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D Jette

Publications and source records attributed to D Jette.

At least 19 recordsLinked to original sources
PubMed1998

Electron dose calculation using multiple-scattering theory: a hybrid electron pencil-beam model.

We have embedded the bipartition model into Fermi-Eyges multiple-scattering theory to produce a more accurate hybrid electron pencil-beam model, by using the fact that away from the edges of a large field, the electron distribution function exactly equals that for an infinitely wide electron beam. The bipartition model calculates various electron transport quantities in a homogeneous or horizontally layered medium with very high accuracy, for an infinitely broad beam. In our hybrid model, we use the bipartition model to calculate the longitudinal part of the pencil-beam distribution function, and the Fermi-Eyges theory to calculate its transverse part. Doing this allows calculation not only of dose distribution, but also of such quantities as electron fluence distribution, energy spectrum, angular distribution, and electron-charge distribution. Using the hybrid electron pencil-beam model, we have calculated the dose distribution for collimated electron beams and compared them with experimental data, for rectangular fields.

Biophysical Phenomena↗
PubMed1997

Electron dose calculation using multiple-scattering theory: energy distribution due to multiple scattering.

In 1951, Yang derived formulas for computing the pathlength distribution of particles traversing foils, considering only the multiple-scattering process. We here improve upon the accuracy of that work, by using our second-order small-angle approximation. We derive the general solution for a broad parallel beam, and find simple formulas for Yang's two special cases: the pathlength distribution of all the particles at a particular point, taken together; and the pathlength distribution at a particular point of only those particles with zero net angular deflection. From the pathlength (or excess pathlength) distribution, residual range and energy distributions can immediately be deduced. All this work assumes relatively small energy loss, and we consider 5 MeV electrons penetrating lead, which provides considerable scattering without major energy loss. The second-order energy distribution is found to differ considerably from the (first-order) Yang energy distribution, and to agree more closely with EGS4 Monte Carlo calculations.

Biophysical Phenomena↗
PubMed1996

Electron dose calculation using multiple-scattering theory: a new theory of multiple scattering.

Starting from the Boltzmann-Fokker-Planck transport equation, we have developed a new theory of multiple scattering which incorporates the advances already made with our Gaussian multiple-scattering theory for electron dose calculation. This incorporation has been accomplished in a natural way, by modifying the scattering power T and by adding a convolution term to the distribution-function equation of the Gaussian theory. Our previous results concerning increasing the accuracy of the small-angle approximation used and dealing with localized tissue inhomogeneities have thus been maintained, and we have arrived at a complete distribution function in both transverse spatial and angular variables. When integrated over the transverse angular variables, for a first-order small-angle approximation this distribution function for a pencil beam is essentially the same as the Moliere multiple-scattering distribution, which includes large-angle single scattering. For a water phantom, we have used comparisons with EGS4 Monte Carlo calculations to demonstrate the greatly increased accuracy of our new multiple-scattering theory over the Gaussian theory, which includes the usual Fermi-Eyges theory. We have also presented a fairly accurate Gaussian approximation to the pencil-beam dose profiles given by our new theory, which can be used in order to maintain the mathematical simplicity of the predictions of the Fermi-Eyges theory.

Biophysical Phenomena↗
PubMed1996

Specificity and affinity of 26 monoclonal antibodies against the CA 125 antigen: first report from the ISOBM TD-1 workshop. International Society for Oncodevelopmental Biology and Medicine.

The specificity of 26 monoclonal antibodies against the CA 125 antigen was investigated in two phases of the ISOBM TD-1 workshop. The binding specificity was studied using CA 125 immunoextracted by specific antibodies immobilized on various solid phases, or on the surface of human cell lines. Immunometric assays using all possible antibody combinations were used to study the topography of antibody binding sites on the antigen. We conclude that the CA 125 antigen carries only two major antigenic domains, which classifies the antibodies as OC125-like (group A) or M11-like (group B). One antibody, OV 197, showed binding specificity related to some of the OC125-like antibodies, but was classified into a separate group C. The OC125-like group of antibodies has four subgroups with different binding specificities. These are A1 = OC 125 and K 95, A2 = K 93, A3 = B43.13, and A4 = ZS 33, B27.1 and CCD 247. Binding of nonlabelled OC 125 or K 95 to CA 125 caused a marked increase in binding of labelled OV 197 to the complex. This conformational change was not observed with any other antibody combinations. Antibody B43.13 could form immunometric assay combinations particularly with antibodies of subgroup A4, indicating that the B43.13 epitope is in the periphery of the binding area of OC125-like antibodies. The M11-like group of antibodies is more homogenous with strong cross-inhibition between most antibodies. Only one antibody, ZR 38, would form an immunoassay combination with other M11-like antibodies and thus represents a distinct subgroup. The main group of M11-like antibodies are M 11, ZR 45, MA602-6, K 91, OV 185, K 101, K 90, K 96, K 97, K 102, CCD 242, 145-9, and 130-22. Antibody OV 197 binds to a domain designated C and is unique, as stated above. Antibody pairs from any two of the three groups may be used in immunometric assays. Three antibodies were not studied by complete cross-inhibition due to low affinity (OV 198 and K 100) or lack of material (MA602-1). OV 198 and K 100 are most likely OC125-like and MA602-1 is M11-like. Antibody affinity was estimated with labelled antigen in solution or with antigen absorbed on microtiter wells. Western blot analysis showed staining both in the stacking gel and corresponding to a molecule of 200 kDa. There was a marked difference between the antibodies in their ability to bind to CA 125 immobilized on a membrane. Strongest binding was observed with the M11-like antibodies, particularly M 11, K 96, K 97, MA602-6, 145-9. Antibodies belonging to the subgroup A4 were the only OC 125-like antibodies which reacted well with CA 125 in Western analysis. Digestion of CA 125 with proteolytic enzymes showed it to be particularly sensitive to trypsin cleavage. However, no low molecular weight fragments with preserved immunoreactivity were found.

Animals↗
PubMed1996

Immunohistochemical characterization of 22 monoclonal antibodies against the CA125 antigen: 2nd report from the ISOBM TD-1 Workshop.

We evaluated the immunohistological (IH) characteristics of 22 different antibodies that were submitted for study in the frame of the TD-1 ISOBM Workshop on monoclonal antibodies against CA125. Information on relative affinities and epitope similarities was obtained from a parallel immunochemical study. Antibodies were tested at concentrations of 10 and 1 micrograms/ml on frozen and paraffin sections. Paraffin sections were stained according to the streptavidin-biotin complex protocol, and frozen sections according to a two-step immunoperoxidase technique. Aminoethylcarbazole served as the chromogen. The tissues were from normal proliferative endometrium (formalin-fixed paraffin-embedded) material and clear-cell adenocarcinoma of the ovary (formalin-fixed paraffin-embedded and frozen material). Sections were scored for staining in epithelial cells, basal, apical and diffuse cytoplasmic and in stromal components. Intensity was graded as 1, 2 or 3 for epithelial cells and as -1, -2 or -3 for stroma. The cumulative scores for each antibody expressed the discriminative properties of specific epithelial staining against background. M11 and M11-like antibodies, as well as OC125 and OC125-like antibodies, in general showed good staining results. Although there was a trend for high-affinity antibodies to show higher scores, there was no clear relationship between affinity and staining result. For nine antibodies (ZR45, MA602-1, K102, K94, K90, OV185, K97, K96, OV198), the reactions in paraffin and frozen sections were of similar intensity. Most of these were of low affinity with one exception: antibody ZR45, a rat monoclonal antibody (MAb) which had a high relative affinity. For eight antibodies (M11, K101, MA602-6, ZS33, B27.1, B43.13, K93, OC125), a loss of specific staining was observed in frozen sections. All but two of these antibodies (MA602-6 and OC125) were of high relative affinity. With four antibodies (K91, ZR38, K95, K100), the reverse situation was observed. One (K100) was of low affinity, two (K95 and K91) of high affinity and the fourth (ZR38) was a rat MAb of high affinity. Mainly due to the increased cytoplasmic staining in carcinoma, the reactivity in paraffin sections was less extensive in normal endometrium compared to ovarian carcinoma for the majority of antibodies, irrespective of their affinity or epitope group. The IH characterization of these antibodies may be of help in selecting antibodies with specific properties for further comparative studies. The reactivity of normal endometrium with all useful antibodies makes it a good candidate for standard external IH tissue control.

Adenocarcinoma, Clear Cell↗
PubMed1984

Quality assurance of radiation dosage: usefulness of redundancy.

Regulations for maintaining the calibration of radiation-measuring instruments generally require that they be recalibrated periodically, and some also specify periodic spot-checks. There is a finite probability that changes in the instrument sensitivity will occur between these calibrations or periodic checks. Routine spot-checks of the output of a therapy unit, made with a given instrument, should detect changes in either device. Comparisons of reliability obtained by these and other procedures for checking on instrument sensitivity are made using calculations based on estimates of the mean time between failures for sources and instruments. These comparisons demonstrate that significantly greater reliability and efficiency should result from considering each machine spot-check and recalibration as a check on the stability of both the machine and the instrument, as opposed to placing complete dependence upon the instrument during the period between separate checks of its sensitivity.

Probability↗
PubMed1979

Colloidal particle-size determination by gel filtration.

The particle sizes of technetium-99m sulfur colloid and technetium-99m antimony sulfide colloid are determined by gel filtration. These results are compared with those obtained by electron microscopy and by ultrafiltration. It is shown that gel filtration is suitable for particle-size determination below 100 nm, whereas above this size ultrafiltration provides the most convenient method.

Chromatography, Gel↗
PubMedDate not supplied

Changes in exercise capacity following cardiac rehabilitation in patients stratified according to age and gender. Results of the Massachusetts Association of Cardiovascular and Pulmonary Rehabilitation Multicenter Database.

BACKGROUND: Using information collected prospectively from a multicenter cardiac rehabilitation database, this study was designed to evaluate baseline exercise tolerance and subsequent change in functional capacity among consecutive patients enrolled in supervised cardiac rehabilitation stratified according to age and gender. In addition, the study evaluated change in functional capacity among those with the lowest initial exercise tolerance (<5 METS) and assessed patient factors that correlate to the highest relative improvements in functional capacity after training. METHODS: A total of 778 patients performed an initial exercise test upon entry into cardiac rehabilitation, during which peak heart rate, blood pressure, and estimated peak MET levels were derived, and ischemic responses were evaluated. After 10 +/- 2 weeks of supervised prescribed exercise, 500 patients who completed the program performed follow-up exercise testing. RESULTS: The subjects included 558 men (72%) and 220 women (28%) of whom 492 (63%) were <65 years, 241 (31%) were 65 to 75 years, and 45 (6%) were >75 years. At baseline, the peak initial MET level for men was 8.6 +/- 3.4 METS and for women was 6.0 +/- 2.6 METs. The peak initial MET level declined with age: age <65 = 8.9 +/- 3.4 METS; age 65 to 75 = 6.6 +/- 2.6 METS; and age >75 = 5.7 +/- 2.9 METS. When stratified according to age and gender, the baseline exercise tolerance for men significantly (P <.0001) declined with age and was higher than that of women <65 and 65 to 75 years of age. After training, the relative improvement in exercise tolerance for each age and/or gender subgroup was: age <65: men 36%, women 41%; age 65 to 75: men 36%, women 50%; and age >75: men 36%, women 32%. Among 163 patients with an initial peak MET level <5, exercise tolerance rose from 4.1 +/- 0.7 to 8.3 +/- 3.5 METS (P <.0001). Multivariate analysis demonstrated that the greatest change in exercise tolerance with training was associated with those compliant patients with initial peak METS <5. No significant net change in the occurrence of exercise-induced ischemia was observed. CONCLUSIONS: Among consecutive patients enrolled in cardiac rehabilitation, baseline exercise tolerance differs relative to age and gender, with male gender and younger age demonstrating the highest functional capacity. Exercise training yielded significant improvements in exercise tolerance among men and women of every age group including those older than 75 years, and particularly among those with an initial peak MET level <5. Thus, referral to cardiac rehabilitation programs should be advocated for both men and women, and should not be limited by age.

Adult↗
PubMedDate not supplied

Analytic representation of electron central-axis depth dose data.

We have examined a number of analytic representations of electron central-axis depth dose data current in the literature, testing them against sets of standard depth dose data. One of them, a two-parameter model of Shabason and Hendee, is recommended in situations in which good accuracy (approximately 2%) is desired, with the values of the parameters determined by an approximation formula which we have developed elsewhere. For higher accuracy, we have developed a polynomial model which gives, typically, a standard deviation of the fitting polynomial from the data points of 1%, and a maximum deviation of 2%. Fitting polynomials obtained with this method possess the property of having zero slope at the position of actual maximum dose, and generally a fifth-order polynomial (requiring four nonzero coefficients) provided the most acceptable fit. The four parameters involved are determined through inversion of a 4 x 4 matrix, and we have tabulated these four coefficients for the standard data sets. The polynomial model is designed for interpolation in the range between the 100% dose depth and the 10% dose depth, and another fitting curve of the same type can be adjoined to cover depths less than the 100% dose depth.

Computers↗
PubMedDate not supplied

Product representations of teletherapy dose distributions.

Product representations are frequently used for teletherapy dose distributions. For example, the dose in a central plane is often written as the product of two factors, one dependent on the depth and the other on the transverse variable. We have answered the following question: given a (two-dimensional) set of data, how closely is it possible to represent these data by a product of two such factors, and what factors would give a best-fit representation? We thus have developed a quantitative test with which to judge any proposed product representation, for a given set of data. As an example, we have applied our method in analyzing the accuracy of a model proposed by van de Geijn for representing central-plane Cobalt-60 dose data through a product representation on decrement lines intersecting the source.

Humans↗
PubMedDate not supplied

Second-order multiple-scattering theory for charged-particle teletherapy beams.

The Fermi-Eyges theory of multiple scattering, applicable to charged-particle teletherapy beams, has been generalized to second order in small quantities representing deviations from the particles' initial lines of travel and direction. The second-order multiple-scattering theory provides increased accuracy, and in particular it takes into account the skewness of the particles' paths, in calculating dose. Only the assumptions and certain results of the second-order theory are presented in this communication, for the immediate use of other investigators. An application to rectangular fields shows that the second-order theory predicts one component of the buildup of electron central axis depth dose, which the (first-order) Fermi-Eyges theory cannot do. (The other major component of buildup, which is not yet incorporated into this theoretical work, is due to high-energy secondary electrons). Various approximate calculations of electron central axis depth dose are compared with the second-order calculation.

Humans↗
PubMedDate not supplied

Collimated electron beams and their associated penumbra widths.

The Fermi-Eyges multiple-scattering theory for electrons is applied to calculate profiles of collimated electron beams. The dose profile below the collimator is a convolution of the intensity distribution of the electrons at the level of the collimator and the distribution arising from the propagation of a Gaussian point source from the collimator to the level of the calculation. The electrons at the level of the collimator possess an angular distribution characteristic of the configuration of the electron beam at the vacuum window. Hence, the dose profile and its associated penumbra width can be expressed in terms of the angular moments of the distribution of the electrons at the collimator. The dependence of the penumbra width on the configuration-dependent angular spread of the electrons at the collimator accounts for differences in the size of the penumbra between two broad-beam configurations. These differences are also seen experimentally. We have also studied the dependence of the angular moments of the electrons upon scattering foils present above the collimator and the position of the beam-broadening device in the accelerator head.

Electrons↗
PubMedDate not supplied

Electron dose calculation using multiple-scattering theory. A. Gaussian multiple-scattering theory.

This article is the first in a series on the calculation of electron dose using multiple-scattering theory. In it we develop a unified theory, which we term Gaussian multiple-scattering theory, starting from a number of contributions already in the literature: the Fermi-Eyges multiple-scattering theory, the Yang path length distribution, the second-order multiple-scattering theory of Jette [Med. Phys. 12, 178 (1985)], and the diffusion theory of Bethe et al. [Proc. Am. Philos. Soc. 78, 573 (1938)]. After examining in detail the ramifications and limitations of Gaussian multiple-scattering theory, we derive basic formulas generalizing the Fermi-Eyges theory, for use in subsequent articles. We also find explicit, accurate expressions for incorporating the scattering power into the theory.

Fourier Analysis↗
PubMedDate not supplied

Electron dose calculation using multiple-scattering theory: second-order multiple-scattering theory.

This article is part of a series on the calculation of electron dose using multiple-scattering theory. It presents systematically the second-order multiple-scattering theory which is a generalization of the (first-order) Fermi-Eyges theory, outlining its derivation and giving explicit formulas for its defining functions. The predictions of the Fermi-Eyges theory and of the second-order theory are compared with modified Monte Carlo calculations, demonstrating the increased accuracy of the latter multiple-scattering theory. We derive and compare broad-beam angular distributions for the two theories, and note the effect of large-angle scattering upon dose profiles. Finally, we present the second-order theory in Fourier-transformed space, which is appropriate to a high-speed dose-calculation algorithm using the fast Fourier transform (FFT) technique.

Algorithms↗