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Biomedical subjects

R C Nelson

Publications and source records attributed to R C Nelson.

At least 19 recordsLinked to original sources
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

Ultrasonography.

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Humans↗
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

Timing of parenchymal enhancement on dual-phase dynamic helical CT of the liver: how long does the hepatic arterial phase predominate?

OBJECTIVE: Dual-phase dynamic helical CT is now being used to detect and characterize benign and malignant hypervascular lesions in the liver. The purpose of this study is to define the timing and degree of parenchymal enhancement of normal liver during the hepatic arterial phase. SUBJECTS AND METHODS: This prospective study included 102 patients with known or suspected hypervascular hepatic lesions who underwent dual-phase helical CT. After unenhanced CT scanning, we injected iopamidol (Isovue 300; Bracco Diagnostics, Princeton, NJ) at 3 ml/sec for 120 ml, then at 2 ml/sec for 55-60 ml. Scan delay for the hepatic arterial phase was 25 sec and for the portal venous phase was 76 sec. Section thickness was 7 mm and pitch was 1:1. Operator-defined regions of interest were obtained from all three phases. RESULTS: Mean unenhanced attenuation of the liver was 51 +/- 12 H. The liver revealed progressive enhancement during the hepatic arterial phase as follows: an increase of 10 H occurred at a mean time of 33 +/- 4 sec, 20 H at 39 +/- 6 sec, 30 H at 44 +/- 8 sec, 40 H at 46 +/- 6 sec, and 50 H at 48 +/- 5 sec. At 20 H and 30 H of enhancement, we found a statistically significant difference (p < .01) for the mean times of men and women. Mean peak enhancement during the portal venous phase was 89 +/- 23 H. CONCLUSIONS: Because the hepatic arterial contribution to liver perfusion is approximately 30%, parenchymal enhancement greater than approximately 30% of peak might indicate portal venous predominance. In our study, this percentage corresponded to an increase of approximately 30 H. Therefore, detection of hypervascular lesions in the hepatic arterial phase may be compromised when imaging lasts longer than approximately 44 sec after the initiation of contrast material injection because 44 sec was the mean time for 30 H of enhancement in our series. However, variability between patients was marked, particularly between men and women. Furthermore, the data suggests that the hepatic arterial phase may be relatively brief and that it may be difficult to image properly using current helical CT technology.

Adult↗
PubMed1995

Ultrasonography.

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Humans↗
PubMed1995

Imaging in the preoperative evaluation of adult liver-transplant candidates: goals, merits of various procedures, and recommendations.

Advances in organ procurement and surgical techniques have made orthotopic liver transplantation (OLT) an accepted treatment for many adult patients with end-stage hepatic disease. At present, OLT is being performed in patients with a variety of diseases, and 5-year survival is estimated at 65-78% [1]. Over 80% of hepatic transplants are performed in patients with cirrhosis or primary cholestatic liver disease, and only 5% of transplants are performed for malignant hepatic neoplasms (Table 1) [2]. Because the supply of donor organs is limited, preoperative clinical and radiologic evaluation of the transplant candidate is critical for appropriate patient selection. The main objective of preoperative imaging is to provide the surgeon with the pertinent information needed to plan and perform OLT and to exclude patients for whom surgery either is not feasible or will be of no benefit.

Algorithms↗
PubMed1995

Adrenal hemorrhage in patients with primary antiphospholipid syndrome: imaging findings.

OBJECTIVE: The primary antiphospholipid syndrome consists of recurrent thromboses, early stroke, recurrent fetal loss, and livedo reticularis in patients with antiphospholipid antibodies and without systemic lupus erythematosus. The purpose of this study was to analyze the imaging findings in patients who had this syndrome as well as adrenal hemorrhage. MATERIALS AND METHODS: The medical records and reports of radiologic examinations of 228 patients with elevated titers of lupus anticoagulant or anticardiolipin antibodies from January 1992 to April 1994 were examined for indications of adrenal hemorrhage. Four patients (two men and two women 38-78 years old) were identified as having adrenal hemorrhage. The abdominal CT and MR imaging findings for three patients and autopsy data for the fourth patient were analyzed. RESULTS: Adrenal hemorrhage was seen in all three patients who underwent abdominal CT and in one patient who underwent MR imaging. Adrenal hemorrhage was bilateral in three patients. Extension of hemorrhage into the perinephric space was present in two patients. Associated clinical findings probably attributable to the presence of antiphospholipid antibodies included amaurosis fugax (two patients), deep venous thrombosis (three patients), and transient ischemic attacks or stroke (two patients). CONCLUSION: Antiphospholipid antibodies appear to be a risk factor for adrenal hemorrhage. The presence of these antibodies should be suspected in patients who have adrenal hemorrhage as well as recurrent thromboses and early stroke.

Abdomen↗
PubMed1994

MR detection of leakage from silicone breast implants: value of a silicone-selective pulse sequence.

OBJECTIVE: The purpose of this study was to determine the value of MR imaging with a silicone-selective pulse sequence for detecting leakage from silicone breast implants. SUBJECTS AND METHODS: Women with silicone breast implants were referred for this study on the basis of clinical or imaging findings suggestive of implant rupture. Twenty-eight patients with 38 implants were examined with silicone-selective MR imaging and also underwent surgical removal of the studied implant. All but four also had mammography before MR imaging. Results of silicone-selective MR imaging for the detection of silicone leakage were compared with mammographic and surgical findings. Surgical proof was considered the gold standard. RESULTS: Silicone-selective MR imaging showed an apparently intact implant in 21 cases; 20 of these were found to be intact at surgery. Silicone-selective MR imaging showed evidence of leakage in 17 implants, all of which showed leakage at surgery. The sensitivity for detection of leakage was 94%; the specificity was 100%. The findings of silicone-selective MR imaging and mammography were in agreement in 30 of 34 cases in which both studies were performed. In the four cases of disagreement, surgical findings agreed with MR findings in three and with mammographic findings in one. When the findings of mammography and silicone-selective MR imaging were combined, the correct status (leakage or no leakage) of all implants examined was determinable. CONCLUSION: Silicone-selective MR imaging is highly effective for detecting leakage from silicone breast implants. Accuracy is improved when mammographic and MR findings are considered together.

Adult↗
PubMed1994

Contrast-enhanced spiral CT of the liver: effect of different amounts and injection rates of contrast material on early contrast enhancement.

OBJECTIVE: Spiral CT allows rapid hepatic imaging during a single breath-hold. The increase in imaging speed potentially allows contrast material to be used more efficaciously than with conventional dynamic CT, perhaps allowing a decrease in the volume of required contrast agent. To determine how this can be accomplished, we studied the effect of different bolus IV injection rates and amounts of contrast material on early hepatic enhancement during dynamic bolus spiral CT. SUBJECTS AND METHODS: A group of 20 healthy male volunteers were divided into four groups of five each. The groups received 75, 100, 125, or 150 ml of contrast material (Omnipaque 300, 300 mg l/ml). Each person within each group was scanned as contrast material was injected at rates of 3, 4, and 5 ml/sec. Hepatic enhancement was evaluated by comparing quantitative regions of interest before and after bolus injection of contrast material. Variations in enhancement produced by changes in volume and injection rate of contrast material were evaluated on early, middle, and late sections of the spiral, corresponding to 32-34, 41-43, and 51-53 sec, respectively, after the injection of contrast material was begun. RESULTS: Hepatic enhancement increased more rapidly when the bolus of contrast material was given at a rate of 5 ml/sec than at the slower rates of 3 or 4 ml/sec. Enhancement of the liver was greatest at the late portion of the spiral (51-53 sec after start of the bolus injection), averaging 73 and 79 H for volumes of 125 and 150 ml, respectively, at 5 ml/sec, and the enhancement was still increasing at that time. Enhancement curves predict 50- and 70-H mean increases in hepatic attenuation on initial slices with scan delays of approximately 40 and 50 sec, respectively, for these two protocols. CONCLUSION: Our results demonstrate that there is a marked dependence on early hepatic enhancement produced by variations in volume and injection rate of contrast material. We found no difference in the results produced by 125- and 150-ml volumes. These results are important for maximizing the effectiveness of IV contrast material during rapid hepatic spiral CT scanning.

Adult↗
PubMed1994

Recurrent tumor after resection of hepatic metastases from colorectal carcinoma: location and time of discovery as determined by CT.

OBJECTIVE: Despite studies showing increased survival rates for patients after surgical resection of hepatic metastases, recurrences occur in 75% of treated patients. The purpose of this study was to determine the location and time of discovery of recurrent tumor on CT scans after resection of hepatic metastases from colorectal carcinoma. MATERIALS AND METHODS: In a 6-year period, 32 patients (16 men and 16 women) who had undergone partial hepatic resection for colorectal metastases had follow-up CT at our institution. A total of 125 CT examinations of the chest and abdomen were retrospectively reviewed for the presence and location of recurrent disease. Recurrence was either confirmed by biopsy (n = 12) or presumed on the basis of growth of new lesions (n = 17). RESULTS: With a mean follow-up of 22 months (range, 1-60 months), recurrence was found at 29 sites in 25 patients. Thirteen sites were hepatic, and 16 were extrahepatic. Three patients had both hepatic and pulmonary disease. Recurrence within the liver was away from surgical margins in 11 (85%) of 13 patients at 14 +/- 7 months and adjacent to a surgical margin in the remaining two patients (15%) at 17 +/- 1 months. Extrahepatic recurrences were discovered in the lung in 11 (69%) of 16 patients at 21 +/- 12 months; in an adrenal gland in two patients (13%) at 19 +/- 5 months; in lymph nodes of the porta hepatis in one patient (6%) at 11 months; at the primary colonic anastomosis in one patient (6%) at 3 months; and in a retroperitoneal lymph node in the remaining patient (6%) at 12 months. CONCLUSION: Surgery was effective in treating the preoperatively detected hepatic metastases. Only two of 25 patients had recurrence related to a hepatic surgical margin. Most recurrences occur more than 1 year after surgery, most often in lung or liver away from surgical margins, and they probably represent small metastases undetectable with current preoperative or intraoperative techniques.

Adenocarcinoma↗