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Biomedical subjects

A C Mamourian

Publications and source records attributed to A C Mamourian.

At least 55 records · Page 3Linked to original sources
PubMed1986

Appearance of Pantopaque on MR images.

Pantopaque was shown to be both a radiographic and magnetic resonance (MR) contrast agent in two patients with suspected cord abnormalities who underwent MR examination following myelography. The Pantopaque appeared as a linear band of high signal intensity along the dependent portion of the spinal canal on MR images obtained with a repetition time of 500 msec and an echo time of 30 msec. MR images of two dogs--one injected with Pantopaque in the cervical subarachnoid space and the other with Amipaque--confirmed that the high signal arose from the Pantopaque. This high signal intensity is due to Pantopaque's short T1 relaxation time. Although Pantopaque will probably not be used as an MR contrast agent, it is important to recognize this property so that its high signal is not mistaken for fat or hemorrhage in the subarachnoid space on MR images.

Aged↗
PubMed1984

The oral administration of MnCl2: a potential alternative to IV injection for tissue contrast enhancement in magnetic resonance imaging.

Mn+2 (as MnCl2) was administered to rabbits intravenously and orally (a route of administration which based upon our previous experiments in rats promises to give selective hepatobiliary enhancement with less systemic toxicity). Nuclear magnetic relaxation dispersion or T1 (NMRD) was performed on selected tissues (heart, liver, kidney, serum, and bile) in both animal groups to examine possible qualitative and semiquantitative differences in T1 relaxation at equivalent sacrifice times. One animal was given an oral dose of MnCl2 (620 micromoles/kg) and imaged sequentially (T1 weighted sequence, .12T) for 30 minutes. The NMRD curves for organ tissues show an increase in relaxation efficacy in the 10-20MHz range characteristic of Mn-macromolecular complexes and are similar irrespective of the route of administration. The lack of increased relaxation enhancement for bile in this frequency range reflects cleavage of this complex upon excretion. Decreased overall relaxation in the liver is observed when oral Mn+2 is compared to IV Mn+2 due to the small fraction of administered dose that is absorbed. However, the images document a significant increase in the intensity of liver signal after the oral dose. We suspect this dose may ultimately be adjusted downward to give selective hepatobiliary effects.

Administration, Oral↗
PubMed1984

Focal renal masses: magnetic resonance imaging.

Thirty patients with focal renal masses were evaluated on a .12-Tesla resistive magnetic resonance unit using partial saturation and spin echo pulse sequences. A short repetition time (TR = 143 ms) was employed for partial saturation images and a spin echo was present in each case (TE = 10 ms). Additional pulse sequences through regions of interest were also obtained. Fifteen patients had cystic lesions, nine patients had renal cell carcinoma, two had metastatic lesions, one had an angiomyolipoma, and three had focal bacterial infection. Cystic lesions were well circumscribed and demonstrated a range of signal intensities. Small intra-parenchymal cysts were difficult to identify. Renal cell carcinomas demonstrated areas of increased signal using a partial saturation sequence (TR = 143-415 ms, TE = 10 ms). Magnetic resonance imaging accurately detected perinephric extension and vascular invasion in all patients. Metastatic disease to the kidney was uniformly low in signal, in contrast to primary renal cell carcinoma; an angiomyolipoma demonstrated very high signal intensity. Two masses resulting from acute focal bacterial nephritis were uniformly low in signal. One additional case of a more indolent pyelonephritis demonstrated high signal in regions of replacement lipomatosis and low signal in sites of active infection. Magnetic resonance imaging appears to be an accurate way of detecting, identifying, and staging focal renal masses.

Adenocarcinoma↗
PubMed1984

Nongated cardiac magnetic resonance imaging: preliminary experience at 0.12 T.

Nongated cardiac magnetic resonance imaging (MRI) has been reported previously to be inadequate for obtaining diagnostic information. This study explored the role of pulse sequence in the degradation of the nongated cardiac image. Images of diagnostic quality were obtained by using single spin-echo sequences with a very short echo time (10-20 msec TE) on a 0.12-T developmental MR unit. Marked degradation of the image was noted with longer TEs, and it is concluded that the previous unfavorable reports using a nongated technique may have been due to the longer TEs used in other units. Short-TE technique was used to examine 34 patients with a variety of cardiac diseases. Eleven patients had ventricular aneurysms. These cases showed thinning of the myocardium, and four of them showed increased signal within the aneurysm, perhaps related to regionally slower blood flow. Twenty patients had enlargement of one or more cardiac chambers. Three of these patients had thrombus within an enlarged chamber, which was readily identified on MRI. Twelve patients had left ventricular hypertrophy that was concentric in 11. One patient demonstrated asymmetric septal hypertrophy. All four pericardial effusions were low in signal intensity, but this was related to the pulse sequence used. Six patients had extrinsic masses displacing the heart and distorting the chamber contour. One patient showed intracardiac invasion of tumor; this finding was not evident on the CT. One patient with ventricular septal defect (VSD) and corrected transposition was scanned. In addition to identifying the VSD and chamber hypertrophy, the malposition of the great vessels at the base of the heart was seen. Four postoperative patients were scanned; wire suture artifact did not preclude imaging. In conclusion, diagnostic information can be obtained from nongated cardiac images provided that the TE is very short (10-20 msec). Although quantitative functional data are not available from nongated images, qualitative and diagnostic information is possible and may suffice in certain circumstances.

Cardiomegaly↗
PubMed1984

Proton relaxation enhancement in tissue due to ingested manganese chloride: time course and dose response in the rat.

MnCl2, a potential NMR contrast agent, was force fed by cannula to 27 fasted rats in an attempt to establish the efficacy of this route of administration. The animals were sacrificed and the relaxation times (T1 and T2) of liver, spleen, kidney, heart, and skeletal muscle were determined in vitro. One group of rats was subject to a range of doses (8.3-333.3 mg/kg) and sacrificed at 90 minutes. Another group received a single large dose (500 mg/kg) with animals sacrificed at intervals from 15-225 minutes. The single large dose caused a rapid and prolonged reduction in liver T1 (-93% of normal) and to a lesser degree affected the other organs. The dose response data shows that liver T1 is also affected at significantly lower dosages than the other tissues tested. These results suggest the oral route as a possible alternative to IV Mn+2. Further studies with inorganic and organic manganese are indicated.

Animals↗
PubMed1983

The chest radiograph in Legionnaires' disease. Further observations.

Chest radiographs of 70 patients with Legionnaires' disease were evaluated and compared to the authors' previous series of 24 patients as well as others in the literature. A larger number of patients in the more recent survey had pleural effusion, and there were 3 with cavitation whereas none was seen previously. Analysis of the radiograph showing the most marked changes in survivors versus patients who died showed no consistent pattern, indicating that the radiograph cannot be used as a prognostic indicator. On long-term follow-up (mean, 104.2 days), the radiograph remained abnormal for many months and demonstrated a variety of slowly resolving or permanent abnormalities.

Adolescent↗
PubMedDate not supplied

Moebius syndrome in association with hypogonadotropic hypogonadism.

The association between hypogonadotropic hypogonadism and multiple CNS lesions in a variety of disorders suggests a possible causative link between these clinical findings. Neural afferent input into the hypothalamus from higher CNS centers modulates GnRH secretion and derangements of these neural pathways could potentially result in diminished gonadotropin secretion and hypogonadism. This report describes a patient with multiple CNS defects secondary to Moebius syndrome and hypogonadotropic hypogonadism whose clinical features support the hypothesis that his CNS and endocrine defects may be causally associated. Comprehensive clinical evaluation in this patient revealed severe mental retardation; cranial nerve palsies; motor, reflex, and gait disturbances; and sexual infantilism secondary to hypogonadotropic hypogonadism. An MRI of the brain revealed atrophy or hypoplasia of the third cranial nerve and the olfactory gyri. Numerous syndromes including the Moebius syndrome are now described in which hypogonadotropic hypogonadism and CNS defects are associated. Detailed neuroanatomic and embryologic studies have demonstrated the important functional interrelationships between higher central nervous system centers and the hypothalamus. Taken together, these findings provide support for the causative association of multiple CNS defects and hypogonadotropic hypogonadism.

Abnormalities, Multiple↗
PubMedDate not supplied

Pineal cysts: MR imaging.

MR brain scans of 672 consecutive patients were examined prospectively to determine the incidence of high-signal pineal glands on T2-weighted images. The scans were obtained on either a 0.15-T or 0.5-T unit. This finding was present in 29 patients, none of whom had hydrocephalus or symptoms of a pineal mass. A CT scan was available in 17 of these cases and none of these demonstrated a solid pineal mass. Because of the frequency of this observation (4.3%) and the absence of associated findings, it was concluded that benign pineal cysts are the most likely explanation for this high signal. It is important for the radiologist to consider benign cysts in the differential diagnosis of a bright pineal gland on T2-weighted MR images.

Adult↗
PubMedDate not supplied

Pantopaque on MR.

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Humans↗