Critical reviews in diagnostic imaging最新文献

The inherent overlap in the T1 and T2 relaxation of benign and malignant breast lesions has hindered progress in the application of MRI to evaluate this organ. Indeed, lesions in a glandular breast may completely blend in with normal breast tissues, a problem unenhanced MRI shares with mammography. However, infusion of intravenous Gd-DPTA accompanied by rapid MR imaging results in successful detection of most invasive breast malignancies. Inspection of the lesion morphology and enhancement profile shows that most malignancies have an irregular border, enhance very rapidly, and display a distinct early washout phase. On the other hand, fibroadenomas have a smooth or gently lobulated border and enhance in a continuous monotonic fashion. Some pitfalls exist such as the variable enhancement associated with DCIS and premenopausal breast tissue. This publication reviews the literature with respect to Gd-enhanced breast MRI, focusing on strengths and weaknesses, and suggests appropriate indications for employing this new approach to breast imaging. Patient preparation and discussion of technical parameters and tradeoffs is also addressed. The exact place of MRI in the work-up of the breast-problem patient has yet to be settled, but already MRI can help radiologists offer a more conclusive diagnosis in mammographically perplexing situations, particularly in patients with radiographically dense breasts.

Spiral CT is ideally suited for evaluation of the kidneys. Continuous data acquisition and uniform contrast enhancement improve characterization of renal pathology. This article provides examples of the spiral CT appearance of various nonneoplastic conditions, with emphasis on renal cystic disease, inflammatory disease, and vascular disease.

Pulmonary tuberculosis is a chronic granulomatous disease characterized radiologically by nodules, air-space consolidation, propensity for cavitation, and calcification, and pathologically by caseating granulomas or pneumonia, and a great propensity for fibrosis and dystrophic calcification. Primary tuberculosis typically appears as air-space consolidation with hilar or mediastinal lymphadenitis. Postprimary tuberculosis appears most commonly as nodular and linear opacities at the lung apex. CT findings of early bronchogenic spread of postprimary tuberculosis are centrilobular 2- to 4-mm nodules or branching linear structure, 5- to 8-mm poorly defined nodules, lobular consolidation, cavities, and thickening of interlobular septa. Centrilobular nodules or branching linear lesions and poorly defined nodules on CT scan correspond to caseation materials filling the bronchioles, and centrilobular air-space consolidation with caseation necrosis. Poorly defined nodule or lobular consolidation usually consists of central caseation necrosis and peripheral nonspecific inflammation. Cavitation usually occurs at the centrilobular area and may progress to a larger coalescent cavity. With antituberculous therapy, resolution typically occurs from the peripheral portion of the poorly defined nodule or lobular consolidation and results in varying degrees of fibrous bands, bronchovascular distortion, emphysema, and bronchiectasis. Miliary tuberculosis appears as well-defined randomly distributed nodules on CT scan that correspond with nodules consisting of central caseation necrosis and peripheral epitheloid and fibrous tissue. Analysis of CT images on the basis of pathologic correlation is helpful in understanding the morphology of pulmonary tuberculosis.

The authors review their experience with magnetic resonance imaging (MRI) of the adrenal gland and discuss the appearance of adrenal diseases where MRI is clinically useful. A basic description of some of the newer pulse sequences is provided. Fat-suppressed MRI is advantageous because of reduction of cardiac and respiratory motion induced artifacts, accentuation of small differences in tissue contrast, and elimination of chemical shift artifacts. These advantages far outweigh the disadvantages of inhomogeneity of fat suppression and the fewer slices obtained per acquisition. Chemical shift imaging is used to differentiate benign from malignant adrenal diseases based on a gradient echo phase cycling technique. Detailed descriptions of MRI findings in adrenal pheochromocytomas, hemorrhage, cysts, adenomas, myelolipomas, and metastases are provided. Most pheochromocytomas appear markedly hyperintense to the liver on T2-weighted images. However, this appearance is not specific as adrenal metastases and adrenal adenomas may occasionally produce a similar appearance. In addition, pheochromocytomas may occasionally be isointense or hypointense to the liver on T2-weighted images. Differentiation of adrenal metastases from adrenal adenomas with MRI is problematic using signal intensity ratios (33% overlap) or T2 calculations. The future of discriminating between adrenal metastases and adenomas may rest with chemical shift MRI, which uses in- and out-of-phase gradient echo pulse sequences for differentiation. This approach relies on the fact that adrenal adenomas contain fat, while adrenal metastases do not. The reported accuracy of chemical shift imaging in differentiating between adrenal adenomas and adrenal metastases ranges from 96 to 100%. An algorithmic approach to differentiating benign from malignant adrenal diseases is presented that relies on an initial noncontrast CT with CT attenuation values obtained from the adrenal mass. If CT attenuation values are less than zero, the mass is characterized as benign. If the mass remains indeterminate after CT, chemical shift MR is performed. If the mass remains indeterminate after MR, biopsy is required.

Breast seromas are tumor-like collections of serosanguineous fluid in breast tissue that occur following excisional biopsy, lumpectomy, mastectomy, and plastic surgery procedures such as augmentation, prosthesis explantation, breast reduction, and breast reconstruction. Mammographically seromas are water-density masses located at the surgical site. They exhibit features characteristic of fluid collections on sonographic evaluation. This article reviews the spectrum of imaging findings associated with breast seromas.

Computed tomography (CT) provides accurate assessment of blunt liver injuries. This article reviews the indications, technique, diagnosis, and role of CT in the management of liver injuries following blunt abdominal trauma. The spectrum of liver injuries and its complications seen on CT have been described and illustrated.

Along with the utilization of radionuclides for ventilation (V) and perfusion (Q) functional imaging of the lungs, massive predominantly unilateral scintigraphic abnormalities had been captured and cumulatively recorded in the literature. Such distinctive imaging findings are infrequent and their reported occurrences are reviewed. The precipitating disorders are categorized according to the corresponding V/Q scintigraphic findings that reflect the underlying pathophysiology. This arrangement may facilitate the interpretation of pulmonary scintigraphy with similar unusual imaging characteristics. The perfusion scan of patients with a variety of congenital heart diseases often show imaging abnormalities that are diffusely unilateral. It has been proven quite useful for evaluation of the pulmonary blood flow in those cardiac disorders before and after palliative or corrective surgery.

Spiral CT offers many advantages in the evaluation of renal masses. It is especially helpful in the detection and characterization of the indeterminate renal mass. This article discusses advantages and some potential pitfalls of spiral CT in the staging of renal cell carcinoma, transitional cell carcinoma, and other renal tumors.

Magnetic resonance imaging (MRI) provides noninvasive functional information as well as a three-dimensional anatomic display of the cardiovascular system. MRI of protons, phosphorus, or sodium nuclei is currently being investigated to characterize cardiovascular pathology, and the potential benefits of paramagnetic contrast agents are becoming apparent. Finally, techniques to quantitate blood flow, vascular pressures, chamber volumes, ventricular ejection fractions, and cardiac output are being developed.

Intraoperative ultrasound of the liver is a versatile and valuable adjunct to surgical inspection and palpation. The technique allows visualization of lesions that cannot be detected by routine cross-sectional imaging studies, allowing for more efficient and effective patient management. Demonstration of the proximity and the interrelationship of lesions to surrounding important vascular structures can be invaluable to the surgeon in choosing the most appropriate therapeutic option and in planning segmental resections. Specially developed intraoperative ultrasound probes can be used on standard diagnostic ultrasound B-mode machines. Electronic linear and curved-array scanners are most commonly used, with a 5-MHz frequency being optimal for liver imaging. Additional intraoperative uses for liver ultrasound include ultrasound-guided tumor cryoablation, ethanol injection, biopsy guidance, and laparoscopic ultrasound.