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Biomedical subjects

T A Powers

Publications and source records attributed to T A Powers.

At least 19 recordsLinked to original sources
PubMed1997

Staging recurrent metastatic colorectal carcinoma with PET.

UNLABELLED: Accurate detection of recurrent colorectal carcinoma remains a diagnostic challenge. The purposes of this study were to assess the accuracy of 18FDG-PET in patients with recurrent colorectal carcinoma in detecting liver metastases compared with computed tomography (CT) and CT portography, detecting extrahepatic metastases compared with CT and evaluating the impact on patient management. METHODS: Fifty-two patients previously treated for colorectal carcinoma presented on 61 occasions with suspected recurrence and underwent 18FDG-PET of the entire body. PET, CT and CT portography images were analyzed visually. The final diagnosis was obtained by pathology (n = 44) or clinical and radiological follow-up (n = 17). The impact on management was reviewed retrospectively. RESULTS: A total of 166 suspicious lesions were identified. Of the 127 intrahepatic lesions, 104 were malignant, and of the 39 extrahepatic lesions, 34 were malignant. Fluorine-18-fluorodeoxyglucose imaging was more accurate (92%) than CT and CT portography (78% and 80%, respectively) in detecting liver metastases and more accurate than CT for extrahepatic metastases (92% and 71%, respectively). Fluorine-18-fluorodeoxyglucose detected unsuspected metastases in 17 patients and altered surgical management in 28% of patients. CONCLUSION: These data identify that 18FDG-PET is the most accurate noninvasive method for staging patients with recurrent metastatic colorectal carcinoma and plays an important role in management decisions in this setting.

Adenocarcinoma↗
PubMed1996

Positron emission tomography to stage suspected metastatic colorectal carcinoma to the liver.

BACKGROUND: Accurate detection of recurrent colorectal carcinoma remains a clinical challenge. Positron emission tomography (PET) using 18F-fluorodeoxyglucose (18FDG) is an imaging technique that allows direct evaluation of cellular metabolism. 18F-fluorodeoxyglucose PET was compared to computed tomography (CT) and CT portography for staging metastatic colorectal carcinoma. PATIENTS AND METHODS: Twenty-four patients previously treated for colorectal carcinoma who had suspected recurrence to the liver underwent an 18FDG PET scan of the entire body. All patients had either a CT scan of the abdomen (n = 17), a CT portogram (n = 18), or both (n = 11). The final diagnosis was obtained by tissue pathology in 19 patients and clinical follow-up in 5 patients. RESULTS: A total of 60 suspicious lesions were identified. Of the 55 intrahepatic lesions, 39 were malignant and 16 were benign. Of the 5 extra-hepatic lesions, 4 were malignant. The 18FDG PET imaging had a higher accuracy (93%) than CT and CT portography (both 76%) in detecting metastatic disease to the liver, and detected unsuspected extrahepatic recurrence in 4 patients. Although the sensitivity of 18FDG PET (90%) was slightly lower than that of CT portography (97%), the specificity was much higher (100% versus 9%), including postsurgical sites. 18FDG PET altered surgical plans in 6 (25%) of 24 patients. CONCLUSIONS: 18FDG PET is extremely useful in staging patients with suspected metastatic colorectal carcinoma to the liver.

Colorectal Neoplasms↗
PubMed1995

Right ventricular performance and mass by use of cine MRI late after atrial repair of transposition of the great arteries.

BACKGROUND: The long-term adaptation of the right ventricle after atrial repair of transposition of the great arteries (TGA) remains a subject of major concern. Cine magnetic resonance imaging (MRI), with its tomographic capabilities, allows unique quantitative evaluation of both right and left ventricular function and mass. Our purpose was to use MRI and an age-matched normal population to examine the typical late adaptation of the right and left ventricles after atrial repair of TGA. METHODS AND RESULTS: Cine MRI was used to study ventricular function and mass in 22 patients after atrial repair of TGA. Images were obtained in short-axis sections from base to apex to derive normalized right and left ventricular mass (RVM and LVM, g/m2), interventricular septal mass (IVSM, g/m2), RV and LV end-diastolic volumes (EDV, mL/m2), and ejection fractions (EF). Results 8 to 23 years after repair were compared with analysis of 24 age- and sex-matched normal volunteers and revealed markedly elevated RVM, decreased LVM and IVSM, normal RV size, and only mildly depressed RVEF. Only 1 of 22 patients had clinical RV dysfunction, and this patient had increased RVM. CONCLUSIONS: Cine MRI allows quantitative evaluation of both RV and LV mass and function late after atrial repair of TGA. Longitudinal studies that include these measurements should prove useful in determining the mechanism of late RV failure in these patients. On the basis of these early data, inadequate hypertrophy does not appear to be the cause of late dysfunction in this patient group.

Adolescent↗
PubMed1992

Staging lung carcinoma with a Tc-99m labeled monoclonal antibody.

Thirty-three patients with biopsy-proven lung cancer and a total of 150 lesions diagnosed by conventional staging procedures were imaged using a Tc-99m labeled monoclonal Fab fragment of an IgG2B murine monoclonal antibody (MoAb) (NR-LU-10, NeoRx Corporation). Immunoscintigraphy demonstrated 100% of primary and 78% of metastatic lesions. MoAb imaging detected 88% of lesions in 12 small cell lung cancer (SCLC) patients and 77% of lesions in 21 non-small cell lung cancer (NSCLC) patients. Based on initial evaluation by other methods, 29 sites of MoAb activity were not associated with evidence of disease. Eleven of these were subsequently shown to represent sites of metastases; 18 remain unconfirmed. Four of ten patients studied with limited NSCLC had eight unsuspected lesions on MoAb imaging. Confirmation of unsuspected lesions in two patients altered initial clinical staging, and surgical therapy was abandoned. This study demonstrates that Tc-99m labeled NR-LU-10 can accurately stage patients with lung cancer.

Carcinoma, Non-Small-Cell Lung↗
PubMed1992

Quantitative imaging of renal blood flow and function.

Noninvasive renal blood flow quantitation has been historically difficult, although radionuclide imaging methods for measuring related parameters of renal function such as glomerular filtration rate and effective renal plasma flow have been successful. Radionuclide methods have long played an important role in the evaluation of renal function, but recent advances in other modalities such as positron emission tomography (PET), computed tomography (CT), and magnetic resonance imaging (MRI) have the potential to provide information not available with nuclear medicine techniques. The high spatial resolution provided by these modalities, coupled with dynamic imaging of contrast agents or radioactive tracers, potentially could allow detailed clinical evaluation of regional renal function and blood flow. A specialized MR technique, diffusion-weighted imaging, also shows promise for providing information not otherwise available concerning the renal microcirculation. This report provides a brief review of the available clinical techniques for the evaluation of renal blood flow and function as well as new methods under investigation.

Animals↗
PubMed1992

Obstruction of the inferior vena cava: a multiple-modality demonstration of causes, manifestations, and collateral pathways.

This article explores the causes and manifestations of obstruction of the inferior vena cava (IVC) with a multiple-modality approach. Caval obstruction may be due to thrombus, extension of a tumor, extrinsic compression, or intrinsic caval disease. Evaluation of the IVC should be tailored to the individual circumstance; no single modality is best in all situations. Although magnetic resonance offers multiplanar imaging, vena cavography or ultrasound are often necessary to exclude intraluminal tumor extension. Computed tomography is sensitive for intracaval thrombus and compression but does not delineate the hepatic IVC well. Nuclear venography demonstrates well the resultant collateral pathways, which can be separated into the deep, intermediate, superficial, and portal systems. Despite the clear visualization of these pathways with this modality, congenital caval anomalies, such as caval interruption with azygos continuation, can be confused with acquired caval disease.

Collateral Circulation↗
PubMed1991

Family origins of adolescent self-criticism and its continuity into adulthood.

We used a prospective longitudinal design to examine the relation between parenting experiences at age 5 and level of self-criticism at age 12 and the stability of self-criticism from age 12 to age 31 in 156 subjects. The results showed that mothers' reports of parenting behaviors that reflect restrictiveness and rejection were related to the development of self-criticism, particularly when received from the same-sex parent. Partial correlational analyses revealed that the parenting-self-criticism relations remained significant when the mother's report of the child's early temperament was statistically controlled. The results also showed that for women, self-criticism was very stable from early adolescence to young adulthood. By contrast, there was no relation between self-criticism at ages 12 and 31 for men; however, there was a strong relation for men between age 12 self-criticism and inhibited aggressive impulses at age 31.

Adolescent↗
PubMed1991

Renal artery stenosis: in vivo perfusion MR imaging.

The intravoxel incoherent motion (IVIM) model of perfusion and diffusion imaging was applied to an in vivo canine model of unilateral renal artery stenosis and was compared with relative renal blood flow determination with radioactive microspheres. The percentage relative renal blood flow as determined with radioactive microspheres correlated closely with the percentage apparent diffusion coefficient. If this method can be adapted to human imaging, it may provide a noninvasive means for detecting renal artery stenosis.

Animals↗
PubMed1990

Imaging of the temporomandibular joint.

Both arthrography and MR imaging are of proven value in the evaluation of internal derangements of the TMJ. Arthrography provides the advantages of a dynamic display of joint mechanics and the easy detection of disc perforation. Its disadvantages include its technical difficulty and its poor visualization of the disc in the medial-lateral plane. MR imaging of the TMJ provides excellent soft-tissue detail and more readily demonstrates medial and lateral displacements of the disc. Unfortunately, perforations of the disc or ligaments are not usually visualized, and bony detail is not seen as well as on plain radiographs or computed tomography. In addition, real-time dynamic imaging of joint mechanics is not readily available. Currently, the choice of imaging modality is based on the specific diagnostic question, and availability of arthrography and MR imaging.

Arthrography↗
PubMed1989

Correlative radionuclide and magnetic resonance imaging in evaluation of the spine.

The authors retrospectively compared magnetic resonance images and bone scintigraphy obtained from 144 patients. Fifty-six patients having a known primary malignancy were evaluated for metastases (Group 1), and 88 patients were evaluated for back pain (Group 2). Interpretation was normal in 36/144 patients (11 in Group 1 and 25 in Group 2), and similar abnormal foci were visualized in the osseous spine in 54/144 patients (32 in Group 1 and 22 in Group 2). Magnetic resonance imaging showed abnormalities in the osseous spine that were not visualized on bone scintigraphy in 43/144 patients (10 in Group 1 and 33 in Group 2); these included bone metastasis, benign neoplasm (hemangioma), Schmorl's node, intervertebral disk disease, and bone disease (osteophyte, spondylolisthesis, facet hypertrophy). In addition, magnetic resonance imaging showed epidural or paravertebral extension of the tumor or infection in 37/144 patients (30 in Group 1 and 7 in Group 2). Bone scintigraphy demonstrated abnormalities not visualized on magnetic resonance imaging in 11/144 patients (3 in Group 1 and 8 in Group 2). Bone scintigraphy showed abnormalities in locations not evaluated by magnetic resonance imaging but relevant to the symptomatology or disease in 42/144 patients (37 in Group 1 and 5 in Group 2). These data indicate that magnetic resonance imaging and bone scintigraphy are complementary. Bone scintigraphy remains the best screening procedure to show the location of abnormal areas in the spine and elsewhere in the skeleton. Magnetic resonance imaging is useful in differentiating neoplasm, infection, intervertebral disk disease, and, in some instances, degenerative bone disease.

Humans↗
PubMed1988

Central nervous system lesions in pediatric patients: Gd-DTPA-enhanced MR imaging.

Twenty pediatric patients, aged 2-18 years, with known or suspected masses in the brain and/or spinal cord were studied with magnetic resonance imaging at 0.6T with and without use of 0.1 mmol/kg gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA). The multisection, multiecho imaging mode was utilized. Surgically proved mass lesions included astrocytoma (n = 6), medulloblastoma (n = 2), ependymoma (n = 1), craniopharyngioma (n = 1), oligodendroglioma (n = 1), germinoma (n = 1) and fibrosarcoma (n = 1). Presumptive diagnoses included astrocytoma (n = 3), arachnoid cyst (n = 1), tuberous sclerosis (n = 1), cryptic vascular malformation (n = 1), and normal (n = 1). There was dramatic enhancement in 11 of 20 patients, with improved definition of the presence and extent of lesions in six patients. No adverse effects were noted in any of the 20 patients. It is concluded that Gd-DTPA is useful in delineating the presence, extent, and number of certain lesions of the central nervous system in children.

Adolescent↗
PubMed1988

Liver volume measurements and three-dimensional display from MR images.

A method was investigated for measuring the volumes of human livers in vivo from magnetic resonance images and subsequently displaying these livers in three dimensions. Volumetric image sets of phantoms, healthy volunteers, and patients with cirrhotic livers were processed. Two image-processing approaches were compared for accuracy of liver measurements, intrasubject and interobserver variation, and speed of processing. Results indicated that both processing methods had a high degree of volume-measuring accuracy (within 8%), the interobserver measurements had a high coefficient of correlation (r = .9994), the intrasubject measurements had a low coefficient of variation (1.8%), and one method was four to five times faster than the other. The faster and easier of the two image-processing approaches provided satisfactory results for measuring liver volumes, but the slower approach provided more realistic-looking three-dimensional images of the liver.

Humans↗
PubMed1987

Combined computerized tomography and angiography in evaluation of hemorrhage into pancreatic pseudocysts.

Hemorrhage into a pancreatic pseudocyst is a rare but frequently lethal complication of pancreatitis, which remains a diagnostic and therapeutic challenge. Angiography alone or in combination with ultrasonography and radionuclide perfusion scans will occasionally fail to identify adequately the source of bleeding. We have presented a case illustrating the superiority of dynamic computerized tomography and angiography in the preoperative evaluation of a patient with pancreatic disease and upper gastrointestinal hemorrhage.

Aged↗
PubMed1985

Pseudoaneurysm detection with Tc-99m-labeled red blood cells.

A technique for the noninvasive diagnosis of pseudoaneurysms is described. This method employs in vivo labeling of red blood cells with Tc-99m to allow better delineation of the vascular anatomy than standard radionuclide angiography. Four cases are illustrated.

Aneurysm↗
PubMed1984

Glucoheptonate measurement of differential renal function.

In previous studies using dogs whose renal function was rendered asymmetric by unilateral infarction or partial ureteral obstruction, the efficacy of technetium-99m diethylenetriamine pentaacetic acid and dimercaptosuccinic acid in the measurement of differential renal function was demonstrated. The present study was undertaken to determine if technetium-99m glucoheptonate could also be used to quantitate differential renal function in these conditions. Five dogs with partial ureteral obstruction, 4 with segmental infarction and 2 with ipsilateral combination of both were studied. Seven to 10 days following these interventions the animals were given a bolus injection of 10 mCi Tc-99m glucoheptonate. This was acquired in the posterior projection on a minicomputer at 2 seconds/frame for 3 minutes. Static images were obtained anteriorly and posteriorly between 3 and 5 hours postinjection. The following day iothalamate and creatinine clearances were measured by ureteral catheterization. There was good correlation between differential function calculated from the 1 to 3 minute portion of the bolus study and that determined by the ureteral catheter studies, r greater than 0.99. Correlations based on the static images were less satisfactory due to pelvic retention in the obstructed animals, r = 0.73. We conclude that technetium-99m glucoheptonate may be used to determine differential renal function.

Animals↗