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A one-dimensional phase-encoded spectroscopy sequence was implemented on a GE 1.5-T Signa imager and the feasibility of its application to monitor the 31P metabolites of superficial tumors was demonstrated. Serial 31P spectra of 1-cm slices with adequate signal-to-noise ratio and insignificant T2 weighting can be obtained in 28 min. The degree of "bleeding" effect was reduced with increased phase-encoding steps.

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The history of invasive radiology is a history of cooperative effort of scientists in physics and chemistry, of engineers in academic settings and industry and of the medical community. Research and development in the technological sciences opened doors to clinical application. Clinical imperatives drove research and development. Parallel advances in catheters, contrast materials and radiologic equipment came together to permit invasive radiologists to pursue advances in diagnosis and therapy, in a setting of patient safety.

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Fluoroscopically guided extraction of retained common duct calculi through a T-tube tract has a high success rate, low complication rate, and negligible mortality rate. It is not unduly uncomfortable and can be performed on an outpatient basis. The only disadvantage is a wait of approximately 6 weeks after surgery to let the T-tube sinus tract mature. If no T tube is present, endoscopic sphincterotomy is usually the treatment of choice. In difficult cases, the radiologist may be able to assist the endoscopist by placing a wire across the sphincter through a percutaneous transhepatic route. If endoscopic sphincterotomy is not successful or feasible, an attempt at percutaneous stone removal can be made from a transhepatic approach. A variety of new devices and dissolution agents is becoming available for stone fragmentation or reduction.

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Major socioeconomic changes in the practice of medicine in the past 2 decades have had a great impact on diagnostic radiology and have encouraged other physicians and entrepreneurs to enter many areas of this specialty. Major alterations in the practice of diagnostic radiology will be required if the specialty is to survive. Diagnostic radiologists must move from a position of dependency to self-sufficiency by encouraging patients to access their services and talents directly.

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In situ phosphorous MRS was employed to study the metabolites of normal and cancerous breasts, and the alterations of tumor response to therapy. In a group of 7 normal volunteers and 12 patients, the total mobile phosphate content of breast carcinomas was found to be at least two to three times higher than that of the normal breast measured off menstruation. The metabolite profiles of normal and tumorous breasts are coarsely similar. In both cases the intracellular pH (pHi) was either neutral or slightly alkaline (pH greater than 7.0). Prior to treatments, the metabolite levels of phosphoryl monoester-to-ATP ratio of breast neoplasms were higher than those of the controls and decreased after the patients received a few treatments while the pHi fluctuated at a value greater than 7.0. The phosphoryl diester-to-ATP ratio also demonstrated to a lesser extent a decreasing trend in response to therapy.

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Thirty-five human neoplasms from various sites and of various histologic types and stages were examined with phosphorus-31 magnetic resonance spectroscopy in situ. The tumors included 13 squamous cell carcinomas of the head and neck (lymph nodes), eight Hodgkin lymphomas, six non-Hodgkin lymphomas, four carcinomas of the breast, one melanoma, one sarcoma, one neuroblastoma, and one mucoepidermoid sarcoma of the salivary glands. Thirty-four of the neoplasms had normal to slightly alkaline pH before irradiation. During fractionated radiation therapy, the pH stayed in a range of from near neutral to alkaline and rose to 7.6-8.0 at several time points of radiation therapy for some tumors. These results suggest that most tumor cells in human neoplasms are well oxygenated and that only a negligible fraction are chronic hypoxic cells. The fluctuating alkaline pH during radiation therapy occurred regardless of the responsiveness of the treated tumors.

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Gadolinium (Gd) labeled diisopropyliminodiacetic acid (DISIDA) was prepared by mixing a Gd solution and a DISIDA solution in appropriate proportions and at controlled pH. Optimal complexation was obtained at a Gd:DISIDA molar ratio of 1:2.5 and the pH of the final solution was 7.3 to 7.5. The complex was found to be stable both in vitro and in vivo. Gd-DISIDA (12.5 mumol/kg) was injected into mice, and T1 and T2 relaxation times of various tissues were measured and compared with those of normal tissues. Only the T1 values of the blood and the liver markedly decreased after Gd-DISIDA administration and also the reduction in T1 values depended on the dose of Gd-DISIDA. Magnetic resonance imaging of the rabbit liver showed considerable contrast enhancement at 30 minutes after administration of 12.5 mumol/kg of Gd-DISIDA.

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High quality 31P MR spectra (signal to noise ratio (S/N) approximately 18, 15 min acquisition for each spectrum) were consistently obtained with surface coils over a period of 6-week RT. Both transient and steady state alterations in metabolites in response to RT were found in this case. The transient changes occurred during the first 3 hr immediately after the 3rd fractionated RT, these changes include the transient elevation of the PCr resonance, a decrease in PDE and an increase in intracellular pH. The monitoring showed that the metabolites approached steady state approximately 2 hr after the fractionated radiation intervention, suggesting that in vivo MRS can be useful for studying the dynamics of tumor response to RT such as repair of potential lethal damage, growth delay, and reoxygenation etc. The steady-state MR spectra showed the net response to each intervention and can clinically be useful for predicting and measuring the result of the fractionated RT. In this case study, the PDE peak which contains the phospholipid metabolites GPC and GPE, is the most sensitive resonance in response to RT. After the 3rd RT, prior to tumor size reduction, the PDE to ATP ratio decreased 33% and intracellular pH increased to 7.34 +/- 0.05 from 7.27 +/- 0.05. In the subsequent RT interventions, both the tumor size and PDE/ATP ratio continually decreased whereas the pH values remained alkaline and fluctuated around 7.34 to 7.65. The data suggest that the phospholipid metabolite PDE may signal important alterations in membrane metabolism that eventually lead to cell death.

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The gross diagnostic factors of intracardiac tumor in four patients imaged by two-dimensional echocardiography (2D echo) and magnetic resonance imaging (MRI) were compared. Three cases had left and one had a right atrial tumor, all histologically identified as myxoma. Gated cardiac MRI depicted the size, shape, and surface characteristics of the tumors more clearly than 2D echo, because MRI provides better spatial and contrast resolution. Depiction of tumor attachment was poor to good with both techniques. Both techniques were highly accurate in localizing the tumor and displaying whether it was fixed or mobile. The global field of view provided by MRI allows better definition of tumor prolapse, secondary valvular obstruction, and cardiac chamber size. This study shows that despite its early stage of development, gated cardiac MRI provides superior image quality and is complementary to 2D echo for characterization and diagnosis of intracardiac tumor.

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The most serious controversy regarding the application of transaxial SPECT technology to 201Tl myocardial perfusion imaging is the choice between 360 degrees compared with 180 degrees data sampling techniques. The present study utilized the original 360 degrees sampled raw data of 25 patients who had both SPECT 201Tl myocardial perfusion imaging and coronary angio/ventriculography for back projection reprocessing to accomplish the 360 degrees/180 degrees comparison. The results show a high incidence, 36% (9/25), of false-positive segmental perfusion abnormality and a high incidence, 24% (6/25), of moderate to severe degree of image distortion with the 180 degrees data sampled reconstructed images. These were not observed in the 360 degrees data sampled reconstructed images. The above findings confirmed our previous preliminary conclusion that even though the 180 degrees data sampling technique has the advantage of providing improved image contrast and reduction in acquisition time it is not a reliable technique and should be abandoned. The 360 degrees data sampling is the technique of choice for transaxial SPECT 201Tl myocardial perfusion imaging.

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Most magnetic resonance imaging has used body orthogonal axes with the Z axis placed along the length of the body and the X and Y axes at right angles to the body. This orientation is not optimum for the heart; visualization of sections along the short and long cardiac axes would best define cardiac structural detail and functional status. The new orientation was accomplished by selection of electronic angulation of the magnetic fields for each subject rather than by attempting to approximate the cardiac axes by altering the position of the patient. This technique improved visualization of comparative wall segments, valvular structures, and the true four-chamber view of the heart, and also gave the best visualization of the pericardium. In addition, more accurate estimates of chamber size and myocardial mass can be made from the short-axis orientation, since the sections are orthogonal to the myocardium.

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Proton spin-lattice and spin-spin relaxation times have been measured in surgically-removed normal CNS tissues and a variety of tumors of the brain. All measurements were made at 20 MHz and 37 degrees C. Between grey and white matter from autopsy human or canine specimens significant differences in T1 or T2 were observed, with greater differences seen in T1. Such discrimination was reduced in samples obtained from live brain-tumor patients due to lengthening in T1 and T2 of white matter near tumorous lesions. Edematous white matter showed T1 and T2 values higher than those of autopsy disease-free white matter. Compared to normal CNS tissues, most brain tumors examined in this study demonstrated elevated T1 and T2 values. Exceptions, however, did exist. No definitive correlation was indicated on a T1 or T2 basis which allowed a distinction to be made between benign and malignant states. Furthermore, considerable variation in relaxation times occurred from tumor to tumor of the same type, suggesting that within a tumor type there are important differences in physiology, biology, and/or pathologic state. Such variation caused partial overlap in relaxation times among certain tumor types and hence may limit the capability of magnetic resonance imaging (MR) alone for the diagnosis of specific disease. Nonetheless, this study predicts that on the basis of T1 or T2 differences most brain tumors are readily detectable by MR via saturation recovery or inversion recovery with appropriate selections of pulse-spacing parameters. In general, tumors can be discriminated against white matter better than grey matter and contrast between glioma and grey matter is usually superior to that between meningioma and grey matter. This work did not consider tissue-associated proton density which should be addressed together with T1 and T2 for a complete treatment of MR contrast.

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The purpose of this investigation was to extend previous steady state flow studies with magnetic resonance (MR) to pulsatile flow measurements obtained with gated cardiac techniques in man with a pulsatile artificial heart device. Bovine blood and a solution of MnCl2 were studied. Correlation was made with complex and time-varying MR signals observed in the descending aorta on cardiac gated images obtained through the midthorax. MR signals from flowing fluids represent velocity distribution as shown in a velocity profile, and laminar flow is distinguished from nonlaminar. At very slow flow rates, signal intensity is lower than background. As the rate is increased, paradoxical enhancement occurs followed by loss of signal, which is complete at 7 liters per minute with fluid and 15 liters per minute with blood. These areas correspond to maximum fluid velocities of 41 and 88 cm/sec, respectively.

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The addition of a magnetic resonance (MR) unit to a hospital radiology environmental poses many unique considerations. Large magnetic fields present health and safety considerations as well as a hostile environment for data recorded magnetically. Radio-frequency shielding is necessary to eliminate a source of background signal that interferes with patient examinations. Magnetic shielding may be necessary in some instances to prevent low-level magnetic field exposure of persons with artificial cardiac pacemakers. Superconducting magnets are heavy and large and may give off large amounts of helium which can temporarily replace the air in the magnet room. Possible solutions to these environmental requirements are presented.

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Forty-three patients with acquired and congenital abnormalities of the thoracic aorta were studied using digital subtraction angiography (DSA) after an intravenous bolus injection of 40 ml of contrast material. Abnormalities studied included coarctation, pseudocoarctation, Marfan syndrome, cervical aorta, double aortic arch, aneurysm, dissection, and tumor. Twenty-four patients also had conventional angiography. DSA was accurate in 95% of cases; in the other 5%, involving patients with acute type I dissection, the coronary arteries could not be seen. The authors concluded that in 92% of their patients, DSA could have replaced the standard aortogram.

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The American College of Radiology's Commission on Nuclear Magnetic Resonance has recommended adoption of the term "Magnetic Resonance" as a replacement. The author offers background and rationale for this shift in terminology.

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Magnetic resonance (MR) gated cardiac imaging was performed in ten subjects using a prototype 0.15-T resistive magnet imaging system. Volume and planar imaging techniques utilizing saturation recovery, proton Tl-weighted relaxation time pulse sequences produced images of the heart and great vessels with exquisite anatomic detail that showed excellent correlation with cadaver sections of the heart. The left ventricular myocardial segments also showed excellent correlation with the thallium-201 cardiac single photon emission computed tomography images. Volume acquisition allowed postprocessing selection of tomographic sections in various orientations to optimize visualization of a particular structure of interest. The excellent spatial and contrast resolution afforded by MR volume imaging, which does not involve the use of ionizing radiation and iodinated contrast material, should assure it a significant role in the diagnostic assessment of the cardiovascular system.

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