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D H Pretorius

Publications and source records attributed to D H Pretorius.

119 records · Page 7Linked to original sources
PubMed1984

Fetal age estimation by ultrasound: the impact of measurement errors.

Ultrasound estimation of fetal age is a routine, safe, and valuable diagnostic procedure. The overall accuracy of ultrasound measurement of femur length and biparietal diameter was investigated using a dowel phantom, chicken bones, and a bottle. Objects were imaged in a water bath using commercially available static, linear, and sector scanners. Transducer type and frequency, depth, object dimension, and observer variation were evaluated. Our results show that there was no appreciable difference between transducer types; the overall accuracy of the measurements improved with increasing transducer frequency; the lateral measurements consistently overestimated the object length; the absolute error in lateral measurements was between 0-12 mm; the absolute error in axial measurements was between 0-4 mm; the interobserver variability was +/- 1.3 mm, and intraobserver variability was +/- 1.0 mm. We conclude that transducer type does not affect measurement accuracy, measurement errors are greater in the lateral dimension as opposed to the axial dimension, proper quality assurance and performance evaluation procedures are necessary to ensure optimal results, and femur length measurements will continue to be useful in evaluation of gestational age.

Age Determination by Skeleton↗
PubMedDate not supplied

Abdominal wall CT: a pictorial essay.

Abdominal CT demonstrates clearly the anatomy of the abdominal wall. This radiographic technique may provide valuable information when pathology is suspected in this region or in the adjacent peritoneum. The muscles, subcutaneous tissues and vascular structures of the abdominal wall should be examined thoroughly when reading routine abdominal CT films. This paper reviews abnormalities identified involving the abdominal wall including hernias, masses, vessels, hematomas, abscesses, ascites, neuromuscular diseases and miscellaneous entities.

Abdominal Muscles↗
PubMedDate not supplied

Menstrual variation of normal breast NMR relaxation parameters.

Nuclear magnetic resonance (NMR) offers great promise in noninvasively distinguishing normal, benign, and malignant tissues in the breast. However, well-documented changes that occur in breast tissues during the normal menstrual cycle suggest that lesion detectability will depend on knowledge of the variations in NMR parameters that occur as a consequence of these changes. Correct selection of optimal NMR pulse sequences and interpulse times, based on spin density and T1 and T2 values, to maximize tissue contrast and lesion detectability, will likewise depend on our understanding of variations in NMR parameters of normal breast tissues. The purpose of this study is to determine the range and variability of NMR parameters (spin density, T1 and T2) associated with changes in normal breast tissues during the menstrual cycle, as measured by NMR imaging. Initial findings suggest that there are measurable differences between breast tissues as a function of time in the menstrual cycle.

Breast↗
PubMedDate not supplied

Magnetic resonance imaging: the basic physical and clinical concepts. Part I.

Noninvasive evaluation of the human body has become an essential tool in the diagnosis of disease processes. Recent developments in nuclear magnetic resonance imaging (MRI) have extended a powerful chemical analytic technique to the medical imaging field. This article presents the fundamental principles of MRI in terms of the concept of transmission and reception of energy. The physical principles of spin resonance are discussed in Part I. Spin relaxation and pulse sequences will be examined in Part II and III. A selected bibliography directs the reader to a more detailed discussion of the pertinent physics.

Humans↗
PubMedDate not supplied

Magnetic resonance imaging: the basic physical and clinical concepts. Part II.

Noninvasive evaluation of the human body has become an essential tool in the diagnosis of disease processes. Recent developments in nuclear magnetic resonance imaging (MRI) have extended a powerful chemical analytic technique to the medical imaging field. This article presents the fundamental principles of MRI in terms of the concept of transmission and reception of energy. The physical principles of spin resonance were discussed in Part I. Spin relaxation and pulse sequences will be examined in Part II and III. A selected bibliography directs the reader to a more detailed discussion of the pertinent physics.

Biophysical Phenomena↗
PubMedDate not supplied

Magnetic resonance imaging: the basic physical and clinical concepts. Part III.

Noninvasive evaluation of the human body has become an essential tool in the diagnosis of disease processes. Recent developments in nuclear magnetic resonance imaging (MRI) have extended a powerful chemical analytic technique to the medical imaging field. This article presents the fundamental principles of MRI in terms of the concept of transmission and reception of energy. A selected bibliography directs the reader to a more detailed discussion of the pertinent physics.

Humans↗