Negative Attenuation Values Research Articles

Liver Lipoma in a Dog: Case Report and Literature Review

ABSTRACT Lipoma of the liver has not been reported in dogs. An 8 yr old spayed female Great Dane was referred for diagnostic workup of abdominal distention. Computed tomography showed fat-attenuating masses with negative attenuation values (variable between −60 to −40 Hounsfield units) and minimal contrast uptake within the left cranial abdomen. Left lateral and right medial liver lobectomies were performed to remove two liver masses. Histopathology showed large lipomas arising from within the hepatic parenchyma. Immunohistochemistry for smooth muscle actin was negative, consistent with true lipomas. The dog was euthanized 8 mo later because of causes likely unrelated to the liver lipoma. This is the first case report of lipoma in the liver of a dog. The purpose of this case report and brief literature review is to provide evidence that surgical excision of fat-attenuating masses within the liver that are consistent with lipoma using immunohistochemistry can be curative.

Mesenteric Lymphangioma Presenting as Ileal Volvulus

Mesenteric Lymphangioma Presenting as Ileal Volvulus

CT and MR Demonstration of 'Diploic Lipomatosis', and Comparison with Craniocerebral Hemiatrophy

This paper presents the cranial CT and MR imaging studies of a 68-year-old female with intermittent headaches in the left parietal region, with diffuse expansion, and fatty replacement of the red marrow of the entire left parietal diploe, which revealed negative attenuation values on CT (-60 H.U.) while this value in the contralateral diploe was very high (+450 H.U). The condition was verified by biopsy. The suggested name for this pathology is 'diploic lipomatosis' because of diffuse involvement of the left parietal diploe resulting in expansion and partial resorption of the diploic trabeculae. The patient did not have asymmetry of the cerebral hemispheres. The condition was compared with that of twenty craniocerebral hemiatrophy (Dyke-Davidoff-Masson syndrome) patients. These patients had unilateral loss of cerebral volume with widening of the ipsilateral diploe, CT attenuation values of which were high (mean= +420 H.U.). It appears that Òdiploic ilpomatosis' is a new clinical entity unrelated to craniocerebral hemiatrophy.

Renal sarcoma and sarcomatoid renal cell carcinoma: CT and angiographic features.

Computed tomographic (CT) and angiographic findings in 14 patients (eight men, six women, aged 30-72 years) with sarcomatoid renal cell carcinoma (SRCC) and various types of renal sarcoma are described. There were four patients with SRCC; three, leiomyosarcoma; two, liposarcoma; two, fibrosarcoma; and one each of unclassified renal sarcoma, clear cell sarcoma, and malignant fibrous histiocytoma. The most frequent presenting symptom was an abdominal mass or pain. All 14 patients underwent CT, and 11 underwent selective renal angiography. The diagnosis of renal sarcoma should be suspected when CT findings suggest that the tumor arises from the renal capsule or renal sinus and when the tumor is hypovascular or avascular on angiograms. The characteristic negative attenuation values for liposarcomas permit a specific diagnosis. Sarcomas that originate in the renal parenchyma and SRCC cannot be easily differentiated from renal cell carcinoma; however, renal sarcomas do not appear to have a propensity for extension into the renal vein or the inferior vena cava.

The radiological appearances of the liver after surgical removal of hydatid cyst

Simple excision of a hydatid cyst from the liver leaves a residual cavity. Depending upon the surgical management of the cavity this can appear cystic, hypoechoic or echogenic on subsequent ultrasound examination. Negative attenuation values on computed tomography are typical of omentoplasty. These appearances can mimic pathological lesions in the liver. Knowledge of the site and nature of previous surgery can prevent diagnostic confusion.

Experiments on the Influence of Flow on Sound Attenuation in Absorbing Ducts

The influence of a turbulent air stream on the sound attenuation in ducts, lined with sound absorbing materials or structures of different kinds, has been experimentally investigated. For linings consisting either of porous materials or sufficiently damped Helmholtz resonators, decrease of absorption with increasing flow velocity has been observed, together with an increase of the frequency of maximum absorption in the case of the resonators. Somewhat surprising results have been obtained for undamped or weakly damped Helmholtz resonators, where an attenuation minimum is observed above the resonant frequency, the frequency of which increases linearly with increasing flow velocity, and which—for undamped resonators—even reaches negative attenuation values. Aside from the negative attenuation, a self-excitation of the duct is observed under certain conditions, the frequency of which is not identical with the attenuation minimum.