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PubMed1999

Parallel conductance determination in cardiac volumetry using dilution manoeuvres: theoretical analysis and practical implications.

Left ventricular volume calibration based on the conductance catheter depends on the correct determination of the parallel conductance (Gp). Baan's saline manoeuvre procedure leads to Gp by finding the end-systolic (Ges) and end-diastolic (Ged) conductances, for each beat of the dilution curve rising limb. After plotting such values in an xy-system, their linear regression is back-projected to intersect the identity line, so yielding an estimated Gp. The objective is to theoretically analyse all possible lines, Ges = aGed + b (Baan's line) and, based on experimental results, to establish their limitations. This was attained by calculating the regression lines using, first Ged = f1(Ges) and thereafter, Ges = f2(Ged), which led to two values, Gp2 and Gp1, for the parallel conductance. The morphology of the saline curve was also modified to assess its effect on the extrapolation. Multiple dilutions were recorded in eight experimental dogs injecting different concentrations. Each curve was classified according to the maximum change (VAR) reached by the total average conductance. Over 138 manoeuvres, 276 regressions were processed yielding correlations higher than 0.65. Of this total, 92.4% gave positive parallel conductances. The rest produced negative values and, thus, were neglected. If the two (Ged, Ges) statistical relationships were ideal, they should yield Gp = Gp1 = Gp2; however, there were differences which, when Gp1 was studied against Gp2, led to: Gp1 = 0.97 Gp2 + 0.055, with r = 0.9476, and n = 85. The remaining 53 were discarded because either some Gp values were negative, or the correlation of Ges which Ged (or vice versa) was < 0.85, and/or VAR < 15%; the two latter conditions were found necessary for reliable calibration. Baan's line high correlation is not a unique condition to ensure the accuracy and precision of Gp determination because the slope a depends on VAR and, thus, different intersections with the identity line may be obtained. Its recommended that manoeuvres be used with at least eight data points, with VAR > 15% and, finally, with (Ges, Ged) correlation better than 0.85. Theoretical analysis of Baan's line offers a reference frame, which contains only a limited number of practical possibilities.

Animals↗

PubMed2000

Volume measurement of cerebral arteriovenous malformations from angiography.

We designed software for measuring the volume of cerebral arteriovenous malformations from angiography and validated it against prescription volumes in radiosurgery. We aimed to create a model for the risk for complications as a function of volume, based on established outcome prediction models for Gamma Knife radiosurgery, but without the need for dose planning. We created an application for computing the volume of cerebral arteriovenous malformations from the intersection of two X-ray cones in stereotactic space. Volume measurements were compared with prescription volumes from dose planning, in phantoms and in patients treated with Gamma Knife radiosurgery for cerebral arteriovenous malformations. Previous studies of 1128 treated patients were used to calculate the risk for complication as a function of the nidus volume. In 63 patients volumes measured with either method correlated, R2 = 0.85. Volume as measured with the intersecting cone model (ICM) correlated with predicted Gamma Knife radiosurgery complication rate, R2 = 0.84. The ICM can thus be used for measurement of AVM volumes less than 10 cm3 from angiography. Outcome models from Gamma Knife radiosurgery may be applied, but with reduced exactness. Standardised AVM volume measurement is valuable for comparing outcome and for quantification of volume reduction after therapy, notably embolisation. Thus the optimal management plan may be selected in conjunction with diagnostic or therapeutic angiography.

Cerebral Angiography↗

PubMed2006

Facet joint violation during pedicle screw insertion: a cadaveric study of the adult lumbosacral spine comparing the two pedicle screw insertion techniques.

This article analyses the incidence of facet joint violation by pedicle screws inserted via the two most commonly used techniques, intersection and mammillary. Pedicle screws were inserted on each side of fresh-frozen human cadevaric specimen lumbosacral spines using the two techniques. All facet joints which were violated were found to be on the right side, where the mamillary process technique was employed. The incidence of facet joint violation was higher in the mammillary technique, which was statistically significant. The intersection technique appears to be safer than the mamillary with respect to violation of the adjacent superior facet joint.

Adult↗

PubMed2003

The inferior hypogastric plexus (pelvic plexus): its importance in neural preservation techniques.

The progress in the surgery of male neurological cancers relies on the anatomico-surgical approach to the pelvic neural structures. The objective of our study was to provide a better understanding of the inferior hypogastric plexus (IHP) and its anatomical relationships in order to spare it during radical prostatectomy. Fifteen male formalin-preserved cadavers which had no sub-umbilical scar were used. In five subjects, the superior hypogastric plexus (SHP) and the pre-sacral plexus were displayed then the IHP and its sacral afferents (pelvic splanchnic nerves or erector nerves of Eckhardt) were dissected out. Serial sections of the IHP were then studied in ten subjects. This allowed its identification on certain imaging sections obtained in pelvic tumor pathology and these made up the "reference cuts". The IHP lies within a fibro-fatty plate which is flat, rectangular, sub-peritoneal, sagittal and symmetrical. It arises at the level of the intersection between the vas deferens and the terminal pelvic ureter and follows the postero-lateral aspect and circumvolutions of the seminal vesicle, with which there is a plane of surgical cleavage. The seminal vesicle is, therefore, an essential landmark for this neural structure. The plane of this cleavage may be used in pelvic cancer surgery. The safest technical means of respecting sexual function and the integrity of the IHP is to keep it at a distance. The preservation of a lateral layer of the seminal vesicle is probably a method of limiting these complications as long as this does not conflict with the oncological clearance. An irregular communicating branch was found in one of five cases between the IHP, the sacral plexus and the pudendal nerve. This communicating branch lay immediately behind the intersection between the vas deferens and the ureter in the sacral concavity. It overhangs the IHP in the seminal vesicle. Impotence remains a frequent complication after radical prostatectomy. The methods of neural preservation at the prostatic apex are known but neural preservation should also be carried out posteriorly at the lateral pole of the seminal vesicle. The possibility of posterior neural preservation may be assessed pre-operatively by study of the "reference sections". The cleavage plane between the seminal vesicle and the IHP may be used intra-operatively to spare the IHP. The cavernous nerve in particular emerges at the antero-inferior border of the IHP before running along the postero-lateral aspect of the prostate. It therefore passes in contact with the seminal vesicle and may as a result be injured during radical prostatectomy with vesiculectomy. A proximal communicating branch between the IHP and the pudendal nerve is irregular. Such communicating branches may explain a better recovery of sexual function in curative neurological cancer surgery. The essential relationship of the IHP is with the seminal vesicle. The two are in tight contact and the seminal vesicle has a true plane of surgical cleavage with IHP. The risk of injuries to the posterior erectile mechanisms can be reduced either by using the cleavage plane between the IHP and seminal vesicle or by leaving a layer of the seminal vesicle when the oncological conditions allow. During celio-surgery, the operator must be careful to retract the little bands of the seminal vesicle and divide the fibrous and vascular tracts which tighten during this maneuver. During an abdominal approach, dissection of the seminal vesicle takes place at the bottom of a real pit. The operator must carry out the division leaving a layer of the seminal vesicle in place rather than trying to extract all the seminal vesicle by placing the forceps blindly. This maneuver is naturally dependent on the oncological situation. The anatomical confirmation of a regular or irregular proximal or distal communicating branch between the IHP and the pudendal nerve is probably an explanation for the sometimes uncertain results of new techniques of neural preservation in curative cancer surgery.

Aged↗

PubMed2006

Morphometric side-to-side differences in human cruciate ligament insertions.

Graft placement in cruciate ligament reconstruction is known to significantly influence postoperative knee stability and range of motion. Improvement of bone tunnel positioning has been advocated by computer-assisted surgical procedures that require reliable input and reference data. This study validates the hypothesis that morphometric reference data can be obtained from the uninjured controlateral knee for accurate bone tunnel and graft positioning. Thirty pairs of human cadaver knees were dissected and the femoral and tibial footprints of the anterior and posterior cruciate ligaments (PCL) were radiopaquely marked. Radiographs were taken of the corresponding left- and right-sided femora and tibiae, and digitally processed. Controlateral specimens were mirrored and overlapped precisely, the areas and intersections of ligament insertion were digitally determined. There were no significant differences in the total area of cruciate ligament insertion between left and right knee specimens or between female and male specimens. Intersection areas (IAs) in femoral and tibial anterior cruciate ligament (ACL) insertions averaged 31.3 and 33.4% of the total insertion area, respectively. The center of gravity for the femoral and tibial ACL footprint differed by 4.7 and 4.5 mm between left and right knees, respectively. IAs in femoral and tibial PCL insertions averaged 46.1 and 61.3% of the total insertion area, respectively. The center of gravity for the femoral and tibial PCL footprint differed by 4.5 and 2.4 mm between left and right knees, respectively. Our study does not support the concept of obtaining morphologic reference data from the uninjured controlateral knee for individual bone tunnel placement.

Aged↗

PubMed2000

Microrelief of the skin using a light transmission method.

The recently developed Skin Visiometer, based on light transmission through blue-coloured silicone replicas, was used to study skin microrelief. Calibrated metal plates displaying lines with depths between 6 and 361 microns, were used to determine the accuracy, sensitivity and reproducibility of the technique as well as the parameters of importance during measurement. The precision of the measurements was particularly good between 10 microns and 361 microns. The sensitivity of the method was between 10 and 20 microns. Replicas of volar forearm skin were taken from four groups (n = 15) of male and female volunteers in the age ranges 20 to 30 years and 55 to 65 years. In addition to the instrumental roughness parameters (Rz, Rt, Rm and Ra), the surface of the furrows, the number of primary and secondary lines and the number of intersections were determined. For both sexes, significantly lower values were observed for Rz, Rm and Rt in the younger age group than in the older age group. In addition, the numbers of primary and secondary lines and the number of intersections were higher, pointing to a more structured microrelief in younger forearm skin. Diurnal rhythm, the relative humidity of the measuring room and the position of the forearm were found to be significant factors, while room temperature and precleansing of the skin with mild products were not. Following the application of a hydrating cream (twice daily for 14 days) to the forearm skin of the older female age group, the Rz, Rt, Rm and Ra decreased, while the other parameters measured, except for the surface taken in by the lines, increased, indicating that the microrelief was modified towards the typical pattern observed in young skin.

Adult↗

PubMed2000

A mean-field model for orientation tuning, contrast saturation, and contextual effects in the primary visual cortex.

Orientation-selective cells in the primary visual cortex of monkeys and cats are often characterized by an orientation-tuning width that is invariant under stimulus contrast. At the same time their contrast response function saturates or even super-saturates for high values of contrast. When two bar stimuli are presented within their classical receptive field, the neuronal response decreases with the intersection angle. When two stimuli are presented inside and outside the classical receptive field, the response of the cell increases with the intersection angle. Both cats and monkeys show iso-orientation suppression, which has sometimes been reported to be combined with cross-orientation facilitation. This property has previously been described as sensitivity to orientation contrast. We address the emergence of these effects with a model that describes the processing of geniculocortical signals through cortical circuitry. We hypothesize that short intracortical fibers mediate the classical receptive field effects, whereas long-range collaterals evoke contextual effects such as sensitivity to orientation contrast. We model this situation by setting up a mean-field description of two neighboring cortical hypercolumns, which can process a nonoverlapping center and a (nonclassical) surround stimulus. Both hypercolumns interact via idealized long-range connections. For an isolated model hypercolumn, we find that either contrast saturation or contrast-invariant orientation tuning emerges, depending on the strength of the lateral excitation. There is no parameter regime, however, where both phenomena emerge simultaneously. In the regime where contrast saturation is found, the model also correctly reproduces suppression due to a second, cross-oriented grid within the classical receptive field. If two model hypercolumns are mutually coupled by long-range connections that are iso-orientation specific, nonclassical surround stimuli show either suppression or facilitation for all surround orientations. Sensitivity to orientation contrast is not observed. This property requires excitatory-to-excitatory long-range couplings that are less orientation specific than those targeting inhibitory neurons.

Animals↗

PubMed1997

Bacillus subtilis 168 RecR protein-DNA complexes visualized as looped structures.

The Bacillus subtilis 168 RecR protein bound to duplex DNA in the presence of ATP and divalent cations (Mg2+ and Zn2+) was visualized by electron microscopy as a nearly spherical particle. A RecR homomultimer is frequently located at the intersection of two duplex DNA strands in an interwound DNA molecule, generating DNA loops of variable length. Two individual DNA molecules bound to the same protein are seen at a very low frequency, if at all. The association of RecR with the intersection of two duplex DNA strands is more often seen in supercoiled than with relaxed or linear DNA. The RecR protein displays a slight but significant preference for negatively supercoiled over linear DNA. The minimum substrate size for RecR protein is about 150 bp in length. A possible mechanism for RecR function in DNA repair is discussed.

Bacillus subtilis↗

PubMed2026

Identification and expression validation of key genes of Xiaozhengtongluo formula in the treatment of diabetic nephropathy by Mendelian randomization.

Xiaozhengtongluo formula (XZTL) has a positive effect on the treatment of diabetic nephropathy (DN), but its mechanism is not fully understood. Therefore, it is important to explore the key genes of XZTL in the treatment of DN. Differentially expressed genes (DEGs) between DN and control obtained from GSE96804, drug target genes of XZTL, and disease target genes of DN obtained from public databases were intersected. Genes of intersection were defined as candidate genes. Next, Mendelian randomization (MR) analysis was used to ascertain the causal associations between candidate genes and DN. Afterwards, key genes were confirmed through receiver operating characteristic (ROC) curve analysis and expression validation. Subsequently, enrichment analysis, molecular regulatory network analysis, and molecular docking were conducted. Finally, experimental verification of the expression levels of key genes was performed through reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Altogether, 29 candidate genes were screened via MR analysis, identifying APOD, IGFBP3, and LPL as significantly associated with DN. IGFBP3 and APOD were risk factors, whereas LPL was protective. Consistent expression trends across training and validation datasets defined them as key genes. All three were co-enriched in 26 pathways, including oxidative phosphorylation. Regulatory networks showed MIR497HG/hsa-miR-19a-3p regulated IGFBP3, and NEAT1/hsa-miR-29a-3p regulated LPL; IGFBP3 and LPL were co-targeted by SP3 and SP1. Molecular docking revealed APOD-baicalein, LPL-oleic acid, and IGFBP3-quercetin binding, suggesting therapeutic potential. RT-qPCR confirmed aberrant expression of these genes in DN, which was normalized by XZTL intervention. In this study, three key genes (APOD, IGFBP3, and LPL) of XZTL in the treatment of DN were finally obtained, providing mechanistic clues for understanding XZTL's multi-target mechanism and providing experimentally tractable candidate targets for DN molecular subtyping, targeted therapeutic development, and precision medicine approaches in TCM.

Diabetic Nephropathies↗

PubMed2026

Integrative multi-omics analyses suggest a candidate microbial metabolite-associated host gene network in ulcerative colitis.

Ulcerative colitis (UC) is associated with gut microbial dysbiosis, but the host molecular alterations potentially linked to microbially derived metabolites remain incompletely understood. We integrated Mendelian randomization (MR), microbial metabolite annotation, computational target prediction, colonic transcriptomics, network analysis, and machine learning. MiBioGen microbiome GWAS data were used as exposures and FinnGen Release 12 ULCERENTER as the outcome. Metabolites linked to MR-prioritized taxa were retrieved from GutMGene, and human targets were predicted using SwissTargetPrediction and SEA. UC-related genes were defined by integrating differential expression analysis and WGCNA and then intersected with predicted metabolite targets. MR prioritized one family and eight genera showing nominal genetically supported associations with UC, but none remained significant after Benjamini-Hochberg FDR correction. Three prioritized genera were linked to 15 microbe-metabolite records, corresponding to 13 unique metabolites; nine were retained for target prediction, yielding 277 unique predicted human targets. Transcriptomic analysis identified 1,530 DEGs and a 312-gene MEgrey60 module, with 273 overlapping genes, producing 1,569 unique UC-related genes. Their intersection with the 277 predicted targets yielded 47 candidate genes. Enrichment analyses highlighted mainly metabolic and lipid-related processes. Random Forest showed the highest mean AUC across the two independent external benchmarking cohorts, and SHAP prioritized EPHX1, HSD17B2, IGFBP5, and MMP10. IBDome analysis showed inflammation-associated expression differences in these genes. This study provides a genomics-informed, hypothesis-generating framework that prioritizes candidate microbe-metabolite-host relationships in UC for future experimental validation.

Humans↗

PubMed1989

Cross-cultural differences in driver risk-taking.

This study investigated differences in simulated driver risk-taking behavior among U.S., Spanish, and West German subjects. The task consisted of performing a simulated intersection crossing on a video display. Subjects were shown an intersection with moving traffic on a horizontal road, and they were asked to attempt (under time pressure) a fixed number of crossings with a car moving vertically. The subjects in all three countries included younger, middle-aged, and older persons of both sexes. The following are the main findings: (1) The performance of West German subjects tended to differ from those of U.S. and Spanish subjects. Specifically, West German subjects attempted fewer crossings, had a higher probability of success, and had greater safety margins. (2) Target risk-level of performance, measured by probability of successful crossings, was not affected by age or sex. (3) Probability of attempted crossings was greater for males and younger subjects than for females and older subjects. (4) Similarly, safety margins during attempted crossings were smaller for males and younger subjects than for females and older subjects. These results suggest that there are differences among countries in the target risk-level of performance. However, the present findings imply that within each country all subjects (regardless of age and sex) tended to have the same target risk-level. To attain this risk-level of performance, males and younger subjects (because of their presumed superior psychomotor skills and/or greater experience with video tasks) attempted to cross more gaps (and, consequently, smaller gaps), with resulting smaller safety margins.

Adult↗

PubMed1993

Elderly in the traffic environment: analysis of fatal crashes in northern Sweden.

Fatal crashes of the elderly (> or = 60 years; N = 379) in northern Sweden in the traffic environment, between 1977 and 1986, were investigated using autopsy and police reports. Males had double the death rate of females. The car occupants made up the largest category (43%) followed by pedestrians, pedalcyclists, and two-wheel-motorvehicle (TWMV) riders, but the risk of fatal injury per unit distance travelled was highest for pedestrians and pedalcyclists. Most car occupants were killed in vehicle-vehicle crashes, mostly in the daylight and at intersections or straight roads. Ice and/or snow (31%) was the major precrash factor. In two-thirds of single car crashes, roadside hazards such as trees were involved. Most elderly fatally injured car drivers were responsible for the crash, and they were commonly involved in collisions with oncoming vehicles. Only 4% of the fatally injured car drivers were driving under the influence of alcohol. Head injuries appeared to be more common in side impact than in frontal impacts. Serious chest injuries were more common than head injuries in car crashes. One-quarter of the pedestrians were injured at pedestrian crossings and about half during darkness. One in six pedestrians were under the influence of alcohol. All pedalcyclists were injured in collisions with motor vehicles and most were injured at intersections. Pedestrians, pedalcyclists, and TWMV riders had more serious head injuries than chest injuries.

Abbreviated Injury Scale↗

PubMed1991

Determination of pulse wave velocities with computerized algorithms.

Careful determination of pulse wave velocity is important in the study of arterial viscoelastic properties, wave reflections, and ventricular-arterial interactions. In spite of its increasingly widespread use, there is as yet no standardized method for its determination. Most studies have manually identified the transit time of the pressure wave front as it travels over a known distance in the arterial system, but the issues of accuracy and reproducibility have not been addressed. This study was designed to investigate the efficacy of four computerized algorithms in the determination of pulse wave velocities in invasive as well as in noninvasive pressure determinations. The four methods were the identification of: (1) the point of minimum diastolic pressure, (2) the point at which the first derivative of pressure is maximum, (3) the point at which the second derivative of pressure is maximum, and (4) the point yielded by the intersection of a line tangent to the initial systolic upstroke of the pressure tracing and a horizontal line through the minimum point. High-fidelity aortic pressure recordings were obtained in 26 patients with a multi-sensor micromanometer catheter. Noninvasive brachial and radial pressure waveforms were recorded in 11 volunteers with external piezoelectric transducers. The results show that the first derivative method consistently provided results that were different from the other methods for both the invasive and noninvasive methods because of changes in the structure of the upstroke as the arterial pulse propagates distally. Although the minimum method worked well for the invasive determinations, it was erratic with the noninvasive determinations, probably because of the higher amount of noise and reflection in the latter. Among the four algorithms, the second derivative and the intersecting tangents methods worked well with both invasive and noninvasive determinations with mean variation coefficients of less than 7% and correlation coefficients between the methods of greater than 0.90 for all data. In conclusion, computerized algorithms allow accurate determination of pulse wave velocity in invasively and noninvasively measured arterial pressure waveforms.

Adult↗

PubMed1981

Relationships between changes in skeletal and integumental points A and B following orthodontic treatment.

The purpose of this study was to explore the changes in points A' and B' which occur in the soft-tissue profile of the face and their interrelationship to concomitant changes in the underlying hard tissue after orthodontic treatment. Pre- and posttreatment lateral cephalometric radiographs of forth Class II. Division 1 patients were studied to determine the relationships between the distal movements of osseous points A and B and the corresponding overlying labial soft tissues. Perpendicular lines were drawn to sella, point A, superior labial sulcus (point A'), point B, and the inferior labial sulcus (point B') from the Frankfort horizontal plane. Linear measurements were taken from the above-mentioned four intersects to the sella intersect. Pretreatment and posttreatment measurements were analyzed statistically and it was found that the average ratios between hard- and soft-tissue changes were point A to point A', 1.40 to 1.00, and point B to point B', 1.09 to 1.00.

Adolescent↗

PubMed1985

Characterization of the solubilization of lipid bilayers by surfactants.

This communication addresses the state of aggregation of lipid-detergent mixed dispersions. Analysis of recently published data suggest that for any given detergent-lipid mixture the most important factor in determining the type of aggregates (mixed vesicles or mixed micelles) and the size of the aggregate is the detergent to lipid molar ratio in these aggregates, herein denoted the effective ratio, Re. For mixed bilayers this effective ratio has been previously shown to be a function of the lipid and detergent concentrations and of an equilibrium partition coefficient, K, which describes the distribution of the detergent between the bilayers and the aqueous phase. We show that, similar to mixed bilayers, the size of mixed micelles is also a function of the effective ratio, but for these dispersions the distribution of detergent between the mixed micelles and the aqueous medium obeys a much higher partition coefficient. In practical terms, the detergent concentration in the mixed micelles is equal to the difference between the total detergent concentration and the critical micelle concentration (cmc). Thus, the effective ratio is equal to this difference divided by the lipid concentration. Transformation of mixed bilayers to mixed micelles, commonly denoted solubilization, occurs when the surfactant to lipid effective ratio reaches a critical value. Experimental evaluation of this critical ratio can be based on the linear dependence of detergent concentration, required for solubilization, on the lipid concentration. According to the 'equilibrium partition model', the dependence of the 'solubilizing detergent concentration' on the lipid concentration intersects with the lipid axis at -1/K, while the slope of this dependence is the critical effective ratio. On the other hand, assuming that when solubilization occurs the detergent concentration in the aqueous phase is approximately equal to the critical micelle concentration, implies that the above dependence intersects with the detergent axis at the critical micelle concentration, while its slope, again, is equal to the critical effective ratio. Analysis of existing data suggests that within experimental error both these distinctively different approaches are valid, indicating that the critical effective ratio at which solubilization occurs is approximately equal to the product of the critical micelle concentration and the distribution coefficient K. Since the nature of detergent affects K and the critical micelle concentration in opposite directions, the critical ('solubilizing') effective ratio depends upon the nature of detergent less than any of these two factors.

Kinetics↗

PubMed1982

Teaching an autistic child pedestrian skills.

An autistic child was taught pedestrian skills in a classroom by use of a model of the streets and the intersection she most often frequented. She manipulated a doll and verbalized what the doll was doing to get to the designated location. After mastering the pedestrian skills on the model, video recordings familiarized her with traffic at local intersections. She successfully generalized the pedestrian skills to the natural environment.

Accident Prevention↗

PubMedDate not supplied

Cross-cultural psychiatry and the DSM-IV.

This report attempts to provide a theoretical framework for exploring the intersection between current work in psychiatric nosology and cross-cultural psychiatry. Three positions at this intersection are constructed and contrasted--a clinical approach, an anthropological approach, and a synthetic clinical-anthropological approach. These positions are used to consider a number of cross-cultural issues in the forthcoming DSM-IV, including a background statement, a cross-cultural axis, diagnostic categories and criteria, and culture-bound syndromes.

Anthropology, Cultural↗

PubMed1979

A method of correction for curvature and inhomogeneities in computer aided calculation of external beam radiation dose distributions.

This paper deals with the problem of finding the effective pathlength along a ray passing through a patient's outline and internal structure. The pathlength contributes to the correction applied for curvature and inhomogeneities in the computer-aided calculation of external beam radiation dose distributions. The pathlength is found by first determining the intersections of the ray with the contours defining the patient's body and the interior inhomogeneities. From these intersections the geometric length within each contour is obtained. This information is then employed in a treatment planning program for high energy gamma and X-rays and electrons, in which the radiation dose distribution is computed taking into account the actual inhomogeneous tissue structures. Other applications of the techniques described to problems in the field of radiation therapy are briefly discussed.

Computers↗