Duane P. Flamig

A physics-based coordinate transformation for 3-D image matching

Many image matching schemes are based on mapping coordinate locations, such as the locations of landmarks, in one image to corresponding locations in a second image. A new approach to this mapping (coordinate transformation), called the elastic body spline (EBS), is described. The spline is based on a physical model of a homogeneous, isotropic three-dimensional (3-D) elastic body. The model can approximate the way that some physical objects deform. The EBS as well as the affine transformation, the thin plate spline and the volume spline are used to match 3-D magnetic resonance images (MRIs) of the breast that are used in the diagnosis and evaluation of breast cancer. These coordinate transformations are evaluated with different types of deformations and different numbers of corresponding (paired) coordinate locations. In all but one of the cases considered, using the EBS yields more similar images than the other methods.

In vivo proton magnetic resonance spectroscopy studies of human brain

In vivo localized proton magnetic resonance spectroscopy (MRS) studies of brain were performed on eighteen normal subjects using the stimulated echo (STE) sequence. The absolute concentrations and proton relaxation times of N-acetyl aspartate (NAA), total creatine (Cr) and choline (Cho) were estimated. The MRS data was quantitatively analyzed for repeatability and intersubject variability. Quantitative analysis indicates excellent spectral repeatability. Significant intersubject variations in [NAA] and [Cr] have been observed while the intersubject variability in [Cho] has been found to be fairly small. Significant intensity distortions have been observed for mixing times longer than 50 msec.

Magnetic resonance imaging: Techniques

Method for MR imaging of an object in which various RF and magnetic field gradient pulse sequences are used to produce transverse magnetization and to generate echoes. The RF pulse sequence may include a sinusoidal waveform component defined by either y=sin x, 0≦x ≦4π; y=cos x, 0≦x ≦4π; or y=sin x, 0≦x≦π/2, y=cos x, π/2≦x≦π; and a phase component defined by either y=0, 0≦x≦2π, y=π, 2π≦x≦4π; or y =-2πcos x, 0≦x≦π/2, y=-2πsin x, π/2≦x≦π. The selected waveform and phase components may be combined to form a first, composite RF signal and the Hilbert transform of the composite RF signal selected as a second RF signal. Alternately, the second RF pulse sequence may be comprised of first and second phase shifting linear ramps. The selected gradient magnetic field pulse sequences may include a first sinusoidal readout pulse sequence defined by y=ax sin x, 0≦x≦nπ and a second sinusoidal readout pulse sequence defined by y=ax cos x, 0≦x≦nπ, first and second constant magnitude phase encoding pulse sequences, or a square wave as a readout pulse sequence and a series of positive amplitude spikes positioned at each transition for the readout pulse sequence as a phase encode pulse sequence.

Diagnostic and therapeutic processes utilizing magnetic resonance imaging techniques

Method for diagnosing and treating tissue suspected of containing a lesion. A shaped pulse sequence is selected for each of waveform, phase and frequency components of an RF signal based upon characteristics of the tissue suspected of containing a lesion and an RF signal comprised of the selected waveform, amplitude and frequency shaped pulse sequences generated. A series of echoes is received in response to the generated RF signal and a real-time MR image of the tissue suspected of containing a lesion is produced using the series of received echoes. The tissue is then diagnostically evaluated for the presence of lesions using the produced real-time MR image. Using the produced real-time MR image of the tissue, boundaries between the tissue and each lesion detected during the evaluation of the tissue are determined and the lesion removed from the surrounding healthy tissue using a therapeutic delivery system while observing the boundary between the lesion and the surrounding healthy tissue using the produced real-time MR image.

Elastic body splines: a physics based approach to coordinate transformation in medical image matching

In a landmark based medical image matching scheme, a coordinate transformation maps a set of landmark locations in one image onto a corresponding set in a second image. A novel approach to this transformation, the elastic body spline, is introduced. The development of the spline is outlined. An example of using the spline to match 3D magnetic resonance images (MRIs) of the breast is described. The elastic body spline is compared to the thin plate spline and, for 3D breast MRIs, is found to have superior performance as assessed by several measures of the similarity of the matched images.<<ETX>>

Silicone-suppressed 3D MRI of the breast using rotating delivery of off- resonance excitation

Objective A new silicone-suppressed MR technique was developed, and its efficacy in identifying free silicone and differentiating it from other breast tissues was investigated. Materials and Methods Silicone-suppressed MRI was performed using the RODEO (rotating delivery of excitation off-resonance) pulse sequence, which selectively eliminated signal from the narrow range of (CH3)4Si resonance. Ninety breasts in 61 patients were evaluated with both a fat-suppressed 3D MR sequence and a silicone-suppressed 3D MR sequence. Results Extracapsular free silicone and silicone injections demonstrated a unique appearance compared with normal breast tissue in all cases. Magnetic resonance identified free silicone in 26 breasts, 10 of which were confirmed pathologically or from a history of previous silicone injections. No free silicone was present on MR in 64 breasts; 8 of these were confirmed by biopsy or mastectomy as showing no evidence of free silicone. This technique was useful in evaluation of prosthesis integrity, free silicone, focal palpable or mammo-graphic lesions, and the breast with silicone injections. Conclusion Silicone-suppressed RODEO MRI of the breast can accurately identify free and intracapsular silicone and can distinguish silicone from other tissues. This provides unique information about the breast in a number of specific applications.

One-dimensional spectroscopic imaging with stimulated echoes: Phantom and human leg studies

One-dimensional phase encoding was incorporated in the stimulated echo single voxel localization sequence for in vivo proton spectroscopic studies. Phantom studies were performed to assess the effect of the number of phase encoding steps on the spectral contamination from the adjacent volumes. Both water suppressed and unsuppressed spectra were obtained in reasonable acquisition times from various regions in the human leg with a spatial resolution of around 1.1 cm3.

Curvature measurement of 3D objects: evaluation and comparison of three methods

Many computer vision techniques (e.g., object recognition) use curvature as an image feature. Arbitrary, discrete, 3D surfaces are often encountered, for instance, in medical images (MRI is used as a particular example), but relatively few methods for estimating the curvature of these 3D surfaces have been proposed. Three such methods (the surface triangulation, cross patch, and partial derivative techniques) are described. These methods are used to locate curvature extrema (corners) in 3D images. The suitability of the methods for this application is evaluated and compared.

Magnetic resonance angiography. Application to the peripheral circulation.

&NA; Harms SE, Flamig DP. Magnetic resonance angiography: application to the peripheral circulation. Invest Radiol 1992;27: S80‐S83. Magnetic resonance angiography (MRA) for application in the musculoskeletal system is progressing at a rapid pace. The clinical role of this new technique is still being developed, although a number of uses have already become well recognized, and MRA is diffusing into clinical practice. This article describes the basic fundamentals of MRA as it applies to the peripheral circulation and to the evaluation of potential clinical procedures.

Coordinate transformation in 3D image matching by a physics based method-elastic body splines

Any image matching scheme that is based on landmarks requires a coordinate transformation that maps landmark locations in one image to corresponding locations in a second image. The development of an approach to this coordinate transformation, called the elastic body spline (EBS), is outlined. The spline is used to match 3D magnetic resonance images (MRIs) of the breast that are used in the diagnosis and evaluation of breast cancer. The elastic body spline is compared to an affine transformation and the thin plate spline. For breast MRIs, the EBS is found to have superior performance as assessed by several measures of the similarity of the matched images.