Functional imaging of the heart with electron-beam computed tomography

PURPOSE: Electron-beam computed tomography (EBCT) enables examinations with a very short acquisition time of 50 ms and thus permits cardiac imaging without motion artifacts. Utilizing eight detector rings simultaneous image acquisition in up to eight levels and complete imaging of the whole heart is possible. In studies, functional imaging with EBCT was compared to our angiocardiography, echocardiography, radionuclide, ventriculography and magnetic resonance tomography. MATERIALS AND METHODS: ECG-triggered long- and short-axis cine studies were performed with the Imatron C-150 Evolution, acquiring 160 and 156 images at 8 and 12 levels. After manual tracing of epicardial and endocardial borders, ventricular size, ejection fraction, wall-thickening and myocardial mass were calculated. RESULTS: A very high correlation between EBCT and direct determination of right and left ventricle (r = 0.98 and r = 0.99) was demonstrated. Compared to echocardiography, angiocardiography and radionuclide ventriculography, assessment of ventricular function was more precise and more reliable. DISCUSSION: EBCT allows the exact and reliable determination of left and right ventricular function. Also precise assessment of myocardial mass is possible. However, the high radiation exposure and diagnostic effort have to be considered.     

Technical bases and acquisition conditions of electron-beam computed tomography

PURPOSE: In this review the technical principle and scanner characteristics of electron beam computer tomography (EBCT) are discussed. METHODS: In contrast to conventional CT, image acquisition in EBCT is achieved without mechanically moving parts. This construction allows for short acquisition times in investigating given anatomical regions (100 ms per slice) or up to 8 levels without table movement and short interscan delays (50 ms per slice). RESULTS: Depending on the nature of the investigation, the scanner can be used in the single slice, continuous volume scanning and multi slice mode. The single slice mode is used for detection and quantification of coronary calcifications and for CT angiography of the coronary vessels. Equivalent to the spiral mode in conventional CT, continuous volume scanning may be used for routine investigation of the chest and abdomen. Functional investigations of the heart and perfusion measurement of different organs can be performed in multi slice mode. Because of the geometry of the electron beam scanner, radiation exposure for certain investigations is above the exposure with conventional CT. CONCLUSION: Future developments will focus on dose efficient radiation collimation, high resolution detector systems and artefact reducing reconstruction kernels.     

Value of electron-beam computed tomography for the noninvasive detection of high-grade coronary-artery stenoses and occlusions

BACKGROUND: Reliable noninvasive assessment of coronary-artery stenoses and occlusions would constitute an advantage in the care of patients with known or suspected coronary artery disease. We investigated the accuracy of contrast-enhanced electron-beam computed tomography (CT) for the detection of high-grade coronary-artery stenoses and occlusions. METHODS: Electron-beam CT was performed in 125 patients. After intravenous injection of a contrast agent, 40 cross-sectional images of the heart were acquired during inspiration, triggered by the electrocardiogram in diastole. Three-dimensional reconstructions of the heart and coronary arteries were rendered to facilitate evaluation of the images. The proximal and middle segments of the major coronary arteries were evaluated for the presence or absence of high-grade stenoses and occlusions. The results were compared with those of invasive coronary angiography in a blinded fashion. RESULTS: Because of technical problems that impaired the quality of the images, 124 (25 percent) of the 500 coronary arteries studied (left main, left anterior descending, left circumflex, and right coronary) in a total of 125 patients were excluded from evaluation. No vessels could be evaluated in 19 patients (15 percent), and another 28 patients (22 percent) had one, two, or three vessels that could not be evaluated. In the remaining coronary arteries with adequate image quality, electron-beam CT permitted visualization of 69 of 75 high-grade stenoses and occlusions (sensitivity, 92 percent), whereas in 282 of 301 arteries, the absence of high-grade stenoses and occlusions was correctly detected (specificity, 94 percent). CONCLUSIONS: When image quality is adequate, electron-beam CT may be useful to detect or rule out high-grade coronary-artery stenoses and occlusions.     

Diagnosis of the abdominal vascular system by means of electron-beam computed tomography (EBT)]

Pokeweed antiviral protein (PAP) from Phytolacca americana is a highly specific N-glycosidase removing adenine residues (A4324 in 28S rRNA and A2660 in 23S rRNA) from intact ribosomes of both eukaryotes and prokaryotes. Due to the ribosome impairing activity the gene coding for mature PAP has not been expressed so far in bacteria whereas the full-length gene (coding for the mature 262 amino acids plus two signal peptides of 22 and 29 amino acids at both N- and C-termini, respectively) has been expressed in Escherichia coli. In order to determine: 1) the size of the N-terminal region of PAP which is required for toxicity to E. coli; and 2) the location of the putative enzymatic active site of PAP, 5'-terminal progressive deletion of the PAP full-length gene was carried out and the truncated forms of the gene were cloned in a vector containing a strong constitutive promoter and a consensus Shine-Dalgarno ribosome binding site. The ribosome inactivation or toxicity of the PAP is used as a phenotype characterized by the absence of E. coli colonies, while the mutation of PAP open reading frames in the small number of survived clones is used as an indicator of the toxicity to E. coli cells. Results showed that the native full-length PAP gene was highly expressed and was not toxic to E. coli cells although in vitro ribosome inactivating activity assay indicated it was active. However, all of the N-terminal truncated forms (removal of seven to 107 codons) of the PAP gene were toxic to E. coli cells and were mutated into either out of frame, early termination codon or inactive form of PAP (i.e., clone PAP delta107). Deletion of more than 123 codons restored the correct gene sequence but resulted in the loss of the antiviral and ribosome inactivating activities and by the formation of a large number of clones. These results suggest that full-length PAP (with N- and C-terminal extensions) might be an inactive form of the enzyme in vivo presumably by inclusion body formation or other unknown mechanisms and is not toxic to E. coli cells. However, it is activated by at least seven codon deletions at the N-terminus. Deletions from seven through to 107 amino acids were lethal to the cells and only mutated forms (inactive) of the gene were obtained. But deletion of more than 123 amino acids resulted in the loss of enzymatic activity and made it possible to express the correct PAP gene in E. coli. Because deletion of Tyr94 and Val95, which are involved in the binding of the target adenine base, did not abolish the activity of PAP, it is concluded that the location previously proposed for PAP enzymatic active site should be reassessed.     

Self-referral of patients for electron-beam computed tomography to screen for coronary artery disease

As the availability of electron-beam CT increases, it is appropriate to question the balance among medical science, patient care, and profits. Broadening patients' sense of empowerment and promoting their autonomy are worthy goals within medicine. Breast-cancer screening with mammography is an example of a radiographic test used successfully in a diagnostic program based on self-referral. But the lessons of such a program, in which the distinction between the disease and the disease-free state is more easily recognized than is the case for age-dependent calcific arterial changes, are not easily extrapolated to screening for coronary disease. Currently, we are facing the possibility that market forces may increase interest in electron-beam CT beyond what is justified by its potential medical benefit. Well-designed clinical trials are required to define fully the appropriate indications for and limitations of electron-beam CT. Such trials will eventually clarify the medical applications of the technique and determine its suitability as a screening procedure for cardiovascular disease. Until then, the use of electron-beam CT, like that of all tests in medicine, should be based on a clearly defined rationale and should be coupled with a medical evaluation by a physician.     

Hysterosalpingographic evaluation of tubal patency in women treated for anovulatory infertility

During therapy of anovulatory infertility, percentage of pregnancies is lower than the ovulation rate. Cause of this phenomenon is connected as well with the inadequate corpus luteum as others anomalies of the genital tract. Hysterosalpingography was performed in 120 infertile women in whom pregnancy did not occur in spite of effective induction of ovulation. Patency of both tubes was observed in 79 percent of patients. Occlusion of right tube has occurred in 8 percent, left tube in 5 percent, and both tubes in 8 percent of women. Authors suggest that laparoscopy should be obligatory as diagnostic and therapeutic procedure in woman with concomitant ovarian failure and abnormal HSG results.     

Role of high-resolution pinhole tomography in the evaluation of thyroid abnormalities

The present study was undertaken to evaluate the contribution of pinhole-single photon emission computed tomography (P-SPECT) to scintigraphy of the thyroid gland. Thirty-six patients, referred for thyroid scintigraphy because of palpatory or ultrasonographic findings, were studied after intravenous administration of technetium-99m pertechnetate (222 MBq) using a rectilinear scanner and a single-headed rotating gamma camera equipped with a pinhole collimator. P-SPECT study was acquired on a 128 x 128 matrix, in 30 projections over 180 degrees and an acquisition time of 40 seconds per step. After transaxial reconstruction, coronal slices were compared with planar views obtained by the scanner. The size of the thyroid gland obtained by P-SPECT matched the life-size image of a rectilinear scan, and it clearly delineated the shape and borders of two huge multinodular glands. Its major contribution was in its improved resolution. Pinhole-SPECT identified 21 foci not visualized on planar views, 19 cold lesions, and 2 "warm" nodules embedded in normal tissue of 13 patients. Furthermore, it clearly delineated 18 discrete ill-defined nodules of 13 patients, (single in 4 patients and multiple in 9 patients): 16 cold lesions, and 2 hot foci. When a distinct palpable nodule was present, whether cold (22 lesions) or hot (2 foci), SPECT was of no additional diagnostic value. However, when the palpable nodule was a toxic one, the contralateral suppressed lobe was visible on SPECT only. Two ultrasonographic findings, of 3- and 5-mm in diameter, were neither identified on planar views nor on P-SPECT. In conclusion, P-SPECT of the thyroid gland improves delineation of huge multinodular glands and detection of small nodules (within the resolution of the camera) that could otherwise have been overlooked on planar views of a thyroid scanner. It allows for definition of tracer uptake in tiny discrete nodules and in multinodular goiter, and is a better guide to the physician in fine-needle aspiration of the cold areas.     

Positron emission tomography for the evaluation of pancreatic disease

Efficient techniques for native-labeling of amino acids have been combined successfully with emission tomography to yield significant improvements in pancreatic imaging. Carbon-11-labeled tryptophan appears to be the best agent available currently for imaging the pancreas. Optimum scanning times begin 30 min after tracer administration. Positron emission tomography with 11C-tryptophan is capable of defining both morphological and functional alterations in the pancreas. Tumors as small as 2 cm in diameter can be detected, but reliable differentiation of pancreatic cancer from pancreatis may not be possible even with this improved imaging technique. Longitudinal multiplane emission tomography in single-photon mode with the Pho/Con provides an efficient and satisfactory approach to pancreatic imaging with the positron-emitting radiopharmaceuticals.     

An evaluation of nasal patency with acoustic rhinometry--preop. and postop. comparisons

PURPOSE: This prospective study was designed to assess the effect of primary hyperparathyroidism on heart muscle, valves, and myocardial function. Echocardiography was used to evaluate changes in mechanical performance, the thickness of the left ventricular wall, myocardial calcific deposits, and valvular calcifications in patients with primary hyperparathyroidism. METHODS: Echocardiography was performed in 54 patients with hyperparathyroidism prior to surgery and 12 +/- 2 months after successful parathyroidectomy. A matched control group was followed for comparison. RESULTS: In a blinded fashion, aortic and mitral valve calcifications were detected in 63% and 49% of patients with primary hyperparathyroidism (controls: 12% and 15%, respectively). Calcific deposits in the myocardium were found in 69% of patients with hyperparathyroidism and 17% of the control subjects. After parathyroidectomy and 12 months of normocalcemia, a significant regression of left ventricular hypertrophy (p < 0.001) was observed. CONCLUSIONS: The present data show a high incidence of left ventricular hypertrophy, calcific deposits in the myocardium, and/or aortic and mitral valve calcification in patients with primary hyperparathyroidism. A 1-year follow-up after parathyroidectomy (and restoration of normocalcemia) discloses regression of hypertrophy, while calcifications persist without evidence of progression.     

Computed tomography in the evaluation of the supraclinoid arteries in suprasellar pituitary gland tumors

The demonstration of the supraclinoid arteries at CT in 38 patients with suprasellar lesions was evaluated. The anterior cerebral artery was visible in 8 per cent, the other supraclinoid arteries in about 80 per cent. In one patient cerebral angiography revealed a giant aneurysm which was erroneously considered as a suprasellar neoplasm at CT and encephalography. The demonstration of the supraclinoid arteries was often inadequate in large suprasellar tumors. Therefore, cerebral angiography is still necessary preoperatively in suprasellar pituitary lesions-at least at the state of technology represented by the Delta 25 Head Scanner.     

Demonstration of two anomalous bypasses in concealed Wolff-Parkinson-White syndrome

Two patients with a history of paroxysmal supraventricular tachycardia but no evidence of the Wolff-Parkinson-White syndrome in the conventional electrocardiograms were studied utilizing atrial and ventricular extrastimuli. The evidence obtained in these patients was consistent with a concealed Wolff-Parkinson-White syndrome. In one patient, ventricular extrastimuli revealed three different responses in the curve of ventriculoatrial conduction, depending upon the interval of stimulus. In the other patient, intracardiac recordings, including the left atrial potential, showed that paroxysmal supraventricular tachycardia was induced by an impulse via an anomalous bypass which diverged from the main bypass or stemmed independently from the left ventricle and was maintained by impulses via the main bypass which lay between the left ventricle and the left atrium. The mechanisms for initiation of the paroxysmal supraventricular tachycardia were discussed.     

Role of computerized tomography in the evaluation of extraductal extension of hilar cholangiocarcinoma

This study was aimed at assessing the role of CT in the investigation of extraductal spread of hilar cholangiocarcinoma. October 1990 to November 1993, twenty-one patients with hilar cholangiocarcinoma were examined. The diagnosis was made on the basis of the following CT findings: intrahepatic bile ducts dilatation, nonunion of the right and the left bile ducts, normal size of extrahepatic bile ducts and the tumor depicted "per se". As for extraductal spread, we considered parenchymal invasion, involvement of vascular structures and parenchymal, lymph node and peritoneal metastases. In all cases CT demonstrated intrahepatic bile duct dilatation and nonunion at the confluence. CT demonstrated a hypodense mass in 10/21 cases and an isodense mass in 11/21 cases. Portal vein involvement was detected in 7/10 cases and hepatic artery involvement was correctly suspected in 1/8 cases; CT demonstrated parenchymal and lymph node metastases in 1/6 and 2/7 cases. In conclusion, CT proved to be a valuable technique, like PTC and US, to assess tumor resectability.     

An evaluation of transverse axial emission tomography of the brain in the clinical situation

The Aberdeen section scanner provides, in addition to conventional views, a display of the distribution of radioactivity in a tomographic section of the brain. This paper examined the value of this additional information. Scans of lesions confirmed pathologically or radiologically, along with normal and doubtful cases, were examined after a careful randomization procedure. During the course of the study each set of conventional views was examined twice, once without and once with a tomographic section view. In two out of 29 cases (7%) the lesion was diagnosed only with the aid of the tomographic section scan. Improved accuracy of diagnosis with the tomographic section view was significant at the 1% level or better.     

Calculation of absolute cerebral blood volume and cerebral blood flow by means of electron-beam computed tomography (EBT) in acute ischemia

The utility of electron beam computed tomography (EBT) to estimate cerebral blood volume (CBV) and cerebral blood flow (CBF) was evaluated. Eleven patients with suspected acute cerebral ischemia were investigated. The EBT was performed with an acquisition time of 50 ms per slice at eight parallel levels. To compare signal/noise and contrast/noise ratios the data from the EBT investigation were compared to a similar examination on a spiral CT. The signal/noise ratio with EBT was about 30%, the contrast/noise ratio 25% of that with spiral CT. The absolute values of CBV were 4.9 +/- 1.2 ml/100 g (EBT); CBF was 50.5 +/- 7.0 ml/100 g/min in normal contralateral brain tissue. In four patients with proven infarcts on follow-up, the ischemic areas had a CBV ranging from 1.7 to 3.8 ml/100 g, while CBF ranged from 9.4 to 24.5 ml/100 g/min. Using a bolus injection of contrast material, calculation of absolute CBV and CBF is feasible using EBT. Advantages of EBT are the absolute measurements possible and it's multislice capability. Disadvantages, however, are caused by the high image noise, limiting the demarcation of ischemic tissue.     

Computed tomography in evaluation of patients with stage III melanoma

BACKGROUND: Metastatic disease is detected infrequently by computed tomography (CT) in early stage melanoma. The diagnostic yield of routine CT for stage III melanoma is less established, despite extensive use in clinical practice. METHODS: Charts from 347 asymptomatic patients with stage III melanoma were reviewed. Findings suggestive of metastatic melanoma identified by head or body CT, chest radiography, bone scan, or liver function studies were confirmed histologically or by progression of disease. RESULTS: Individual CT scans identified 33/788 (4.2%) instances of metastatic melanoma, with 66/788 (8.4%) false positive studies. No metastases were identified among 104 head CT scans. Chest CT had the highest yield in patients with cervical adenopathy (7/35, 20%), and the lowest yield with groin adenopathy (1/50, 2%). Pelvic CT diagnosed metastases in 7/94 (7.4%) patients with groin adenopathy, but no patients with palpable axillary (n = 76) or cervical (n = 21) nodes. Metastatic melanoma was diagnosed in 11/136 (8.1%) patients having complete body CT imaging (chest, abdomen, and pelvis), including six patients (4.4%) identified by CT alone. CONCLUSIONS: Routine CT in patients with clinical stage III melanoma infrequently identifies metastatic disease. Head CT in the asymptomatic patient, chest CT in patients with groin adenopathy, and pelvic CT in the presence of axillary or cervical adenopathy are not indicated. Selective use of chest CT in patients with cervical adenopathy or pelvic CT in the presence of groin disease may be useful.     

Interactive 3-dimensional computerized tomography reconstruction in evaluation of the living renal donor

OBJECTIVE: This study investigated the findings revealed by dynamic helical CT of proximal arterioportal shunting associated with hepatocellular carcinoma. We also evaluated the diagnostic capability of this imaging technique to reveal the mass in patients with hepatocellular carcinoma. CONCLUSION: On dynamic helical CT, proximal arterioportal shunting altered liver perfusion and tumor enhancement. Heterogeneous enhancement of liver parenchyma and decreased enhancement of hepatomas diminished diagnostic capability on the arterial dominant phase image. However, with the addition of imaging in the arterial portal phase, lesion conspicuity improved.     

CT-angiography as a non-invasive method for the evaluation of the patency of TIPSS (transjugular intrahepatic portasystemic shunt)

PURPOSE: To evaluate the feasibility of determining patency of the transjugular intrahepatic portosystemic shunt (TIPSS) by non-invasive CT angiography (CTA). MATERIALS AND METHODS: (1) Non-enhanced scanning of the shunt. (2) Bolus tracking by injecting 20 ml of non-ionic contrast material through a cubital vein access to determine the time to maximal shunt enhancement. (3) Contrast-enhanced spiral CT study applying a delay according to the time to peak of the shunt, 3 mm collimation, 5 mm table feed and 3 mm reconstruction interval. (4) 3D and multiplanar reconstructions. (5) Evaluation of the questions: intrahepatic shunt patent or not; evidence of intimal hyperplasia; evidence of stenosis and potential location. (6) Transjugular portography via the stent. (7) Comparison of angiographic findings and CT morphology. RESULTS: Eight patients had inconspicuous CTA. Four of them had a normal shunt at angiography, four had slight intimal hyperplasia. No intervention was necessary in these patients. CTA of three patients showed intimal hyperplasia (lumen reduction between 10% and 50%). The diagnosis was angiographically confirmed in all cases. Due to a high portosystemic gradient intervention was required in all. In five patients CTA and angiography showed a stenosis (reduction of shunt lumen > 50%). All required a revision including stent placement or PTA of the shunt tract. Four shunts were occluded; all occlusions were shown both in CTA and angiography. CONCLUSIONS: None of the shunts with normal findings at CTA required revision. All shunts conspicuous on CTA resulted in revision. In this study, CTA turned out to be an accurate, non-invasive method to evaluate the patency of TIPSS.