Search PubMed⌕ Search

Biomedical subjects

C M Mills

Publications and source records attributed to C M Mills.

At least 55 records · Page 3Linked to original sources
PubMed1988

Hemodynamic response to treadmill exercise in normal volunteers: an assessment by Doppler ultrasonic measurement of ascending aortic blood velocity and acceleration.

Accurate assessment of ascending aortic blood velocity indices and reproducibility of a Doppler ultrasonic system during exercise were determined; the Doppler technique was then used to assess the effects of age, sex, and beta blockade on exercise hemodynamics. Doppler-determined velocity correlated well with an invasive electromagnetic system. Reproducibility of Doppler variables during three exercise tests was high (coefficient of variation less than 10%) and did not deteriorate appreciably with exercise. Peak velocity (PV) and maximum acceleration (MA) were inversely related to age, the relationship being more significant during exercise, whereas the systolic velocity integral showed no such relationship either at rest or during exercise. Doppler variables showed no difference between sexes, except at high levels of exercise. Beta blockade markedly attenuated the exercise response as shown by significant decreases in both MA and PV during exercise. The Doppler velocity data presented in this study provide a reference against which previously documented changes in exercising ischemic patients can be better related.

Adult↗
PubMed1988

White matter disease in AIDS: findings at MR imaging.

A review of the magnetic resonance (MR) images of 365 patients with acquired immunodeficiency syndrome (AIDS) revealed that 112 (31%) had signal abnormalities confined to the white matter. Four patterns were observed: (a) diffuse: widespread involvement of a large area; (b) patchy: localized involvement with ill-defined margins; (c) focal: well-defined areas of involvement; and (d) punctate: small foci less than 1 cm in diameter. Clinical or pathologic findings were available in 60 of the 112 patients and were correlated with the white matter patterns seen on MR images. The diffuse pattern correlated with AIDS dementia complex (ADC), which was the most common clinical diagnosis. Patchy or punctate lesions may be seen with ADC but are less common. Focal white matter lesions were not seen in patients with ADC but were seen in all six patients with progressive multifocal leukoencephalopathy, in both patients with lymphoma, and in one patient with toxoplasmosis. The authors conclude that white matter lesions are are common in AIDS and are often secondary to direct infection of the brain with human immunodeficiency virus, which causes the ADC and usually produces a diffuse white matter pattern. Biopsy is probably not indicated in these patients. Focal white matter lesions suggest a focal infection or tumor, and biopsy may be warranted.

Acquired Immunodeficiency Syndrome↗
PubMed1986

Meningovascular syphilis: CT and MR findings.

The radiologic findings in three cases of meningovascular syphilis are presented. Angiography demonstrated varying degrees of narrowing and ectasia of the supraclinoid carotid, basilar, and proximal anterior and middle cerebral arteries, as well as distal branches. Computed tomography (CT) showed multifocal infarction with variable enhancement. Similarly, in the one case studied with magnetic resonance (MR), several regions of high signal intensity on T2-weighted sequences were found, which were compatible with foci of ischemia. Although the radiologic findings are nonspecific, the diagnosis of meningovascular syphilis should be considered in patients with vasculitis of uncertain etiology.

Adult↗
PubMed1985

Multiple spin-echo magnetic resonance imaging.

Spin-echo magnetic resonance (MR) imaging detects a variety of pathologic states with great sensitivity. A technique for producing multiple spin-echo images in multisection operation is presented. This method of intensity-image acquisition is compared with retrospective intensity-image synthesis from routine data sets. Both yield long echo time (TE) images with similar image contrast and comparable and often increased diagnostic utility. Technical and clinical considerations are addressed, including signal-to-noise levels, flow effects, and patient throughput.

Brain Diseases↗
PubMed1985

Variable magnetic resonance imaging parameters: effect on detection and characterization of lesions.

With change in the imaging technique and magnetic field strength used in magnetic resonance imaging, wide variations in the delineation of pathologic features occur. Using imaging data from patients with known pathologic conditions, we evaluated the intensity images in spin-echo and inversion-recovery imaging at varying repetition times, echo times, and inversion times over broad ranges and changing magnetic field strengths. Differences in conspicuity and the apparent size of the lesions are important to consider in diagnosing and evaluating pathologic conditions, especially when different imagers and techniques are employed.

Brain Diseases↗
PubMed1985

Hydrogen MR imaging of the head at 0.35 T and 0.7 T: effects of magnetic field strength.

To determine whether hydrogen magnetic resonance imaging at 0.7 T provides added clinical value over imaging at 0.35 T, images of the heads of patients with various intracranial disorders were obtained at these field strengths. Measurements of tissue contrast (C), signal-to-noise (S/N) ratio, and T1 and T2 relaxation times were determined. For a given spin-echo sequence with equal imaging time, resolution, and data sampling window, the product C X S/N was somewhat lower for the lower field strength. Under conditions of imaging with equal chemical shift artifact, C X S/N at 0.35 T was equal to or greater than that measured at 0.7 T. With an increase in field strength, T1 of pathologic areas and surrounding normal tissues increased, resulting in a corresponding loss of absolute signal level and decrease in contrast. Lesions were equally well seen at both 0.35 T and 0.7 T. The increased T1 and decreased C X S/N for higher magnetic fields--when measured with a fixed imaging time, resolution, chemical shift, and sequence--suggest that such field strengths may not improve tissue contrast, diagnostic ability, or clinical throughput when compared with lower field strength systems.

Brain↗
PubMed1984

High-resolution magnetic resonance imaging. Technical concepts and their implementation.

In magnetic resonance (MR) imaging manipulating spatial resolution, contrast resolution, and imaging time separately results in improvement in some parameters without degradation of others. The authors have found that MR imaging of the head with a repetition time TR = 2.0 seconds produces images with high signal-to-noise levels and excellent sensitivity to demyelinating disease and brain water content. In the body, a long TR yields large signal levels that permit delineation of low-intensity structures such as patent vessels and bone. The long TR technique can be used in a high-resolution mode (256 X 256 data acquisition elements, each 0.8 X 0.8 mm) while maintaining image times of 50 or 100 sec/section. For normal resolution (1.7 X 1.7 mm), imaging time is 25 or 50 sec/section. It is concluded that the combination of slow-imaging techniques with simultaneous multisection imaging will prove practical for clinical MR.

Brain↗
PubMed1984

Cerebral abnormalities: use of calculated T1 and T2 magnetic resonance images for diagnosis.

The potential clinical importance of T1 and T2 relaxation times in distinguishing normal and pathologic tissue with magnetic resonance (MR) is discussed and clinical examples of cerebral abnormalities are given. T1 and T2 values may be used in three ways: (a) Relative values, obtained by an analysis of intensity images with varying dependence on T1 and T2, may be used if absolute values for T1 and T2 are not required for diagnosis. (b) If an absolute value is desired, the numerical values for the relaxation times may be generated using a region of interest on the intensity images. (c) In cases in which both T1 and T2 change may require a calculated image to indicate the contribution of each to the signal intensity, the numerical value may be used to generate analogue images of T1 or T2 calculations. Five patients with cerebral infarction, 15 with multiple sclerosis, two with Wilson disease, and four with tumors were imaged. Hemorrhagic and ischemic cerebrovascular accidents were distinguished using the spin echo technique. In the patients with multiple sclerosis, lesions had prolonged T1 and T2 times, but the definition of plaque was limited by spatial resolution. No abnormalities in signal intensity were seen in the patient with Wilson disease who was no longer severely disabled; abnormal increased signal intensity in the basal ganglia was found in the second patient with Wilson disease. Four tumors produced abnormal T1 and T2 relaxation times but these values alone were not sufficient for tumor characterization.

Brain Diseases↗
PubMed1984

Primary intracranial tumor imaging: a comparison of magnetic resonance and CT.

Twenty-six patients with primary intracranial tumors were evaluated by magnetic resonance (MR) and a comparison was made with CT findings. The SE technique with TR = 2,000 ms and TE = 56 ms was most useful in delineating normal anatomy, in differentiating gray and white matter, and in optimizing the visualization of edema. The use of TR = 500 ms optimized sensitivity to T1 relaxation time differences in disparate tissue and best defined the cerebrospinal fluid spaces. Although prolongation of T1 and T2 relaxation values was seen with most malignant lesions, several cases produced no obvious prolongation of T1. Separation of tumor from surrounding edema was possible in several instances. In 16/26 patients information not available on CT was obtained with MR. This included detection of altered tissue characteristics where CT showed only mass effect, more accurate depiction of full extent and location of tumor, and visualization of associated abnormalities. However, a small inner ear epidermoid tumor seen with high-resolution CT (1.5-mm sections) was difficult to identify with certainty on MR, and in two other cases punctate foci of calcification were not identified on MR.

Adolescent↗
PubMed1984

Magnetic resonance of the brain: the optimal screening technique.

Seventy consecutive patients were examined with magnetic resonance (MR) and computed tomography (CT) of the brain. Each study was independently reviewed. Focal abnormalities were detected by one or both modalities in 51 patients. Neoplastic, infectious, vascular, demyelinating, metabolic, and congenital disorders of the brain were included. The MR pulse sequence that best detected these abnormalities was a spin-echo multisection technique that used a long interval between RF excitations (TR = 1500 or 2000 msec). Forty-eight of 51 patients showed focal lesions with this technique. A supplementary MR pulse sequence with a short TR (500 msec) was useful in helping to characterize certain lesions with a long T1 relaxation component, but in 10 of 26 positive cases in which this sequence was added it would have missed the abnormality had it been the sole sequence used. MR missed focal lesions in 3 of 51 patients. These were lesions that required thin-section (1.5 mm) CT techniques. Two were intrasellar, and one was an intracanalicular neurinoma. In 17 of 48 patients, CT missed the focal lesion seen with MR. Based on this experience, it is concluded that the long TR multisection spin-echo sequence is the optimal MR screening technique for detection of most brain abnormalities, and is more sensitive than CT. Currently, CT remains the screening modality of choice when high-resolution, thin-section studies in the pituitary, inner ear, and orbital regions are indicated.

Brain Diseases↗
PubMed1984

Magnetic resonance imaging of the nasopharynx.

Thirty subjects with normal nasopharyngeal anatomy and 12 patients with a variety of abnormalities were examined with computed tomography (CT) and magnetic resonance imaging (MR), using a prototype 0.35-T superconducting system. A spin-echo technique, a repetition time (TR) of 2.0 sec., and echo times (TE) of 28 and 56 msec. were optimal for depiction of both normal and abnormal anatomy. MR was superior to CT for display of both superficial and deep nasopharyngeal soft tissues in all 30 normal subjects and 10 of the 12 abnormal patients, clearly differentiating mucosal and lymphoid tissue (adenoids, lingual and palatine tonsils) from the surrounding musculature. MR was also superior to CT in distinguishing tumor from soft tissues and more sensitive to carotid sheath adenopathy, permitting a more detailed evaluation of retropharyngeal and deep cervical nodal metastases in 2 cases. Bones, calcification, and subtle abnormalities at the base of the skull were shown better by CT. The specificity of MR and its ability to differentiate nodal metastases from reactive lymphadenopathy require further evaluation.

Adolescent↗
PubMed1984

Analytical tools for magnetic resonance imaging.

The response of different magnetic resonance (MR) techniques to tissue parameters - T1, T2, and N(H) - is a determinant of clinical efficacy. The large possible number of imaging techniques and range of variable parameters for each make it difficult to perform exhaustive evaluations in a single patient or even in animal models. In addition, changes in operating magnetic field strength change the relaxation times sufficiently so that the efficacy of a technique at a given field does not imply similar results at another field value. Tools are demonstrated that permit the evaluation of the efficacy of any model of response to tissue parameters, and also allow the investigation of the effects of changing magnetic field. Global maps of signal difference between tissues as well as calculated images are obtainable from a minimally sufficient data set. These tools serve as an important adjunct to experimental work.

Electron Spin Resonance Spectroscopy↗
PubMed1984

Nuclear magnetic resonance: principles of blood flow imaging.

Nuclear magnetic resonance (NMR) imaging with spin-echo techniques defines vascular structures with superb anatomic detail. Contrast agents are not necessary as there is intrinsic contrast between flowing blood and the vascular wall. The signal intensity from blood within the vessel lumen varies with the sequence of gradient and radiofrequency pulses used to generate the image as well as with the velocity of blood flow. Appropriate imaging techniques can optimize anatomic detail, distinguish slow from rapidly flowing blood, and serve to identify marked impairment or complete obstruction of flow in an artery or vein. Some examples of these principles in the intracranial circulation are illustrated.

Adolescent↗
PubMed1983

NMR demonstration of cerebral abnormalities: comparison with CT.

Sixty-eight patients with a wide spectrum of brain pathology were imaged with both computed tomography (CT) using a G.E. 8800 scanner and nuclear magnetic resonance (NMR) imaging with a 3.5 kG prototype device. NMR was more advantageous in the detection and/or characterization of pathology in 20 of the 68 patients, especially when demyelination was part of the disease process or when the lesion was obscured on CT by beam-hardening artifact. Punctate foci of calcification identified on CT were not detected on NMR, but larger calcifications were seen. NMR was sensitive to detection of both normal and abnormal vascular structures. The ability of NMR to differentiate among different pathologic entities remains to be fully evaluated. NMR currently complements CT in the evaluation of many disease entities and may actually supplant CT in some. The full future potential of NMR and its role with respect to CT has only begun to be elucidated.

Adolescent↗
PubMed1983

Magnetic resonance imaging of the spinal cord and canal: potentials and limitations.

Preliminary experience with magnetic resonance imaging (MRI) of the spinal cord and canal in 17 patients indicates considerable promise in the diagnosis of neoplastic, degenerative, and congenital lesions. The ability to image the cord directly rather than indirectly as in myelography, the absence of bone artifact as in computed tomography, and the multiplanar capabilities indicate that MRI will be the procedure of choice in the examination of the spinal cord. Current limitations include partial-volume effects due to slice thickness and the inability to perform contiguous sections when using multiplanar techniques. The relative increase in signal from cerebrospinal fluid with long TR and TE sequences in spin-echo imaging may result in less sensitivity than in the brain for detection of cord edema and/or infarction.

Humans↗