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Biomedical subjects

D Townsend

Publications and source records attributed to D Townsend.

At least 55 records · Page 3Linked to original sources
PubMed1986

Tomographic imaging of the human thyroid using 124I.

After receiving between 100 and 300 mu Ci of the positron-emitting radioisotope 124I (half-life, 4.2 days), 64 patients with a variety of thyroid disorders were imaged with a high resolution positron camera. A 3-dimensional image of the distribution of radioiodine uptake within the thyroid was obtained from a single 10- to 15-min scan. This image may be viewed as a sequence of 2-mm thick transverse, sagittal, or frontal sections or as a 3-dimensional shaded surface. The functional volume of the thyroid may be estimated by counting the volume elements (voxels) inside the thyroid surface. The precision of the estimate varied from 6-15%, depending on the size and clinical status of the thyroid. The volume estimation procedure was validated with phantoms and with the thyroids of patients who subsequently underwent partial thyroidectomy. This 3-dimensional imaging technique may be useful for diagnosis and management of thyroid diseases.

Adenoma↗
PubMed1985

In vivo imaging of the human thyroid with a positron camera using 124I.

A high-density avalanche chamber (HIDAC) positron camera was used for tomographic imaging of the human thyroid in vivo. Images were made 7 and 24 h after the oral administration of the positron-emitting radionuclide, sodium iodide 124I (with activities varying between 0.3 and 1 mCi), to patients scheduled for either partial thyroidectomy or radioiodine treatment. The results of thyroid imaging performed on 38 patients and their clinical relevance are discussed; as an illustration, three typical cases are presented. In Graves' disease, it was found that, whereas standard 131I and 124I scintigrams showed a diffuse goitre, positron images indicated a marked heterogeneity of the activity distribution, with "cold" areas in 8 out of the 11 cases studied. In conventional scintigrams, multinodular goitre showed a non-uniform radioiodine distribution, while positron images revealed considerable regional differences of activity uptake, with hot and cold areas in all of the 13 cases studied. As a consequence of the high spatial resolution of the camera [2.5 mm full width at half maximum (FWHM)], the functional volume of the thyroid may be estimated from 2 mm-thick transverse tomographic sections to within about 13%. This estimate may be compared with the measured volume after partial thyroidectomy, and in a follow-up scan, a further estimate can be made of the residual thyroid tissue remaining within the patient's body. In the case of radioiodine treatment in Graves' disease and multinodular goitre, the appropriate therapeutic dose of 131I can calculated according to the functional volume of the thyroid estimated from 124I tomographic images.

Adult↗
PubMed1985

Pathology of colposcopic findings in 2635 diethylstilbestrol-exposed young women.

An analysis of 6055 colposcopically directed biopsy specimens from 2635 diethylstilbestrol (DES)-exposed women and 445 biopsy specimens from 277 nonexposed women was undertaken to correlate microscopic findings with colposcopic patterns. All examinations were performed using a standardized protocol which required that each participant have colposcopy, cytologic smears, and biopsy of abnormal colposcopic lesions. The findings of colposcopic "columnar epithelium, gland openings, and Nabothian cysts" correlated most often with glandular epithelium in the biopsy specimen. "White epithelium," which includes three related colposcopic patterns, mosaicism, punctation, and white epithelium, was associated most frequently (82-93% of cases) with squamous metaplasia, but occasionally with dysplasia and carcinoma in situ (CIS)(0-6%). The presence of dysplasia or CIS in any individual biopsy specimen occurred most frequently with the observation of higher graded lesions by colposcopy or a prior diagnosis of dysplasia.

Carcinoma in Situ↗
PubMed1985

Brown oculocutaneous albinism. Clinical, ophthalmological, and biochemical characterization.

The clinical, ophthalmological, and biochemical characteristics of a 28-year-old black woman with brown oculocutaneous albinism were determined. Hair color was medium brown and skin color was light brown, and a faint tan developed with sun exposure. The irides were light brown in the central one-third, blue-gray in the peripheral two-thirds, and showed punctate and radial translucency. Visual acuity was 20/60 in the right eye and 20/100 in the left eye. There was a moderate pendular nystagmus, and previous surgeries had corrected an exotropia. The foveal reflex was muted, and the retinal pigment was reduced. Hairbulb tyrosinase activity was 1.75 pmoles/120 min/hairbulb, hairbulb glutathione content 0.83 nmoles/hairbulb, and urine excretion of 5-S-cysteinyldopa 174.9 ng/mg creatinine. Electron microscopy of hairbulb and skin melanocytes showed arrested melanosomal development. These findings suggest that there is a partial block in the distal eumelanin pathway in this form of albinism. The ophthalmological characteristics of six additional cases of this form of albinism are also presented.

Adult↗
PubMed1985

Cobalt-57 bleomycin scanning for lung cancer detection: a prospective study in thoracic surgery.

Patients displaying an abnormal chest X-ray, in some cases, cause a difficult diagnostic problem. A differential diagnosis between benign and malignant lesions is important to determine the choice of treatment i.e. whether or not to perform a thoracotomy. In a prospective study, we have examined the role of 57Co-bleomycin scanning for prethoracotomy assessment of 60 patients with a high clinical probability of lung cancer. For these patients, a sensitivity of 89%, a specificity of 84% and an accuracy of 88% were found. However, as a consequence of the six false-negative scans (two in-situ carcinomas and four stage I carcinomas), bleomycin scanning cannot be regarded as adequate for obviating thoracotomy in patients with a high clinical probability of lung cancer but a negative scan. Nevertheless, the technique is useful for the assessment of tumour size and for the detection of hilar, mediastinal and extra-thoracic metastases, with consequences for TNM staging. It has been found that the tumour dimension correlates well with the actual anatomo-pathologic size determined after surgical examination (r2 = 0.65 and p less than 0.01). Therefore, with an accuracy around 90% for the diagnosis of lung cancer, 57Co-bleomycin scanning offers a major tool for use in clinical investigation.

Adenocarcinoma↗
PubMed1985

Single photon emission computed tomography study of human cancer: utilization of 57Co-labelled bleomycin.

The sensitivity and specificity of single photon emission tomography with 57Co-labelled bleomycin (57Co-BLM) for the detection of cancer was determined from a prospective study involving a large group of patients selected to investigate roentgenographic abnormalities. Eighty-four of the 104 patients studied had malignant disease, of whom 76 had a positive scintigram. Eighteen of the 20 patients with benign disorders had a negative scintigram. The sensitivity and specificity was therefore 90.5 and 90% respectively. For the subset of patients who underwent investigation below the diaphragm, the sensitivity was 85.7%, while for investigation above the diaphragm, it reached 95.2% (this excluded reconstructions on the bladder level, because it produced large artifacts). This study leads to the conclusion that SPECT can be used specifically to investigate unidentified X-ray abnormality and diagnose malignancy using 57Co-BLM. In addition, we propose further investigation to evaluate the usefulness of this method in staging cancer.

Aged↗
PubMed1985

Tomographic imaging of the human thyroid with a positron camera before and after partial thyroidectomy.

A high-density avalanche chamber positron camera was used for tomographic imaging of the human thyroid before and after partial thyroidectomy. Images were made between 6 and 24 h after oral administration of the positron-emitting radionuclide, Na-124I with activities varying between 0.1 and 0.3 mCi before the surgical intervention and with activities between 0.03 and 0.05 mCi following partial thyroidectomy. The results of thyroid imaging performed on 50 patients and their surgical relevance are discussed; as an illustration, one typical case is presented. As a consequence of the high spatial resolution of the camera (2.5 mm full width at half maximum), the functional volume of the thyroid may be estimated from the transaxial tomographic sections before and following partial thyroidectomy, correct to about 10%. The thyroid surface, defined by the contours from each transaxial section, may be displayed using three-dimensional shaded-graphics techniques. This new imaging technique makes possible a fully three-dimensional description of the thyroid in vivo and contributes significantly to the surgical follow-up.

Goiter, Nodular↗
PubMed1985

57Co-labelled bleomycin scintigraphy for the detection of lung cancer: a prospective study.

The sensitivity and specificity of scanning with 57Co-labelled bleomycin for the diagnosis of lung cancer were determined from a prospective study involving a large group of patients with an abnormal chest roentgenogram. A semi-quantitative analysis of the scintigram was obtained by defining an index in terms of the excess isotope uptake within the tumour. Malignant pulmonary lesions were found in 121/175 patients and 113 had a positive scan. Benign pulmonary disorders were found in 54 patients, 45 of whom had a negative scan. The sensitivity and specificity were therefore 93% and 83% respectively. Bayes' theorem was then used to determine the predictive value of this test, either positive or negative, when the prevalence of disease varied from 10 to 90%. A receiver operating characteristic curve permits the choice of an appropriate value of the tumour uptake index to minimize the false positive fraction without classifying too many true positives as false negatives.

Adenocarcinoma↗
PubMed1985

SPECT study of the fluid distribution in the intra-abdominal space during intraperitoneal treatment of ovarian cancer.

Only limited progress has been achieved in the treatment of ovarian cancer, the most common fatal gynaecological malignancy. Peritoneal dialysis with drugs known to be effective in ovarian cancer and large intraperitoneal fluid volumes (Belly Bath) have been used. The two critical determinants for a successful intraperitoneal chemotherapy programme are: (1) complete accessibility of the drug to all tumour-bearing areas; and (2) drug penetration into the residual tumour masses. We show that the scintigraphic technique in tomographic mode after administration of MAA-99Tcm-containing dialysate is a valuable adjunct for evaluation of patients undergoing intraperitoneal chemotherapy.

Adenocarcinoma↗
PubMed1984

Increased incidence of cervical and vaginal dysplasia in 3,980 diethylstilbestrol-exposed young women. Experience of the National Collaborative Diethylstilbestrol Adenosis Project.

The incidence rates of dysplasia and carcinoma in situ (CIS) of the cervix and vagina were determined in 3,980 young women exposed prenatally to diethylstilbestrol. Strict criteria were developed to minimize selection bias among the subset of 744 pairs of matched exposed and unexposed (control) cohort participants, all of whom were identified through review of prenatal obstetrical records. A high degree of compliance was achieved throughout the seven-year study period since in each group about 90% of the women remained as active participants, kept 77% of the annual anniversary examinations, and had separate Papanicolaou smears of the cervix and vagina performed in 99% of the anniversary examinations. The incidence rate for dysplasia and CIS was significantly higher in the women exposed to diethylstilbestrol than in those not exposed in the matched cohort (15.7 v 7.9 cases per 1,000 person-years of follow-up). The rates were higher in the exposed women if squamous metaplasia extended to the outer half of the cervix or onto the vagina. In other respects, the matched cohorts were strikingly similar.

Adult↗
PubMed1984

Optimized assay for mammalian tyrosinase (polyhydroxyl phenyloxidase).

Tyrosinase is an important enzyme in the formation of pigment throughout the animal kingdom and many assays have been described for measuring its activity. This paper describes an assay which has been optimized to measure the enzymatic activity of mammalian tyrosinase and describes the procedures from which the optimum conditions were determined. The preparation and storage of the stock reagents required to perform the assay are also described in detail as well as some discussion pertaining to the preparation of samples prior to assay.

Animals↗
PubMed1984

Dopachrome oxidoreductase: a new enzyme in the pigment pathway.

We report our preliminary characterization of a new enzyme in the pigment pathway which we propose to call dopachrome oxidoreductase (DCOR). This enzyme, prepared from mouse melanoma, catalyzed the conversion of dopachrome to 5,6-dihydroxyindole and also appeared to block the pigment pathway at this latter compound in the absence of tyrosinase. DCOR was protease-sensitive, heat-labile, and showed maximum stability in the range of pH 6-8. The molecular weight of DCOR was estimated to be 34,000 by gel filtration. DCOR had a subcellular distribution within the melanocyte which was similar to that of tyrosinase, but DCOR activity was found in melanocytes devoid of tyrosinase activity and was not inhibited by tyrosinase inhibitors. DCOR may prove to be an active regulatory enzyme in melanogenesis.

Animals↗
PubMed1983

A general method for three-dimensional filter computation.

Application of the Fourier space deconvolution algorithm to three-dimensional (3D) reconstruction problems necessitates the computation of a frequency space filter; which requires taking the 3D Fourier transform of the system response function. In this paper, it is shown that for system response functions of the specific form d(theta, phi)/r2, with d(theta, phi) an angular function describing the imaging system, the filter computation can always be reduced to a single integration which, in many cases, may be performed analytically. Complete expressions are derived for the general 3D filter, and two examples are given to illustrate the use of such expressions.

Mathematics↗
PubMed1983

Effect of megavitamin treatment on mental performance and plasma vitamin B6 concentrations in mentally retarded young adults.

Other workers have reported preliminary results suggesting that vitamin and mineral supplements might improve the mental performance of mentally retarded children. The current study examined the effect of 20 wk of the suggested supplement on Stanford Binet scores in mentally retarded adults with nonspecific diagnoses, Down's syndrome, and subjects receiving anticonvulsant medication. No improvement in Stanford Binet scores was observed. However, serum pyridoxal phosphate concentrations were significantly (p less than 0.05) increased in subjects with Down's syndrome receiving the supplement compared with subjects with nonspecific diagnoses receiving the same treatment thus providing further evidence of abnormal vitamin B6 metabolism in Down's syndrome.

Adolescent↗
PubMed1981

Dysplasia and cytologic findings in 4,589 young women enrolled in diethylstilbestrol-adenosis (DESAD) project.

This report presents the cytologic findings and the rates of dysplasia for 4,589 young women enrolled in the National Cooperative Diethylstilbestrol-Adenosis (DESAD) Project. Mucinous columnar cells and/or metaplastic squamous cells with or without mucinous droplets were encountered in 22% of vaginal scrape smears from all diethylstilbestrol (DES)-exposed participants identified by review of prenatal records and in 43% of women in whom vaginal epithelial changes (VEC) were observed by colposcopy or by iodine staining. The frequency of cellular findings in the vaginal scrape smears was closely related to the timing of the administration of the DES to the mother. With increasing age of the daughters, the overall frequencies of both the mucinous and metaplastic cells decreased; relative to each other, an increasing proportion was metaplastic squamous cells. These data suggest that, as the women grow older, vaginal adenosis regresses by the process of squamous metaplasia. Endometrial type cells were found in 2% of vaginal scrape smears. Their cyclical occurrence during the menstrual cycle and lack of correlation with the presence of VEC indicated an origin from the uterine corpus rather than the tuboendometrial type of adenosis. Squamous cell dysplasia of the vagina and cervix was detected by biopsy or scrape smear specimens in 1.8% of DES-exposed women in the record review group. The rate of unexposed women was twice as high. In general, the rates of dysplasia were higher in the cervix than vagina, and the more severe degrees of dysplasia were encountered only in those women who were referred to the DESAD Project or who themselves requested entry. Four patients who were referred or who themselves requested entry were found to have clear cell adenocarcinoma of the vagina. The vaginal smear provided the first clue to the presence of an abnormality in three of them.

Adenocarcinoma↗
PubMed1981

Tyrosinase subcellular distribution and kinetic parameters in wild type and C-locus mutant C57BL/6J mice.

The distribution and kinetic parameters of tyrosinase (EC 1.14.-18.1) from anagen hair follicles of the C57BL/6J mouse and several c-locus mutants were investigated. The results showed that c-locus mutations not only influenced the total tyrosinase activity, but the subcellular distribution as well. The kinetic parameters of tyrosinase were not influenced by the pigment mutations, suggesting that the mutations were not influencing the structure of the enzyme.

Animals↗
PubMed1981

Filters for three-dimensional limited-angle tomography.

One approach to the three-dimensional, tomographic reconstruction of data from a planar dual-detector stationary positron camera necessitates frequency-space filtering of the image obtained from back-projection. It is therefore useful to have a closed-form expression for the appropriate filter, but the derivation is complicated by the fact that the camera measures only a limited angular range of projections. Nevertheless, suitable expressions can be obtained and are here derived for detectors of rectangular and circular cross-section.

Humans↗