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Biomedical subjects

F T Lee

Publications and source records attributed to F T Lee.

At least 73 records · Page 4Linked to original sources
PubMed1995

Lesion visualization by targeted computed tomography liver enhancement in dogs.

RATIONALE AND OBJECTIVES: We conducted a pilot study to determine the potential advantages of using liver-specific targeted computed tomography (CT) contrast agents for lesion detection. METHODS: Eight dogs had liver infarcts created by percutaneous injections of ethanol. Each dog underwent CT scans with four imaging techniques: unenhanced, intravenous contrast enhanced (IVCE), CT arterial portography (CTAP), and targeted liver enhancement with iodipamide ethylester (IDE) particles. Lesions were assessed quantitatively to determine liver-to-lesion density differences and the drop in density across liver edge as a quantitative measure of edge sharpness. Expert readers subjectively analyzed data to determine lesion visibility and edge sharpness. RESULTS: Liver-to-lesion density differences were greatest with CTAP (56.4 +/- 35.5 Hounsfield units [H]) followed by IDE (41.1 +/- 7.0 H), i.v. (22.7 +/- 6.0 H), and unenhanced scans (13.6 +/- 4.1 H; ps < .05 for CTAP versus unenhanced and IDE versus unenhanced). Edges were best defined both subjectively and quantitatively on IDE-enhanced scans. CONCLUSION: Targeted liver-specific contrast agents have potential to increase lesion visibility when compared with standard i.v. contrast enhancement of the liver by increasing lesion edge definition and liver-to-lesion attenuation differences. Further work in animal tumor models, and clinical trials as agents become available, appears justified.

Animals↗
PubMed1995

Prostate cancer: US-guided percutaneous cryoablation. Work in progress.

PURPOSE: To present early results of cryosurgical ablation of prostate cancer with an ultrasound-guided percutaneous technique. MATERIALS AND METHODS: Cryosurgery was performed in 210 patients; near complete 3- and 6-month follow-up data were available for 130. Androgen ablation therapy was used to decrease the size of the prostate gland for optimal freezing. Prostate-specific antigen (PSA) and prostatic biopsy studies were performed at 3, 6, and 12 months. RESULTS: Gland volume decreased from 29 cm3 +/- 14.1 to 20.4 cm3 +/- 8.4 (P < .0001) after androgen ablation. Rates of positive biopsy findings at 3, 6, and 12 months were 7.7%, 3.3%, and 2.3%, respectively. Serious complications were minimal and included no deaths, urethrorectal fistulas in five patients, and total incontinence in three. Mean PSA levels decreased from 12.6 +/- 16.1 preoperatively to 0.35 +/- 0.75 at 3 months, 0.54 +/- 1.1 at 6 months, and 0.43 +/- 0.78 at 12 months (persistent cancers excluded). CONCLUSION: These preliminary results demonstrate that cryosurgery can cause necrosis of prostate cancer. Long-term results and randomized trials are necessary to determine if this means longer disease-free intervals and increased patient survival compared with results of current therapeutic methods.

Aged↗
PubMed1995

Abdominal hernias: CT findings.

Abdominal hernias remain a common and vexing problem for both clinicians and radiologists. Unlike inguinal hernias, which are usually diagnosed clinically and are amenable to minor surgical repair, internal hernias can be difficult to diagnose, require more extensive surgical intervention, and have an increased risk of serious complications. Additionally, it is important to recognize structures contained within a hernia sac, so that precautions are taken at surgery. Therefore, accurate preoperative diagnosis can lead to more timely and appropriate surgical management. Abdominal imaging is often the first clue to the correct diagnosis. In the past, the diagnosis of a hernia was either made clinically, with plain radiographs, or with barium studies [1]. Currently, specific diagnoses are made more frequently by CT in patients with nonspecific abdominal complaints [2]. The CT findings may be subtle or confusing; therefore, familiarity with a broad range of imaging appearances can help the radiologist make an early and specific diagnosis of abdominal hernia.

Adolescent↗
PubMed1995

Acute cholecystitis in an animal model: findings on color Doppler sonography.

OBJECTIVE: The purpose of our study was to evaluate the color Doppler findings of acute cholecystitis in a controlled canine model. MATERIALS AND METHODS: Fourteen animals had a laparotomy: cystic duct ligation was done in eight, and incision with closure was performed in six control subjects. Animals were scanned in a blinded fashion preoperatively, immediately postoperatively, and on postoperative days 1-5. On postoperative day 5, a hepatobiliary scan was done with 2 mCi (74 MBq) 99mTc-mebrofenin. Blinded histopathology was performed and correlated with imaging. RESULTS: Flow was seen in the wall of each gallbladder at some point during the postoperative course, demonstrating vascular patency. Hepatobiliary scintigraphy confirmed cystic duct status in 12 cases; two animals died before radionuclide imaging was complete. Color Doppler signal decreased in the gallbladder wall in ligated dogs from postoperative day 1 to postoperative day 3 (p = .03 versus controls at postoperative day 2) and increasingly returned by postoperative day 5. Hyperemia was seen in only two cases (both with severe necrotizing cholecystitis) and only at postoperative day 5. Although not statistically significant, a weak trend of increasing flow with more severe pathologic grades of cholecystitis was observed (p = .20). CONCLUSIONS: In this animal model, loss of vascular signal (not hyperemia) at postoperative day 2 was the finding to diagnose early acute cholecystitis, although lack of flow can also be seen in some normal subjects. Flow tended to return by postoperative day 5, and it increased in some of the more severe cases of cholecystitis. Hyperemia was a somewhat useful sign of acute necrotizing cholecystitis.

Acute Disease↗
PubMed1994

Laparoscopic cholecystectomy. Do preoperative factors predict the need to convert to open?

We reviewed our experience with the last 587 laparoscopic cholecystectomies performed between May 1990 and January 1993 to correlate preoperative findings that may predict the conversion of a laparoscopic cholecystectomy to that of an open procedure. The prediction of a need to convert to an open cholecystectomy would allow the surgeon to discuss the higher risk of conversion with the patient and also allow for an earlier intraoperative decision to convert if difficulty was encountered. In addition to routine demographic data, ultrasound reports were available for 526 patients and the following information was recorded: presence of stones, thickened gallbladder wall, common bile duct dilatation, gallbladder sludge, and cystic duct impaction. Overall, a two times higher rate of conversion was found for male patients and patients with a body mass index > 27.2 kg/m2. Additionally, a thickened gallbladder wall on preoperative ultrasound was correlated with a six times higher conversion rate to open cholecystectomy. As expected, the positive intraoperative cholangiogram was associated with a higher incidence of conversion. Additionally, finding a dilated common bile duct on ultrasound was found to be associated with a nearly seven times higher rate of positive intraoperative cholangiogram. No statistical significance was found between conversion and age, previous abdominal operations, the presence of stones, common bile duct dilatation, gallbladder sludge, cystic duct impaction, or a distended gallbladder. Thus, these predictive findings allow the surgeon to preoperatively discuss the higher risk of conversion and allow for an earlier judgment decision to convert if intraoperative difficulty is encountered.

Acute Disease↗
PubMed1994

Contrast nephrotoxicity: predictive value of urinary enzyme markers in a rat model.

RATIONALE AND OBJECTIVES: We tested whether urinary enzymes are an accurate and useful marker of renal damage in a rat model of contrast media nephrotoxicity. METHODS: Thirty rats were pretreated with a combination of salt depletion, indomethacin, and contrast material. Alanine aminopeptidase (AAP), gamma-glutamyltranspeptidase (GGT), and N-acetyl-beta-D-glucosaminidase (NAG) were measured before and 24 hr after injection of contrast material. Enzyme concentrations were correlated with glomerular filtration rate (GFR) and histology. RESULTS: Decreasing GFR and histopathologic changes were found only in rats treated with all three variables. NAG levels increased from baseline for both diatrizoate meglumine- and ioversol-treated animals (from 83.9 +/- 48.6 to 145.5 +/- 55.4 and from 69.41 +/- 43.6 to 123.1 +/- 50.7, respectively; P < 0.05 from baseline for ioversol) and declined in other groups. GGT and AAP levels did not correlate well with structural and functional changes. CONCLUSIONS: In this model of contrast nephrotoxicity, NAG concentration appears to correlate with structural and functional changes associated with contrast media nephrotoxicity. However, the large range of baseline values makes this of dubious clinical use. AAP and GGT levels appear less helpful in detecting renal damage.

Acetylglucosaminidase↗
PubMed1994

US-guided percutaneous cryoablation of prostate cancer.

A tailored approach to cryosurgery of prostate cancer is presented. The authors have performed 214 cryoprocedures to date with use of this protocol. The technique requires pretreatment with androgen ablation therapy, preoperative diagnosis and staging with ultrasound (US)-guided biopsies, and detailed knowledge of prostate and rectal anatomy. Five cryoprobes are placed in the prostate under US guidance in a configuration that depends on tumor location, sites of extracapsular extension, the size of the tumor, and gland geometry. Freezing starts anteriorly to keep from obstructing the ultrasound beam. Two freezes are performed at the known cancer site, and additional freezes are performed, if necessary, to include the remainder of the gland. Thermosensors enable monitoring of the cryosurgical ice ball and determination of the number of freezes. Cryosurgery is always performed by a urologist and a radiologist working together.

Cryosurgery↗
PubMed1994

Detection of deep venous thrombi and pulmonary embolus with technetium-99m-DD-3B6/22 anti-fibrin monoclonal antibody Fab' fragment.

UNLABELLED: Technetium-99m-labeled anti-fibrin DD-3B6/22 Fab' monoclonal antibody fragments, which specifically target human cross-linked fibrin with high affinity, were evaluated in humans for safety and their capacity to detect deep vein thrombi and pulmonary embolism. METHODS: Twenty patients with proven deep-vein thrombosis, documented by contrast venography, or venous duplex scan, were injected with a 600 MBq (0.5 mg) dose of antibody. Planar images of the lower limbs were recorded at 0, 2, 6 and 24 hr and chest scintigrams were recorded at 6 and 24 hr. RESULTS: All venography documented thrombus sites, calves, popliteal and femoral, were detected with the radioimmunoconjugate. For the venous duplex scan-proven thrombus sites, all except two calf thrombi in two patients with bilateral disease and other positive sites were detected. Five patients had bilateral deep-vein thrombosis with multiple sites being visualized with the radioimmunoconjugate in the calf, popliteal and femoral regions. One case of pulmonary embolus was also definitively demonstrated. Documented thrombus sites were detected at 2 and 6 hr postinjection. Nineteen patients were on heparin. No adverse reactions to the injected dose were observed and one low titer human anti-mouse antibody response may have occurred. CONCLUSION: The results indicate that 99mTc-DD-3B6/22 Fab' has potential for noninvasive detection of deep-vein thrombosis and pulmonary embolism.

Adult↗
PubMed1993

MR imaging of adrenal lymphoma.

A case of lymphoma of the adrenal glands is presented. Both computed tomography (CT) and magnetic resonance imaging (MRI) demonstrated large bilateral adrenal masses with no other associated abdominal abnormalities. MR was better able to demonstrate inferior vena caval patency than CT, and effectively exclude pheochromocytoma as a differential diagnostic consideration due to signal characteristics of the masses.

Adrenal Gland Neoplasms↗
PubMed1993

Technetium-99 m labelling of DD-3B6/22 antifibrin monoclonal antibody fragment Fab' for thrombus imaging.

The antifibrin DD-3B6/22 monoclonal antibody Fab' fragment, a murine immunoglobulin, IgG3, has been labelled with technetium-99 m (99mTc) via a transchelation reaction, to specific activity in excess of 30 mCi/mg protein. The radiolabelling of Fab' was dependent on time, temperature, pH, antibody concentrations and nature of intermediary transchelation complex used. The resultant radioconjugate was stable in vitro and in vivo. Blood clearance of 99mTc-Fab' in rat followed two compartment kinetics with the half time of the fast phase being 0.5 h. The main route of excretion was via the kidneys with little uptake indicated by other tissues. The results suggest that the inherent specificity of the antibody, small molecular size, rapid plasma clearance, high specific radioactivity, together with the physical properties of the 99mTc label, combine to make this labelled monoclonal antibody (MoAb), potentially suitable as a radiopharmaceutical for the scintigraphic detection of thrombi in humans.

Animals↗
PubMed1992

Evaluation of thrombus detection in a rabbit model using a technetium-99m-labelled anti-fibrin monoclonal antibody.

Technetium-99 m (99mTc)-labelled conjugates of an anti-fibrin monoclonal antibody, DD-3B6/22, have been assessed for their detection of vascular thrombi in a rabbit model. DD-3B6/22 binds to a D-dimer epitope present on cross-linked fibrin but absent from the fibrin monomer or fibrinogen. Injection of a 99mTc-labelled Fab' fragment of DD-3B6/22 allowed delineation of model thrombi as early as 30 min postinjection (p.i.) with optimal localization at 4-5 h. Thrombus label uptake at 4 h p.i. was 0.304 +/- 0.106% injected dose/g (% ID/g) compared with 0.022 +/- 0.001% ID/g after the injection of a control Fab' fragment. These results suggest that the 99mTc-labelled Fab' fragment of DD-3B6/22 has excellent potential for scintigraphic detection of vascular thrombi in humans.

Animals↗
PubMed1992

Effect of serum pH on bilirubin-protein binding.

Progressive increase of the serum pH upon standing and storage in different conditions is documented. Bilirubin albumin titration studies were performed on serum of different pH by Sephadex gel filtration and horseradish peroxidase oxidation methods. Results showed that different pH produced different titration curves and that more reproducible and consistent results were obtained with the peroxidase oxidation titration method. Addition of HCl and CO2 to the serum also produced different bilirubin-protein titration results. For bilirubin albumin binding studies, we suggest to adjust the pH to 7.4 with CO2 to obtain clinically meaningful data.

Bilirubin↗
PubMed1990

Effect of a popular Chinese herb on neonatal bilirubin protein binding.

A study on the effects of a popular Chinese herb commonly given to newborn infants was undertaken. 'Chuen-Lin', Coptis chinensus/japonicum, which is consumed by 28-51% of Chinese infants, was found to have a significant effect in displacing bilirubin from its serum protein binding as assessed by the peroxidase oxidation method. Taking this herbal tea may thus increase the risk of brain damage by free bilirubin in jaundiced infants. As neonatal hyperbilirubinaemia is highly prevalent among Southern Chinese, the use of Chuen-Lin in the perinatal period must be strongly discouraged.

Bilirubin↗