Article

Reconsidering the definition of a dose-volume histogram

Harvard University, Cambridge, Massachusetts, United States
Physics in Medicine and Biology (Impact Factor: 2.92). 07/2005; 50(11):L17-19. DOI: 10.1088/0031-9155/50/11/L01
Source: PubMed

ABSTRACT The full text of this letter is given in the PDF file below.

0 Bookmarks
 · 
180 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Currently, determination of body composition is the most useful method for distinguishing between certain diseases. The prompt-gamma in vivo neutron activation analysis (IVNAA) facility for non-destructive elemental analysis of the human body is the gold standard method for this type of analysis. In order to obtain accurate measurements using the IVNAA system, the activation probability in the body must be uniform. This can be difficult to achieve, as body shape and body composition affect the rate of activation. The aim of this study was to determine the optimum pre-moderator, in terms of material for attaining uniform activation probability with a CV value of about 10% and changing the collimator role to increase activation rate within the body. Such uniformity was obtained with a high thickness of paraffin pre-moderator, however, because of increasing secondary photon flux received by the detectors it was not an appropriate choice. Our final calculations indicated that using two paraffin slabs with a thickness of 3 cm as a pre-moderator, in the presence of 2 cm Bi on the collimator, achieves a satisfactory distribution of activation rate in the body.
    Journal of Radiation Research 02/2013; 54(3). DOI:10.1093/jrr/rrs124 · 1.45 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Purpose: To introduce the concept of dose-mass-based inverse optimization for radiotherapy applications. Materials and Methods: Mathematical derivation of the dose-mass-based formalism is presented. This mathematical representation is compared to the most commonly used dose-volume-based formulation used in inverse optimization. A simple example on digitally created phantom is presented. The phantom consists of three regions: a target surrounded by high- and low-density regions. The target is irradiated with two beams through those regions and inverse optimization with dose-volume and dose-mass-based objective functions is performed. The basic properties of the two optimization types are demonstrated on the phantom. Results: It is demonstrated that dose-volume optimization is a special case of dose-mass optimization. In a homogenous media, dose-mass optimization turns into dose-volume optimization. The dose calculations performed on the digital phantom show that in this very simple case dose-mass optimization tends to penalize more the dose delivery through the high-density region and therefore it results in delivering more dose through the low-density region. Conclusion: It was demonstrated that dose-mass-based optimization is mathematically more general than dose-volume-based optimization. In the case of constant density media, dose-mass optimization transforms into dose-volume optimization.
    Frontiers in Oncology 11/2014; 4:331. DOI:10.3389/fonc.2014.00331
  • [Show abstract] [Hide abstract]
    ABSTRACT: Experimental evidence supports an association between heterogeneity in tumor perfusion and response to chemotherapy/radiotherapy, disease progression and malignancy. Therefore, changes in tumor perfusion may be used to assess early effects of tumor treatment. However, evaluating changes in tumor perfusion during treatment is complicated by extensive changes in tumor type, size, shape and appearance. Therefore, this study assesses the regional heterogeneity of tumors by dynamic contrast-enhanced MRI (DCE-MRI) and evaluates changes in response to isolated limb perfusion (ILP) with tumor necrosis factor alpha and melphalan. Data were acquired in an experimental cancer model, using a macromolecular contrast medium, albumin-(Gd-DTPA)45. Small fragments of BN 175 (a soft-tissue sarcoma) were implanted in eight brown Norway rats. MRI of five drug-treated and three sham-treated rats was performed at baseline and 1 h after ILP intervention. Properly co-registered baseline and follow-up DCE-MRI were used to estimate the volume transfer constant (K(trans) ) pharmacokinetic maps. The regional heterogeneity was estimated in 16 tumor sectors and presented in cumulative map-volume histograms. On average, ILP-treated tumors showed a decrease in regional heterogeneity on the histograms. This study shows that heterogenic changes in regional tumor perfusion, estimated using DCE-MRI pharmacokinetic maps, can be measured and used to assess the short-term effects of a potentially curative treatment on the tumor microvasculature in an experimental soft-tissue sarcoma model. Copyright © 2013 John Wiley & Sons, Ltd.
    Contrast Media & Molecular Imaging 07/2013; 8(4):340-9. DOI:10.1002/cmmi.1528 · 2.87 Impact Factor

Preview

Download
1 Download
Available from