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Biomedical subjects

R J Cowan

Publications and source records attributed to R J Cowan.

At least 37 records · Page 2Linked to original sources
PubMed1985

The utility of adrenal scintigraphy in Cushing's syndrome and hyperaldosteronism.

Thirty-three adrenal scintigrams in 30 patients were reviewed to determine the utility of this noninvasive imaging technique. It was found to be very accurate in distinguishing bilateral from unilateral hyperfunction in patients who have clinical and biochemical evidence of adrenal cortical hyperfunction. The technique proved correct in 12 of 12 cases of Cushing's syndrome and 14 of 19 cases of hyperaldosteronism. Specific clinical questions were also answered in three miscellaneous cases.

19-Iodocholesterol↗
PubMed1985

Gastroesophageal scintigraphy: is it a sensitive screening test for gastroesophageal reflux disease?

Dynamic radionuclide imaging potentially offers a convenient, noninvasive technique for detecting gastroesophageal (GE) reflux disease. Initial studies suggested a high degree of sensitivity, although subsequent reports have been less encouraging. We sought to clarify this controversy by assessing the sensitivity of GE scintigraphy in 15 patients with severe esophagitis at endoscopy and 15 health volunteers. After acid loading, scintigraphy was performed in the basal state and after maneuvers (Valsalva, abdominal compression) which provoke GE reflux. Computer analysis permitted calculation of a reflux index for each maneuver. An index greater than 4% was considered a positive test. We found that the mean reflux index for the patients was significantly greater (p less than 0.01) than the healthy volunteers; 4.55 +/- 1.75% versus 0.42 +/- 0.11%, means +/- S.E.M. Only 30% of the patients had a reflux greater than 4%. Using data from our healthy volunteers, we redefined an abnormal reflux index as greater than 1.7%, but that only improved the test sensitivity to 60% and the specificity to 100%. Scintigraphy for reflux is primarily limited by the short duration of imaging. We cannot recommend GE scintigraphy as a useful screening test for reflux.

Adult↗
PubMed1985

Amplification of the antitumor activity of phleomycins and bleomycins in rats and mice by caffeine.

While having no antitumor effect per se, caffeine substantially enhanced the antitumor effects of the phleomycins PLM-CHP and PLM-PEP, and the bleomycins BLM-CHP and Blenoxane in rats carrying Walker 256 carcinosarcoma and/or mice carrying Ehrlich ascites tumor, even at doses of phleomycin and bleomycin below the minimum effective level. Positive but less conclusive results were also obtained with PLM-A4A4G and PLM-G.

Animals↗
PubMed1984

Iatrogenic hyperthyroidism secondary to dextrothyroxine administration.

Two patients are reported who presented with clinical hyperthyroidism, increased serum thyroid function studies, and depressed radioactive iodine uptake, secondary to chronic ingestion of D-T4. Symptoms abated, and function studies returned to normal, following discontinuation of D-T4. This uncommon effect of D-T4 may be more prevalent than is generally realized and must be recognized as another potential cause of low radioiodine uptake in patients with clinical hyperthyroidism.

Aged↗
PubMed1984

Esophageal radionuclide transit tests. Potential false-positive results.

Esophageal radionuclide transit testing is a sensitive technique for assessing esophageal clearance. Experience with the technique in 150 patients has led to an awareness of several pitfalls which might lead to false-positive results. Potential problems may be grouped into technical factors, clinical aspects, and misinterpretations. Examples of these are presented and techniques to minimize such problems are discussed.

Deglutition Disorders↗
PubMed1984

A computer-assisted radiologic reporting system.

The patient registration and interpretation/reporting modules of a computer-assisted radiologic reporting system are described. Entries may be made at several levels of complexity, using bar codes or keyboard input. Several functions allow convenient access to the database. Output may be reformatted without programmer intervention via a maintenance file. The system allowed improved turnaround time, reduced costs, and better understanding of work patterns.

Computers↗
PubMed1984

Relative lesion detection ability of Tc-99m HMDP and Tc-99m MDP: concise communication.

To compare the efficacy of Tc-99m HMDP and Tc-99m MDP to define skeletal lesions, 28 adult patients were examined in a double-blind, randomized, crossover study. Each patient was imaged with both agents over a period of 7-14 days. Both quantitative and qualitative evaluations were performed on the resulting images. Both agents detected the same number of skeletal lesions, and the number of lesions detected was the same whether the imaging was performed 2 or 4 hr after injection. Relative uptake of the tracer in the lesion relative to normal bone was also the same for both agents. Lesions were easier to see at 4 hr after injection than at 2 hr, presumably because soft-tissue levels were lower. Retention of tracer in bone compared with soft tissue was greater, and image quality was judged to be better, with Tc-99m HMDP than with Tc-99m MDP.

Adult↗
PubMed1984

Radionuclide techniques for brain imaging.

Over the past decade, many of the prime indications for radionuclide brain scanning have become instead indications for CCT, and nuclear medicine studies of the brain have assumed more of a complementary, supportive role. However, there is great promise for improvement in central nervous system radionuclide applications with advances anticipated in both radiopharmaceuticals and instrumentation. Nuclear medicine is continuing to function as a powerful research tool and, in the relatively near future, may regain its role as a major clinical test of the central nervous system.

Brain Abscess↗
PubMed1982

Tc-99m pertechnetate uptake in a thymoma: case report.

A case is reported to Tc-99m pertechnetate accumulation within an anterior mediastinal thymoma during a search for substernal goiter. This reemphasizes the non-specificity of Tc-99m pertechnetate uptake and the need for caution in using this agent to detect ectopic thyroid tissue.

Diagnosis, Differential↗
PubMed1980

Special characteristics and potential of single photon emission computed tomography in the brain.

Single photon emission tomographic techniques for evaluation of the brain have as their major advantage the ability to employ readily available radionuclides, such as technetium-99m. With present radiopharmaceuticals, single photon emmision tomography of the brain primarily provides morphological information that may be complimentary to standard gamma camera images. Particular areas of assistance have included detection of basal lesions, delineation of multiplicity of lesions, definition of medial extent of abnormalities, clear separation of skull and intracranial abnormalities, and perhaps improved lesion characterization. Overall, however, the reported improvement in sensitivity has been relatively small. To optimally utilize the tomographic and quantiative capabilities of single emission tomography, new classes of radiopharmaceuticals must be developed that can penetrate the blood-brain barrier and provide information on CNS function and pathophysiology. If such radiopharmaceuticals can be labeled with single emission radionuclides, this technique has the potential to provide critically important information. The ultimate outcome of single emission tomographic techniques for the study of the brain may depend on radiopharmaceutical advances.

Blood-Brain Barrier↗
PubMed1980

Comparison of Tc-99m pyrosphosphate and Tc-99m hydroxymethylene diphosphonate in acute myocardial infarction: concise communication.

A clinical comparison between a new bone seeking radiopharmaceutical, Tc-99m hydroxymethylene diphosphonate (TcHMDP) and the standard agent, Tc-99m pyrophosphate (TcPPi), was performed in 18 patients with acute myocardial infarction. Each patient was imaged initially with either TcHMDP or TcPPi, and imaged 24 hr later with the other tracer. All 18 patients had images positive for acute myocardial infarction with TcPPi, whereas 16 of 18 patients (89%) had positive studies with TcHMDP. The TcPPi images were graded significantly superior to those obtained with TcHMDP in 61% of the patients, and they were equal in 33%. In only one patient (6%) was TcHMDP better. The results indicate that compared with TcHMDP, TcPPi not only has a superior sensitivity for acute myocardial infarction but also has a significantly increased intensity of uptake in positive areas. TcPPi remains the agent of choice for myocardial infarct imaging.

Acute Disease↗
PubMed1980

A comparison of brain imaging with gamma camera, single-photon emission computed tomography, and transmission computed tomography: concise communication.

We have evaluated the utility of a single-photon axial tomographic scanner (ECT) in brain imaging, using routine tracers in 238 patients. When compared with routine delayed gamma-camera images (DGCI), there was agreement in 191 negative studies and 39 positive studies. Four patients had positive DGCI and negative ECT studies, and four had positive ECT and negative DGCI. In the 102 patients in this series who also had transmission CT (TCT) studies, there were five who had positive emission studies and negative TCT, and 38 with an abnormal TCT and normal ECT. The ECT was occasionally helpful in distinguishing brain and skull metastases, in better portrayal of deep lesions, and in resolving equivocal DGCI findings. For the ECT to become clinically rewarding, however, we feel that it will need development of new tracers that will provide functional information in addition to that already attainable by routine gamma-camera images.

Adult↗
PubMed1979

Efficacy of radionuclide scanning in patients with lung cancer.

Ninety-two patients with histologically proved carcinoma of the lung were studied retrospectively to determine the usefulness of liver, brain, and bone imaging in their examination and treatment. Occult metastatic liver disease was observed in two (5.3%) of 38 asymptomatic patients, while four (6.6%) of 58 neurologically intact patients had abnormal brain scans. Eight (13.6%) of 59 asymptomatic patients had metastatic bone disease. Seven (18.4%) of 38 patients with no clinical evidence of metastatic disease to liver, brain, or bone had at least one type of abnormal radionuclide study. More than half (52.5%) of the patients studied had at least one abnormal scan exclusive of symptoms. Radionuclide imaging is a useful procedure in the initial evaluation and subsequent management of lung cancer.

Adult↗
PubMed1979

Serum alkaline phosphatase determination. Value in the staging of advanced breast cancer.

A retrospective study of 146 patients with metastatic disease was undertaken to verify the clinical impression that radionuclide scanning rarely, if ever, discloses hepatic metastases in breast cancer patients with normal serum alkaline phosphatase (AP) levels. Only two of 39 patients with abnormal liver scans had normal AP levels, and we conclude that liver scans are not necessary as a routine screening method for liver metastases when the AP level is normal. In contrast AP levels were not predictive of bone scan results. All patients with a twofold or greater elevation of the AP level had abnormal bone, liver, or bone and liver scans. Routine AP determinations provide accurate staging information, and their proper use can decrease the cost of initial and follow-up examination of patients with breast cancer.

Alkaline Phosphatase↗