Cardiac magnetic resonance in the differentiation of neoplastic and nonneoplastic pericardial effusion.

BACKGROUND: Cardiac magnetic resonance (CMR) is the imaging modality of choice for cardiac tumors in people. Although neoplastic pericardial effusion (PE) carries a poor prognosis, benign idiopathic pericardial effusion does not. Definitive diagnosis is critical for surgical intervention, but currently available diagnostic techniques such as echocardiography and pericardial fluid cytology often are inconclusive. HYPOTHESIS/OBJECTIVE: Describe CMR findings associated with PE and determine whether CMR aids in differentiation of benign and neoplastic causes of PE. ANIMALS: Eight client-owned dogs with PE diagnosed by transthoracic echocardiography (TTE). METHODS: CMR was performed with a 1.5 T, including dark blood, steady-state free procession cine, pre- and postcontrast T1-weighted imaging, and delayed inversion recovery prepped imaging. RESULTS: CMR confirmed a cardiac mass and supported suspected tumor type in 4 dogs with suspected hemangiosarcoma. In 1 equivocal TTE case, CMR did not demonstrate a mass, but neoplasia was later diagnosed. In another equivocal case, CMR did not demonstrate a mass but showed findings consistent with a pericardiocentesis complication. In 1 dog without evidence of cardiac neoplasia, abdominal magnetic resonance imaging identified presumptive hepatic and splenic metastases. On reevaluation of the original CMR study, the 2 equivocal cases that were interpreted as tumor negative were reassessed as tumor positive. CONCLUSIONS AND CLINICAL IMPORTANCE: CMR did not substantially improve diagnosis of cardiac tumors compared with TTE in these 8 cases, but it yielded useful descriptive information regarding extent, anatomic location, and potential tumor type and confirmed that CMR requires extensive additional training for tumor identification.

CT imaging features and frequency of left ventricular myocardial fat in patients with CT findings of chronic left ventricular myocardial infarction.

AIM: To determine the frequency of left ventricular myocardial fat in patients with computed tomography (CT) findings of chronic left ventricular myocardial infarction, and to review the typical CT imaging features. MATERIALS AND METHODS: A retrospective search of the CT and nuclear scintigraphy reports from 1998-2005 for chronic left ventricular myocardial infarction was performed. The study group comprised those cases with available CT examinations revealing findings of chronic left ventricular myocardial infarction. Assessment for the presence of various imaging characteristics of left ventricular myocardial fat was performed in all cases. RESULTS: The frequency of left ventricular myocardial fat in 47 patients with CT evidence of chronic left ventricular myocardial infarction was 51%. Typical CT imaging features include thin linear or curvilinear fat attenuation within left ventricular myocardium, most commonly subendocardial, often associated with left ventricular wall thinning and/or calcification, predominantly in elderly men. CONCLUSIONS: Fat in the left ventricular myocardium is a common additional finding in patients with CT findings of chronic left ventricular myocardial infarction. The potential, but as yet unproven, use of this CT imaging finding is that the radiologist may be able to suggest a potential diagnosis of chronic left ventricular myocardial infarction on unenhanced, thick-section, non-gated or non-triggered chest CT imaging where identification of myocardial wall thinning may be difficult.

BaSO4-loaded agarose: a construction material for multimodality imaging phantoms.

RATIONALE AND OBJECTIVES: Phantom studies are an important part of the evaluation of imaging techniques; however, presently available phantom construction materials are not adequate for studies involving both magnetic resonance (MR) imaging and computed tomography (CT). The purpose of this study was to design a phantom construction material useful for multimodality imaging experiments. MATERIALS AND METHODS: Iodinated contrast agent or BaSO4 was added during the formation of agarose gels. Both CT and MR imaging were performed, and T1 and T2 values and CT numbers (in Hounsfield units) were obtained for multiple combinations of contrast material and agarose. Results. The T2 values of agarose gels span the range of those values found in biologic tissues. Phantoms containing iodinated contrast agent were not stable; contrast agent diffused across concentration gradients. BaSO4-loaded agarose phantoms were stable, however, and varying barium concentrations produced phantoms that spanned the range of CT numbers found in biologic tissues. Addition of BaSO4 did not substantially alter T1 or T2 values of agarose gels. Agarose concentration had only a small effect on the CT numbers of BaSO4 suspensions. CONCLUSION: BaSO4-loaded agarose is an effective material for construction of multimodality imaging phantoms. It provides adequate signal intensity for MR imaging and attenuation for CT, with independently variable contrast in both modalities.

Digital patient records and the medical desktop: an integrated physician workstation for medical informatics training.

The Institute of Medicine and others have advocated a shift from a paper-based to an electronic medical record and many authorities have advanced the concept of a physician workstation that can provide access to a wide variety of both clinically and reference oriented medical information. We have developed a working model of an integrated physician workstation based on a graphically oriented "Medical Desktop," for personal computers. This system gives the user access to much of the information necessary for the practice of medicine, by integrating an electronic medical record (notes, orders, consults, lab values, and radiological studies, organized both independently and in a "Visual Chart") with tools such as drug references, clinical manuals, textbooks of medicine, literature searching, expert system decision support, and electronic communication. It contains an on-line help system that facilitates use and allows access to all the systems' capabilities. This system has been used to teach students and physicians the methods and potential of computer-based medical information management to prepare them for the impact of computers in their practices and educate them concerning the imperative for the involvement of all health care providers in implementing these changes.

NMR characteristics of "visible" intracellular myocardial potassium in perfused rat hearts.

Nuclear magnetic resonance (NMR) spectroscopy provides a unique view of ions through its noninvasive character and relaxation time measurements. Several previous studies have demonstrated that only approximately 20% of cardiac intracellular potassium is visible with current NMR techniques. This study investigates the NMR visible intracellular potassium in a perfused rat heart preparation. When shift reagents were used to separate the intra- and extracellular signals, an intracellular T1 of 11.8 +/- 0.6 ms, and an intracellular T2 with two time constants of 1.3 +/- 0.6 ms (33 +/- 8%) and 10.1 +/- 1.9 ms (67 +/- 4%) were measured. Curve stripping techniques used to separate the intra- and extracellular components of a bulk relaxation decay yielded an intracellular T1 of 8.4 +/- 0.3 ms and an intracellular T2 with two time constants of 1.1 +/- 0.6 ms (38 +/- 10%) and 8.0 +/- 1.6 ms (62 +/- 12%). These results demonstrate that there are at least two distinct pools of potassium within the cardiac cell in slow exchange with each other on the NMR time scale. Studies with an enriched 41K perfusate demonstrated that the exchange rate for the visible intra- and extracellular potassium is on the order of 15 min.