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M T Keogan

Publications and source records attributed to M T Keogan.

At least 37 records · Page 2Linked to original sources
PubMed1998

Dynamic helical CT of the abdomen: prospective comparison of pre- and postprandial contrast enhancement.

PURPOSE: To investigate effects of a liquid meal on contrast material enhancement at dynamic helical computed tomography (CT). MATERIALS AND METHODS: Twenty healthy, fasting subjects underwent intravenous injection of nonionic contrast material at 4 mL/sec. Axial CT sections were obtained at a single level 15 seconds after injection, then every 5 seconds for 2 minutes. This protocol was repeated 1 week later, after ingestion of a 360-calorie liquid meal. Hepatic, splenic, and aortic attenuation were measured before and after contrast material administration. Peak enhancement level, time to peak enhancement, slope of hepatic enhancement, and hepatic, splenic, and aortic enhancement ratios were determined. RESULTS: Postprandial time to peak enhancement was 4.4 seconds earlier than preprandial (59.6 seconds +/- 9.0 [1 standard deviation] vs 64.0 seconds +/- 9.5; P < .02). No differences in maximum attenuation were found (P > .27). Postprandial maximum slope of hepatic enhancement and temporal and quantitative enhancement characteristics in aorta and spleen did not significantly differ. Postprandial hepatic-to-splenic enhancement ratios increased (P = .04), and aortic-to-hepatic ratios decreased (P = .01). Aortic-to-splenic ratios did not differ (P = .45). CONCLUSION: A liquid meal before intravenous injection of contrast material produces more rapid peak hepatic enhancement, with slightly increased relative hepatic enhancement. A patient's dietary status, however, should not influence the CT protocol.

Adult↗
PubMed1998

Diagnosis of pancreatic carcinoma: role of FDG PET.

OBJECTIVE: The purpose of this study was to investigate the role of positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) in differentiating benign from malignant disease in patients with possible pancreatic malignancy. SUBJECTS AND METHODS: All patients with a possible diagnosis of pancreatic carcinoma based on CT or ERCP findings were eligible for inclusion in this prospective study. PET imaging of the abdomen was performed in 37 patients and was interpreted as positive if FDG activity in the pancreas exceeded background activity and as negative if activity was less than or equal to background activity. Semiquantitative analysis was performed by calculating a standardized uptake ratio. Studies were reviewed independently by two radiologists, and results were correlated with biopsy results and with CT and ERCP findings. Sensitivity and specificity of FDG PET for revealing pancreatic malignancy was determined. RESULTS: FDG activity in the pancreas was increased in 24 patients, and adenocarcinoma was diagnosed in 22 of these patients (92%). Two patients (8%) with increased activity had benign disease, including one patient with chronic pancreatitis who showed no evidence of tumor at laparotomy and one patient with a mucinous cystic tumor who showed no malignant features at laparotomy. FDG uptake was low or normal in 13 patients, 10 of whom (77%) had benign disease. FDG uptake was also low in three patients with adenocarcinoma, whose tumor size ranged from 2 to 4 cm in diameter. The mean standardized uptake ratio value for malignant disease was 5.1 (range, 1.0-10.1) and for benign disease was 1.9 (range, 0.0-5.8) (p < .001). The sensitivity of FDG PET for revealing malignant disease in the pancreas was 88% and the specificity was 83%. CONCLUSION: FDG PET is a sensitive and specific noninvasive technique for the diagnosis of pancreatic malignancy.

Adenocarcinoma↗
PubMed1997

Humanized anti-CD4 monoclonal antibody therapy of autoimmune and inflammatory disease.

We have investigated the biological and therapeutic properties of a humanized anti-CD4 MoAb, hIgG1-CD4, in patients with refractory psoriasis and rheumatoid arthritis (RA). hIgG1-CD4 is a modulating, non-depleting MoAb, which induced a first-dose reaction in most patients treated. It provided brief symptomatic relief in both conditions, and psoriasis appeared easier to control with conventional agents after MoAb therapy. At the doses used, hIgG1-CD4 did not synergize therapeutically with the panlymphocyte MoAb CAMPATH-1H (C1H) in patients with RA treated sequentially with both agents. There were no serious adverse effects definitely attributable to therapy. Our results are compared with those of other CD4 MoAb studies, and factors influencing the outcome of therapy are discussed.

Adolescent↗
PubMed1997

Doppler US measurement of portal venous flow: variability in healthy fasting volunteers.

PURPOSE: To describe the intrinsic sampling variability of measurements of portal venous flow in healthy volunteers and to estimate the variability attributable to the sonographer, the subject, and the measurement. MATERIALS AND METHODS: In a randomized controlled fashion, nine sonographers measured portal venous flow in five subjects. Each sonographer measured portal venous flow in each volunteer during three separate sessions with three measurements per session. Analysis of variance was used to estimate the contribution of several factors to the observed variability. RESULTS: Overall mean portal venous flow was 390 mL/min +/- 234 (range, 18-1,511 mL/min). The estimated variance components were 1.1 (3%), 2.5 (7%), 7.2 (21%), and 24.0 (69%) for the subject, the sonographer, the interaction between subject and sonographer, and the measurement or intrinsic variability. Similar results were obtained when the analysis of variance was fit by using the rank and median of the measurements. CONCLUSION: Substantial variability exists in measurement of portal venous flow. Variability attributed to inherent differences in repeat measurements contributes more to overall variability than that attributed to either sonographers or subjects.

Adult↗
PubMed1997

Zebra pattern: a diagnostically challenging hepatic parenchymal enhancement pattern at CT arterial portography.

PURPOSE: To investigate the effect of arterial injection site and splenic volume on the hepatic zebra pattern seen at computed tomographic (CT) arterial portography. MATERIALS AND METHODS: Images from CT arterial portographic examinations, performed via either the splenic artery (SA)(n = 47) or superior mesenteric artery (SMA)(n = 51) in 98 patients, were reviewed. The hepatic parenchymal enhancement pattern was assessed by three blinded reviewers. Splenic volume was determined. RESULTS: Twenty-two of 98 (22%) CT arterial portographic studies showed a zebra pattern: 10 of 47 (21%) with injection via the SA and 12 of 51 (24%) with injection via the SMA. The mean percentage of hepatic parenchyma with nontumorous perfusion defects was 55% with the zebra pattern versus 12% without (P < .001). For SA injections, the mean splenic volume was lower in patients with the zebra patterns (321 vs 409 cm3, P = .09). For SMA injections, it was higher in patients with zebra patterns (372 vs 291 cm3, P = .10). CONCLUSION: The zebra pattern can cause difficulties in interpreting images. It is due to alternating, well-defined regions of portal venous hyper- and hypoperfusion; it likely has a multifactorial cause and is likely due to technical parameters such as the injection site, the volume of the spleen, and the hemodynamic effects of the tumor.

Adult↗
PubMed1997

Abdomen after a Puestow procedure: postoperative CT appearance, complications, and potential pitfalls.

PURPOSE: To evaluate the postoperative computed tomographic (CT) appearance, complications, and potential pitfalls after a Puestow procedure (lateral side-to-side pancreaticojejunostomy). MATERIALS AND METHODS: Forty CT examinations were performed after the Puestow procedure in 20 patients. Images were retrospectively reviewed by three radiologists. RESULTS: The pancreaticojejunal anastomosis was identified at 30 examinations and was immediately anterior to the pancreatic body or tail. The anastomosis contained fluid or gas on 11 scans and oral contrast material on four scans. On 15 scans, the anastomosis appeared as collapsed bowel without gas, fluid, or oral contrast material. The Roux-en-Y loop was identified on 28 (70%) scans and contained fluid or gas on 16 scans and oral contrast material on six scans. The Roux-en-Y loop appeared as collapsed bowel on six scans. When the anastomosis or Roux-en-Y loop contained fluid and gas, the appearance mimicked that of a pancreatic or parapancreatic abscess. Peripancreatic stranding was present on 28 scans and was due to either ongoing pancreatitis or postoperative change. Complications included 15 transient fluid collections, three abscesses, four pseudocysts, one hematoma, and one small-bowel and Roux-en-Y obstruction. CONCLUSION: Knowledge of the anatomy after a Puestow procedure is essential for accurate interpretation of CT scans.

Abscess↗
PubMed1997

Early systole in the healthy kidney: variability of Doppler US waveform parameters.

PURPOSE: To determine the sampling variability of intrarenal Doppler ultrasound (US) indexes of early systole in a screened population of healthy individuals. MATERIALS AND METHODS: Doppler US measurements were obtained in the superior, middle, and inferior regions of 132 kidneys in 66 healthy, potential kidney donors. All individuals subsequently underwent angiography. Systematic measurement differences and random effects were estimated for sampling from a particular parenchymal region, from a kidney in a subject, from an individual in a population, and from a vascular territory. RESULTS: Coefficients of variations ranged from 20% to 30%. Most (55%-66%) of the observed variation was attributable to random differences between repeated measurements in the same kidney. No systematic variations attributable to kidney region, vascular territory, right versus left kidney, or subject age were found for acceleration time, acceleration, or waveform shape. Some evidence of fixed variation between kidneys and between regions was found for peak systolic velocity, but the magnitude of this variation was small. Averages of repeated measurements may decrease the probability of exceeding the normal threshold for acceleration but not for acceleration time. CONCLUSION: Measurements of Doppler parameters of the early systole have substantial intrinsic variability. Thus, caution is needed when interpreting small changes in these measurements within a kidney or between individuals.

Adult↗
PubMed1997

Pancreatic malignancy: effect of dual-phase helical CT in tumor detection and vascular opacification.

PURPOSE: To determine the relative value of hepatic arterial and portal venous phase helical computed tomographic (CT) scans for tumor detection and vascular opacification in patients with pancreatic malignancy. MATERIALS AND METHODS: Ninety-five patients who had or were suspected of having pancreatic disease underwent dual-phase helical CT. Arterial phase scans were acquired 20-40 seconds after contrast material administration; venous phase scans, 70-100 seconds after administration. Three readers independently scored images in a blinded fashion for the presence of tumor, for lesion attenuation relative to normal pancreas, and for vascular opacification. RESULTS: The final diagnosis was pancreatic malignancy (n = 60), acute or chronic pancreatitis (n = 22), and normal pancreas (n = 13). The readers identified possible or definite tumors on arterial phase studies in 47-50 patients and on venous phase studies in 48-53 patients (P > .10). There was no statistically significant difference in tumor attenuation between scans from the two phases (P > .05). Agreement between the readers for tumor detection was not affected by the scanning phase (P > .10). Opacification of arteries and of veins was greater on arterial phase scans and on venous phase scans, respectively (P < .001). CONCLUSION: The acquisition of arterial phase scans in addition to venous phase scans does not result in improved detection of pancreatic malignancies.

Adult↗
PubMed1997

Contrast-enhanced CT of intrahepatic and hilar cholangiocarcinoma: delay time for optimal imaging.

OBJECTIVE: The purpose of this study was to determine the optimal time for obtaining delayed images with contrast-enhanced CT in patients who have intrahepatic or hilar cholangiocarcinoma. SUBJECTS AND METHODS: CT studies were performed in 25 consecutive patients with proven cholangiocarcinoma, including six patients who had undergone radiotherapy or chemotherapy. Dynamic images of the liver were obtained after 150 ml of IV contrast material was administered at 3 ml/sec. Delayed CT images were then obtained at 10, 20, and 30 min. Tumor-liver attenuation difference was determined quantitatively for each time period. Images were qualitatively evaluated by three observers for attenuation of the tumor (hypoattenuating, isoattenuating, or hyperattenuating) relative to the liver. Observer confidence for tumor detection was graded on a four-point scale. Dynamic and delayed images were compared for tumor conspicuity. RESULTS: On dynamic images, 18 tumors (72%) were hypoattenuating, six (24%) were isoattenuating, and one was heterogeneous. On delayed images, 15 (60%) of these 25 tumors were isoattenuating and nine (36%) were hyperattenuating compared with the liver. Tumor-liver attenuation difference was greatest on dynamic studies (p < .01) and did not differ significantly among the three delay times (p > .20). All tumors seen on delayed images were also seen on dynamic images; however, in three patients (12%), the confidence level for presence of tumor was better on delayed than on dynamic images. Confidence levels for presence of tumor did not vary significantly among the three delay times. Attenuation values on dynamic and delayed images did not differ for the groups of patients who had or had not undergone prior radiotherapy or chemotherapy (p > .05). CONCLUSION: In the evaluation of hilar or intrahepatic cholangiocarcinoma, delayed CT images are helpful for tumor characterization and may improve observer confidence for the presence of tumor. The optimal time for acquisition of delayed images is 10-20 min after contrast media injection.

Bile Duct Neoplasms↗
PubMed1996

Use of time during body computed tomography scanning in a tertiary care teaching hospital: focus on patient throughput.

RATIONALE AND OBJECTIVES: To control costs, it is increasingly important to make efficient use of imaging technology. We sought to determine and analyze the time required to complete each step of a body computed tomography (CT) scan, focusing on factors that influence patient throughput. METHODS: Over 4 weeks, we prospectively monitored the time required for each step of a body CT scan (i.e., image time, check time, and clear time). Covariate data were collected by patient status: outpatient, inpatient, emergency department (ED), and intensive care unit (ICU); work shift; and radiologist training level (junior resident, senior resident, fellow, and attending). Technologists also predicted whether repeat images would be requested by the radiologist. RESULTS: Three hundred eighty CT examinations were studied: 277 for outpatients, 90 for inpatients, 9 for ED patients, and 4 for ICU patients. The mean total examination time was 44.7 min (mean image time = 33.1 min, mean review time = 8.2 min, and mean clear time = 3.4 min), which did not differ significantly with patient status. A second opinion was sought from a consultant radiologist on the scans of 44 patients. Consultation was requested significantly more frequently (1) by junior residents than by senior residents or fellows and (2) for ED and ICU patients (22% and 50%, respectively) than in outpatients and inpatients (10% and 14%, respectively). Repeat images were obtained from 75 patients, and this was not significantly related to patient status, scan type, or radiologist training level. When the technologist predicted that no repeat images were needed, this prediction agreed with the radiologist in 86% of the cases. When the technologist predicted that repeat images were necessary, this prediction agreed with the radiologist in 56% of the cases. CONCLUSION: Reviewing scans before the patient leaves the CT suite adds considerably to the total time required to complete a scan, particularly if junior residents review scans. If technologists obtain repeat images at their discretion, time would be saved.

Hospitals, Teaching↗
PubMed1996

Renal resistive indexes: variability in Doppler US measurement in a healthy population.

PURPOSE: To determine the variability in resistive index (RI) in normal kidneys, possible causes of variability, and consequences of reporting a single value. MATERIALS AND METHODS: Doppler ultrasound RI measurements were obtained in the upper, middle, and lower regions of 118 kidneys in 58 healthy subjects (aged 24-70 years; 35 women, 23 men) who subsequently underwent angiography. The effects of sampling a particular parenchymal region, vascular territory, or kidney were assessed. RESULTS: Kidney region, vascular territory, and right versus left kidney had no consistently significant effect (P < or = .05) on RI. Age had a statistically significant effect. RI readings were highly correlated with each other both within a subject and within a kidney. The probability that a single RI value would exceed 0.70 in a healthy 45-year-old subject was 6%; this decreased to 3% when three readings were averaged. CONCLUSION: The variability of RI measurements in a kidney suggests that a number of RI readings should be averaged before a single representative value is reported.

Adult↗
PubMed1996

CT during arterial portography: comparison of injection into the splenic versus superior mesenteric artery.

PURPOSE: To determine whether the diagnostic quality of computed tomography (CT) during arterial portography (CTAP) performed via the splenic artery (SA) is better than that performed via the superior mesenteric artery (SMA). MATERIALS AND METHODS: The authors evaluated CTAP images obtained in 98 patients from 1991 to 1994; 47 examinations were performed via the SA and 51 were performed via the SMA. Images were reviewed, by consensus, by three radiologists blinded to catheter location. Hepatic enhancement was quantitatively assessed in 53 patients (31 in the SA group, 22 in the SMA group). RESULTS: The numbers of low-attenuation non-tumor-related perfusion defects (19 in the SA group, 17 in the SMA group), high-attenuation non-tumor-related perfusion defects (six in the SA group, six in the SMA group), diffuse mottled perfusion abnormalities (six in the SA group, five in the SMA group), and portal venous flow defects (20 in the SA group, 20 in the SMA group) were similar in both groups (P > .05). Peak hepatic enhancement was similar in both groups (SMA group = 111 HU; SA group = 112 HU) (P > .05). CONCLUSION: There is no difference in quality between CTAP performed via the SA versus CTAP performed via the SMA.

Adult↗
PubMed1996

Hepatic artery: variability in measurement of resistive index and systolic acceleration time in healthy volunteers.

PURPOSE: To determine the intrinsic sampling variability of measurements of hepatic artery resistive index and systolic acceleration time in healthy subjects and to estimate the components of variability attributable to the sonographer, individual measurement, and subject. MATERIALS AND METHODS: In a randomized, controlled (blinded) fashion, nine sonographers measured hepatic artery resistive index and systolic acceleration time in five healthy subjects by using Doppler ultrasound (US). Analysis of variance was used to estimate the contribution of several factors to the observed variability in measurements. RESULTS: The standard deviation for a single measurement was 0.08 for resistive index and 39 msec for systolic acceleration time. For resistive index, the estimated variance components were 0.0012 (18%), 0.0004 (6%), and 0.0050 (76%) for the subject, sonographer, and intrinsic variability, respectively. For systolic acceleration time, the estimated variance components were 59 msec (4%), 264 msec (17%), and 1,250 msec (79%) for the subject, sonographer, and intrinsic variability, respectively. CONCLUSION: Because of substantial variability in hepatic arterial measures, caution is indicated when interpreting small changes in the measurement of these Doppler US indexes.

Adult↗
PubMed1996

Malignant melanoma metastatic to the gastrointestinal tract.

Malignant melanoma, a common malignancy whose prevalence is increasing, represents 1-3% of cancers in the United States [1]. At autopsy, metastatic deposits to the gut are frequently found, but less than 9% of melanoma patients are diagnosed with gastrointestinal metastases while living [2]. Modern management includes aggressive surgical therapy to prolong survival and to palliate the disease [3]. Therefore, imaging of metastatic melanoma is clinically important to detect extent and determine whether the patient would benefit by surgery. Gastrointestinal metastases may manifest as mucosal or submucosal masses, serosal implants, or carcinomatosis [4]. They arise more commonly in the mesentery or distal small bowel than the proximal gastrointestinal tract or colon. The purpose of this essay is to illustrate the appearance of melanoma metastatic to the gastrointestinal tract on luminal contrast studies and on CT and to emphasize the importance of early investigation of gastrointestinal symptoms in a patient with a history of malignant melanoma.

Adult↗
PubMed1996

Urinary bladder diverticula: sonographic diagnosis and interpretive pitfalls.

Diverticula of the urinary bladder can occasionally appear as complex pelvic masses not obviously connected to the bladder. Such presentations can lead to diagnostic confusion and interpretative error. Sonographic findings and clinical histories were reviewed in 11 patients in whom bladder diverticula were initially mistaken for other types of pathologic pelvic processes. Sonographic techniques that were helpful in elucidating the true nature of the lesions included scanning from different perspectives with increasing increments of bladder distention, postvoid images, endovaginal views, and color Doppler interrogation. The diagnosis of bladder diverticula should be considered and actively pursued when sonologists are confronted with pelvic masses of ambiguous origin.

Adolescent↗
PubMed1996

Doppler sonography in the evaluation of corporovenous competence after penile vein ligation surgery.

Doppler ultrasonographic findings in patients after penile vein ligation surgery are described and compared to the results of cavernosometry and cavernosography. Peak systolic and end diastolic velocities were recorded for both cavernosal arteries at 5 min intervals after papaverine injection for a total of 30 min. Peak end diastolic flow rates were compared with cavernosometric and cavernosographic results at 0-10 min, 11-20 min, and 21-30 min. Cavernosography identified venous leakage in nine patients. The end diastolic velocities were greater than the 5 cm/s threshold level generally considered to be indicative of venous leakage in nine of the nine patients (100%) at 0-10 min, in eight of the nine (89%) at 11-20 min, and in nine of the nine (100%) at 21-30 min. Although peak end diastolic velocities at or near the 5 cm/s threshold could be found in patients both with and without recurrent venous leakage in the initial 10 min of the studies, only patients with recurrent venous leakage had diastolic velocities that exceeded the 5 cm/s level when measured 10 min or more after injection. Measurement of end diastolic velocities between 21 and 30 min after injection seemed to discriminate most effectively the patients with recurrent venous leakage from those without leakage in the postoperative population.

Adult↗
PubMed1996

Doppler sonography in the diagnosis of antepartum pyelonephritis: value of intrarenal resistive index measurements.

This study aims to define the effects of pyelonephritis on intrarenal resistive indices and to determine the role of Doppler sonography in the diagnosis of pyelonephritis in pregnant patients. Twenty pregnant women with pyelonephritis underwent renal Doppler sonography with calculation of intrarenal resistive indices. The resistive index was calculated for the upper, lower, and interpolar areas of each kidney in the patients with pyelonephritis (40 kidneys) and was compared to the resistive indices for a control group of 153 normal asymptomatic pregnant women (306 kidneys). Doppler findings were correlated with the location (sidedness) of flank pain in the pyelonephritis group. The mean resistive index values of patients with pyelonephritis were 0.04 higher than in the controls, and this difference was statistically significant (P < 0.001). Four patients with pyelonephritis had a mean resistive index > or = 0.70, whereas the remaining 16 patients had resistive indices within the normal range of < or = 0.70. In patients with confirmed pyelonephritis and unilateral pain, the average resistive index in the kidney on the side of pain was 0.03 greater than that on the asymptomatic side (P = < 0.01). The mean renal resistive index is significantly greater in pregnant patients with pyelonephritis than in pregnant women without pyelonephritis. Even so, the magnitude of the differences in resistive index is too small and the overlap between the groups too large for this parameter to be of discriminating clinical value.

Diagnosis, Differential↗