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Biomedical subjects

T L Lawson

Publications and source records attributed to T L Lawson.

At least 37 records · Page 2Linked to original sources
PubMed1988

Efficacy of quantitative hepatobiliary scintigraphy and fatty-meal sonography for evaluating patients with suspected partial common duct obstruction.

In this study we evaluated by blinded design the diagnostic efficacy of two noninvasive techniques, quantitative hepatobiliary scintigraphy (QHS) and fatty-meal sonography (FMS), for evaluating patients with suspected partial common duct obstruction. Quantitative hepatobiliary scintigraphy was performed on 56 cholecystectomized individuals (22 asymptomatic controls, 28 patients with suspected partial common duct obstruction, and 6 nonjaundiced cirrhotics) and FMS was done in 51 cases. For QHS, time-activity curves were generated for regions of interest over the liver, hepatic hilum, and common duct. For FMS, we measured common duct diameter before and 45 min after a fatty meal (Lipomul, 1.5 ml/kg). Each of the 28 patients with suspected partial common duct obstruction and 6 cirrhotic patients underwent endoscopic retrograde cholangiography, often accompanied by sphincter of Oddi manometry. Findings from these examinations were taken as the gold standard to determine the presence or absence of conditions that could account for intermittent symptomatic partial common duct obstruction. The most sensitive indicators for a positive test were a 45-min isotope clearance of less than 63% for QHS and a common duct increase of greater than or equal to 2 mm after the fatty meal for FMS. Of 28 patients with suspected partial common duct obstruction, 15 were judged to be true-positive and 13 true-negative. The 6 cirrhotic patients were without common duct obstruction. The study findings showed that each test had a 67% sensitivity that improved to 80% when the findings from both test results were combined. The specificity of QHS was 85% and that of FMS was 100%. All 6 cirrhotic patients had negative findings on FMS and 4 were false-positive on QHS. The true-positives included 8 patients with a small common duct stone and 6 with obstructive sphincter of Oddi dysfunction (4 stenosis, 2 dyskinesia). We conclude that noninvasive QHS and FMS afford good sensitivity and specificity for evaluating cholecystectomized patients with suspected partial common duct obstruction.

Adult↗
PubMed1988

Computed tomography examination of periampullary neoplasms.

The hospital records of 24 patients with periampullary neoplasms were reviewed. The clinical triad of jaundice, pain, and weight loss and the radiographic imaging triad of dilated biliary ducts, dilated pancreatic duct, and periampullary mass should suggest the diagnosis of periampullary neoplasm.

Adenocarcinoma↗
PubMed1988

Flow reversal in the normal carotid bifurcation: color Doppler flow imaging analysis.

One hundred carotid bifurcations in young asymptomatic volunteers were examined with color Doppler flow imaging in an attempt to determine the frequency, configuration, magnitude, and duration of flow reversal. Areas of flow reversal were identified in all but one bifurcation. Just proximal to the bifurcation, flow reversal was typically located peripherally, opposite the origin of the external carotid artery. Distal to the bifurcation, flow reversal in the internal carotid artery typically assumed a linear configuration in the center of the vessel, extending from the superficial to the deep wall. Variations of these patterns were common. On the average, flow reversal occupied 33% of the lumen of the carotid bulb and extended for a distance of 14 mm. The average duration of flow reversal was 22% of the total cardiac cycle, with reversal typically occurring at peak systole and being replaced by static blood during diastole. These findings indicate that flow reversal in the carotid bifurcation is a normal phenomenon with a variable configuration, magnitude, and duration.

Adult↗
PubMed1988

Renal calculi: sensitivity for detection with US.

The sensitivity of sonography in the detection of renal calculi was tested in a three-phase study in 100 patients. In phase 1, ultrasonographic (US) scanning was performed after review of abdominal radiographs and renal tomograms in 30 patients who had undergone extracorporeal shock wave lithotripsy (ESWL). In this group the sensitivity of US for detecting stones was 98%. In phase 2, scanning was performed in 30 post-ESWL patients without prior review of radiographs or tomograms. The sensitivity of US for stone detection in this group was 95%. In phase 3, sonography was performed in a blinded fashion on a random mix of post-ESWL patients and patients who had undergone urography for reasons unrelated to nephrolithiasis. The sensitivity of US for stone detection in this group of 40 patients was 91%. The overall sensitivity in all three groups was 96%, which was superior to the performance of abdominal radiography and slightly inferior to the combination of abdominal radiography and renal tomography. The ability to detect kidney stones with US depended on stone size but was independent of stone location or patient size. The study findings suggest that US is an effective means for detecting kidney stones in patients with suspected nephrolithiasis.

Humans↗
PubMed1988

Roscoe Miller award. Fatty-meal sonography for evaluating patients with suspected partial common duct obstruction.

We evaluated the efficacy of fatty-meal sonography for identifying patients with partial common duct obstruction. The test consisted of initial control measurements of common duct diameter followed by repeated measurements every 15 min for 60 min after a fatty meal consisting of Lipomul (1.5 ml/lb). The rationale proposed for the fatty-meal test is that in the presence of partial common duct obstruction, fat-induced increases in bile flow related to increased circulating levels of cholecystokinin are associated with an increase in the diameter of the common duct. Initial analysis of our data indicated that a change in diameter of +/- 1 mm was within the range of measurement error or possibly physiologic variation. In 44 control subjects (24 without a gallbladder), the common duct diameter either remained unchanged, showed an insignificant change of +/- 1 mm, or decreased (greater than or equal to 2 mm). The common duct diameter never showed an increase of more than 1 mm. The results of fatty-meal sonography in 47 patients with suspected partial common duct obstruction were negative in all 28 true-negative cases (specificity, 100%) and were positive (common duct increased by greater than or equal to 2 mm) in 14 of 19 true-positive cases (sensitivity, 74%). Thus, in this study a positive test finding always indicated partial common duct obstruction. Of the true-positive cases, fatty-meal sonography correctly identified seven of eight patients with cryptic obstructive sphincter-of-Oddi dysfunction (stenosis or dyskinesia) and five of nine patients with commun duct stones. We conclude that fatty-meal sonography is a useful noninvasive screening test for evaluating patients with suspected partial common duct obstruction.

Adolescent↗
PubMed1987

High resolution surface coil magnetic resonance imaging of the joints: anatomic correlation.

Magnetic resonance imaging appears to be a particularly promising approach to the evaluation of articular and periarticular abnormalities. Its ability to produce images in multiple planes directly (without reconstruction) provides a unique advantage over CT for the radiologist when he attempts to interpret the complex three dimensional anatomy of most joints. The inherent contrast resolution of MR is excellent, and with the use of surface coils, spatial resolution is sufficient to permit the identification of the small soft tissue structures in and around joints. Artifacts generated by respiratory and cardiac motion are not a problem in MRI of the joints as they are in MR scanning of the body. Based on all these qualities, we believe that MRI will play an important role in the diagnosis of joint abnormalities.

Ankle Joint↗
PubMed1987

Enlarged parathyroid glands: high-resolution local coil MR imaging.

Twenty-two patients with primary hyperparathyroidism underwent high-resolution magnetic resonance (MR) imaging with local (surface) coils for preoperative localization of enlarged parathyroid glands. The MR studies were interpreted prospectively and the results compared with findings at surgery and the results of computed tomography (CT), ultrasonography (US), and thallium-technetium scintigraphy (TTS). The sensitivity and specificity of MR imaging were .74 and .88, respectively. The sensitivity/specificity for the other modalities were as follows: 74/.95 for CT, .59/.82 for US, and .82/.98 for TTS. Enlarged parathyroid glands displayed a medium-intensity signal on T1-weighted images and a marked increase in intensity on T2-weighted images, but the degree of increase varied considerably.

Adenoma↗
PubMed1987

Treatment of blunt hepatic injuries: role of CT.

Serial dynamic upper abdominal computed tomography (CT) studies were performed on 20 patients as part of the conservative treatment of blunt hepatic injuries (hematoma, laceration, or fracture). Fourteen of these patients had either major or minor associated hemoperitoneum. In 13 patients, hemoperitoneum was either significantly reduced or absent by 1 week. A severe delayed hemorrhage occurred in one patient 7 1/2 days after admission; a large and unchanged volume of intraperitoneal fluid had been seen on a preceding abdominal CT scan. One other patient who had a satisfactory response underwent surgery for a pancreatic laceration. Serial abdominal CT studies are an integral part of the conservative treatment of blunt hepatic injuries and seem to be useful in monitoring resorption of hemoperitoneum and the pattern of healing of intrahepatic hematomas, lacerations, and fractures.

Hemoperitoneum↗
PubMed1987

Sonographic evaluation of resting gallbladder volume and postprandial emptying in patients with gallstones.

We investigated fasting gallbladder volume and gallbladder emptying in response to a fatty meal in 20 patients with asymptomatic gallstones and compared the results with findings from healthy controls. Compared with control subjects without gallstones, the majority of patients with gallstones exhibited a higher resting gallbladder volume, less fractional emptying after a fatty meal, and a higher postmeal residual volume. These abnormalities all appeared to stem from an abnormally high resting gallbladder volume. Whether the increased gallbladder volume and decreased postprandial fractional emptying in the gallstone patients represents a primary or secondary abnormality remains to be determined. The results suggest that in some patients decreased gallbladder contractility may contribute to gallstone development or proliferation.

Adult↗
PubMed1987

False-positive CT diagnosis of gallstones due to thickening of the gallbladder wall.

An erroneous CT diagnosis of cholelithiasis was made at our institution during the past year in seven patients who had thickening of the gallbladder wall. In all cases the mucosa, which had a high attenuation value, was misinterpreted as a calcified stone, and the low-attenuation thickened submucosa was misinterpreted as intraluminal bile surrounding the stone. Depending on the attenuation of the actual intraluminal bile, the pseudostone appeared peripherally calcified (five patients) or uniformly calcified (two patients). Careful analysis of the position and configuration of a suspected stone and of the outer margin of the gallbladder can help avoid an incorrect CT diagnosis of gallstones when high-attenuation thickened mucosa simulates a gallstone and low-attenuation submucosa looks like surrounding bile.

Adult↗
PubMed1987

Contrast optimization for the detection of focal hepatic lesions by MR imaging at 1.5 T.

The relative efficacies of different spin-echo pulse sequences at 1.5 T were evaluated in the detection of focal hepatic disease. Pulse sequences compared were spin-echo with a repetition time (TR) of 200 msec and echo time (TE) of 20 msec, with six excitations; TR = 300 msec, TE = 20 msec, with 16 excitations (T1-weighted sequences); and a double spin-echo with TR = 2500 and TE = 25 and 70, with two excitations (proton-density-weighted and T2-weighted pulse sequences, respectively). Respiratory-motion compensation, which involved a recording of the phase-encoding gradients (Exorcist), was used for the last two sequences. Spin-echo with TR = 2500 msec and TE = 70 msec was superior in lesion detection and contrast-to-noise ratio. The proton-density-weighted and T2-weighted sequences with respiratory compensation produced better artifact suppression than did the short TR, short TE T1-weighted sequence with temporal averaging. In contradistinction to prior results at 0.6 T, T2-weighted pulse sequences appear superior to T1-weighted pulse sequences with multiple excitations for both lesion detection and artifact suppression at 1.5 T.

Cysts↗
PubMed1986

Digital and conventional chest images: observer performance with Film Digital Radiography System.

The Film Digital Radiography System (FilmDRS) is a device with a laser optical film digitizer, 2,000 X 2,000 X 12-bit memory, and a 1,000-line video display. To evaluate the adequacy of this device for general radiography of the chest, four readers independently analyzed both radiographs and the corresponding video display of the digitized chest images of 150 patients, consisting of 100 images of abnormalities and 50 normal images. The overall results indicate equal sensitivity for the two systems. The FilmDRS, with interactive windowing, proved superior in the detection of hilar and mediastinal disease. X-ray film was superior in allowing detection of hyperlucent states. There was equivalent sensitivity for other disease categories. Superior specificity was achieved with conventional radiographs.

Analog-Digital Conversion↗
PubMed1986

Focal hepatic masses and fatty infiltration detected by enhanced dynamic CT.

A prospective evaluation of 185 consecutive patients with abdominal pain or suspected hepatic malignancy was performed to compare the diagnostic accuracy of contrast material-enhanced incremental dynamic computed tomography (IDCT) scans with plain CT scans for detection of hepatic masses and fatty infiltration of the liver. After a series of nondynamic plain CT scans, patients were examined at 7.5 scans/min during intravenous injection of 50 g of iodinated contrast material. Enhanced IDCT study was found to be an accurate, reproducible technique for liver evaluation. Of 155 neoplasms measured in 59 patients, liver-to-lesion differences of less than 10 HU were seen in only two tumors in IDCT scans as compared with 31 in plain CT scans. These differences were not significantly affected by lesion size for neoplasms greater than 6 mm in diameter. A confident diagnosis of fatty infiltration (23 patients) could be made when the spleen-minus-liver difference was 25 HU on enhanced IDCT scans and 10 HU on plain CT scans. In eight patients with liver metastases, there was little variation in the attenuation values of normal-appearing liver between serial examination studies (8 HU average).

Contrast Media↗
PubMed1986

CT of aortic dissections.

Dissecting aortic aneurysms are one of the few medical emergencies where prompt recognition is crucial. Contrast-enhanced computed tomography combined with dynamic scanning offers an excellent noninvasive means to evaluate patients with suspected aortic dissection. At the Medical College of Wisconsin, we retrospectively reviewed all patients who were referred to the Section of Computed Body Tomography with the diagnosis of suspected aortic dissection. Over 100 patients were studied. The sensitivity, specificity, and overall accuracy of computed tomography was greater than 95%.

Adult↗