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Biomedical subjects

R C Nelson

Publications and source records attributed to R C Nelson.

At least 55 records · Page 3Linked 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

Superparamagnetic iron oxide particles (SH U 555 A): evaluation of efficacy in three doses for hepatic MR imaging.

PURPOSE: To evaluate the efficacy of SH U 555 A in three doses for magnetic resonance (MR) imaging in the liver and to establish the best postinjection time point for liver MR imaging. MATERIALS AND METHODS: Pre- and postcontrast image sets obtained in 169 patients after injection of SH U 555 A (randomly, 4, 8, or 16 mumol of iron per kilogram of body weight). Three blinded readers evaluated the precontrast and 10- and 40-minute postcontrast MR images of 54, 58, and 57 patients, respectively. RESULTS: Statistically significant differences were observed in diagnostic confidence between images obtained with a dose of 4 or 16 mumol Fe/kg (P = .011) and in good or excellent improvement, respectively, in delineation of lesions on 10-minute postcontrast images (P = .001). No apparent differences in the efficacy evaluation were seen between the 10- and 40-minute postcontrast imaging time points. CONCLUSION: There was a dose-dependent postcontrast improvement in evaluated efficacy parameters (diagnostic confidence, visual evaluations) after injection of SH U 555 A. Accumulation phase imaging could begin as early as 10 minutes after administration.

Contrast Media↗
PubMed1998

Abdominal percutaneous interventional procedures: comparison of CT and US guidance.

PURPOSE: To compare ultrasound (US) with computed tomography (CT) as a guidance modality for percutaneous interventional procedures. MATERIALS AND METHODS: A database of abdominal interventional procedures was reviewed for the 6 months preceding and 6 months after the opening of a dedicated US interventional suite. Changes in the number and type of procedures performed, room time, number of needle passes, and complication rates were calculated. RESULTS: In the first 6 months, 305 interventional procedures (138 tissue biopsies and 167 fluid aspirations) were performed (CT guidance in 87% [n = 120] and 95% [n = 159], respectively). In the 6 months after installation of the suite, 395 procedures (195 tissue biopsies and 200 fluid aspirations) were performed (US guidance in 76% [n = 148] and 34% [n = 67], respectively). The largest increase in US utilization was for guidance of tissue biopsies, rising from 6% (18 of 305) to 37% (148 of 395) of all procedures. Room time was significantly less for US-guided procedures (mean US room time, 77 minutes +/- 33 [1 standard deviation]; mean CT room time, 99 minutes +/- 38; P < .0001). CONCLUSION: US guidance often allows performance of quicker, more accurate procedures than does CT guidance, probably because of its real-time capabilities.

Abdomen↗
PubMed1998

Doppler sonography of the portal vein and hepatic artery: measurement of a prandial effect in healthy subjects.

PURPOSE: To determine if the prandial effect outweighs variability in the measurement of portal venous blood flow and hepatic arterial resistive index. MATERIALS AND METHODS: Fourteen healthy adult volunteers fasted overnight. For eight of the subjects, two sonographers performed three determinations of portal venous blood flow and hepatic arterial resistive index before and 30 minutes after a liquid meal (5 mg per kilogram of body weight). In the remaining six volunteers, determinations were made at the same time intervals but without a meal. The sonographers were blinded to on-screen measurements and the subject's prandial status. RESULTS: For subjects examined after the meal by sonographers A and B, respectively, portal venous blood flow increased from 144.2 to 201.7 mL/min and from 209.2 to 331.9 mL/min and hepatic arterial resistive index increased from 0.70 to 0.77 and from 0.67 to 0.78. After repeated-measures analysis of variance, ingestion of a meal was estimated to increase portal venous blood flow by 96.3 mL/min (P < .001)--a change in sonographers could affect the measurement by 76.7 mL/min (P < .001)--and to increase hepatic arterial resistive index by 0.089 (P < .001)--a change in sonographers did not affect the measurement (P > .1). CONCLUSION: The prandial effect on portal venous blood flow is only marginally greater than the interobserver variation in the measurement. Hepatic arterial resistive index also increases after a meal, but interobserver differences between sonographers are minimal; therefore, it is a more robust measurement.

Adult↗
PubMed1998

Helical liver CT with computer-assisted bolus-tracking technology: is it possible to predict which patients will not achieve a threshold of enhancement?

PURPOSE: To determine how often a prescribed threshold of hepatic contrast material enhancement is not reached at helical computed tomography (CT) of the liver in patients in a tertiary teaching hospital-based practice and which variables are predictive of failure. MATERIALS AND METHODS: Hepatic helical CT was performed in 250 consecutive patients with computer-assisted bolus-tracking technology after either mechanical injection at 3 mL/sec (n = 177) or manual injection (n = 73) of 150 mL of iopamidol. Demographic variables were recorded. After 17 seconds, low-milliamperage monitoring scans were obtained every 6 seconds until hepatic enhancement of 50 HU over baseline was achieved. Time-enhancement curves were reviewed. RESULTS: The threshold was not reached by 60 seconds in 88 patients (35%; default group). The success and default groups were similar in most variables and differed only in weight (P = .002), patient status (inpatient, outpatient, or emergency department; P < .001), and injection type (mechanical vs manual; P < .001). Ten patients (4%) did not achieve the threshold because of inappropriate placement of elliptic regions of interest. CONCLUSION: By using computer-assisted bolus-tracking technology, 35% of patients in a tertiary teaching hospital-based practice will not achieve a threshold of 50 HU above baseline by 60 seconds after injection initiation and will require the use of a set delay. Failures are more frequent in patients who are heavy and in inpatients. No historic or demographic factors are strongly predictive of failure.

Adult↗
PubMed1998

Contrast media extravasation during dynamic CT: detection with an extravasation detection accessory.

To detect extravasation of contrast media during mechanical power injection at dynamic computed tomography, a 5 x 8-cm pliable adhesive patch was applied to the skin over the intravenous cannula and connected to the power injector with a cable to monitor electrical skin impedance. If the rate of change or the slope of impedance over time indicated an extravasation event, the power injector was set into a pause mode. In animal and human studies, monitoring with the device was successful. Extravasation of ionic contrast agents decreased impedance and that of nonionic agents increased impedance.

Adult↗
PubMed1997

Outcome of examinations self-referred as a result of spiral CT of the abdomen.

RATIONALE AND OBJECTIVES: The interpretation of an abdominal computed tomographic (CT) scan is occasionally inconclusive. In many of these cases, the radiologist suggests an additional imaging test for further confirmation or clarification. The purpose of this study was to evaluate the outcome of self-referral by the radiologist after abdominal CT scanning. MATERIALS AND METHODS: Reports from 545 consecutive abdominal CT scans were reviewed to track recommendations for additional imaging. In patients who underwent the additional work-up, a determination of the effect of the study was attempted. In patients who did not, explanations were sought. Wording of the recommendations was also recorded. RESULTS: Recommendations were made for additional imaging studies in 105 (19.3%) patients. Of these, 32 (30.5%) were performed and 31 (96.9%) were helpful by confirming malignancy (n = 5), confirming a benign process (n = 24), or being therapeutic (n = 2). In one, no information was added. There were 63 (60.0%) patients who did not undergo the recommended studies. Reasons included "no clinical indication" (n = 51), alternative study performed (n = 9), or study previously performed (n = 3). In eight (7.6%) patients the chart provided insufficient information about whether the patient underwent the study, and in two (1.9%) the chart was unavailable. Wording of the recommendation had no effect on whether the study was performed (P > .05). CONCLUSION: Although interpretation of abdominal CT scans leads to recommendations for additional imaging in a minority of cases, these recommendations were infrequently followed. When followed, however, the findings from the recommended studies were usually helpful. Better clinical information is perhaps the best way to reduce self-referral by radiologists.

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

Fine-needle aspiration of the liver and pancreas: a cytology primer for radiologists.

Fine-needle aspiration (FNA) is increasing in popularity as a means of diagnosing mass lesions in intraabdominal organs. With use of radiologic guidance for needle placement, this technique is an effective way to obtain diagnostic material. In selected instances, FNA is superior to core-needle or open biopsy in terms of cost, procedure-associated morbidity, and timeliness of diagnosis. This article summarizes the cytologic features of hepatic and pancreatic lesions most likely to be seen in an active interventional radiologic practice. The specific cytopathologic findings of the more common lesions are emphasized. The authors also discuss some of the limitations of FNA and how to optimize the procurement and utilization of specimen material to obtain the best possible diagnostic outcome.

Biopsy, Needle↗
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

Small lymph nodes of the abdomen, pelvis, and retroperitoneum: usefulness of sonographically guided biopsy.

PURPOSE: To evaluate the usefulness of sonographically guided percutaneous biopsy of small lymph nodes in the abdomen, retroperitoneum, and pelvis. MATERIALS AND METHODS: From May 1995 through January 1997, 35 sonographically guided lymph node biopsies were performed in 34 patients. All biopsies were performed with a 20- (n = 18) or 22-gauge (n = 10) self-aspirating needle alone or in combination (n = 7). To determine the amount of compression achieved with the transducer, the skin-to-lesion distance on reference computed tomographic (CT) scans was compared with that on sonograms. A biopsy was considered successful if a specific benign or malignant diagnosis was rendered by the pathologist. RESULTS: Of 35 sonographically guided biopsies, 30 (86%) were successful. Diagnoses included 26 (74%) cases of carcinoma, three (9%) cases of benign reactive lymphocytosis confirmed at open biopsy, and one (3%) case of a lymph node with a positive acid-fast bacilli stain. The average lymph node diameter was 2.1 cm (range, 0.9-4.3 cm). With sonography, a mean of 2.5 needle passes (range, 1-5) were made per biopsy. Transducer compression reduced the skin-to-lesion distance from an average of 8.8 cm (at CT) to 4.5 cm. CONCLUSION: Sonographic guidance seems to provide a reasonable alternative to CT in biopsy of small abdominal, pelvic and retroperitoneal lymph nodes.

Abdomen↗
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

Quality of adverse drug experience reports submitted by pharmacists and physicians to the FDA.

The US Food and Drug Administration (FDA)'s Spontaneous Adverse Experience Reporting System is a computerized database with over one million adverse drug experience (ADE) reports. In 1992, the FDA received over 100,000 ADE reports and pharmacists were major contributors to these reports. In 1993, the FDA launched MEDWatch, a new initiative to enhance direct reporting of adverse events by health professionals. thus far, majority of reports to MEDWatch are from pharmacists. Drug regulatory agencies of some countries do not accept reports submitted by pharmacists. We performed a study to assess the quality of information in ADE reports submitted directly to the FDA by pharmacists and physicians and compared that with manufacturer-channelled 15-day reports. We evaluated 589 ADE reports with serious outcomes associated with nine new molecular entities. Data were analysed using Epi Info. Our results showed no substantial difference in a subjective assessment of the quality of information in the reports submitted by pharmacists or physicians, irrespective of whether these reports were submitted directly or via manufacturers. This study suggests that reports from hospital pharmacists are valuable and of comparable quality. We believe that all health professionals contribute to the success of FDA's MEDWatch programme and thereby play an important part in protecting public health by promptly reporting serious adverse events.

Journal Article↗
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↗