignments of the AIF, TRF, and sampling grid. These effects arise from the model's inherent sensitivity to error in either the AIF or TRF, which is dependent on the values of the tracer kinetic parameters and increases with AIF width. Based on the results of the simulations, to ensure that the error in FE and Ve will be under 10% of their true values, we recommend a rapid bolus injection of contrast agent (approximately 10 s), that the AIF be sampled every second, and that the TRF be sampled every 16 s or less. An accurate measurement of Vb requires that the TRF be sampled at least every 4 s. The results of these investigations can be used to set minimum dynamic imaging rates for tracer kinetics modeling of the breast.

Machinery-related injuries: regional rural injury study--I (RRIS--I)

Although it is known that farm machinery is a source of serious and catastrophic farm work-related injuries, little is known about the magnitude of, and potential risk factors for, this problem. The study population is from the five-state Regional Rural Injury Study--I (RRIS--I) that included 3,939 farm households and 13,144 persons who were interviewed about their injury experience and farming operation-related exposures during 1990. Rates were calculated for sociodemographic variables and various exposures pertinent to large farm machinery (excluding tractors). Multivariate analyses were conducted using logistic regression, based on a model developed a priori and further confirmed using backward stepwise logistic regression. Among the total farming-related injury events (n = 764), 151 (20%) were related to large machinery use (1,127 injured persons per 100,000 persons per year). Through multivariate analyses, several variables were associated with elevated rate ratios that were important in both models: hours worked per week on the farm (40-59, 60-79, 80+); operation of an auger; field crops as the enterprise requiring the most time; and male gender. In addition, in the backward stepwise model, certain marital status categories (married; separated/widowed/divorced) were also associated with elevated rate ratios that were important. The majority of injury events occurred while persons were lifting, pushing, or pulling (21%), adjusting a machine (20%), or repairing a machine (17%). While only 5% of the cases were hospitalized, 79% required some type of health care. Among all injured persons, 34% were restricted from regular activities for 1 week or more and 19% were restricted for 1 month or more; 25% continued to have persistent problems. In summary, the RRIS-I permitted one of the most comprehensive studies of agricultural machinery-related injuries, to date. The findings indicate that these injuries represent a significant problem, based on the relevant rates, potential risk factors, and consequences from trauma.

CT features of calcifications in abdominal malignant fibrous histiocytoma

The purpose of this study was to describe the computed tomographic (CT) features of intralesional calcifications in abdominal malignant fibrous histiocytomas (MFH). Forty-three pathologically proven abdominal MFH with preoperative CT were retrospectively reviewed, of which seven tumors with intralesional calcifications were studied with pathohistologic correlation. All seven calcified abdominal MFH belonged to the storiform-pleomorphic subtype with peripherally located calcifications that appeared as either lumpy (three cases) or ringlike (four cases), which were due to the presence of variable amounts of osseous (six cases) and chondroid metaplasia (two cases). About 16% of abdominal MFH, especially the storiform-pleomorphic subtype, exhibited metaplastic calcifications which were characteristically located at the periphery of the tumor and appeared as either lumpy or ringlike on CT.

Subclavian mycotic aneurysm presenting as mediastinal abscess

A 60-year-old man was admitted to a hospital for evaluation of intermittent fever, dysphagia, hoarseness, and general chest discomfort. Great vessel mycotic aneurysm was suspected when antibiotic trials failed and chest X-ray showed paraaortic mass with pleural effusion mimicking mediastinitis. Although the correct diagnosis of mycotic aneurysm of innominate artery was made thereafter and vigorous treatment was initiated immediately, this patient succumbed to overwhelming sepsis, probably due to a 2-week delay in another hospital. This case is reported to remind readers of the possibility of this unusual location of mycotic aneurysm. A high index of suspicion should be maintained to make an earlier diagnosis and obtain better prognosis. Computed tomography and 3D magnetic resonance angiography also significantly improve the diagnosis when mycotic aneurysm location is unusual and presentation is equivocal.

Congenital bilateral cystic neuroblastoma with liver metastases and massive intracystic haemorrhage

A case of bilateral cystic neuroblastoma with liver metastases in a newborn is reported. CT showed a 10 cm right suprarenal multicystic mass and numerous hepatic cystic masses with intracystic fluid-fluid levels. Multiple smaller cystic lesions were also present in the left adrenal gland. To our knowledge, the CT findings of neonatal bilateral cystic neuroblastoma with liver metastasis and massive acute intracystic haemorrhage has not been previously documented.