Biomedical subjects

S C Strother

Publications and source records attributed to S C Strother.

41 records · Page 3Linked to original sources

PubMed1987

[13N]cisplatin PET to assess pharmacokinetics of intra-arterial versus intravenous chemotherapy for malignant brain tumors.

The biodistribution, blood clearance, and in vivo transformation of cisplatin (cisdiaminedichloroplatinum, DDP) were studied in rats using 13N-labeled and unlabeled DDP. Following the i.v. injection of [13N]DDP, virtually no 13N activity was detected in brain tissue, and no measurable amount of the 13N label was displaced from [13N]DDP. Based on these results, [13N]DDP/positron emission tomographic (PET) scans were performed in two glioblastoma patients undergoing Phase II intra-arterial (i.a.) DDP chemotherapy: [13N]DDP was infused i.v. over 13-15 min, during which time serial PET scans were obtained. One hour later, [13N]DDP mixed with cold DDP (100 mg/m2 therapeutic dose) was infused at the same rate i.a., and a second sequence of PET scans was acquired. The pharmacologic advantage of i.a. administration was calculated as the ratio of integrated tumor/brain count ratios for the i.a. and i.v. studies. Our preliminary results demonstrate the feasibility of quantifying the pharmacologic advantage of i.a. DDP chemotherapy in individual brain tumor patients using [13N]DDP and PET.

Animals↗

PubMed1984

An improved approach for measurement of regional cerebral rate constants in the deoxyglucose method with positron emission tomography.

A new experimental approach was designed to measure regional rate constants for [18F]2-fluoro-2-D-deoxyglucose in the three-compartment model. A programmed infusion was used to keep the plasma tracer concentration constant for the first 20 min. Positron emission tomography images of the brain were taken every minute for 20 min in a low-resolution mode, then every 15-20 min for 2-3 h in a medium-resolution mode. Two simplified operational equations for the calculation of the regional rate constants were derived that incorporated the contribution of the vascular compartment to tissue activity. The first equation was applied to data collected during the initial 20 min (when the concentration of plasma tracer was constant) to estimate the values of k1*, k2*, k3*, and the fraction of the vascular compartment. The second equation was applied to data collected during the whole experimental period to find the value of k4* and to provide a better estimate of k3*. The regional rate constants measured experimentally in three dogs and a brain tumor patient agreed well with those in the literature. This method permits estimation of the local CMRglu under pathological conditions using regionally measured rate constants and provides new information on the pathophysiological meaning of the rate constants.

Aged↗

PubMedDate not supplied

Graphical analysis of MR feature space for measurement of CSF, gray-matter, and white-matter volumes.

The problem of volume averaging in quantitating CSF, gray-matter, and white-matter fractions in the brain is solved using a three-compartment model and a simple graphical analysis of a multispectral MR feature space. Compartmentalization is achieved without the ambiguities of thresholding techniques or the need to assume that the underlying pixel probability distributions have a particular form. A 2D feature space is formed by double SE (proton density- and T2-weighted) MR data with image nonuniformity removed by a novel technique in which the brain itself serves as a uniformity reference. Compartments other than the basic three were rejected by the tailoring of limits in feature space. Phantom scans substantiate this approach, and the importance of the careful selection and standardization of pure tissue reference signals is demonstrated. Compartmental profiles from standardized subvolumes of three normal brains, based on a 3D (Talairach) coordinate system, demonstrate slice-by-slice detail; longitudinal studies confirm reproducibility. Compartmentalization may be described graphically and algebraically, complementing data displays in feature space and images of compartmentalized brain scans. These studies anticipate the application of our compartmentalization technique to patients with neurological disorders.

Adult↗

PubMedDate not supplied

Quantitative comparisons of image registration techniques based on high-resolution MRI of the brain.

OBJECTIVE: A variety of methods for matching intrasubject MRI-MRI, PET-PET, or MRI-PET image pairs have been proposed. Based on the rigid body transformations needed to align pairs of high-resolution MRI scans and/or simulated PET scans (derived from these MRI scans), we obtained general comparisons of four intrasubject image registration techniques: Talairach coordinates, head and hat, equivalent internal points, and ratio image uniformity. In addition, we obtained a comparison of stereotaxic Z frames with a customized head mold for MRI-MRI image pairs. MATERIALS AND METHODS AND RESULTS: Each technique was quantitatively evaluated using the mean and maximum voxel registration errors for matched voxel pairs within the brain volumes being registered. CONCLUSION: We conclude that fiducial markers such as stereotaxic Z frames that are not rigidly fixed to a patient's skull are inaccurate compared with other registration techniques, Talairach coordinate transformations provide surprisingly good registration, and minimizing the variance of MRI-MRI, PET-PET, or MRI-PET ratio images provides significantly better registration than all other techniques tested. Registration optimization based on measurement of the similarity of spatial distributions of voxel values is superior to techniques that do not use such information.

Algorithms↗

PubMedDate not supplied

Iterative algebraic reconstruction algorithms for emission computed tomography: a unified framework and its application to positron emission tomography.

In this paper, a unified framework of iterative algebraic reconstruction for emission computed tomography (ECT) and its application to positron emission tomography (PET) is presented. The unified framework is based on an algebraic image restoration model and contains conventional iterative algebraic reconstruction algorithms: ART, SIRT, Landweber iteration (LWB), the generalized Landweber iteration (GLWB), the steepest descent method (STP), as well as iterative filtered backprojection (IFBP) reconstruction algorithms: Chang's method, Walters' method, and a modified iterative MAP. The framework provides an effective tool to systematically study conventional iterative algebraic algorithms and IFBP algorithms. Based on this framework, conventional iterative algebraic algorithms and IFBP algorithms are generalized. It is shown from the algebraic point of view that IFBP algorithms are not only excellent methods for correction of attenuation (either uniform or nonuniform) but are also good general iterative reconstruction algorithms (they can be applied to either attenuated or attenuation-free projections and converge very fast). The convergence behavior of iterative algebraic algorithms is discussed and insight is drawn into the fast convergence property of IFBP algorithms. A simulated PET system is used to evaluate IFBP algorithms and LWB in comparison with the maximum likelihood estimation via expectation maximization algorithm (MLE-EM) and the filtered backprojection (FBP) algorithm. The simulation results indicate that for both attenuation-free projection and attenuated projection cases IFBP algorithms have a significant computational advantage over LWB and MLE-EM, and have performance advantages over FBP in terms of contrast recovery and/or noise-to-signal ratios (NSRs) in regions of interest.

Algorithms↗