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Biomedical subjects

V M Rao

Publications and source records attributed to V M Rao.

At least 37 records · Page 2Linked to original sources
PubMed1998

Practice patterns of radiologists and nonradiologists: nationwide Medicare data on the performance of chest and skeletal radiography and abdominal and pelvic sonography.

OBJECTIVE: We assessed the relative roles of radiologists and nonradiologists in performing chest and skeletal radiography and nonobstetric abdominal and pelvic sonography. MATERIALS AND METHODS: Information was extracted from the 1993 Medicare file on procedure volume for 65 imaging procedures. Claims were categorized by the specialty of the physician and the location (office or hospital) where the service was performed. RESULTS: In hospitals, radiologists performed virtually all chest and skeletal radiography and nonobstetric abdominal and pelvic sonography. In nonhospital settings such as offices or imaging centers, nonradiologists performed approximately two thirds of the chest and spinal radiography and nonobstetric abdominal and pelvic sonography and larger percentages (78-86%) of the pelvic, hip, lower extremity, and upper extremity radiography. CONCLUSION: Although radiologists perform virtually all chest and skeletal radiographs and abdominal and pelvic sonograms obtained in hospitals, they perform a distinct minority of these procedures in nonhospital settings. The data we present have certain implications for the amount of training nonradiologists receive in diagnostic imaging.

Bone and Bones↗
PubMed1997

A mechanistic study of griseofulvin dissolution into surfactant solutions under laminar flow conditions.

The in vivo dissolution of many poorly soluble drugs is enhanced by the action of surfactants secreted into the upper gastrointestinal (GI) tract. These substances may act by solubilizing individual drug molecules into two separate liquid phases: the free aqueous phase and a micellar phase in which the drug is incorporated into a complex of two or more surfactant molecules. This complex process, micellar solubilization, was the subject of this in vitro study, wherein griseofulvin (gris) dissolution was observed in flowing surfactant solutions. Aqueous solutions of sodium dodecyl sulfate (SDS), an anionic surfactant, were pumped over a gris tablet embedded in a laminar flow device to simulate flow in the human upper GI tract. SDS solutions were well above the critical micellar concentration (cmc approximately 6-7 mM), and flow rates ranged from 4 to 7 mL/min. Gris solubility in premicellar (4 mM), near-micellar (6 mM), and micellar (>6 mM) SDS solutions was also determined. The measured solubility of gris increased linearly with SDS concentrations above the cmc. Drug solubility in SDS concentrations below the cmc was also higher than that in water. Gris diffusion coefficients were measured using pulsed-field gradient NMR spectroscopy. To determine the controlling mechanism for surfactant-enhanced dissolution, a mathematical model was developed. The model solution, an equation for drug dissolution rate, was compared with experimental data to demonstrate that drug transport away from the solid surface is the slow step in the process. Measured gris diffusion coefficients and solubility values were used as constants in the mathematical model solution and were combined to calculate an effective gris diffusion coefficient. Using these experimentally determined properties, model-calculated dissolution rates were within 7% of the measured values. As hypothesized, dissolution rates were found to be directly proportional to the transport properties of the system (effective drug diffusion coefficient and fluid flow rate) as well as to the drug solubility. To further verify transport-limited dissolution, the measured dissolution rates were found to be proportional to the surrounding medium flow rate to the 1/3 power, as predicted by the model dissolution rate equation.

Antifungal Agents↗
PubMed1997

Papillary endolymphatic sac tumors: CT, MR imaging, and angiographic findings in 20 patients.

PURPOSE: To determine the computed tomographic (CT), magnetic resonance (MR) imaging, and angiographic findings of papillary endolymphatic sac tumors. MATERIALS AND METHODS: Clinical and imaging studies in 20 patients (aged 17-65 years) with histopathologically proved papillary endolymphatic sac tumors were retrospectively reviewed. Patients underwent CT (n = 18), MR imaging (n = 15), or angiography (n = 12). CT scans were evaluated for bone erosion and calcification; MR images, for signal intensity, enhancement patterns, and flow voids; and angiograms, for tumoral blood supply. RESULTS: All tumors were destructive and contained calcifications centered in the retrolabyrinthine region at CT. The MR imaging appearance varied with lesion size; 12 of 15 tumors showed increased signal intensity at T1-weighted imaging. The high-signal-intensity area was circumferential in lesions 3 cm or smaller and was scattered throughout the lesion in advanced tumors. Only tumors larger than 2 cm had flow voids. The blood supply arose predominantly from the external carotid artery. Large tumors had additional supply from the internal carotid and posterior circulation. CONCLUSION: Papillary endolymphatic sac tumors are destructive, hypervascular lesions that arise from the temporal bone retrolabyrinthine region. Increased signal intensity at unenhanced T1-weighted MR imaging is common and may help distinguish these lesions from more common, aggressive temporal bone tumors.

Adenocarcinoma↗
PubMed1997

Who performs neuroimaging? Results from the 1993 National Medicare Database.

PURPOSE: To determine the level of participation of nonradiologists in computed tomography (CT) and magnetic resonance (MR) imaging of the brain, head and neck, and spine at hospitals and at private offices and imaging centers in the United States. MATERIALS AND METHODS: The 1993 Part B Medicare Annual Database was used to determine the number of procedures performed by radiologists and nonradiologists at hospitals and at private offices or imaging centers. The fourth edition of the Physicians' Current Procedural Terminology was used to classify procedures. RESULTS: Of the 3,883,391 neurologic CT and MR imaging studies billed to Medicare in 1993, 3,148,088 (81%) were obtained in a hospital setting; only 58,005 (2%) of these studies were interpreted by nonradiologists. Of the 735,303 imaging studies (19%) obtained at a private office or imaging center, only 63,115 (9%) studies were interpreted by nonradiologists. Overall, nonradiologists performed only 121,120 (3%) of the neuroimaging examinations billed to Medicare nationwide in 1993. CONCLUSION: The level of participation of nonradiologists in the interpretation of results from neurologic CT and MR imaging billed to Medicare is minimal.

Central Nervous System Diseases↗
PubMed1997

Comparison of dynamic contrast-enhanced gradient-echo and spin-echo sequences in MR of head and neck neoplasms.

PURPOSE: To investigate the utility of dynamic contrast-enhanced gradient-echo MR imaging of head and neck lesions and to compare this technique with the commonly used spin-echo contrast-enhanced fat-saturation technique. METHODS: Twenty-two patients with a total of 23 head and neck neoplasms underwent dynamic gradient-echo and spin-echo MR imaging studies. The spin-echo and dynamic gradient-echo images were compared in each case by consensus of three observers for differences in tumor conspicuity and delineation of margins, particularly with regard to invasion of adjacent structures. When possible, pathologic and/or surgical confirmation of tumor extent was obtained. Relative contrast was also calculated to determine objectively the degree of tumor enhancement with respect to background mucosa. RESULTS: The dynamic gradient-echo images showed better or equal delineation of the tumor margins by subjective observation in all but two cases. Temporally different enhancement patterns were noted for lesions, background mucosa, and adjacent reaction and edema. The dynamic gradient-echo technique provided better relative contrast than the spin-echo technique in 17 (77%) of 22 lesions. CONCLUSION: Dynamic gradient-echo MR imaging is superior to conventional contrast-enhanced spin-echo imaging in delineating the margins and extent of tumor. This technique provided observers with added confidence in their interpretations and suffered from fewer technical limitations.

Adult↗
PubMed1996

MRI of orbital hydroxyapatite implants.

Our aim was to use MRI for the postsurgical assessment of a new form of integrated orbital implant composed of a porous calcium phosphate hydroxyapatite substrate. We studied ten patients 24-74 years of age who underwent enucleation and implantation of a hydroxyapatite ball; 5-13 months after surgery, each patient was examined by spinecho MRI, with fat suppression and gadolinium enhancement. Fibrovascular ingrowth was demonstrated in all ten patients as areas of enhancement at the periphery of the hydroxyapatite sphere that extended to the center to a variable degree. The radiologist should aware of the MRI appearances of the coralline hydroxyapatite orbital implant since it is now widely used following enucleation. MRI is a useful means to determine successful incorporation of the substrate into the orbital tissues. The normal pattern of contrast enhancement should not be mistaken for recurrent tumor or infection.

Adult↗
PubMed1996

A perspective on radiology residency curriculum guidelines: results of the 1995 survey of program directors.

RATIONALE AND OBJECTIVES: The development of curriculum guidelines for radiology residency has been found to be favored by 80% of program directors (PDs) nationwide. I surveyed PDs to develop a consensus of opinion concerning minimum training requirements in the subspecialty rotations. METHODS: A survey developed by members of the Ad Hoc Curriculum Committee of the Association of Program Directors in Radiology was mailed to all U.S. PDs. RESULTS: One hundred forty-one (82%) completed responses were received. There was agreement among the PDs about the minimum length of training needed in the various subspecialties. Seventy-four percent of the PDs supported the concept of developing educational objectives and goals in each subspecialty and of specifying procedures in which residents should be trained. Only a minority of PDs thought that the training guidelines should specify minimum numbers of procedures. CONCLUSION: The consensus of PDs is that the radiology residency curriculum should include a minimum of 3 months in each of the following categories: chest radiology, gastrointestinal radiology, musculoskeletal radiology, pediatric radiology, cardiovascular and interventional radiology, sonography, and body computed tomography (CT) scanning. In neuroradiology, inclusive of neuroangiography, neuro CT scanning, and neuro magnetic resonance (MR) imaging, a resident should spend 4 months. At least 2 months should be devoted to each of the following: uroradiology, mammography, body MR imaging, and emergency radiology. A majority of PDs also favored developing educational objectives for each of the subspecialty rotations.

Curriculum↗
PubMed1996

Peak expiratory flow rate in a random healthy population of Coimbatore.

Results of measurement of Peak Expiratory Flow Rate PEFR made on 1315 healthy persons ranging in age from 7-67 who attended a Medical Exhibition in the city of Coimbatore is analysed. Wide variation in parameters in Indian subjects observed, is attributed to regional variation in population and climate. Also, data collected on highly selected groups like students, sportsmen may not be truly representative of average population. Hence this study was conducted to obtain normal data of PEFR from healthy South Indians living in this region. A multiple regression equation has been developed. The relation of PEFR to age was found to be curvilinear with an increase to peak around the age group of 26-30 years in males and 21-25 years in females and then gradually declines.

Adolescent↗
PubMed1995

Functionally mature olfactory neurons from two anosmic patients with Kallmann syndrome.

Patients with Kallmann syndrome (KS) exhibit hypogonadotropic hypogonadism and anosmia [Kallmann et al., Am. J. Mental Def., 48 (1944) 203-236] secondary to failure of gonadotropin-releasing hormone (GnRH)-producing neurons to migrate from the olfactory placode to the brain, and to agenesis of the olfactory bulbs. It has been hypothesized that olfactory neurons (ON) from individuals with KS are immature partly on the basis of studies in animals showing that lack of synaptic connection of ON with the olfactory bulb results in expression of immature ON [Schwob et al., J. Neurosci., 12 (1979) 880-883]. To test this assumption, we obtained olfactory tissue samples from two males diagnosed with KS on the basis of medical history and MRI studies. Both patients were anosmic. The functioning of cells isolated from biopsies taken from the upper middle turbinate and septum was studied by measuring changes in intracellular Ca2+ concentration ([Cai]) using dual excitation fluorescence microscopy. Biopsies from both patients yielded cells that morphologically appeared to be ON. Seven of 16 cells that morphologically resembled ON responded with a change in [Cai] upon stimulation with an odorant mixture. These studies show that at least some ON in KS individuals are functionally mature and suggest that complete development of the olfactory bulbs is not required for differentiation of mature human ON.

Adolescent↗
PubMed1995

Imaging of the temporomandibular joint.

Recent advances in imaging technology have greatly contributed to the understanding of diseases of the temporomandibular joint (TMJ). MRI is now the modality of choice in the evaluation of TMJ-related symptoms. This article describes normal anatomy and MRI characteristics of diseases affecting the TMJ including internal derangement, inflammation, and tumors.

Diagnosis, Differential↗
PubMed1995

MR imaging: quality assessment method and ratings at 33 centers.

PURPOSE: To outline a quality assessment method with peer review for magnetic resonance (MR) imaging. MATERIALS AND METHODS: Thirty-three providers in the Philadelphia area were rated on a random sample of 132 brain, 124 cervical spine, and 113 lower extremity MR imaging examinations performed during 1990. Blinded peer review was performed by panels of three subspecialty-trained academic radiologists. Technical performance, completeness, and report appropriateness of each MR imaging examination were evaluated. Aggregated scores were calculated to rate provider performance for each of the three parameters of quality. RESULTS: Two or three panelists assessed technical performance as inadequate in 15 cases, completeness as incomplete in 58 cases, and the interpretative report as inappropriate and affecting treatment in 72 cases. Eleven providers received an unsatisfactory rating on one or more parameters of quality. The association between unsatisfactory ratings and the use of low-field-strength (< or = 0.6-T) imagers was statistically significant (P < .008). CONCLUSION: Substantial deficiencies were identified in the performance of examinations and interpretation of MR images in the Philadelphia area in 1990. These findings indicate the need for a program to monitor quality of MR imaging.

Brain↗