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Biomedical subjects

J A Brink

Publications and source records attributed to J A Brink.

At least 19 recordsLinked to original sources
PubMed1996

Imaging for ureteropelvic junction obstruction in adults.

The three goals of imaging for ureteropelvic junction (UPJ) obstruction are to determine the presence and degree of renal obstruction, to assess renal function, and to determine the cause of the problem. The diagnostic techniques are intravenous urography, which is unreliable; ultrasonography, with the addition of pulsed Doppler technology; diuretic scintigraphy; and pressure-flow studies (Whitaker test), which is the only direct clinical test of renal outflow resistance. Voiding cystography, retrograde ureteropyelography, and CT have utility in some patients. In determining the cause of obstruction, the patient often is evaluated for crossing vessels using angiography, endoluminal ultrasonography, or spiral CT. It is not possible to formulate a single algorithm for radiographic evaluation of suspected UPJ obstruction, but in the average adult patient, urography and diuretic scintigraphy are sufficient.

Adult↗
PubMed1996

Bowel wall thickening: differentiation of inflammation from ischemia with color Doppler and duplex US.

PURPOSE: To determine whether ultrasonography (US) can be used to differentiate inflammatory from ischemic bowel wall thickening. MATERIALS AND METHODS: Thirty-five patients (aged 23-96 years) with inflammatory or ischemic bowel wall thickening underwent US. Thickness was recorded, echotexture categorized, color Doppler flow graded, presence of intramural arterial signal recorded, and resistive index calculated. RESULTS: The difference between inflammatory and ischemic bowel wall thicknesses was not significant (P = .49). Differences in color Doppler flow (P < .0001), arterial signal (P = .0005), and bowel wall echotexture (P < or = .0200) between patients with inflammatory and ischemic bowel wall thickening were significant. Absence of or barely visible color Doppler flow and absence of arterial signal suggested ischemia; readily visible color Doppler flow and a stratified echotexture suggested inflammation. A resistive index less than 0.60 indicated inflammation. The difference in resistive index between the two groups was not significant (P = .12). CONCLUSION: Duplex and color Doppler flow US are helpful in differentiation between ischemic and inflammatory bowel wall thickening.

Case-Control Studies↗
PubMed1996

Anatomic distribution of pulmonary emboli at pulmonary angiography: implications for cross-sectional imaging.

PURPOSE: To determine how often emboli detected angiographically in peripheral pulmonary arterial branches would be missed with cross-sectional imaging. MATERIALS AND METHODS: Seventy-nine of 88 consecutive pulmonary angiograms interpreted as positive for pulmonary emboli were reviewed retrospectively to detect pulmonary emboli. Three angiograms interpreted as negative when reviewed retrospectively were excluded. Findings of 76 angiograms in 76 patients (32 men, 44 women; aged 19-85 years) were correlated with the results of scintigraphy (n = 72) and Doppler ultrasound (n = 60), clinical presentation (n = 76), and follow-up with chart review (n = 72). RESULTS: Two hundred five emboli were identified. Nineteen patients had solitary emboli. Sixty emboli were in the upper lobes. The largest arterial branch with pulmonary embolism was lobar in 14 patients, segmental in 38, subsegmental in 20, and smaller in three. CONCLUSION: If cross-sectional imaging can depict emboli in only segmental and larger arterial branches, then emboli in 23 of 76 patients (30%) would have been missed with cross-sectional imaging.

Female↗
PubMed1996

Helical (spiral) CT angiography for identification of crossing vessels at the ureteropelvic junction.

OBJECTIVE: The purpose of this study was to determine the feasibility of imaging crossing vessels at the ureteropelvic junction (UPJ) with helical (spiral) CT angiography for planning surgical repair of symptomatic UPJ obstruction. SUBJECTS AND METHODS: Twenty-four consecutive patients with symptomatic UPJ obstruction were imaged with dual-phase, contrast-enhanced helical CT (collimation, 3 mm; pitch, 1.3-1.7; reconstruction interval, 2 mm; early phase, 20-42 sec; and delayed phase, 90-112 sec after initiation of IV contract material injection [125 ml of ioversol containing 320 mg of iodine per ml, delivered at 4-5 ml/sec]). All imaging data were viewed interactively on an imaging workstation. Prospective on-line interpretations were correlated with subsequent surgical and clinical findings at laparoscopy (n=3), open surgical repair (n=2), or ureteronephroscopic endopyelotomy (n=11). Vessels at the UPJ that were 2 mm or more in diameter were believed to be significant. Review of the transaxial images was performed to determine qualitatively the relative usefulness of the early versus the delayed phases for distinguishing arteries from veins. Multiplanar reformations also were retrospectively reviewed and compared with direct pyelograms to determine the accuracy with which the location of the UPJ and the proximal ureteral course were depicted with helical CT. RESULTS: Eleven of 24 (46%) patients collectively had 11 anterior and three posterior vessels (> or = 2 mm in diameter) crossing the UPJ on helical CT. Distinction between arteries and veins was significantly better on early-phase than on delayed-phase images (p=.01). Visualization of the UPJ and the proximal ureteral course was good or excellent for 18 (78%) of 23 patients for whom pyelograms were available, regardless of the presence of a ureteral stent (p>.05). Laparoscopy and open surgery findings were in agreement with helical CT angiograms for five of five patients. Uncomplicated endopyelotomy was performed for 11 patients in whom no significant vessels were seen posterior or posterolateral to the UPJ. CONCLUSION: Helical CT angiography can depict vessels crossing the UPJ and is valuable in planning surgical management.

Adolescent↗
PubMed1996

Ghosting of pulmonary nodules with respiratory motion: comparison of helical and conventional CT using an in vitro pediatric model.

OBJECTIVE: The study was designed to compare helical CT with varying pitch and reconstruction intervals and conventional CT for revealing pulmonary nodules in a model that simulates respiratory motion in children. MATERIALS AND METHODS: CT scans were obtained in an experimental model with one nodule (3 or 10 mm) in each scan. One-second scans were obtained at rates of 10, 20, and 30 respirations per minute using conventional CT with 4-mm collimation and table incrementation and helical CT with 4-mm collimation and either 4-mm/sec (pitch, 1:1) or 8-mm/sec (pitch, 2:1) table speed. Reconstructions were at 1-, 2-, and 4-mm intervals for scans obtained using 4-mm/sec table speed and at 1- and 4-mm intervals for scans obtained using 8-mm/sec table speed. Images were independently reviewed by three radiologists who estimated the number of nodules on each image. RESULTS: Ghosting (depiction of more than one nodule in a study) was seen in 79%, 80%, and 75% of helical CT scans obtained with a 1:1 pitch using 1-, 2-, and 4-mm reconstruction intervals, respectively. By comparison, ghosting was seen in only 54% and 58% of helical CT scans with a 2:1 pitch using 1-mm reconstruction intervals and 4-mm reconstruction intervals, respectively, and in 56% of conventional CT scans (p < .0001). A single nodule was detected on all other scans, and at least one nodule was seen on all scans. CONCLUSION: Ghosting of nodules is common in this model. Ghosting was seen less often on conventional scans and helical scans with 2:1 pitch than it was on helical scans with 1:1 pitch. Nonetheless, ghosting was seen on more than 50% of all scans with each technique.

Artifacts↗
PubMed1995

Technical optimization of spiral CT for depiction of renal artery stenosis: in vitro analysis.

PURPOSE: To determine empirically the effect of scan parameters and postprocessing techniques on depiction accuracy of renal artery stenosis with spiral computed tomographic angiography. MATERIALS AND METHODS: Critical (85%) and noncritical (45%) stenoses in the coronal plane were modeled in vitro and scanned with 12 combinations of collimation (1, 2, or 3 mm), table increment (pitch = 1-2),2 and reconstruction interval (0.5 or 1.0 mm). Five test images were generated for each spiral scanning technique: multiplanar reformation (MPR), maximum-intensity projections (MIPs: coronal MIP [MIPcor], coronal MIP targeted to phantom vessel and surrounding fat [target MIPcor]), transaxial imaging, and transaxial MIP. RESULTS: With 3-mm collimation, critical stenosis was overestimated to the point of occlusion on MIPcor images and underestimated on MPR and target MIPcor images. A 0.5-mm reconstruction interval was marginally beneficial for 1- and 2-mm collimation, but noise was prohibitive with 1-mm collimation. CONCLUSION: Critical renal artery stenosis is best depicted with 2-mm collimation, 2-4-mm table increment, and 1-mm reconstruction interval.

Humans↗
PubMed1995

Dynamic incremental CT: effect of volume and concentration of contrast material and patient weight on hepatic enhancement.

PURPOSE: To develop an individualized approach to the intravenous administration of contrast material for hepatic computed tomography (CT). MATERIALS AND METHODS: Two hundred patients were randomized into eight protocols. Each group received different volumes and concentrations of contrast material. For each protocol, maximum hepatic enhancement (MHE) was calculated, with an adjustment for iodine dose and patient weight. The contrast enhancement index (CEI) and optimum scanning interval were calculated for hepatic enhancement thresholds of 10-60 HU. RESULTS: The MHE calculated as a function of patient weight was 96 HU +/- 19 per gram of iodine per kilogram of body weight. CEIs obtained with a contrast material concentration of 240 mg of iodine per milliliter were inferior to those obtained with a concentration of 320 or 350 mg I/mL. At low enhancement thresholds, the volume of contrast material had a more important effect than the concentration on CEI and optimum scanning interval; at high thresholds, concentration had a more important effect. CONCLUSION: For a patient of known weight, one can calculate the iodine dose needed to provide a desired level of hepatic enhancement. Use of a contrast material with a concentration of 240 mg L/mL is not recommended for dynamic incremental hepatic CT, except in small patients (eg, those weighing less than 73 kg).

Body Weight↗
PubMed1995

Hepatic spiral CT: reduction of dose of intravenous contrast material.

PURPOSE: To assess the potential for reduction of contrast material dose in hepatic spiral computed tomography (CT). MATERIALS AND METHODS: Four hundred eighty-seven outpatients were randomized prospectively into nine biphasic and eight uniphasic injection protocols: 75, 100, or 125 mL of 240, 300, or 350 mg of iodine per milliliter of iohexol (18-44 grams of iodine). Protocols were compared according to the maximum hepatic enhancement (MAX) and the contrast enhancement index (CEI). RESULTS: Uniphasic injection was superior to biphasic injection for all protocols. No statistically significant difference in contrast enhancement was present for 38-44 grams of iodine with the uniphasic technique. Adequate enhancement thresholds (MAX > 50 HU, CEI at 30 HU > 300 HU x sec) were exceeded in more than 70% of heavy patients ( > 183 lb [83 kg]) with uniphasic injection of 38 g. For thin patients ( < 183 lb [83 kg]), uniphasic injection of 26 g produced adequate enhancement. CONCLUSION: Contrast material dose may be reduced by up to 40% in thin patients undergoing hepatic spiral CT after uniphasic injection of contrast material; this may result in substantial cost savings.

Adult↗
PubMed1995

Diagnosis of venoocclusive disease of the liver after bone marrow transplantation: value of duplex sonography.

OBJECTIVE: The purpose of this study was to determine if duplex sonography of the hepatic vasculature can be used to detect venoocclusive disease in patients who have had bone marrow transplantation. SUBJECTS AND METHODS: Twenty-seven bone marrow transplant recipients were serially studied with hepatic duplex sonography before (n = 27) and biweekly after (n = 136) transplantation. Duplex waveforms were obtained from the hepatic artery and the portal and hepatic venous systems. Clinical records were reviewed to confirm the clinical diagnosis of venoocclusive disease (n = 5), including its time of onset and duration. Patients with venoocclusive disease were further split into two groups: those with clinically active disease and those with clinically inactive disease. The resistive index in the hepatic artery, the velocity in the portal vein, and the differences among bone marrow transplant values before and after transplantation were compared among the groups. RESULTS: On the basis of data obtained before transplantation, a resistive index greater than 0.76 and a change in resistive index greater than 0.10 after transplantation were considered abnormal. Similarly, velocity in the portal vein after transplantation was considered abnormal when the value was less than 4.3 cm/sec or more than 50.3 cm/sec. There was no statistically significant difference in the resistive index in the hepatic artery or velocity in the portal vein among patient groups. Hepatopetal portal venous flow was shown in 26 of 27 patients during the study. Portal venous flow was reversed in one patient with venoocclusive disease. Appropriately directed hepatic venous flow was demonstrated in all 27 patients. CONCLUSION: Our study shows that resistive index in the hepatic artery, velocity and flow direction in the portal vein, and flow direction in the hepatic vein as detected by duplex sonography are of no value in the diagnosis of venoocclusive disease after transplantation.

Adult↗
PubMed1995

Imaging of the common bile duct during laparoscopic cholecystectomy: sonography versus videofluoroscopic cholangiography.

OBJECTIVE: The purpose of this prospective study was to compare the accuracies of laparoscopic sonography and laparoscopic videofluoroscopic cholangiography in detecting common bile duct stones and in identifying ductal anomalies during laparoscopic cholecystectomy. SUBJECTS AND METHODS: Ninety-five patients who underwent laparoscopic videofluoroscopic cholecystectomy were prospectively studied with laparoscopic sonography and laparoscopic videofluoroscopic cholangiography. The number of successful studies, the time required to complete the study, and complications resulting from the study were recorded. The biliary system was evaluated for complete visualization of the common bile duct, visualization of the cystic duct, ductal anomalies, maximum diameter of the common bile duct, and common bile duct stones and/or debris. Also determined was whether laparoscopic sonographic findings altered operative management. RESULTS: Laparoscopic sonography was successfully performed in 93 of 95 patients, and laparoscopic videofluoroscopic cholangiography was successfully performed in 90 of 95 patients. The time required to complete laparoscopic sonography ranged from 3 to 18 min (mean +/- SD, 8 +/- 3 min), and that required to complete laparoscopic cholangiography ranged from 5 to 28 min (mean +/- SD, 14 +/- 6 min). Laparoscopic sonography visualized the complete common bile duct in 84 of 93 patients, and laparoscopic cholangiography did so in 86 of 90 patients. Laparoscopic sonography showed the cystic duct in 87 of 93 patients, and laparoscopic cholangiography did so in 80 of 90 patients. Laparoscopic sonography showed no ductal anomalies in any of the 93 patients. Laparoscopic cholangiography showed ductal variants in 13 of 90 patients; however, 11 of the variants were proximal to the sonographic scan plane. Laparoscopic sonography showed common bile duct stones in 12 of 93 patients, and laparoscopic cholangiography did so in five of 90 patients. Laparoscopic sonography altered operative management in two of 93 patients. CONCLUSION: Our results show that laparoscopic sonography is as accurate as laparoscopic videofluoroscopic cholangiography in visualizing the common bile duct and cystic duct and in detecting common bile duct stones. However, the data are too limited to determine whether laparoscopic sonography is as accurate as laparoscopic cholangiography in detecting ductal anomalies.

Adult↗
PubMed1995

Technical aspects of helical (spiral) CT.

Care must be taken to optimally select settings for collimation, table feed, and reconstruction interval for successful helical CT and associated special application such as CT angiography. Thus, prospective planning is critical for optimal 3-D imaging. Generally, one wishes to minimize all of these parameters to maximize longitudinal resolution; however, one must be aware of the tradeoffs associated with these choices. Pixel noise increases with decreasing collimation. Limiting the table feed to a value equal to the collimation (pitch of 1:1) limits broadening of the effective slice thickness associated with the table motion but also limits the scan coverage. Generally, one may accept a table feed up to twice the collimation (pitch of 2:1) on modern equipment with current software. Reconstruction intervals should also be selected to satisfy the clinical need. When multiplanar and 3-D imaging is desired, the reconstruction interval should be selected such that at least two slices are generated per table increment.

Algorithms↗
PubMed1995

MR imaging of the biliary system.

MR imaging has a distinct role to play in two areas of hepatobiliary imaging that continue to challenge the radiologist--evaluation of the gallbladder and evaluation of the jaundiced patient. The distinction between primary gallbladder carcinoma and chronic cholecystitis remains a diagnostic dilemma for all cross-sectional imaging modalities. MR imaging may be useful in detection of local invasion or metastatic disease. Gallstones are commonly seen coincidentally on cross-sectional imaging studies; the imaging characteristics of gallstones must be well-understood for the interpretation of routine abdominal MR examinations. The evaluation of jaundice is a multimodality process, often requiring three or four separate imaging techniques to determine the cause of biliary obstruction. MR may supplant more invasive techniques for anatomic depiction prior to therapeutic intervention.

Biliary Tract↗
PubMed1994

Dissolution of calcified gallstones. Part I. Correlation of in vitro dissolution kinetics in methyl tert-butyl ether with patterns of calcification by computed tomography.

RATIONALE AND OBJECTIVES: The authors evaluated the relationship between stone computed tomography (CT) attenuation patterns and the kinetics of dissolution with methyl tertbutyl ether (MTBE). METHODS: Single moderately and heavily calcified gallstones from 40 patients were selected from a gallstone library and classified for pattern of calcification by in vitro CT scan (dense, rim, core, and laminated). Each stone was placed in a 10-mL aliquot of MTBE for 24 hours. Stone residue was blotted dry and weighted at 8, 16, and 24 hours. Results were normalized with respect to stone size. RESULTS: Only 1 of 40 (4%) specimens dissolved to particulate matter that was smaller than 2 mm. All (6 of 6) stones that were densely calcified showed virtually no dissolution. The rate of gallstone dissolution varied temporally within the rim, core, and laminated stone categories and was related to the composition of the layer exposed to the solvent at any given time. CONCLUSION: The success and rate of dissolution may be predicted by the pattern of calcification as determined by computed tomography (CT).

Cholelithiasis↗
PubMed1994

Dissolution of calcified gallstones. Part II. Evaluation of edetic acid preparations for dissolution of residue after in vitro methyl tert-butyl ether treatment.

RATIONALE AND OBJECTIVES: The authors assessed the potential of edetic acid (EDTA) preparations to dissolve the residue of calcified gallstones partially treated with methyl tert-butyl ether (MTBE). METHODS: Nineteen triplets (57 gallstones) were submitted to dissolution in EDTA, urea-EDTA, and an MTBE control for 48 hours after initial partial dissolution in MTBE for 24 hours. Results were compared with findings at specimen computed tomography and crystallographic analysis. All data were corrected for differences in stone size. RESULTS: In all three treatment groups (EDTA, urea-EDTA, MTBE), almost identical dissolution outcomes were observed within each triplet. Most triplets that dissolved displayed a laminated or a core-calcification pattern and consisted primarily of cholesterol. Specimens that dissolved poorly in all three groups displayed dense calcifications or thick calcified rims and were classified as pigment stones. CONCLUSION: Because no statistically significant differences in dissolution were found among the EDTA, urea-EDTA, and MTBE treatments, we conclude that EDTA preparations are not superior to the continued use of MTBE for dissolution of residue after initial MTBE treatment.

Chelating Agents↗
PubMed1994

Helical CT: principles and technical considerations.

The performance of helical CT requires several user-defined parameters that exceed the requirements of conventional CT. One needs to carefully select the collimation, table increment, and reconstruction interval. Minimizing these parameters maximizes longitudinal resolution but with various trade-offs. Decreasing the collimation decreases the effective section thickness but increases pixel noise. Limiting the table increment to a pitch of 1 limits the broadening of the effective section thickness associated with the helical technique but also limits the coverage that can be achieved with a given helical scan. Our general practice is to minimize the collimation to cover the volume of interest and to accept a pitch up to 2, provided that we are using 180 degree interpolation. The reconstruction interval is also minimized to maximize longitudinal resolution but with trade-offs of increased image processing time, data storage requirements, and physician time for image review. For routine diagnosis, we recommend reconstruction of one to two sections per table increment, and, for multiplanar and three-dimensional imaging, we recommend at least three sections be reconstructed per table increment. The scan duration is dictated by both patient and machine factors.

Artifacts↗
PubMed1994

Prediction of gallstone composition: synthesis of CT and radiographic features in vitro.

PURPOSE: To test a morphoradiographic algorithm designed to predict the composition of gallstones with use of computed tomography (CT) to define calcification patterns. MATERIALS AND METHODS: Two reviewers retrospectively evaluated the radiographic features of 120 separate in vitro specimens (59 radiopaque and 61 radiolucent), then classified the stones into several categories of composition with the algorithm. RESULTS: The most useful features for prediction of cholesterol composition were, in order of decreasing importance, stone shape, absence of dense calcification on plain radiographs, overall CT attenuation not higher than that of water, presence of a second generation of smaller stones, and a peripheral cover of calcification detected on CT scans of aging cholesterol stones. The greatest error occurred in distinction between stones with mixed composition (50%-79% cholesterol) and older stones with higher cholesterol content (80%-95% cholesterol). CONCLUSION: The range of qualitative CT appearances advances the possibility of predicting gallstone composition and potential outcome of nonsurgical treatment.

Bile Pigments↗