Reevaluation of plain radiographic findings in the diagnosis of aortic rupture: the role of inspiration and positioning on mediastinal width.

Despite the advent of newer imaging modalities, conventional radiography and clinical examination remain the primary screening method in evaluation of the mediastinum following blunt thoracic trauma. Mediastinal width (MW) is generally considered an important finding in assessing for aortic rupture. The degree of inspiration and patient positioning clearly affects MW, but is largely ignored in the literature. This study investigates the mediastinal widths of normal volunteers with differing degrees of inspiration and positioning, and compares them to radiographs of patients with known aortic ruptures. Mediastinal widths were obtained from chest radiographs of 16 patients with known aortic rupture, and from 50 volunteers using AP-inspiratory-supine, AP-expiratory-supine, and PA-inspiratory-upright technique. Upper 95% confidence limits were obtained for normals. A statistically significant difference in MW of normals was found between inspiratory-supine, expiratory-supine, and upright-inspiratory techniques. Compared to the same degree of inspiration in normals, 12 of 16 patients with aortic rupture had a MW above the upper 95% confidence limits. It is concluded that mediastinal width in normals is significantly affected by the degree of inspiration and positioning. When comparing mediastinal widths for normals and ruptures, there was a significant difference in MW for most degrees of inspiration. As depth of inspiration increased, differences between MW in controls and rupture patients increased. We conclude that patient positioning and degree of inspiration are important factors in assessing the mediastinum, and every effort should thus be made to obtain an upright-inspiratory film if clinically feasible prior to declaring a mediastinum as abnormal.

Sonoelasticity imaging: results in in vitro tissue specimens.

The authors present a method for imaging tissue stiffness (sonoelasticity) that has been developed and tested in a laboratory setting by using in vitro canine and human prostate glands. A low-frequency acoustic source was used to induce vibration in tissue under examination, and a color Doppler ultrasound (US) instrument was modified to detect vibration amplitude. The resulting image is a color "map" of tissue vibration superimposed on conventional gray-scale US images. Stiffer tissues vibrated less in response to audible sound, regardless of echogenicity. Normal human and canine prostate glands demonstrated a uniform vibration pattern. Four of four human prostatic adenocarcinomas and two stiff inclusions injected into canine prostate glands demonstrated a lack of vibration in comparison with normal surrounding tissue. The authors conclude that while further study is necessary, sonoelasticity imaging may enhance the detection of neoplasms by enabling their identification solely on the basis of stiffness.

Nonpalpable cancer of the prostate: assessment with transrectal US.

Palpable cancer of the prostate is widely believed to be clinically significant. The authors compared the clinical significance of palpable prostate cancer with nonpalpable prostate cancer discovered with transrectal ultrasound (US). A strong association between lesion volume measured with preoperative transrectal US and volumetric measurements in 60 radical prostatectomy specimens permitted the use of tumor size measured with transrectal US as a reasonable estimation of gross tumor volume. In a subsequent clinical series, 147 biopsy-proved cancers were grouped according to size measured at US, the findings at digital rectal examination (DRE), and the Gleason score. For the 147 patients with known prostate cancer, a statistically significant difference between Gleason scores of palpable and nonpalpable cancers could not be demonstrated when the size of the tumor and its location within the prostate were held constant. Assuming that the Gleason score is a reliable indication of malignant potential and clinical significance, the authors conclude that nonpalpable prostatic cancer detected with transrectal US alone may be just as clinically significant as prostatic cancer discovered with DRE.