The dose-volume histogram DVH has been accepted as a tool for treatment -plan evaluation. However, DVH lacks spatial information. A new concept, the z-dependent dose-volume histogram zDVHis presented as a supplement to the DVH in three-dimensional 3D treatment planning to provide the spatial variation, as well as the size and magnitude of the different dose regions within a region of interest.
Three-dimensional dose calculations were carried out with various plans for three disease sites: DVHs were calculated for the entire volume.
A zDVH is defined as a differential dose-volume histogram with respect to a computed tomographic CT slice position. In the irradiation of lung, DVH calculation indicated that the treatment plan satisfied the dose-volume constraint placed on the lung and zDVH of the lung revealed that a sizable fraction of the lung centered about the central axis CAX received a significant dosea situation that warranted a modification of the treatment plan due to the removal of one lung.
Taking into account the hollow structure of both the bladder and the rectum, the dose -surface histograms DSH showed larger hot-spot volumeabout. Dose-volume histograms for optimization of treatment plans illustrated by the example of oesophagus carcinoma. Using the example of oesophagus carcinoma, dose-volume histograms for diverse treatment techniques are calculated and judged by means of multiplanar isodose representations.
The selected treatment plans are with the aid Julie nulens accommodating the dose-volume histograms. We distinguish the tissue inside and outside of the target volume. The
Julie nulens accommodating of the spatial dose distribution in dependence of the different volumes and the respective fractions of the tumor dose therein with the help of dose-volume histograms brings about a correlation between the physical parameters and the biological effects.
In addition one has to bear in mind the consequences of measures that influence the reaction and the side-effects of radiotherapy e.
Taking all that into account it is evident that the dose-volume histograms are a powerful tool for assessing the quality of treatment plans. Geometrical considerations in dose volume analysis in intracavitary treatment. The present work was aimed at to study the relationship between the volume enclosed by reference iodose surface and various geometrical parameters of the intracavitary applicator in treatment of carcinoma of cervix.
Pearshape volume of the reference isodose derived from the Total Reference Air Kerma TRAK and the product of its dimensions, height H, width W and thickness T which is dependent
Julie nulens accommodating the applicator geometry, were estimated for intracavitary applications treated by Selectron LDR machine.
Orthogonal radiographs taken for each patient were used for measurement of actual geometric dimensions of the applicator and carrying out the dosimetry on TP treatment planning system. The dimensions H, W and T of reference isodose surface 60 Gy were also noted. Ratio of the product HWT and the pearshape volume was found mainly to be a function of colpostat separation and not of other geometrical parameters like maximum vertical and anterio-posterior dimension of Julie nulens accommodating applicator.
The ratio remained almost constant for a particular combination of uterine tandem and colpostat. Variation in the ratios were attributed to the non-standard geometry. The ratio of the volume of reference isodose surface to the product of its dimensions in the applicator depends upon the colpostat separation.
Comparison of doses according to change of bladder volume in treatment of prostate cancer. Kwon, Kyung Tae [Dept. In the case of radiation therapy for prostate cancer, a balloon infused with a certain amount of air through the anus is used to reduce rectal dose.
Because of the reason, radiation therapy for prostate cancer has acquired CBCT for daily image induction. In order to maintain the anatomical structure most similar to the first CT taken before treatmentit is pretreated, but it can not be said to be perfectly consistent. In two actual treatment regimens, the volume of the bladder was measured as As a result of this study, the mean volume of the bladder was estimated to be The mean dose of CBCT was 1. In case B, PTV mean dose was 4.
The changes in the volume of the bladder resulted in changes in the dose of PTV and bladder. It was found that the dose change
Julie nulens accommodating PTV was larger than that of bladder according to the change of bladder volume. Calculation of complication probability of pion treatment at PSI using dose-volume histograms.
In the conformation technique a target volume is irradiated uniformly as in conventional "Julie nulens accommodating," whereas surrounding tissue and organs are nonuniformly irradiated. Clinical data on radiation that accumulate with conventional radiation are not applicable without appropriate compensation.
Recently a putative solution of this problem was proposed by Lyman using dose-volume histograms. This histogram reduction method reduces a given dose-volume histogram of an organ to a single step which corresponds to the equivalent complication probability by Julie nulens accommodating.
As a result it converts nonuniform radiation into a unique dose to the whole organ which has the equivalent likelihood of radiation injury.
This method is based on low LET radiation with conventional fractionation schedules. When it is applied to high LET radiation such Julie nulens accommodating negative pion treatmenta high LET dose should be to an equivalent photon dose using an appropriate value of RBE. In the present study the histogram reduction method was applied to actual patients treated by the negative pion conformation technique at the Paul Scherrer Institute.
The 90 cases were divided into roughly equal groups according to the equivalent doses to the entire bladder and rectum. Complication rates and equivalent doses to the full organs in these groups could be represented by a sigmoid dose -effect relation.
When RBE from a pion dose to a photon dose is assumed to be 2. When the RBE value Julie nulens accommodating 2. These values are close to the conversion factor of 2. This agreement suggests the clinical feasibility of the histogram reduction method in conformation radiotherapy. Towards the elimination of Monte Carlo statistical fluctuation from dose volume histograms for radiotherapy treatment planning. The Monte Carlo calculation of dose for radiotherapy treatment planning purposes introduces unavoidable statistical noise into the prediction of dose in a given Julie nulens accommodating element voxel.
When the doses in these voxels are summed to produce
Julie nulens accommodating volume histograms DVHsthis noise translates into a broadening of differential DVHs and correspondingly flatter DVHs.
A brute force approach would entail calculating dose for long periods of time - enough to ensure that the DVHs had converged. In this paper we introduce an approach for deconvolving the statistical noise from DVHs, thereby obtaining estimates for converged DVHs obtained about times faster than the brute force approach described above. There are two important implications of this work: The dose-volume constraint satisfaction problem for inverse treatment planning with field segments.
The prescribed goals of radiation treatment planning are often expressed in terms of dose-volume constraints. We present a novel formulation of a dose-volume constraint satisfaction search for the discretized radiation therapy model.
This approach does not rely on any explicit cost function. Inverse treatment planning uses the aperture-based approach with predefined, according to geometric rules, segmental fields. The solver utilizes the simultaneous version of the cyclic subgradient projection algorithm.
This is a deterministic iterative method designed for solving the convex feasibility problems. A prescription is expressed with the set of inequalities imposed on the dose at the voxel resolution.
Additional constraint functions control the compliance with selected points of the expected cumulative dose-volume histograms. The performance of this method is tested on prostate and head-and-neck cases. The relationships with other models and
Julie nulens accommodating of similar conceptual origin are discussed.
The demonstrated advantages of the method are: The technique reported here will deliver approximate solutions for inconsistent prescriptions. Improvement in treatment planning efficiency using NTCP calculation independent of the dose-volume -histogram. The calculation of the NTCP is based on the dose-volume -histogram DVH which Julie nulens accommodating generated by the treatment planning system after calculation of the 3D dose distribution.
Including the NTCP in the objective function for intensity modulated radiation therapy IMRT plan optimization would make the planning more effective in reducing the postradiation effects.
However, doing so would lengthen the total planning time. The purpose of this work is to establish a method for NTCP determination, independent of a DVH calculation, as a quality assurance check and also as a Julie nulens accommodating of improving the treatment planning efficiency. In the study, the CTs of ten randomly selected prostate patients were used.
The function was 'geometrically' normalized using a prostate-prostate ratio PPR of the patients' prostates. The R NTCPs of another group of patients were calculated by the new method and the resulting difference was dose. Lung and heart dose volume analyses with CT simulator in radiation treatment of breast cancer. Radiation pneumonitis and cardiac effects Julie nulens accommodating directly related to the irradiated lung and heart volumes in the treatment fields.
The central lung distance CLD from a tangential breast radiograph is shown to be a significant indicator of ipsilateral irradiated lung volume.