Biomedical subjects
Publications and source records attributed to A Karellas.
Postmortem high-detail skeletal radiography of 78 infants who died of the sudden infant death syndrome was performed during a 3-year period. Review of the studies reveals a variety of distinct radiologic variants that should not be confused with the metaphyseal injuries caused by infant abuse.
Focal (irregular, partial) fatty infiltration of the liver may simulate neoplastic or other hypodense masses on CT. On the basis of previous observations of the phenomenon that differences in X-ray attenuation diminish with increasing energy of X-rays used, we performed a preliminary study to determine if dual-energy CT could be used to discriminate between fatty infiltration and hypodense liver masses. Dual-energy CT at 140 and 80 kVp was performed in 14 patients undergoing liver biopsy and in seven control subjects with presumedly normal liver. Attenuation measurements were taken, and the changes in attenuation between 140 and 80 kVp were calculated. The mean changes in attenuation were 3.5 H for normal liver (n = 7), 2.5 H for hypodense liver masses (n = 6), 13 H for fatty liver (n = 5), 0.3 H for fatty liver combined with hemochromatosis or hemosiderosis (n = 3), and 2 H for the spleen (n = 18). The change in attenuation increased as the fat content in the liver increased. Analysis of variance showed a statistically significant difference (p less than .001) between fatty liver and the other groups. A difference greater than 10 H was unique to fatty infiltration. These results suggest that dual-energy CT may help to differentiate focal fatty infiltration of the liver from low-density neoplastic or other lesions, but only if the iron content of the liver is not increased.
It is estimated that 44,500 American women will die of breast cancer in 1991. The breast cancer screening guidelines of the American Cancer Society and the National Cancer Institute calling for annual mammography for all women older than 50 years have been endorsed by numerous professional groups. Third-party reimbursement for screening mammography is becoming more prevalent, and payment for screening mammography is now a Medicare benefit. Our studies, conducted as part of a National Cancer Institute grant to increase the routine use of screening mammography and clinical breast examination in women 50 to 75 years of age, have uncovered a number of significant barriers to the implementation of screening guidelines among women, primary care physicians, and providers of mammography services. These barriers, as well as methods to assure the quality of mammography, need to be addressed before universal screening is feasible.
The effect of dietary calcium on vertebral bone mass in women is controversial. In a randomized study we have investigated the effect of dietary modification in the form of dairy products on vertebral bone mass in 30- to 42-yr-old premenopausal women over a 3-yr period. Twenty women increased their dietary calcium intake by an average of 610 mg/day (P less than 0.03) for 3 yr, while 17 age- and weight-matched women served as controls. Calcium intake was monitored by 3-day diet histories and 24-h urinary calcium excretion. The consumption of the dairy products did not alter serum calcium or PTH levels or the fasting urinary calcium to creatinine ratio. Twenty-four-hour urinary calcium excretion increased by 28% (P less than 0.03) in the supplemented women. Dairy product intake was accompanied by increased dietary fat intake, but there were no statistically significant changes in serum cholesterol, low density lipoprotein cholesterol, or high density lipoprotein cholesterol levels. The vertebral bone density in the women consuming increased calcium did not change over the 3-yr period (-0.4 +/- 0.9%). In contrast, the vertebral bone density in the control women declined (-2.9 +/- 0.8%; P less than 0.001) and was significantly lower than that in the supplemented group at 30 and 36 months. The study suggests that dietary modification in the form of dairy products retards vertebral bone loss in premenopausal women. Therefore, increased calcium intake in estrogen-replete premenopausal women may prevent age-related bone loss.
In 1984 we started a two-year program in Worcester (Mass.) and Boston to provide additional radiologic data for the medical investigation of suspected fatal infant abuse. During that period the investigation of 12 cases of unexplained infant death included the review of complete radiographic skeletal surveys by a pediatric radiologist. Autopsies were supplemented with resection, high-detail radiography, and histologic study of all non-cranial sites of suspected osseous injury. Thirty-four bony injuries were noted, including 12 acute and 16 healing fractures of the long-bone metaphyses and posterior-rib arcs in patterns indicative of infant abuse. The investigations determined that there were eight cases of abuse, two accidental deaths, and two natural deaths (sudden infant death syndrome). At this writing, the radiologic and osseous histologic studies appear to have influenced the determination of the manner of death in six of the eight cases of abuse and the criminal prosecution in four of the five convictions. These findings suggest that a thorough postmortem radiologic evaluation followed by selected histologic studies can have an impact on the investigation and prosecution of cases of fatal infant abuse.
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Bone ultrasound attenuation of the calcaneus, and vertebral and femoral bone density measured by dual photon absorption were determined in 22 women with osteoporosis, 10 women with hip fractures, and 29 normal, age-matched controls to determine the utility of the ultrasound technique as an indicator of axial osteopenia. Vertebral and femoral neck density and bone ultrasound attenuation were significantly decreased (P less than 0.01) in the women with osteoporosis and those with hip fractures. The sensitivity and specificity of bone ultrasound attenuation was 80% at a value of 50 dB/MHz. At 90% specificity the sensitivity of bone ultrasound attenuation was 65%. The results of this pilot study suggest that ultrasound attenuation, a safe, simple, and radiation-free procedure, may be utilized as an indicator of decreased axial bone mass.
Visualization of the head of the pancreas by CT was prospectively evaluated in two groups of 100 patients who did not have pancreatic disease. Patients were given either a fat-density oral contrast material (12.5% corn-oil emulsion and metoclopramide) or a conventional high-density oral contrast material (barium suspension or iodinated solution). There was no statistically significant difference in the subjects' tolerance to the two regimens. There was, however, a significant improvement in ability to distinguish the head of the pancreas from the duodenal C-loop when the fat-density contrast material was given. When pancreaticoduodenal discrimination was graded, patients given corn-oil emulsion and metoclopramide received an average score of 0.94, whereas those given the high-density agent received an average score of 0.74, with 1.00 being the highest possible score (p less than .005). These data suggest that for routine CT evaluation of the head of the pancreas, a combination of corn-oil emulsion and metoclopramide may be superior to the conventional high-density oral contrast agents given without metoclopramide.
To overcome the problem of inadequate mixing of gastrointestinal (GI) tract contents with conventional high-density oral contrast agents in abdominal computed tomography (CT), a flavored 12.5% corn oil emulsion (COE) was tested as an oral contrast agent in 62 patients. The results were compared with those obtained from 105 patients who received high-density oral contrast agents. A simple patient preparation regimen for the COE was developed, which appears to be reasonably well tolerated by the patients and yields diagnostic studies comparable to those obtained with conventional agents. Use of the COE resulted in consistent discrimination of the GI tract and depiction of the GI wall. Preliminary data suggest that it may be particularly useful for CT evaluation of the stomach, duodenum, and pancreas; in patients suspected of having solid tumors; and in thin people.
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Trabecular bone mineral density (TBMD) was measured in vivo in the calcaneus by a new method that uses the ratio of coherent to Compton-scattered photons arising from irradiation of a small volume of trabecular bone by a gamma ray source with highly collimated geometry. TBMD values for healthy men (22-77 years) were in the range of 180-357 mg/ml, and values for healthy women (18-73 years) were in the range of 160-321 mg/ml. In contrast, values in a small group of paraplegics were in the range of 90-199 mg/ml.
Dilatation of unobstructed extrahepatic bile ducts was observed in patients with conditions associated with intestinal hypomotility. For further investigation of this association, a prospective study was undertaken in which the common hepatic duct was measured in 15 patients before and 1 day after laparotomy, when all patients had postoperative paralytic ileus. A statistically significant (p less than 0.01) increase in the mean diameter of the hepatic duct was observed postoperatively. When compared with the preoperative measurement, the mean diameter of the duct almost doubled, from 3.3 to 5.9 mm. This phenomenon may be due to persistent contraction of the sphincter of Oddi that occurs when intestinal hypomotility eliminates the stimuli for cholecystokinin release.
The changes of the biliary tree following distal bile duct obstruction and its release were confirmed by biliary scintigraphy and monitored by serial ultrasonography, computed tomography, and values of serum bilirubin and alkaline phosphatase in 14 mongrel dogs. The degree and rate of biliary dilatation were independent of cholecystectomy. The most rapid rate of extrahepatic dilatation occurred within the first 48 hours, while dilated intrahepatic ducts were first recognized three to six days after obstruction. Following release of the obstruction, the degree and rate of resolution of the biliary dilatation were independent of the duration of ligation (one vs. two weeks) and cholecystectomy. The dilatation resolved slowly. Dilated intrahepatic ducts were recognized for as long as eight to 13 days, while extrahepatic biliary dilatation was still present for 13 weeks, at which time the experiment was terminated. It is postulated that the extrahepatic biliary dilatation will approach a plateau approximately one month after total biliary obstruction. It appears that if the obstruction lasts more than one week, it results in irreversible damage to the elasticity of the extrahepatic ducts. Thus, after release of the obstruction, serial biliary imaging is indicated until a new baseline of the biliary tree diameter has been established.
PURPOSE: Our goal was to assess the performance of high resolution CT on breast biopsy specimens before considering the reevaluation of refined CT techniques in patients with breast abnormalities. METHOD: High resolution CT was done in 44 surgical biopsy specimens following conventional X-ray specimen mammography. The specimens comprised 38 palpable and nonpalpable soft tissue abnormalities with mean size of 19 mm and 6 specimens with clustered microcalcifications only. There were 21 carcinomas, 10 fibroadenomas, and 13 other benign conditions. Evaluation of CT and conventional images was done separately, and a feature-grading list was used to compare the two modalities. RESULTS: In fatty specimens, grading of morphologic features of masses and the confidence to detect a soft tissue abnormality were equal with both techniques. CT significantly improved the confidence to detect a mass in 17 specimens with dense tissue: On a scale of 0-10, the mean score for detection was 3.8 with radiography and 5.8 with CT (p<0.008). For clustered microcalcifications, X-ray was superior to CT. The mean CT attenuation of 18 malignant masses (82 HU) was significantly lower than the mean attenuation of 10 fibroadenomas (131 HU; p = 0.003). CT scans of the American College of Radiology test phantom met the requirements for X-ray accreditation. CONCLUSION: For soft tissue abnormalities, CT specimen mammography performed equally as or better than specimen radiography. These in vitro results suggest potential advantages for increased sensitivity and specificity with CT and justify further investigations.
A photon scattering method for measuring the trabecular bone mineral density (TBMD) in vitro is described. This method involves the measurement of the ratio of coherent to Compton 90 degrees scattered photons from Am-241 by using a narrow beam geometry with an intrinsic germanium detector. The feasibility of using smaller scattering angles for better counting efficiency and the associated problems in their application for in-vivo measurements were investigated. Calibration of the system with fresh trabecular bone samples showed a linear relationship between the coherent to Compton ratio R of the detected counts and the TBMD (r = 0.94). The effect of the overlying soft tissue on the R ratio was significant while the effect of self-attenuation by the trabecular bone itself and the cortical layer was negligible. It was found that the marrow fat content could alter the value of the R ratio. Our results show that for a 10% increase in the fat content in the interstices of the trabecular bone there is a 2.5% decrease in the R ratio. This technique together with soft tissue corrections will enable us to measure the TBMD of the calcaneum in vivo, assuming a small variation in the trabecular fat content. The estimated absorbed dose to the bone marrow is about 139 mrad.
It is known that the ratio (R) of the detected coherent and Compton scattered photons from bone can be used in order to determine its mineral density. This technique utilizes the dependence of the coherent scattering on the effective atomic number (Z) of the scattering medium. It is generally accepted that a small scatter angle is preferred in order to ensure adequate counting statistics by favoring the detection of more coherent photons. Moreover, it has been assumed that a change in the scatter angle does not affect the sensitivity of the measurement. Our theoretical calculations for 60-keV photons and for the range of Z that corresponds to trabecular bone, indicate that increasing the scatter angle results in a stronger power dependence of the measured ratio on Z. This implies that by increasing the scatter angle, smaller changes in the mineral density can be detected, thus improving the sensitivity of the measurement. This effect was investigated experimentally by using a collimated beam of 59.54-keV photons from Am-241 (44.4 GBq) and a collimated intrinsic germanium detector. Solutions of K2HPO4 with different concentrations were used in order to simulate trabecular bone. The scatter spectra were recorded for all solutions at six scatter angles between 37 degrees and 98 degrees and the value of R was computed for each spectrum. The sensitivity of the measurement, evaluated from these experiments increased, with the increase of the scatter angle.
The ratio of coherent to Compton photon scattered by a tissue-like material depends on its effective atomic number. This ratio can, therefore, be used for the in vivo characterization of tissues. The intrinsic sensitivity of this measurement is defined as the change in the coherent-to-Compton ratio for a given change in the atomic number. The effect of the scatter angle on the sensitivity has already been described by us in a paper recently submitted to this journal. In this study, the dependence of the sensitivity on the energy of the incident photons is investigated in two ways. The first approach is quasitheoretical and is based on computations of the cross sections of the coherent and Compton scattering for various energies. The second approach is experimental and it involves the measurement of the scatter ratio from a series of K2HPO4 solutions for three primary photon energies: 60, 81, and 140 keV. The combined effect of both the photon energy and the scatter angle on the sensitivity can be described by a single parameter which is the momentum transfer. It is concluded that for the limited range of the atomic numbers which apply to trabecular bone (8 less than or equal to Z less than or equal to 11) the momentum transfer reflects completely the effect of the scatter angle and photon energy on the sensitivity.
A method to determine the bone mineral density of the calcaneum has been reported earlier by our laboratory. In this method, the calcaneum is irradiated by a 60-keV photon beam from 241Am source and both the coherent and Compton scattered photons are detected by a high-purity Ge detector. The bone mineral density is determined by measuring the ratio of coherent-to-Compton scattered photons. The accuracy and the precision (in vitro) of the method are reported in this paper. The accuracy was determined to be 5%. This was obtained by comparing the bone mineral density values of cadaver calcanea measured directly by Archimedes' volume displacement method with the values measured by the scattering method. The precision was determined to be 3% by measuring the bone mineral density of a calibration phantom intermittently over a ten-month period by the scattering method.