Hereditary nephropathy: unusually large protein loss during peritoneal dialysis.
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Adult↗
Biomedical subjects
D M Weber
Publications and source records attributed to D M Weber.
Intraoperative, real-time, functional MRI.
Functional MRI (fMRI) methods have been demonstrated to noninvasively identify motor-sensory, visual, and other areas of eloquent cortex for guiding surgical intervention. Typically, fMRI data are acquired preoperatively during a conventional surgical planning MRI examination. Unlike direct cortical stimulation at the time of surgery, however, preoperative fMRI methods do not account for the potential movement of tissues (relative to the time of functional imaging) that may occur in the surgical suite as a direct result of the intervention. Recently, an MRI device has been demonstrated for use in the surgical suite that has the potential to reduce the extent of cortical exposure required for the intervention. However, the invasive requirements of cortical mapping may supersede the invasive requirements of the surgical intervention itself. Consequently, we demonstrate here a modification to the intraoperative MRI device that facilitates a noninvasive, real-time, functional MR examination in the surgical suite.
Brain↗
Combined MRI and MRA for limb salvage planning.
Magnetic resonance angiography (MRA) was performed in two patients with primary bone neoplasms being staged for differing types of limb-salvage procedures. A gated two-dimensional (2D) phase contrast MRA sequence that is capable of variable velocity encoding throughout the cardiac cycle was used to acquire the MRA images. The resulting cardiac phase images were added with a matched filter algorithm to create a single high signal-to-noise ratio image. An SE MR image in the same plane and field of view was then added to the MRA image. This displayed the relationship of vascular and stationary tissues within a composite picture: a "2D combined angiographic-stationary tissue" image. The anatomy represented gave information equivalent to conventional angiography. While this technique is not an ideal 3D rendering, it is easier to use. Along with other SE sequences acquired as needed for staging, it provides a complete preoperative evaluation of a tumor bed or donor site for a vascularized graft harvest.
Adolescent↗
Absolute diameter measurements of coronary arteries based on the first zero crossing of the Fourier spectrum.
Current edge detection methods used to determine coronary artery dimensions from digital (DSA) images suffer a strong dependence on the system's modulation transfer function (MTF). The videodensitometric algorithms are less sensitive to MTF blurring, yet still result in an overestimation of the vessel size of 10% to 25% for blurring aperture sizes of 50% to 80% of the vessel diameter. We propose a new algorithm to measure the absolute diameter of a vessel which has a lower sensitivity to the system MTF for blurring aperture sizes up to 80% of the vessel diameter. A consequence of the similarity theorem of Fourier transform pairs is that the "width" of the Fourier transform, as characterized by the first zero crossing in frequency space, is inversely proportional to the width of the vessel profile. For an ideal (unblurred) vessel image, the width of the vessel profile is equal to the diameter of the vessel. For a blurred image this is not true. In frequency space, however, the transform of the blurred profile is simply the product of the transformed ideal profile and the system MTF. Thus, if the blurring aperture of the system is below some critical value, the first zero of the unblurred profile will still dominate the transform of the blurred profile. For vessels of circular cross section and a rectangular blurring aperture, this critical aperture size is approximately 80% of the vessel diameter. A more detailed explanation of the theory and calculations involved in this measurement, along with measurements of computer simulated and phantom vessels is presented.
Algorithms↗