Biomedical subjects

C M Moran

Publications and source records attributed to C M Moran.

27 records · Page 2Linked to original sources

PubMed1995

Ultrasonic propagation properties of excised human skin.

Eight human skin samples were excised postmortem from the upper and lower back, chest and abdomen from two cadavers. The acoustical speed, attenuation and backscatter were measured as a function of frequency (20 to 30 MHz) at 100 positions on a uniform grid over a cross-sectional slice through each sample with the sound incident in a direction parallel to the skin surface. Measurements were made at 24 +/- 0.5 degrees C. Samples were then frozen, cut and stained for histological examination and quantification of fibrous proteins and fat content. The mean attenuation coefficients obtained for whole skin agreed well with previously published results. Employing the model alpha = alpha 1f" where alpha is the attenuation coefficient in decibels per centimeter, alpha 1 is the value of the attenuation coefficient at 1 MHz and f is frequency raised to the power n, mean values (+/- 1 standard deviation) for epidermis were alpha 1 = 0.44 +/- 0.26 and n = 1.55 +/- 0.12, and for dermis alpha 1 = 0.264 +/- 0.17 dB cm-1 and n = 1.69 +/- 0.084. Using a similar model the mean backscatter coefficient was defined by mu 1 = (5.01 +/- 25.76) x 10(-8) Sr-1 cm-1, n = 3.77 +/- 1.5 for the epidermis, and mu 1 = (1.79 +/- 19.5) x 10(-6) and n = 2.76 +/- 1.4 for the dermis. The speed of sound values fell within the range to be found in the literature with a mean value in the epidermis of 1645 m s-1 and in the dermis of 1595 m s-1. Significant, strong correlation existed between the spatially averaged fibrous protein content in the epidermis and dermis and the spatially averaged integrated attenuation measurements. Likewise, strong correlation existed between integrated backscatter and fibrous protein content in the epidermis but not in the dermis. Further research is required to confirm these preliminary findings and to evaluate the role of collagen fibre orientation as a source of variation in the backscattering coefficient of dermis.

Abdomen↗

PubMed1994

A comparison of methods used to calculate ultrasonic myocardial backscatter in the time domain.

The cyclic variation of ultrasonic integrated backscatter from the left ventricular posterior wall and interventricular septum of the heart is now well documented in the literature, with minimal values occurring at end-systole and maximal at end-diastole. However, little work has been performed to date to determine whether cyclic cardiac variation of other, more easily derived, backscatter parameters exists. In this study, 20 baseline, epicardial, long-axis cardiac-cycle sequences were obtained from eight open-chest pigs, yielding a total of 285 ultrasonic frames of RF data, which were analysed off-line on a Sun workstation. In addition, the video data from these studies was digitised and collected from each scan. Five backscatter parameters, calculated in the time-domain, including (1) the average integrated backscatter; (2) the average of the backscatter power from the log-compressed data; (3) the square of the average of the uncompressed radio frequency (RF) amplitude; (4) the square of the average of the RF amplitude from the log-compressed data; and (5) the square of the average grey-scale video data, were analysed and their variation throughout the cardiac cycle correlated against that obtained from integrated backscatter measurements. The backscatter values obtained were referenced to a gel calibration phantom widely used for 2-D calibration studies. Significant (p < 0.001), good correlation existed between the four backscatter parameters derived from the RF data. Reduced correlation was obtained between the video backscatter parameter and those derived from the RF data. Maximum cyclic variation between systole and diastole was measured from the integrated backscatter parameter and minimum from the three log-compressed data sets.

Analog-Digital Conversion↗

PubMed1992

Colour Doppler velocity imaging of the myocardium.

A technique has been developed for producing images of the velocity of tissue motion within the myocardium. It has been demonstrated that Colour Flow Doppler imagers can be operated to depict the velocities within the myocardium rather than moving blood in the cardiac chambers. The technique exhibits the normal advantages of diagnostic ultrasound, i.e., real-time imaging with relatively inexpensive equipment and no hazard to the patient. Further work requires to be done to determine the optimum signal processing algorithms for moving tissue echoes and to ascertain whether the technique is of value in clinical applications.

Echocardiography↗

PubMedDate not supplied

The variation of integrated backscatter in human hearts in differing ultrasonic transthoracic views.

It has been shown previously that in normal subjects the interventricular septum imaged in the long-axis view (LAX) and the left ventricular posterior wall imaged in both the LAX and the short-axis view (SAX) exhibit cyclic variation of integrated backscatter (IB) throughout the cardiac cycle, with maximum values occurring at end diastole (ED) and minimum at end systole (ES). The ability to demonstrate this cyclic variation within these myocardial regions in only two ultrasonic views has limited the potential clinical utility of an IB imaging system. To determine whether clinically useful information on the variation of IB is available from different myocardial regions in different ultrasonic views, we measured ED to ES variation of IB from the parasternal and apical views in normal subjects with a radiofrequency acquisition technique. Two independent clinical observers analyzed ED to ES variation of IB from 14 normal volunteers (mean age 32 +/- 6 years; range 21 to 45 years) in reconstructed two-dimensional ultrasonic images obtained from the parasternal LAX and SAX and apical two-chamber (2C) and four-chamber (4C) views. ED to ES variation of IB was measured from manually traced regions of interest (ROI) within the myocardium. These ROIs were chosen interactively and were located within the midposterior wall and the midanteroseptum in LAX views; within the midposterior wall, midanteroseptum, midseptum, and midlateral wall in SAX views; within the midseptum and the midlateral wall in 4C views; and within the midinferior wall and the midanterior wall 2C views. In all analyzed ROIs within the parasternal and apical views, ED to ES variation of IB was found. We have shown that the maximum magnitude of IB was at ES within the midseptum and in 10 out of 14 volunteers in the midanteroseptum measured from SAX views, the midanterior wall from 2C views, and the midlateral wall from 4C views. The rest of the ROIs analyzed exhibited the maximum value of IB cyclic variation at ED. We have confirmed that the ED to ES variation of IB is present not only when measured from the two standard parasternal views but also from the two apical views in all analyzed myocardial walls, and the minimum of this cyclic variation was not always coincident with ES nor the maximum with ED.

Adult↗

PubMedDate not supplied

Color Doppler myocardial imaging: a new technique for the assessment of myocardial function.

Color Doppler myocardial imaging is a new technique that has been developed specifically to allow color Doppler imaging of myocardial wall motion rather than blood pool imaging. Such a technique has the potential to interrogate velocities, accelerations, and Doppler signal strength within the myocardial wall. Moreover, the concomitant enhancement of the myocardial Doppler signal after an intravenous injection of a transpulmonary echocardiographic contrast agent could permit the noninvasive assessment of regional myocardial perfusion. Thus this new imaging modality could be a valuable adjunct to the ultrasound assessment of myocardial ischemia.

Animals↗

PubMedDate not supplied

Peak mean myocardial velocities and velocity gradients measured by color M-mode tissue Doppler imaging in healthy cats.

We sought to assess the feasibility of recording the myocardial velocity gradients (MVGs) and mean myocardial velocities (MMVs) measured by color M-mode tissue Doppler imaging (TDI) in the free wall of unsedated normal cats (n = 18) with a 7.4-MHz probe equipped to record TDI images. The peak MVG and MMV values during the different phases of the cardiac cycle corresponded to certain color velocity patterns occurring in the left ventricular free wall (LVFW). Biphasic shifts were recorded in the tracings of both the MVG and MMV during early diastole (E1 and E2) as well as during the isovolumic relaxation (IVR) and isovolumic contraction (IVC) phases. Stepwise regression analysis showed that age was the only significant predictor for the peak MVG values during the 2nd phase of early diastole (E2) (r = -0.79, r2 = 0.63, and P < .001). The peak late diastolic MVG values were associated positively with age (r = 0.50, r2 = 0.25, and P < .05). The peak MMV values showed a negative association with age during E2 (r = -0.71, r2 = 0.50, and P < .001) as well as during early systole (Se) (r = -0.55, r2 = 0.30, and P < .05) and late systole (SI) (r = -0.62, r2 = 0.39, and P < .01). A positive association was found between age and the peak MMV values during late diastole (r = 0.54, r2 =- 0.29, and P < .05). The MVG values showed cyclic variations consistent with wall thickness changes. The accuracy of velocity determination and the spatial resolution of the system used were validated with a phantom. To our knowledge, this study is the 1st report of the application of this technique to the myocardium of cats,providing insights into the physiology of myocardial motion. It provides reference ranges of the peak MVG and MMV values for future studies of feline myocardial diseases.

Animals↗

PubMedDate not supplied

Pulsed tissue Doppler imaging in normal cats and cats with hypertrophic cardiomyopathy.

Myocardial motion was quantified in normal cats (n = 25) and cats with hypertrophic cardiomyopathy (HCM) (n = 23) using the pulsed tissue Doppler imaging (TDI) technique. A physiologic nonuniformity was documented in the myocardial motion of normal cats, which was detected as higher early diastolic velocities, acceleration, and deceleration in the interventricular septum compared with the left ventricular free wall (LVFW). HCM cats exhibited lower early diastolic velocities, acceleration, and deceleration and also prolonged isovolumic relaxation time compared with normal cats. These differences were detected mainly along the longitudinal axis of the heart. A cutoff value of E' in the LVFW along the longitudinal axis >7.2 cm/s discriminated normal from HCM cats with a sensitivity of 92% and a specificity of 87%. The physiologic nonuniformity of myocardial motion during diastole was lost in affected cats. Systolic impairment (decreased late-systolic velocities in most segments along the longitudinal axis and decreased early systolic acceleration in both mitral annular sites) was evident in HCM cats irrespective of the presence of left ventricular outflow tract obstruction and congestive heart failure. Postsystolic thickening was recorded in the LVFW along the longitudinal axis only in affected cats (n = 6) and was another finding indicative of systolic impairment in the HCM of this species. This study identified both diastolic and systolic impairment in cats with HCM compared with normal cats. The study also documents the normal physiologic nonhomogeneity in myocardial motion in cats and the subsequent loss of this feature in the HCM diseased state.

Animals↗

PubMedDate not supplied

Sir Winston Churchill.

Explore the source record for details and available documents.

History, Modern 1601-↗

PubMedDate not supplied

An investigation of the relationship between low back pain and lumbar posteroanterior stiffness.

OBJECTIVE: To investigate the relationship between low back pain (LBP) and lumbar posteroanterior (PA) stiffness. DESIGN: A repeated-measures design was used to measure lumbar posteroanterior stiffness on two occasions in subjects with and without LBP. SUBJECTS: Twenty-five subjects with acute or subacute LBP and twenty-five pain-free subjects participated. Pain subjects reported pain on the application of a manual PA force to the lumbar spine and had no contraindication to PA stiffness testing. Pain-free subjects reported no history of LBP requiring treatment, and obtained a score of 0 on the McGill Pain Questionnaire. METHODS: PA stiffness was measured in subjects with LBP when (a) they first presented with pain and (b) when pain had resolved by more than 80%. Pain-free subjects, matched with pain subjects on gender, age, vertebral level to be tested and time between tests, were also measured on two occasions, to control for the effects of repeated stiffness testing and the passing of time. RESULTS: In subjects with low back pain stiffness decreased by 1.21 N/mm between test 1 and test 2. A paired t test found a significant difference between the tests (t = 3.04, df = 24, p = .006). In subjects without pain, there was an increase in stiffness of 0.74 N/mm between test 1 and test 2; a paired t test found no significant difference between the tests (t = -1.673, df = 24, p = .107). CONCLUSIONS: Subjects with LBP showed increased PA stiffness compared with when they had little or no pain, whereas pain-free subjects showed unchanged PA stiffness over time.

Adult↗