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Biomedical subjects

T H Shawker

Publications and source records attributed to T H Shawker.

At least 73 records · Page 4Linked to original sources
PubMed1987

The role of sonography in pediatric gynecology.

Sonography has a major role in the evaluation of children with gynecologic disorders. The size, consistency, and origin of pelvic masses and the status of the internal genitalia can be evaluated. Sonography is useful in evaluation of children with precocious puberty because it can demonstrate adult-size ovaries in true precocious puberty, which distinguishes this from premature thelarche and adrenarche. Specific causes of precocious sexual development such as adrenal and ovarian tumors and cysts also can be diagnosed.

Child↗
PubMed1987

Localization of parathyroid adenomas in patients who have undergone surgery. Part I. Noninvasive imaging methods.

The authors evaluated computed tomography (CT), ultrasound (US), technetium/thallium scintigraphy, and magnetic resonance (MR) imaging as localization procedures in 53 patients with proved parathyroid adenomas and previous unsuccessful parathyroid surgery. CT had the highest overall sensitivity (47%), followed by US (36%) and scintigraphy (27%). There is still too little data to assess MR imaging. Adenoma size affected the sensitivity of CT, scintigraphy, and MR imaging but not US. When all three studies were used, at least one study depicted a lesion in 78% of patients, but definitive localization (two positive studies) was achieved in only 31%.

Adenoma↗
PubMed1987

Localization of parathyroid adenomas in patients who have undergone surgery. Part II. Invasive procedures.

The authors studied intraarterial digital subtraction angiography (DSA), conventional selective angiography, parathyroid venous sampling (PVS), and intraoperative ultrasound (US) as localization procedures for parathyroid adenomas in 53 patients with proved parathyroid adenomas and previous unsuccessful parathyroid surgery. PVS had the highest overall sensitivity as a single study (80%), followed by intraoperative US (78%), angiography (60%), and DSA (49%). Invasive procedures permitted successful localization of adenomas in 41 of 43 patients studied (95%). False-positive studies were uncommon. The optimum sequence of invasive localization procedures is determined by clinical factors and not by the sensitivity of individual tests. The authors recommend DSA be performed first, followed by angiography, PVS, and intraoperative US, in that order.

Adenoma↗
PubMed1987

Quantitative estimation of liver attenuation and echogenicity: normal state versus diffuse liver disease.

A method based on broad-band amplitude for obtaining attenuation and echogenicity estimates from homogeneous phantoms and tissues is described. Although a number of assumptions about the beam and scattering properties must be made, the attenuation results are as accurate as those obtained by the spectral-difference method and show less variability. The method was applied to the livers of 18 healthy volunteers and 76 patients with liver disease, including 29 patients with chronic hepatitis and 30 patients with Gaucher disease. Patients with chronic hepatitis formed a bimodal distribution, with one group having lower than normal attenuation and echogenicity values and another having elevated values. Six patients with type I glycogen storage disease and fatty infiltration of the liver had highly attenuating, echogenic livers as did patients with fatty livers from other causes. This finding confirms the subjective impressions already reported in the literature. In contrast to previous literature reports, patients with cirrhosis had normal attenuation and echogenicity values. Reasons for this discrepancy are discussed.

Gaucher Disease↗
PubMed1987

Hepatic metastasis detection: comparison of three CT contrast enhancement methods.

A prospective, blinded comparison of three methods of hepatic contrast enhancement in computed tomography (CT) was conducted in 15 patients with colorectal carcinoma metastatic to the liver. Arterial portography (AP-CT) was performed with injection of contrast material into the superior mesenteric artery during CT. Delayed scanning (DS-CT) was performed 4 hours after intravascular administration of contrast material (mean dose, 280 mL). CT with an ethiodized oil emulsion (EOE-CT) was performed 1 hour after slow intravenous infusion of the emulsion. All patients underwent laparotomy following imaging studies. A lesion-by-lesion analysis of 56 metastases showed no significant differences in sensitivity (AP-CT, 77%; DS-CT, 83%; EOE-CT, 82%), but the false-positive rate for AP-CT was significantly higher than that for DS-CT (P less than .001) or EOE-CT (P less than .01). False-positive rates for EOE-CT and DS-CT were not significantly different. The predictive value of a positive test was 63% for AP-CT, 90% for DS-CT, and 81% for EOE-CT. AP-CT does not appear to be clinically useful for detection of hepatic metastases because of the high false-positive rate. No difference could be demonstrated between DS-CT and EOE-CT. DS-CT is a valuable method for hepatic contrast enhancement.

Adult↗
PubMed1987

CT of cerebral abnormalities in precocious puberty.

True precocious puberty occurs as a result of the premature release of luteinizing hormone-releasing hormone from the hypothalamus, which stimulates the secretion of the pituitary gonadotropins, which in turn stimulate the gonadal sex steroids. The differential diagnosis of true precocious puberty includes cerebral and idiopathic categories. This differentiation, which cannot be made endocrinologically due to similarities in pituitary gonadotropin and sex steroid levels, may be facilitated by high-resolution CT. A CT study of 90 children (73 girls and 17 boys) with true precocious puberty was performed at the NIH to detect cerebral causes of their precocious puberty. Thirty-four cerebral abnormalities were demonstrated in 32 children, 16 boys and 16 girls. These included hypothalamic hamartomas (17), hypothalamic astrocytoma (one), optic chiasm lesions (six), ventricular abnormalities (eight), arachnoid cyst (one), and teratoma (one). The CT appearance of these cerebral abnormalities is discussed and related to the endocrinologic findings and natural history of true precocious puberty. A practical neuroradiologic approach to the evaluation of children with precocious puberty is presented.

Astrocytoma↗
PubMed1987

Ultrasound appearance of extramedullary hematopoiesis.

Extramedullary hematopoiesis accompanies a wide variety of diseases and is defined as the abnormal production of blood outside the normal confines of the bone marrow. Most of the time, extramedullary hematopoiesis is found as microscopic foci in soft tissues; however, on occasion this process may reach a size that is detectable with ultrasound. Two forms are possible: "paraosseous"--in which the normal medullary tissue of the bone marrow ruptures through the bone to present as a paraosseous soft tissue mass,--and "extraosseous"--in which extramedullary hematopoiesis occurs within soft tissue. These "masses" of hematopoietic tissue can appear almost anywhere in the abdomen and pelvis and can mimic a wide variety of more serious diseases.

Adolescent↗
PubMed1986

Long-acting gonadotropin hormone-releasing hormone analog used to treat uteri.

Because the size of leiomyomata uteri often decreases significantly after menopause, the authors elected to employ a long-acting gonadotropin hormone-releasing hormone analog (GnRH-alpha) (imbzl-D-His6-Pro9-Net-GnRH) to create a state of pseudomenopause in six patients with leiomyomata uteri diagnosed on the basis of pelvic examination and confirmed by pelvic ultrasonography. Patients received daily, subcutaneous injections of GnRH-alpha (4 micrograms X kg-1 X 24 hour-1) for 6 months. Uterine size (13.8 +/- 4 weeks [mean +/- standard deviation (SD), n = 6]) was determined by pelvic examination and uterine volume (533.9 +/- 394 ml [mean +/- SD, n = 6]) was determined by pelvic ultrasonography before medical therapy was begun. They observed a decrease in uterine size by pelvic examination within 4 weeks of the initiation of therapy, and all patients experienced a decrease in uterine size (9.5 +/- 4 weeks [mean +/- SD, n = 6]) (P less than 0.05) within 8 weeks of initiation of therapy. After 6 months of therapy, uterine size was 229.5 +/- 145 ml (mean +/- SD, n = 6). During treatment, plasma estrogen concentrations were assessed intermittently (every 1 to 4 weeks) and remained less than 4 pg X ml-1 throughout the period of therapy. All six patients have discontinued therapy. There has been no increase in uterine size in these patients for a period from 3 to 7 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Gaucher disease: sonographic appearance of the spleen.

Ultrasonographic (US) examinations of the upper abdomen were performed in 80 patients with Gaucher disease. Of the 49 patients that had not undergone splenectomy, 47 had splenic enlargement. Sixteen patients had multiple lesions in the spleen. Most patients had discrete hypoechoic lesions that corresponded pathologically to focal homogeneous clusters of Gaucher cells. Several patients had similar lesions that were hyperechoic and were composed of Gaucher cells and fibrosis or infarction. A few patients had a geographic pattern of irregular areas of involvement of Gaucher cells among normal splenic parenchyma. The liver was often enlarged but otherwise sonographically unremarkable. Patients with Gaucher disease often have US examinations of the left upper quadrant for abdominal pain. A variety of US findings in the spleen typical for Gaucher disease should be recognized and not interpreted as acute changes.

Adolescent↗
PubMed1986

Pattern recognition methods for optimizing multivariate tissue signatures in diagnostic ultrasound.

Described is a supervised parametric approach to the detection and classification of disease from acoustic data. Statistical pattern recognition techniques are implemented to design the best ultrasonic tissue signature from a set of measurements and for a given task, and to rate its performance in a way that can be compared with other diagnostic tools. In this paper, we considered combinations of four ultrasonic tissue parameters to discriminate, in vivo, between normal liver and chronic active hepatitis. The separation between normal and diseased samples was made by application of the Bayes decision rule for minimum risk which includes the prior probability for the presence of disease and the cost of misclassification. Large differences in classification performance of various tissue parameter combinations were demonstrated using the Hotelling trace criterion (HTC) and receiver operating characteristic (ROC) analysis. The ability of additional measurements to increase or decrease discriminability, even measurements from other diagnostic modalities, can be evaluated directly in this manner.

Humans↗
PubMed1986

Ovarian function in girls with McCune-Albright syndrome.

We measured plasma estradiol levels and ovarian volumes in eight girls with precocious puberty due to McCune-Albright syndrome. Six girls had gonadotropin-independent ovarian estrogen secretion and two girls had pubertal gonadotropin levels. Mean ovarian volume in all patients was significantly greater than in normal prepubertal girls. Mean ovarian volumes of the girls with McCune-Albright syndrome overlapped the range found in girls with idiopathic central precocious puberty or central precocious puberty associated with central nervous system lesions. However, the degree of asymmetry between the right and left ovaries was significantly greater in girls with McCune-Albright syndrome. Asymmetry was due, for the most part, to the presence of large solitary cysts in the larger of the two ovaries. In the six girls with McCune-Albright syndrome and gonadotropin-independent precocious puberty, both mean ovarian volume and the degree of asymmetry between the right and left ovaries were significantly correlated with plasma estradiol. Serum follicle-stimulating hormone bioactivity was increased in two patients but did not vary with ovarian cyst size. Thyroid-stimulating hormone levels were normal but serum prolactin was slightly elevated in one of the six girls with gonadotropin-independent precocious puberty. Fluctuation in the size of unilateral ovarian cysts appears to result in changes in the plasma estradiol level, leading to advancement and spontaneous regression of secondary sexual characteristics and menses in girls with McCune-Albright syndrome. The cause of the cyst formation is unknown but may be related to periodic elevation of as yet undefined serum factors such as follicle-stimulating hormone bioactive substances.

Animals↗
PubMed1986

Ultrasonography of Turner's syndrome.

Pelvic sonographic studies were performed on 15 phenotypic females with Turner's syndrome and varying X chromosome abnormalities. In those individuals with the 45XO karyotype, the ovaries were not visible, consistent with the classic description of absent or fibrous streak ovaries. The patients who were chromosomal mosaics showed a range of findings from absent to infantile to normal adult-size ovaries. Turner's syndrome should be suggested in individuals with delayed onset of puberty, primary amenorrhea, and short stature in whom pelvic ultrasonography fails to reveal ovaries. On the other hand, the detection of ovarian tissue by pelvic ultrasonography does not exclude the diagnosis of Turner's syndrome but does suggest that an X chromosomal abnormality other than 45XO is probably present.

Adolescent↗