Faculty Bibliography

When Einstein formulated his special relativity, he developed his dynamics for point particles. Of course, many valiant efforts have been made to extend his relativity to rigid bodies, but this subject is forgotten in history. This is largely because of the emergence of quantum mechanics with wave-particle duality. Instead of Lorentz-boosting rigid bodies, we now boost waves and have to deal with Lorentz transformations of waves. We now have some nderstanding of plane waves or running waves in the covariant picture, but we do not yet have a clear picture of standing waves. In this report, we show that there is one set of standing waves which can be Lorentz-transformed while being consistent with all physical principle of quantum mechanics and relativity. It is possible to construct a representation of the Poincare group using harmonic oscillator wave functions satisfying space-time boundary conditions. This set of wave functions is capable of explaining the quantum bound state for both slow and fast hadrons. In particular it can explain the quark model for hadrons at rest, and Feynman's parton model hadrons moving with a speed close to that of light

PURPOSE: To demonstrate a method to extract the meaningful biologic information from (111)In-radiolabeled capromab pendetide (ProstaScint) SPECT scans for use in radiation therapy treatment planning by removing that component of the (111)In SPECT images associated with normal structures. METHODS AND MATERIALS: We examined 20 of more than 80 patients who underwent simultaneous (99m)Tc/(111)In SPECT scans, which were subsequently registered to the corresponding CT/MRI scans.A thresholding algorithm was used to identify (99m)Tc uptake associated with blood vessels and CT electron density associated with bone marrow. Corresponding voxels were removed from the (111)In image set. RESULTS: No single threshold value was found to be associated with the (99m)Tc uptake that corresponded to the blood vessels. Intensity values were normalized to a global maximum and, as such, were dependent upon the quantity of (99m)Tc pooled in the bladder. The reduced ProstaScint volume sets were segmented by use of a thresholding feature of the planning system and superimposed on the CT/MRI scans. CONCLUSIONS: ProstaScint images are now closer to becoming a biologically and therapeutically useful and accurate image set. After known sources of normal intensity are stripped away, the remaining areas that demonstrate uptake may be segmented and superimposed on the treatment-planning CT/MRI volume

The energy-momentum relations for massive and massless particles are E = p(2)/2m and E = pc respectively. According to Einstein, these two different expressions come from the same formula E = root(cp)(2) + m(2)c(4). Quarks and partons are believed to be the same particles, but they have quite different properties. Are they two different manifestations of the same covariant entity as in the case of Einstein's energy-momentum relation? The answer to this question is YES. It is possible to construct harmonic oscillator wave functions which can be Lorentz-boosted. They describe quarks bound together inside hadrons. When they are boasted to an infinite-momentum frame, these wave functions exhibit all the peculiar properties of Feynman's parton picture. This formalism leads to a parton distribution corresponding to the valence quarks, with a good agreement with the experimentally observed distribution

It has been almost 100 years since Einstein formulated his special theory of relativity in 1905. He showed that the basic space-time symmetry is dictated by the Lorentz group. It is shown that this group of Lorentz transformations is not only applicable to special relativity, but also constitutes the scientific language for optical sciences. It is noted that coherent and squeezed states of light are representations of the Lorentz group. The Lorentz group is also the basic underlying language for classical ray optics, including polarization optics, interferometers, the Poincare sphere, one-lens optics, multi-lens optics, laser cavities, as well multilayer optics

BACKGROUND: It is difficult to assess the orientation of the acetabular component on routine radiographs. We present a method for determining the spatial orientation of the acetabular component after total hip arthroplasty (THA) using computed tomography. PATIENTS AND METHODS: Two CT-scans, 10 min apart, were obtained from each of 10 patients after THA. Using locally developed software, two independent examiners measured the orientation of the acetabular component in relation to the pelvis. The measurements were repeated after one week. To be independent of the patient position during scanning, the method involved two steps. Firstly, a 3D volumetric image of the pelvis was brought into a standard pelvic orientation, then the orientation of the acetabular component was measured. The orientation of the acetabular component was expressed as operative anteversion and inclination relative to an internal pelvic reference coordinate system. To evaluate precision, we compared measurements across pairs of CT volumes between observers and trials. RESULTS: Mean absolute interobserver angle error was 2.3 degrees for anteversion (range 0-6.6 degrees), and 1.1 degrees for inclination (range 0-4.6 degrees). For interobserver measurements, the precision, defined as one standard deviation, was 2.9 degrees for anteversion, and 1.5 degrees for inclination. A Student's t-test showed that the overall differences between the examiners, trials, and cases were not significant. Data were normally distributed and were not dependent on examiner or trial. INTERPRETATION: We conclude that the implant angles of the acetabular component in relation to the pelvis could be detected repeatedly using CT, independently of patient positioning

OBJECTIVE: Our goal was to evaluate the impact of image fusion on the interpretation of indium-111 Prosta-Scint SPECT scans. MATERIALS AND METHODS: Sixty-seven consecutive patients referred for rising prostate-specific antigen (PSA) levels after initial therapy for primary prostate cancer underwent SPECT 96 hr after infusion of (111)In Prosta-Scint, with simultaneous technetium-99m blood pool imaging. Volume data sets from the SPECT scans were then fused with those from CT and MR images of the pelvis using a 3D landmark-based warping program. The SPECT scans were initially interpreted without benefit of MRI or CT fusion. The fused Prosta-Scint MRI-CT volumes were reevaluated by a nuclear radiologist and an MRI radiologist. Independent reviews before and after fusion were available in these patients. Validation of results after fusion was performed through correlation with PSA changes after radiation therapy. RESULTS: Six patients with sites that could not be evaluated and three without their original Prosta-Scint scanning reports were excluded; thus, 58 patients were studied clinically. Seventy-four of 161 prefusion-positive sites were found to be negative after fusion. These 74 sites subsequently were identified primarily as showing bowel, vessel, or marrow uptake after fusion. In two patients, nodal disease was identified although the review before perfusion indicated none. Twenty-five patients previously thought to have nodal disease appeared to have only local disease after fusion. After local radiation therapy, PSA levels decreased in 12 of 25 patients, increased in five, and were unavailable in eight. CONCLUSION: Although Prosta-Scint SPECT alone can help in the proper management of recurrent prostate cancer, fusion with MRI-CT of the pelvis can improve the specificity of the examination

PURPOSE: 3D detection of centerpoints of prosthetic cup and head after total hip arthroplasty (THA) using CT. MATERIAL AND METHODS: Two CT examinations, 10 min apart, were obtained from each of 10 patients after THA. Two independent examiners placed landmarks in images of the prosthetic cup and head. All landmarking was repeated after 1 week. Centerpoints were calculated and compared. RESULTS: Within volumes, all measurements of centerpoints of cup and head fell, with a 95% confidence, within one CT-voxel of any other measurement of the same object. Across two volumes, the mean error of distance between center of cup and prosthetic head was 1.4 mm (SD 0.73). Intra- and interobserver 95% accuracy limit was below 2 mm within and below 3 mm across volumes. No difference between intra- and interobserver measurements occurred. A formula for converting finite sets of point landmarks in the radiolucent tread of the cup to a centerpoint was stable. The percent difference of the landmark distances from a calculated spherical surface was within one CT-voxel. This data was normally distributed and not dependent on observer or trial. CONCLUSION: The true 3D position of the centers of cup and prosthetic head can be detected using CT. Spatial relationship between the components can be analyzed visually and numerically

PURPOSE: To validate a CT method for detecting changes in acetabular cup orientation after THA. MATERIAL AND METHODS: 26 CT examinations were obtained from a pelvic model with an uncemented acetabular cup. The model position was altered between acquisitions, but the cup axis angle vis-a-vis the pelvis was maintained. Data sets were combined into 37 pairs, each containing a unique positioning error. The pelvi in different examinations were fused, creating transformed volumes. Landmarks corresponding to the cup before and after fusion were placed interactively by two independent examiners. The orientation of the acetabular axis was calculated for each volume and compared across volumes. RESULTS: Before fusion the mean angle error between the acetabular axes was 4.17 degrees (SD +/- 1.95 degrees ). After fusion the mean angle error was 0.36 degrees (SD +/- 0.17). The 95% repeatability limits were below 0.7 degrees. There was no significant interobserver difference. Analysis of the cup landmarking pattern by condition numbers and individual landmark errors showed stability. CONCLUSION: Non-invasive fusion of CT volumes and a stable landmarking pattern for the acetabular cup outperforms routine plain radiography in detecting changes in the orientation of the acetabular axis over time. The method delivers both visual and numerical output and could be used in clinical practice

PURPOSE: Subtraction of interictal from ictal single-photon emission computed tomography (SPECT) yields numerous foci that encompass a range of pixel values scattered in the brain. This preliminary study evaluated the significance of this range of values. METHODS: Subtraction images were obtained by registering, normalizing, and subtracting interictal from ictal SPECT for 13 patients. Pixel values of the resulting foci were divided into two groups: group I with 75-100% and group II with 50-75% of the maximal pixel value. Locations of these foci were determined, and concordance with surgical outcomes and scalp and invasive EEG findings was evaluated. RESULTS: In 10 of 13 cases, group I foci showed good concordance with ictal scalp EEG. In addition, group I foci corresponded well to invasive EEG findings in nine of 10 cases. Group I foci had bilateral distributions in seven of 13 cases. In 10 of 13 cases, group I foci corresponded well to regions of surgical resection. Of these 10 patients, nine showed good concordance with scalp EEG, eight showed good invasive EEG concordance, and eight were seizure free after resection. Conversely, group II foci had good concordance with ictal scalp EEG in only five of 13 cases, and invasive EEG findings, in only five of 10 cases. Group II foci had bilateral distributions in 10 of 13 cases. All 10 cases underwent unilateral surgical resections, and all had good surgical outcomes. In six of 13 cases, group II foci showed concordance with surgical sites. Of these six foci, four had poor concordance with scalp EEG, one had poor concordance with invasive EEG, and five had good surgical outcomes. Sensitivity and specificity for seizure localization of Group I foci were 40% and 88% respectively while sensitivity and specificity of Group II foci were 20% and 79% respectively. CONCLUSIONS: Our data demonstrate that foci with 75-100% of maximal pixel values show good concordance with seizure foci, whereas foci of 50-75% may not. Therefore stratifying ictal/interictal differences may improve the specificity and localizing value of subtraction SPECT

OBJECTIVES: This paper evaluates a semi-automatic segmentation procedure to enhance utilizing atlas based treatment plans. For this application, it is crucial to provide a collection of 'reference' organs, restorable from the atlas so that they closely match those of the current patient. To enable assembling representative organs, we developed a semi-automatic procedure using an active contour method. METHOD: The 3D organ volume was identified by defining contours on individual slices. The initial organ contours were matched to patient volume data sets and then superimposed on them. These starting contours were then adjusted and refined to rapidly find the organ outline of the given patient. Performance was evaluated by contouring organs of different size, shape complexity, and proximity to surrounding structures. We used representative organs defined on CT volumes obtained from 12 patients and compared the resulting outlines to those drawn by a radiologist. RESULTS: A strong correlation was found between the area measures of the delineated liver (r=0.992), lung (r=0.996) and spinal cord (r=0.81), obtained by both segmentation techniques. A paired Student's t-test showed no statistical difference between the two techniques regarding the liver and spinal cord (p>0.05). CONCLUSION: This method could be used to form 'standard' organs, which would form part of a whole body atlas (WBA) database for radiation treatment plans as well as to match atlas organs to new patient data