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Results for “Dose-volume analysis”

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At least 109 records · Page 6Linked to original sources

PubMed1999

Analysis of the relationship between tumor dose inhomogeneity and local control in patients with skull base chordoma.

PURPOSE: When irradiating a tumor that abuts or displaces any normal structures, the dose constraints to those structures (if lower than the prescribed dose) may cause dose inhomogeneity in the tumor volume at the tumor-critical structure interface. The low-dose region in the tumor volume may be one of the reasons for local failure. The aim of this study is to quantitate the effect of tumor dose inhomogeneity on local control and recurrence-free survival in patients with skull base chordoma. METHODS AND MATERIALS: 132 patients with skull base chordoma were treated with combined photon and proton irradiation between 1978 and 1993. This study reviews 115 patients whose dose-volume data and follow-up data are available. The prescribed doses ranged from 66.6 Cobalt-Gray-Equivalent (CGE) to 79.2 CGE (median of 68.9 CGE). The dose to the optic structures (optic nerves and chiasm), the brain stem surface, and the brain stem center was limited to 60, 64, and 53 CGE, respectively. We used the dose-volume histogram data derived with the three-dimensional treatment planning system to evaluate several dose-volume parameters including the Equivalent Uniform Dose (EUD). We also analyzed several other patient and treatment factors in relation to local control and recurrence-free survival. RESULTS: Local failure developed in 42 of 115 patients, with the actuarial local control rates at 5 and 10 years being 59% and 44%. Gender was a significant predictor for local control with the prognosis in males being significantly better than that in females (P = 0.004, hazard ratio = 2.3). In a Cox univariate analysis, with stratification by gender, the significant predictors for local control (at the probability level of 0.05) were EUD, the target volume, the minimum dose, and the D5cc dose. The prescribed dose, histology, age, the maximum dose, the mean dose, the median dose, the D90% dose, and the overall treatment time were not significant factors. In a Cox multivariate analysis, the models including gender and EUD, or gender and the target volume, or gender and the minimum target dose were significant. The more biologically meaningful of these models is that of gender and EUD. CONCLUSION: This study suggests that the probability of recurrence of skull base chordomas depends on gender, target volume, and the level of target dose inhomogeneity. EUD was shown to be a useful parameter to evaluate dose distribution for the target volume.

Adult↗

PubMed1999

Clinical and dosimetric predictors of radiation-induced esophageal toxicity.

PURPOSE: To evaluate the incidence, severity, and clinical/dosimetric predictors of acute and chronic esophageal toxicities in patients with non-small cell lung cancer (NSCLC) treated with high-dose conformal thoracic radiation. METHODS AND MATERIALS: Ninety-one patients with localized NSCLC treated definitively with high-dose conformal radiation therapy (RT) at Duke University Medical Center (DUMC) were reviewed. Patient characteristics were as follows: 53 males and 38 females; median age 64 yr (range 46-82); stage I--16, II--3, IIIa--40, IIIb--30, X--2; dysphagia pre-RT--6 (7%). Treatment parameters included: median corrected dose-78.8 Gy (range 64.2-85.6); BID fractionation-58 (64%); chemotherapy-43 (47%). Acute and late esophageal toxicities were graded by RTOG criteria. Using 3D treatment planning tools, the esophagus was contoured in a uniform fashion, the 3D dose distribution calculated (with lung density correction), and the dose-volume (DVH) and dose-surface histograms (DSH) generated. At each axial level, the percentage of the esophageal circumference at each dose level was calculated. The length of circumferential esophagus and the maximum circumference treated to doses >50 Gy were assessed. Patient and treatment factors were correlated with acute and chronic esophageal dysfunction using univariate and multivariate logistic regression analyses. RESULTS: There were no acute or late grade 4 or 5 esophageal toxicities. Ten of 91 patients (11%) developed grade 3 acute toxicity. On univariate analysis of clinical parameters, both dysphagia pre-RT (p = 0.10) and BID fractionation (p = 0.11) tended toward significantly predicting grade 3 acute esophagitis. None of the dosimetric parameters analyzed significantly predicted for grade 3 acute esophagitis. Twelve of 66 assessable patients (18%) developed late esophageal toxicity. Of the clinical parameters analyzed, only dysphagia pre-RT (p = 0.06) tended toward significantly predicting late esophageal toxicity. On univariate analyses, the effects of percent organ volume treated >50 Gy (p = 0.05), percent surface area treated >50 Gy (p = 0.05), length of 100% circumference treated >50 Gy (p = 0.04), and maximum percent of circumference treated >80 Gy (p = 0.01) significantly predicted for late toxicity of all grades. On multivariate analysis, percent organ volume treated >50 Gy (p = 0.02) and maximum percent of circumference treated >80 Gy (p = 0.02) predicted for late toxicity. CONCLUSIONS: Late esophageal toxicity following aggressive, high-dose conformal radiotherapy is common but rarely severe. Dosimetric variables addressing the longitudinal and circumferential character of the esophagus have biologic rationale and are predictive of late toxicity. Further studies are needed to assess whether these parameters are better predictors than those derived from traditional DVHs.

Acute Disease↗

PubMed1997

[Hyperfractionated reirradiation after salvage surgery in cervico-facial carcinoma. Result of a pilot study in 14 patients].

PURPOSE: Between November 1988 and May 1992, 14 patients were enrolled in a pilot study to evaluate the feasibility and results of hyperfractionated reirradiation for the treatment of head and neck recurrences or of second primary tumors developed in a previously irradiated volume. MATERIALS AND METHODS: All patients underwent a surgical resection for the treatment of their recurrence or second cancer. Reirradiation was proposed because of positive margins and/or lymph node metastasis with extra-capsular spread. The planned reirradiation dose was 60 Gy over 5 weeks, with two daily fractions of 1.2 Gy delivered 6-8 hours apart. RESULTS: Of the 14 patients, 10 received the reirradiation scheduled dose (ie, 60 Gy). All patients experienced an acute mucositis that never led to disruption of the treatment. Ten patients died 3 to 41 months after reirradiation (mean: 14 months), three were disease-free 48 to 71 months after reirradiation and one was alive with local progressive disease 74 months after reirradiation. The overall local control rate within the reirradiated volume was 43%. The 24- and 36-month overall survival rates were 50 and 35%, respectively. Overall, 13 late complications were noted: four were grade 1, seven were grade 2, and two were grade 3. Three patients still alive in September 1993 and whose initial files were available were enrolled in an additional study to assess from dose-volume histograms the cumulative doses delivered by the two irradiations. CONCLUSION: Despite poor local control, reirradiation using a hyperfractionation schedule with high dose level is feasible in terms of acute and late toxicity.

Adult↗

PubMed1999

An improved technique for comparing Gamma Knife dose-volume distributions in stereotactic radiosurgery.

A function derived from the geometry of brachytherapy dose distributions is applied to stereotactic radiosurgery and an algorithm for the production of a novel dose-volume histogram, the Anderson inverse-square shifted dose-volume histogram (DVH), is proposed. The expected form of the function to be plotted is checked by calculating its value for single focus exposures, and its application to clinical examples of Gamma Knife treatments described. The technique is shown to provide a valuable tool for assessing the adequacy of radiosurgical plans and comparing and reporting dose distributions.

Algorithms↗

PubMed1992

Proton beams in radiation therapy.

The rationale for study of proton radiation therapy is that, for some anatomic sites and tumors, the treatment volume is smaller; i.e., there is less irradiation of nontarget tissue while the target is included in three dimensions at each treatment session. As a result, the dose to the target can be raised. The consequence is that the tumor control probability improves and the frequency and severity of treatment-related morbidity decrease. These results come about from the physical fact that the proton range in tissue is finite; in comparison, absorption of photons is an exponential function and, hence, some dose is received for the full-beam path through the body. Accordingly, the dose deep to the target for proton treatments can be zero for each beam path. This situation provides a virtually certain means of improving the treatment outcome for selected categories of patients. Experience to date with proton radiation therapy has been quite limited. As of June 1991, the total number of proton radiation-treated patients was 11,763 from the various centers. Of that number, approximately 46% and 32% have been treated for small benign intracranial lesions (principally pituitary adenomas and arteriovenous malformations) and for tumors of the eye, respectively. Thus, only some 2500 patients have been treated for all other tumor types. The results from three centers and approximately 2800 patients with uveal melanoma are that the local control rate was 96% (for failures in-field, marginal, and in other parts of the eye). The local control results for chondrosarcomas and chordomas of the skull base are 91% and 65%, respectively. These percentages compare with some 35% achieved with conventional treatment. Experience with arteriovenous malformations indicates that control of bleeding and disappearance of the lesion are comparable to those achieved by other procedures. The developments from the proton therapy programs have contributed greatly to radiation treatment planning, e.g., the first three-dimensional treatment planning system put into regular clinical use (uveal melanoma), beam's eye view, digital-reconstructed radiograph, dose-volume histograms, and definitions of the uncertainty in dose around any defined point. The potential for clinical gains is high. In May 1991, the Proton Radiation Oncology Group was formed to design, supervise, and coordinate clinical trials and to assist in data analysis. The efficacy of proton radiation therapy will be compared with that of photon therapy of the very highest technology.

Arteriovenous Malformations↗

PubMed1995

Alternating conformal neutron and photon irradiation for locally advanced adenocarcinoma of the prostate.

The substantial local failure rate for patients with locally advanced carcinoma of the prostate (LACaP) following photon irradiation, the association of local failure with a poor prognosis, and the promising results of mixed neutron/photon (40%/60%) radiotherapy supplied the rationale for this study. The purpose of this study was to evaluate the combined advantages of mixed neutron/photon (75%/25%) irradiation, 3D treatment planning, as well as fully conformal beam shaping capabilities in reducing the morbidity associated with neutron irradiation. The first 35 patients treated with this technique are the basis for this analysis. After CT stimulation and treatment planning, the normal tissue and target structures were entered into the 3D planning system. The neutron dose was delivered in 15 fractions at 1.0 Gy/fraction (NGy) to the prostate and seminal vesicles (PSV) and 0.6 NGy/fraction to the pelvic lymph nodes (LN). The photon dose was given in 10 fractions of 1.8 Gy each to both the PSV and LN volumes. Neutron and photon dose-volume histograms (DVHs) were generated in each patient for the prostate, seminal vesicles, lymph nodes, bladder, and rectum. The adequacy of the neutron and photon components of the treatment were compared with respect to target volume and normal tissue irradiation. Based on the DVH analysis, the prostate and seminal vesicles received the prescribed dose with both neutrons (99% +/- 2%) and photons (99% +/- 2%). There was no significant difference in the dose to the bladder and rectum for both the neutrons and photons. The acute treatment related reactions have been mild, with only one grade III bladder reaction. The 3D conformal technology utilized in this study has been shown to allow for the delivery of neutron irradiation with no increase in dose to the adjacent normal tissues compared with that achieved with conformal photon treatment. Further follow-up will reveal whether the dosimetric advantage demonstrated by this technique translates into an improved therapeutic ratio.

Adenocarcinoma↗

PubMed1997

Results of re-irradiation of primary intracranial neoplasms with three-dimensional conformal therapy.

We evaluated the potential of three-dimensional conformal therapy for re-irradiation of selected intracranial neoplasms and reviewed the retreatment of 20 patients at the University of Michigan between May 1988 and August 1991. All patients had previously undergone a full course of external beam radiotherapy (RT) to a median dose of 5,940 cGy (range 5,100-6,500 cGy), including five whole brain treatments. All recurrences were unsuitable for brachytherapy or radiosurgery. Various histologies were retreated, including 14 high-grade gliomas. Median time to re-irradiation was 38 months (range 9 months to 19 years, 6 months). RT was delivered with complex plans designed using fully integrated computed tomography/magnetic resonance imaging (CT/ MRI) tumor volume information, and regions of previous parenchymal treatment were avoided if possible. Composite (initial+retreatment) dose-volume histograms (DVH) of dose to nontarget brain allowed comparison of alternative plans to select beam orientations which minimized normal brain irradiation. Mean target dose of re-irradiation was 3,600 cGy (range 3,060-5,940 cGy). Total cumulative dose ranged from 8,060 to 11,940 cGy. Median survival was 9 months, and 1-year actuarial survival was 26%. After retreatment, 8 of 12 patients (67%) had steroid dose decrement and neurologic improvement at 4-48 months (median duration 14 months). Radiographic regression or stabilization of disease was noted in 11 of 16 patients (68%). Re-irradiation with highly conformal three-dimensional planning provides frequent clinical improvement with acceptable morbidity and should be considered in selected patients with recurrent intracranial neoplasms.

Actuarial Analysis↗

PubMedDate not supplied

3-D dose-volume compensation using nonlinear least-squares regression technique.

A method for external beam dose-volume optimization is presented. The Gauss-Marquardt nonlinear least-squares regression technique is applied to compensator design and determination. The dose distribution (uniform or otherwise) desired throughout a volume is specified. Compensators optimized to produce the necessary variation of beam intensity across the surface of each beam are simultaneously determined for all the beams. Solutions for homogeneous dose, homogeneous target dose, and restricted dose to exterior target volume structures, and inhomogeneous target dose cases are presented. Dependence of the results on the number of parameters as well as the role of degree of desirability weighting is explained and illustrated via examples. Discussion of the significance and limitations of this optimization method is also presented.

Humans↗

PubMedDate not supplied

Dose-volume histogram computations for small intracranial volumes.

A sampling formalism is presented to accurately compute the absolute volumes and integral dose-volume histograms of small volumes treated in stereotactic radiosurgery. The presence of small volumes and sharp dose gradients places special constraints on the computational formalism and the accuracy required to compute the dose-volume relationships. We use a spatially nonuniform random sampling method to allow an efficient and accurate computation of the dose-volume histograms for an arbitrary number of volumes. The computation of absolute volume vs dose allows intercomparison of dose delivered to target and dose-critical volumes and allows a quantitative trade-off analysis often critical to an optimal treatment of the lesion.

Algorithms↗

PubMed1994

Dose-volume distributions: a new approach to dose-volume histograms in three-dimensional treatment planning.

A new approach to calculating and displaying dose-volume relationships in 3D radiation therapy is presented. We have developed a concept of a dose-volume distribution (DVD) and its corresponding differential dose-volume distribution (DDVD), based on organization of the data in the volume rather than in the dose domain. The new concepts make full use of the information that can be obtained from the dose calculation points and the sampling pattern and are designed to overcome shortcomings of the classical concepts of dose-volume histograms (DVH) and differential dose-volume histograms (DDVH). The new concepts can be applied to any number of dose calculation points, but they are especially advantageous when a small number of points is used. DVDs are particularly well suited to pseudo- and quasi-random sampling of dose distributions. We have developed an error analysis for DVDs and DDVDs in the case of pseudorandom sampling. We also describe an adaptive technique for minimizing the amount of data needed for purposes of display.

Biophysical Phenomena↗

PubMed1995

Dose-surface histograms as treatment planning tool for prostate conformal therapy.

Dose-surface histograms are studied and compared with dose-volume histograms, as an evaluation tool for prostate treatment planning. For thin walled hollow organs, such as the rectum and bladder, the surface area irradiated is a more appropriate measure of the biological effect than the full volume. It is also more accurate and efficient to define the surface for a hollow structure and compute the surface area histograms. Application of the dose-surface histograms provide new insights into prostate treatment planning. A simple idealized geometry model demonstrates that the percentage surface area intersected by the geometric beam edge differs from the percentage volume intersected. For a group of prostate patients, it is shown that the dose-surface histograms yield substantially different results from the dose-volume histograms in ranking four-, six-, and, eight-field treatment plans and in calculating the fraction of the rectum irradiated to high dose. The difference in terms of surface area between these plans in the high-dose region is usually less than that in terms of the volume, and a reverse of plan ranking order can consequently occur. The percentage of organ surface irradiated to high dose is typically greater than the percentage volume by 5% to 10%. The use of the dose-surface histograms in analysis of organ motion and/or patient setup uncertainty, and analysis of rectal complications, is also discussed.

Biophysical Phenomena↗

PubMed1997

Reporting and analyzing dose distributions: a concept of equivalent uniform dose.

Modern treatment planning systems for three-dimensional treatment planning provide three-dimensionally accurate dose distributions for each individual patient. These data open up new possibilities for more precise reporting and analysis of doses actually delivered to irradiated organs and volumes of interest. A new method of summarizing and reporting inhomogeneous dose distributions is reported here. The concept of equivalent uniform dose (EUD) assumes that any two dose distributions are equivalent if they cause the same radiobiological effect. In this paper the EUD concept for tumors is presented, for which the probability of local control is assumed to be determined by the expected number of surviving clonogens, according to Poisson statistics. The EUD can be calculated directly from the dose calculation points or, from the corresponding dose-volume distributions (histograms). The fraction of clonogens surviving a dose of 2 Gy (SF2) is chosen to be the primary operational parameter characterizing radiosensitivity of clonogens. The application of the EUD concept is demonstrated on a clinical dataset. The causes of flattening of the observed dose-response curves become apparent since the EUD concept reveals the finer structure of the analyzed group of patients in respect to the irradiated volumes and doses actually received. Extensions of the basic EUD concept to include nonuniform density of clonogens, dose per fraction effects, repopulation of clonogens, and inhomogeneity of patient population are discussed and compared with the basic formula.

Cell Division↗

PubMed1998

A gradient inverse planning algorithm with dose-volume constraints.

An inverse planning algorithm for determining the intensity-modulated beams that will most closely generate a desired dose distribution is presented. The algorithm is three-dimensional and does not explicitly depend on beam energies and modalities. It allows a single prescription dose or a window of acceptable doses to be specified for the target, with additional constraints to account for under- or over-dosing. For the protection of organs at risk, it provides maximum-dose and dose-volume constraints. The latter apply to the entire volume of the organ exposed to the corresponding dose levels. Several levels of each type of constraint, with varying penalty weights, may be specified for each organ. The objective function that serves as the measure of the goodness of the solution is of the least-squares type and is minimized using conjugate gradient methods. Typical clinical cases involving 40,000 points and 4000 rays to be determined require about 10 min of CPU time on a DEC AlphaStation. Results are presented for two clinical sites, prostate and lung. The optimization algorithm yielded plans that featured higher target dose homogeneity, compared with the human planner's plan, while selectively sparing more of the normal organs at the desired dose regions.

Aged↗

PubMed1999

A computerized dosimetric database for conformal stereotactic irradiations.

An innovative computerized dosimetric database (DDB) is proposed to enable the analysis of the stereotactic radiosurgical dose distributions; it contains relationships between the irradiation parameters and the dose-volume data. Dose-volume data provide guidance to the physicist-physician team by facilitating the initialization of the irradiation parameters and the treatment planning. The presented DDB contains dose-volume data such as the 70% isodose widths and the 70%-30% isodose penumbra along the right-left, anterior-posterior, and superior-inferior directions as a function of the irradiation parameters defined by the user. In order to demonstrate the usefulness of the DDB, the effects of the collimator diameter, the number of arcs, and their length on the shape of the prescription isodose surface are shown and are related to practical considerations for the treatment plan. However, the presented DDB is one example that can be generated by the DDB system. The planner can define as many different DDBs as he/she wishes, which can then be used for different investigations. This type of DDB enables us to investigate the irradiation technique used, to compare different irradiation techniques, to inspect the feasibility of planning different lesion types, or to define some dosimetric rules. The DDB provides useful interactive guidelines for the treatment planning process and replaces the voluminous dosimetric atlas. It has now been in clinical use for a year in a conformal procedure which automatically proposes collimator diameters, arc positions, and lengths allowing rapid conformal planning.

Algorithms↗

PubMed1999

Use of dose-volume histograms and biophysical models to compare 2D and 3D irradiation techniques for non-small cell lung cancer.

For non-small cell lung cancer (NSCLC), unsatisfactory local control (LC) still remains an important cause of failure. It has been suggested that improved LC can be achieved with both higher radiation dosage and adequate target coverage. Modern three-dimensional treatment planning systems (3D-TPSs) offer many tools for planning optimization. Biophysical models, which estimate the normal tissue complication probability (NTCP), are gaining in importance in comparing plans. This study compares conventional two-dimensional (2D) with 3D irradiation techniques using parameters related to volumetric dose distribution and two different biophysical models predicting normal tissue tolerance to radiotherapy (RT). Nine patients with inoperable locally advanced NSCLC were treated with a beam's eye view-based 3D technique. For the same patients, a conventional treatment was simulated; the irradiation geometry and beam contour were fully defined at the simulator and then transferred to the 3D-TPS to calculate the dose distribution. Both techniques gave the same prescribed dose at the reference point. Dose-volume histograms (DVHs) and dose statistics of organs at risk (OARs) (heart, lung(s), parenchyma lung, spinal cord and oesophagus) were analysed. The probability of side effects was estimated using two different biophysical models: the integrated normal ("empirical") model and the relative seriality model. Apart from contralateral lung, the 3D irradiation technique significantly reduced the average mean doses to all OARs. The current analysis suggests that in the treatment of locally advanced NSCLC, the use of 3D irradiation techniques allows a large sparing of OARs; this advantage is confirmed by both dose statistics analysis and NTCP values.

Aged↗

PubMed1999

Phase I/IIa study of concurrent paclitaxel and cisplatin with radiation therapy in locally advanced non-small cell lung cancer: analysis of early and late pulmonary morbidity.

Recent efforts to improve survival outcome in patients with locally advanced non-small cell lung cancer have focused on the use of chemoradiotherapy regimens containing vinblastine/cisplatin or etoposide/cisplatin. However, the overall treatment outcome with these regimens remains poor, emphasizing the need for new therapeutic options. Based on the activity of paclitaxel in advanced non-small cell lung cancer, its additive cytotoxicity with cisplatin, and the radiation-sensitizing effect of both agents, a phase I/IIa study was designed to examine the feasibility of paclitaxel/cisplatin concurrently with conventional thoracic irradiation in patients with locally advanced tumors. One major concern regarding combined modality therapy has been the enhancement of pulmonary toxicity. This report describes the incidence and severity of pulmonary toxicities observed in this trial according to the Radiation Therapy Oncology Group scoring criteria. A literature-based review was performed in an attempt to determine the impact of paclitaxel-based versus non-paclitaxel-based chemoradiotherapy regimens on the early and late pulmonary morbidity. Twenty-four evaluable patients died and 14 (37%) are still alive without evidence of disease. The 1- and 2-year survival rates are 62% and 40%, respectively, with a median survival of 17 months. Pulmonary toxicity >/=grade 2 was more frequently manifested as late toxicity in approximately 70% of the patients. In most, prompt symptomatic and radiologic improvement was observed with the early administration of corticosteroids. There were three late grade 5 toxicities characterized by diffuse (bilateral) rapidly progressive interstitial infiltrates. Protracted lymphocytopenia was noted in the great majority of patients, and its role in the pathogenesis of this complication remains to be determined. There were minor changes in pulmonary function parameters, except in the forced vital capacity and diffusion capacity to carbon monoxide. In a univariate analysis, no relationship was noted between paclitaxel dose level, degree of lymphocytopenia, changes in pulmonary function indices, and incidence of pulmonary toxicity. However, there was a significant dose-volume relationship (using conventional dose-volume histograms) with late pulmonary toxicity at radiation doses between 15 Gy and 30 Gy. Based on a literature review, paclitaxel-based chemotherapy regimens seem to be associated with a slightly higher risk of pulmonary toxicity; however, comparison of such toxicity between trials has many limitations that require that the conclusion reached be viewed with caution.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1999

Can current models explain the lack of liver complications in Y-90 microsphere therapy?

Normal liver complications have not been observed in Y-90 microsphere therapy of hepatic tumors [selective internal radiation (SIR)], despite clinical studies reporting estimated absorbed doses to normal liver between 100 and 150 Gy. The purpose of the study was to see whether predictions of normal tissue complication probability (NTCP) models for liver based on clinical data from external beam therapy are consistent with clinical results of SIR. Liver NTCP was calculated using a parallel architecture model and normal liver dose-volume histograms that have been proposed for SIR. A parallel model including internal functional subunit structure is also proposed. Dose rate effects are incorporated. A criterion for comparing model calculations with clinical data is presented. For the parallel architecture model, the predicted NTCP is sensitive to the dose distribution in normal liver and to the model parameters, particularly the repair time. With reasonable assumptions about the microsphere distribution, the parallel model with parameters deduced from external beam therapy outcome analysis is consistent with the observed lack of liver complications. Inclusion of FSU structure widens the range of assumptions under which consistency is found. The parallel model can be consistent with the clinically observed lack of liver complications in SIR. More information about the activity distribution and the radiobiology of normal liver under conditions typical of microsphere therapy should be sought.

Humans↗

PubMed1975

[The dose-volume factor in radiotherapy. Significance of the focal or tumor volume for the evaluation of radiotherapeutic effect].

The absorbed energy dose, in dependence on the irradiated tissue volume or tumor volume (dose-volume-relations) has great significance for the valuation of radiation injuries and of the prognosis of the disease. The present paper includes an analysis, formal demonstrations and interpretation of these relations. Clinical observations and radiobiological experiments in literature were the basis of the present investigation. The assessment is kept simple, the models derived from it interprete well the clinical findings. Through these models, radiobiological findings and clinical experimental principles are connected. This results in a clear conception of the future development of irradiation planning, and the application technique of radiation. The range of validity of the cited models includes the treated volumes usual in radiotherapy. An extrapolation to the cellulary area or to the whole body may only be made with great reservations.

Humans↗