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Biomedical subjects

P R Mueller

Publications and source records attributed to P R Mueller.

At least 73 records · Page 4Linked to original sources
PubMed1997

Patterns of anesthesia and nursing care for interventional radiology procedures: a national survey of physician practices and preferences.

PURPOSE: Through a survey of interventional radiologists, to document patterns of conscious sedation, nursing assistance, and care before and after the intervention and to compare demographics and different interventional radiology practices. MATERIALS AND METHODS: The survey was sent to the 1,713 members of the Society of Cardiovascular and Interventional Radiology. The levels of sedation were categorized according to the following grading scale commonly employed by anesthesiologists: awake/alert, drowsy/arousable, asleep/arousable, deep sedation, and general anesthesia. The drugs used for sedation were recorded. The procedures were categorized as diagnostic vascular or visceral or therapeutic vascular or visceral. Data were available for most standard vascular and visceral procedures. RESULTS: Six hundred thirty-four (37%) interventional radiologists responded, and 500,000 procedures were analyzed. Most (90%) therapeutic procedures employed the drowsy/arousable level of sedation. Eighty-seven percent of respondents had the assistance of a full-time radiology nurse, 90% reported routine use of blood pressure or pulse oximetry monitoring, and 75% reported daily rounds were performed by physicians. CONCLUSION: The data supply useful background information regarding the use of anesthesia, periprocedural monitoring, clinical assessment, and nursing care.

Anesthesia↗
PubMed1997

Focal liver lesions: characterization with conventional spin-echo versus fast spin-echo T2-weighted MR imaging.

PURPOSE: To compare prospectively the diagnostic accuracy of T2-weighted conventional spin-echo (SE) and fast SE magnetic resonance (MR) imaging for differentiation of benign (hemangiomas or cysts) from malignant (metastases or hepatocellular carcinoma) liver lesions. MATERIALS AND METHODS: Fifty-three patients with 55 confirmed liver lesions (20 hemangiomas, eight cysts, 22 metastases, four hepatocellular carcinomas, one malignant fibrous histiocytoma) underwent T2-weighted conventional SE (repetition time msec/echo time [TE] msec = 3,100/ 80,160) and fast SE (5,000-5,000/99-104 [effective TE]) MR imaging at 1.5 T. The images were evaluated quantitatively (lesion-liver signal intensity ratio and lesion T2 index [SIlesion TE80/SIlesion TE160, where SI = signal intensity] and qualitatively (blinded reading) by using receiver operating characteristic analysis. RESULTS: Quantitatively, the T2 index (Az = .988) was more accurate than the signal intensity ratio at conventional SE (Az = .920) and fast SE (Az = .910) imaging (P < .05). Qualitatively, there was no statistically significant difference between the blinded reading of conventional SE (Az = .988) and fast SE (Az = .986) images in lesion characterization (benign vs malignant). There was a trend, however, toward superiority of conventional SE imaging for evaluation of "hypervascular" metastases (n = 9). CONCLUSION: With the specific parameters used, conventional SE and fast SE images provide equal accuracy for characterization of focal liver lesions. In patients with hypervascular metastases, double-echo conventional SE images may be preferable.

Adult↗
PubMed1997

Adrenal masses: characterization with delayed contrast-enhanced CT.

PURPOSE: To evaluate the use of attenuation measurements from early delayed computed tomographic (CT) scans to differentiate benign from malignant lesions of the adrenal glands. MATERIALS AND METHODS: Forty-four patients (19 men, 25 women; age range, 21-88 years; mean age, 63 years) with 46 adrenal masses underwent dynamic contrast material-enhanced CT and early delayed CT (range, 12-18 minutes; mean delay, 14 minutes) with similar scanning parameters. Each patient also underwent non-contrast-enhanced CT within 3 months of the contrast-enhanced examination. Attenuation of adrenal masses on each type of scan was measured, and receiver operating characteristic analysis was performed. RESULTS: An attenuation threshold of 24 HU was selected; thus, all lesions with attenuation values of 24 HU or less were considered benign. When this threshold was applied to the results, the sensitivity of characterization of adrenal masses on early delayed scans was 96%, and the specificity was 96%. CONCLUSION: Adrenal masses detected with contrast-enhanced CT can be characterized as benign or malignant on early delayed scans of the adrenal glands.

Adrenal Gland Neoplasms↗
PubMed1997

Percutaneous gastrostomy with T-fastener gastropexy: results of 316 consecutive procedures.

PURPOSE: To assess the rates of technical success and complications associated with radiologic gastrostomy or gastrojejunostomy performed with T-fastener gastropexy. MATERIALS AND METHODS: In 316 consecutive patients, radiologic gastrostomy or gastrojejunostomy with T-fastener gastropexy was performed over a 10-year period. Results of the procedures were reviewed. Results of follow-up were available for all patients. RESULTS: Of 316 procedures, 314 were successful (technical success rate, 99.4%). Six (1.9%) major complications occurred; 50% occurred in patients with peritoneal involvement from ovarian carcinoma. Ten (3.2%) minor complications occurred. Four minor complications occurred in patients with ovarian cancer and ascites. The 30-day mortality rate was 3.8% (12 patients) with one procedure-related death (0.3%). CONCLUSION: A T-fastener gastropexy may have a protective role in prevention of leakage of gastric contents into the peritoneum in patients with ascites. Ascites need no longer be considered a contraindication for radiologic gastrostomy. A gastropexy enables routine use of larger gastrostomy tubes and ready replacement of a displaced tube even before the development of a mature tract.

Adult↗
PubMed1997

US-guided thoracentesis: requirement for postprocedure chest radiography in patients who receive mechanical ventilation versus patients who breathe spontaneously.

PURPOSE: To identify a population of patients who may not need chest radiography after diagnostic thoracentesis by assessing and comparing the pneumothorax rates in patients with mechanical ventilation (intubation) versus spontaneously breathing patients (no intubation). MATERIALS AND METHODS: A retrospective review of all radiographs, clinical records, and ultrasound (US) scans obtained in 434 patients who underwent US-guided thoracentesis was performed. Three hundred forty-two patients were not intubated and 92 were intubated. Nine patients were excluded because of preexisting pneumothorax. The size of the effusion, the needle size used, and whether a pneumothorax occurred after the procedure were determined. RESULTS: Results demonstrated that only 10 pneumothoraces occurred (six in intubated and four in nonintubated patients). None of the nonintubated patients with pneumothorax and two of the six intubated patients with pneumothorax needed chest tubes. The difference in the pneumothorax rate between intubated and nonintubated patients was statistically significant (P < .01). CONCLUSION: Spontaneously breathing patients who undergo diagnostic thoracentesis do not need postprocedure chest radiography.

Adolescent↗
PubMed1997

Enhancement of hepatic parenchyma, aorta, and portal vein in helical CT: comparison of iodixanol and iopromide.

OBJECTIVE: The purpose of this study was to determine hepatic, aortic, and portal vein enhancement with a new dimeric, nonionic, isotonic contrast medium (iodixanol) in a routinely performed helical CT protocol and compare enhancement characteristics with those of a monomeric, nonionic, low-osmolality contrast medium (iopromide). SUBJECTS AND METHODS: In 81 patients, we injected 150 ml of iodixanol (320 mg I/ml), iodixanol (300 mg I/ml), or iopromide (300 mg I/ml). Injection rate was 5 ml/sec. A dual-phase helical CT scan was obtained (first helical scan began at 30 sec. second helical scan began at 70 sec), and enhancement characteristics were assessed. Results were analyzed taking into account various intrinsic parameters of patients. RESULTS: During the second imaging phase, iodixanol at 320 mg I/ml and iodixanol at 300 mg I/ml provided significantly higher enhancement of the liver (75 H, 69 H, 62 H), aorta (144 H, 140 H, 122 H), and portal vein (147 H, 147 H, 118 H) than did iopromide at 300 mg I/ml. No significant differences were observed during the first imaging phase. CONCLUSION: The combination of higher vascular and parenchymal enhancement levels after injection of the isotonic agent may represent a different quality of tissue enhancement. Such an enhancement would be characterized more by a higher contribution of the blood pool compartment to absolute enhancement levels than by a contribution of the interstitial compartment. Further studies are needed to determine whether the use of isotonic agents effects lesion conspicuity.

Aorta, Abdominal↗
PubMed1997

The frequency and significance of adnexal lesions incidentally revealed by CT.

OBJECTIVE: This paper describes the frequency of incidental adnexal findings revealed by routine CT scanning and determines the significance of these lesions in premenopausal and postmenopausal women, particularly in those with an already known malignancy other than ovarian carcinoma. MATERIALS AND METHODS: A computerized search of all radiology reports from 1992 identified 3448 women who underwent abdominopelvic or pelvic CT scans for an indication other than ovarian carcinoma or a known or suspected pelvic mass. Patients were divided into two subgroups: premenopausal and postmenopausal. CT reports were reviewed to identify patients with incidentally discovered adnexal lesions. Imaging characteristics and lesion size were recorded. To determine the significance of the lesions, we also reviewed clinical, radiologic, and histopathologic data. Lesions were judged to be benign on the basis of 12-month clinical follow-up, additional imaging that revealed stability or resolution, or histopathology. Lesions were judged to be malignant on the basis of progression of the lesion on subsequent imaging or histopathology. Lesions were classified as undetermined in patients with a serious or life-threatening illness who consequently underwent no further evaluation of the lesion. RESULTS: An incidental adnexal lesion was revealed by CT scanning in 168 cases (5%). Seventeen of these patients were lost to follow-up. Of the remaining 151 patients, 104 (69%) had incidental adnexal lesions that represented benign disease, 45 (30%) had undetermined lesions, and two (1%) had malignant lesions. In analyzing the two subgroups of patients, we determined that 56 (81%) of 69 premenopausal patients and 48 (59%) of 82 postmenopausal patients had benign adnexal lesions. On the basis of chart review, 67 patients had a known malignancy. Of these patients, 30 (46%) had benign adnexal disease, and 31 (48%) had undetermined findings. Four (6%) were lost to follow up, and the remaining two patients (3%) who were postmenopausal had metastatic disease of the ovaries. No primary ovarian malignancies were discovered incidentally in our study population. CONCLUSION: Our results indicate that in both premenopausal and postmenopausal women a significant proportion of adnexal lesions incidentally revealed on routine CT scanning are benign, even in women with known malignancies other than ovarian carcinoma.

Adnexal Diseases↗
PubMed1997

Anatomic variants of mesenteric veins: depiction with helical CT venography.

OBJECTIVE: The purpose of this study was to describe the variable anatomy of mesenteric veins on axial CT images and on volume-rendered CT venograms that use maximum intensity projection and shaded-surface display. SUBJECTS AND METHODS: Fifty-seven patients undergoing helical CT of the pancreas were included in the study. The mesenteric venous system was analyzed in 54 patients. Three patients were excluded because the helical CT data were unsatisfactory. RESULTS: On helical CT with maximum intensity projection and shaded-surface display, the superior mesenteric vein (SMV) was seen as a single trunk of variable length in 40 patients. In seven other patients, two mesenteric trunks merged separately with the splenic vein. In the remaining seven patients, the SMV was occluded by tumor. The inferior mesenteric vein drained into the splenic vein in 28 patients (56%), into the SMV in 14 patients (26%), and into the splenomesenteric angle in nine patients (18%). CONCLUSION: Both axial and volume-rendered CT venograms accurately reveal the variable mesenteric venous anatomy. CT venograms may replace conventional angiography in presurgical planning.

Female↗
PubMed1997

Arterial versus portal venous helical CT for revealing pancreatic adenocarcinoma: conspicuity of tumor and critical vascular anatomy.

OBJECTIVE: The purpose of this study was to determine the conspicuity of pancreatic adenocarcinoma and surrounding critical pancreatic vascular structures on helical CT scans obtained during the arterial and portal venous phases of enhancement. SUBJECTS AND METHODS: Forty patients with pancreatic adenocarcinomas under-went dual-phase helical CT (3-mm collimation; l-mm overlapping reconstructions; 160 ml contrast medium injected at 4 ml/sec; scan delay: 18 sec for arterial phase, 60 sec for portal venous phase). Tissue enhancement and differences in tumor-to-pancreas contrast were compared. Quantitative evaluation was also done for the aorta, the superior mesenteric artery and vein, and the splenic and portal veins. RESULTS: Tumor conspicuity was significantly greater in the portal venous phase, when the tumor-to-pancreas contrast difference was 54 +/- 31 H, than in the arterial phase, when the difference was 31 +/- 29 H. Enhancement values of critical pancreatic venous structures were significantly greater in the portal venous phase than in the arterial phase. CONCLUSION: Arterial-phase helical CT in patients with pancreatic adenocarcinoma is of limited benefit: lesion conspicuity is suboptimal and depiction of venous anatomy is inferior to the depiction possible with venous-phase helical CT.

Adenocarcinoma↗
PubMed1996

Role for a Xenopus Orc2-related protein in controlling DNA replication.

The six-subunit origin recognition complex (ORC) is essential for the initiation of DNA replication at specific origins in the budding yeast Saccharomyces cerevisiae. An important issue is whether DNA replication in higher eukaryotes, in which the characteristics of replication origins are poorly defined, occurs by an ORC-dependent mechanism. We have identified a Xenopus laevis Orc2-related protein (XORC2) by its ability to rescue a mitotic-catastrophe mutant of the fission yeast Schizosaccharomyces pombe. We show that immunodepletion of XORC2 from Xenopus egg extracts abolishes the replication of chromosomal DNA but not elongation synthesis on a single-stranded DNA template. Indirect immunofluorescence indicates that XORC2 binds to chromatin well before the commencement of DNA synthesis, and even under conditions that prevent the association of replication licensing factor(s) with the DNA. These findings suggest that Orc2 plays an important role at an early step of chromosomal replication in animal cells.

Amino Acid Sequence↗
PubMed1996

Radiofrequency tissue ablation: increased lesion diameter with a perfusion electrode.

RATIONALE AND OBJECTIVES: We sought to induce large zones of coagulation necrosis using radiofrequency (RF) with perfusion electrodes and to define optimal parameters for this system. METHODS: We developed RF electrodes with internal cannulas to enable tip perfusion. Lesions were created with monopolar RF in ex vivo and in vivo liver and muscle tissue with and without perfusion of the electrode tip using 0 degree C saline. In separate experiments, wattage, current, procedure duration, tip exposure, and perfused tip temperatures were studied. RESULTS: In ex vivo liver tissue, a maximum lesion diameter of 3.1 cm without charring occurred with perfusion at 12 min and 50 W. In in vivo liver tissue with perfusion (tip temperature = 25-35 degrees C) and a 3-cm tip exposure, 80 W were deposited in muscle tissue and 65 W in liver tissue for 12 min without inducing charring. Lesion diameters were 4.5 cm and 2.4 cm, respectively. By comparison, without perfusion a maximum of 20 W could be deposited into either tissue type, resulting in 1.8-cm muscle lesions and 1.2-cm liver lesions. Tip temperatures between 45 degrees C and 55 degrees C resulted in charring. Smaller but predictable lesion diameters were created with a lower power, a shorter tip exposure, or both. Of all the parameters, diameter correlated best with the current applied. CONCLUSION: Perfusion of RF electrodes with chilled saline allows for increased power deposition without tissue charring, increasing the volume of coagulation necrosis created with a single electrode insertion. Perfusion electrodes therefore might decrease the number of probe insertions required for percutaneous tumor ablation therapy or allow for the treatment of larger lesions.

Animals↗
PubMed1996

Radio-frequency tissue ablation of VX2 tumor nodules in the rabbit lung.

RATIONALE AND OBJECTIVES: The authors investigated whether small pulmonary malignancies could be treated with computed tomography (CT)-guided, percutaneously placed radio-frequency (RF) electrodes. METHODS: Pulmonary tumors were created in 11 New Zealand white rabbits by using CT-guided injection of a VX2 sarcoma cell suspension into the lower portion of the right lung. Tumors were allowed to grow 14-21 days to achieve a diameter of 6-12 mm. Electrodes were placed coaxially into the tumors via insulated 19-gauge Turner needles. Seven tumors were treated with RF for 6 minutes at 90 degrees C. Four tumors served as controls and were not treated. Follow-up CT and histopathologic analysis were performed on days 0-28. Specimens from treated rabbits were examined histopathologically on days 0 and 3 (n = 2 each), and days 1, 5, and 28 (n = 1 each). RESULTS: Immediately following treatment, CT images showed rounded opacities enveloping the tumor. This corresponded histologically to coagulation necrosis of tumor and surrounding alveoli. In all cases, at least 95% of treated tumor nodules were necrotic at histopathologic analysis. Peripheral residual nests of histologically viable tumor were seen in three rabbits (43%). Control rabbits showed growing tumor nodules without necrosis at autopsy (mean survival, 23 days after inoculation). Two RF-treated rabbits (29%) and one control rabbit (25%) had pneumothoraces. CONCLUSION: Percutaneous RF tissue ablation can be used to successfully treat small parenchymal tumor nodules within the lung in an animal model.

Animals↗
PubMed1996

Radiofrequency tissue ablation: importance of local temperature along the electrode tip exposure in determining lesion shape and size.

RATIONALE AND OBJECTIVES: We determined whether heat distribution along a radiofrequency (RF) electrode would be uniform when longer tip exposures are used and whether local temperature effects would influence the shape of induced tissue coagulation. METHODS: Thermistors were embedded within 18-gauge RF electrodes at both ends and in the middle of the exposed tip. The length of tip exposure varied from 1 to 7 cm. RF was applied in vitro to pig liver for 6 min using a constant tip temperature, which was varied in 10 degrees C increments from 60 degrees C to 110 degrees C. Experiments were performed in triplicate. The 3- and 5-cm probes were used at a 90 degrees C tip temperature to create lesions in live pig liver and muscle using similar parameters. Temperature was measured throughout the procedure. Observable coagulation necrosis was measured at the end of the treatment. Regression analysis was used to evaluate the local temperature-lesion diameter relationship. RESULTS: Temperatures were not uniform along the tip exposure for any given trial. Temperature variation increased with higher tip temperatures and longer tip exposures. The diameter of local coagulation necrosis was a function of the local mean temperature. For in vitro trials, no coagulation was seen when the local temperature was less than 50 degrees C. Temperatures above this threshold resulted in progressively greater lesion diameter, with a minimum of 1 cm of necrosis occurring at 71 degrees C. Additional increases in lesion diameter (1.4-1.6 cm) were observed at approximately 90 degrees C. Mathematical modeling demonstrated a best-fit curve: lesion diameter (in cm) = ¿1.4 + 0.03 (tip exposure)¿ ¿1 - e [-0.067(local temp - 49.5 degrees C)]¿, r2 = .986, SD = 0.14 cm for each curve. In living tissue, less uniformity in the shape of coagulation necrosis was seen around the electrodes. Local temperature-lesion diameter data fit the same logarithmic relation, but the threshold for coagulation necrosis was 8.5 degrees C higher than for in vitro specimens. CONCLUSION: Using a single-probe technique for RF-induced tissue necrosis, the diameter of tissue coagulation may be predicted by the local temperature along the exposed electrode. The uniformity of temperature decreases with increased tip exposures. This effect may be partially corrected by creating lesions at higher tip temperatures, where necrosis diameter is increased. Because effects are more pronounced in vivo, uniform volumes of tissue necrosis are limited to tip exposures of 3 cm or less.

Animals↗
PubMed1996

Attenuation effects of biliary endoprostheses on therapeutic radiation.

Seven commercially available biliary stents were tested to determine if they caused any clinically important attenuation of therapeutic radiation. Attenuation effects were evaluated in models of brachytherapy (iridium-192 source) and external beam radiation therapy (cobalt-60 source), with use of parameters that mimicked those used in patient treatment for biliary neoplasms. No stent demonstrated clinically important attenuation or scatter of therapeutic radiation, so local dosimetry was not affected.

Bile Duct Neoplasms↗
PubMed1996

Imaging and interventional radiology in laparoscopic injuries to the gallbladder and biliary system.

Laparoscopic cholecystectomy has been prevalent in the United States since the late 1980s. Because of its increased use and potential for complications that can often be treated with interventional means, radiologists have become involved in treating patients with postlaparoscopic injury. This review details the imaging and interventional procedures involved in the care of patients with gallbladder and biliary problems due to laparoscopic cholecystectomy.

Bile Duct Diseases↗
PubMed1996

Endoscopic sonography of the upper gastrointestinal tract and pancreas.

Endoscopic sonography is a new approach to visualizing upper gastrointestinal lesions. The sonographic device, which incorporates a sonographic transducer mounted on a standard fiberoptic endoscope, makes it possible to obtain high-resolution images of mucosal and mural lesions of the gastrointestinal tract, as well as of adjacent masses. This technique has substantially improved preoperative staging of esophageal and gastric cancers. In addition, high-resolution sonographs of the pancreas can be obtained without degradation by overlying bowel gas, making identification of small, previously occult lesions of the pancreatic head possible. We have used endoscopic sonography in staging esophageal, gastric, and pancreatic cancers in more than 200 patients. This essay illustrates our experience with this new technique.

Endoscopy, Digestive System↗