Image‐based 3D modeling study of the influence of vessel density and blood hemoglobin concentration on tumor oxygenation and response to irradiation. Issue 2 (9th January 2013)

• Record Type: Journal Article
• Authors: Lagerlöf, Jakob H.; Kindblom, Jon; Cortez, Eliane; Pietras, Kristian; Bernhardt, Peter
• Is Part Of: Medical physics. Volume 40:Issue 2(2013)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2013-01-09
• Subjects: Segmentation -- Function theory, analysis -- Diffusion -- Peripheral vascular dynamics; biochemistry -- biological effects of radiation -- blood -- blood vessels -- cellular biophysics -- diffusion -- Green's function methods -- medical disorders -- medical image processing -- oxygen -- radiation therapy -- tumours; tumor control probability -- dosimetry -- modeling -- hypoxia -- radiotherapy; Radiation therapy -- Biochemistry; Beer; Spirits; Wine; Vinegar; Microbiology; Enzymology; Mutation or genetic engineering -- Digital computing or data processing equipment or methods, specially adapted for specific applications -- Image data processing or generation, in general; Cancer -- Medical imaging -- Diffusion -- Tissues -- Statistical properties -- Green's function methods -- Radiation therapy -- Radiation treatment -- Numerical modeling -- Dosimetry; Medical physics -- Periodicals; Medical physics; Geneeskunde; Natuurkunde; Toepassingen; Biophysics; Periodicals; Periodicals; Electronic journals; 610.153
• DOI: 10.1118/1.4773886
• Languages: English
• ISSNs: 0094-2405

Abstract

Abstract : Purpose: : Hypoxia is one of the most important factors influencing clinical outcome after radiotherapy. Improved knowledge of factors affecting the levels and distribution of oxygen within a tumor is needed. The authors constructed a theoretical 3D model based on histological images to analyze the influence of vessel density and hemoglobin (Hb) concentration on the response to irradiation. Methods: : The pancreases of a Rip‐Tag2 mouse, a model of malignant insulinoma, were excised, cryosectioned, immunostained, and photographed. Vessels were identified by image thresholding and a 3D vessel matrix assembled. The matrix was reduced to functional vessel segments and enlarged by replication. The steady‐state oxygen tension field of the tumor was calculated by iteratively employing Green's function method for diffusion and the Michaelis‐Menten model for consumption. The impact of vessel density on the radiation response was studied by removing a number of randomly selected vessels. The impact of Hb concentration was studied by independently changing vessel oxygen partial pressure (pO2 ). For each oxygen distribution, the oxygen enhancement ratio (OER) was calculated and the mean absorbed dose at which the tumor control probability (TCP) was 0.99 (D99 ) was determined using the linear‐quadratic cell survival model (LQ model). Results: : Decreased pO2 shifted the oxygen distribution to lower values, whereas decreased vessel density caused the distribution to widen and shift to lower values. Combined scenarios caused lower‐shifted distributions, emphasising log‐normal characteristics. Vessel reduction combined with increased blood pO2 caused the distribution to widen due to a lack of vessels. The most pronounced radiation effect of increased pO2 occurred with tumor tissue with 50% of the maximum vessel density used in the simulations. A 51% decrease in D99, from 123 to 60 Gy, was found between the lowest and highest pO2 concentrations. Conclusions: : Our results indicate that an intermediate vascular density region exists where enhanced blood oxygen concentration may be beneficial for radiation response. The results also suggest that it is possible to distinguish between diffusion‐limited and anemic hypoxia from the characteristics of the pO2 distribution.