SU-E-T-457: Multi-Mode Model - A Consistent Approach for Conventionally Fractionated Radiotherapy and Stereotactic Body Radiotherapy

PURPOSE

The accuracy of dosimetric analysis and outcome comparison between conventionally fractionated radiation therapy(CFRT) and stereotactic body radiotherapy(SBRT) requires reliable radiobiological modeling. The aim of this work was to further improve the multi-mode model(MMM) for both CFRT and SBRT.

METHODS

MMM assumes the existence of different modes of cell killing as a Result of radiation damage to different parts of a cell, e.g., a single severe damage to the DNA or two or more small damages to the membrane or DNA. The cell survival probability can then be calculated by s=Product_(i=1,n){1-(1-ê(-d/Di))̂(i)}, where i represents the i-th mode of cell killing that requires i potentially unrepairable damages to the cell as a result of radiation dose d and Di is the dose that gives 63% probability to cause an unrepairable damage for the i-th mode. The dose rate effect is included in MMM assuming 1/D_i=(k_i- r_i/U), where k_i is the radiation damage rate, r_i the repair rate and U the dose rate. The low-dose hypersensitivity is also included in the new model.

RESULTS

A comparison of the goodness-of-fit of the LQ, multitarget, USC and MMM to the survival curve of the H460 non-small-cell lung cancer cell line showed the same agreement between USC and MMM with the survival data, which was significantly better than the fits to the LQ and multitarget models. The parameters used for the LQ, multitarget and USC models were alpha=0.33Gy, alpha/beta=10Gy, D_T =6.2Gy, D_0 =1.25Gy and D_q =1.8Gy. The parameters for MMM(n=4) were D_1=4.0Gy, D_2=4.01Gy, D_3=3.08Gy and D_4=41Gy.

CONCLUSIONS

MMM offers a superior description of the mammalian cell survival curve in both conventional and ablative dose ranges, which can be used for designing new fractionation schemes and predicting and understanding treatment outcomes for both CFRT and SBRT.

SU-E-T-586: Comparison between CT-and FLT-PET-Defined Target Volumes and Dosimetry for Radiotherapy Planning in Esophageal Carcinoma

PURPOSE

To study the advantage of fused 3-deoxy-3-18F-fluorothymidine (FLT) positron emission tomography (PET) and computed tomography (CT) images on radiotherapy planning for esophageal carcinoma patients .

METHODS

Ten patients with esophageal carcinoma were referred for radiotherapy. Each patient underwent CT and FLT PET scan for simulation plan in the same treatment position. FLT PET images were coregistered with CT images. GTVCT was initially performed on CT images, GTVPET-CT were automatically segmented on FLT PET/CT images using a fixed threshold values at 1.4. Two kinds of treatment plans were designed based on GTVCT and GTVPET-CT. The radiation dose was prescribed as 60 Gy in 30 fractions. The dose-volume parameters of target volume and normal tissues, CI and HI of based on the GTVPET- CT and GTVCT were compared.

RESULTS

The mean GTV delineated on CT and PET- CT were 39.28 cm^s and 34.48 cm^s , respectively . The values for mean lung dose, total-lung volume receiving =5, = 10, = 20 and = 30Gy;mean heart dose, heart volume receiving =30Gy and normal tissues of plan based on the GTVPET- CT were significant lower than plan based on the GTV-CT.

CONCLUSIONS

In our study, FLT PET use has an impact on target delineation for radiotherapy planning. GTVPET-CT is significantly smaller than GTVCT with a mean volume reduction of 16%. CT and FLT/PET image fusion appeared to have an advantage on dose reduction of organ at risk in radiotherapy planning of esophageal carcinoma.

Comparative proteomic analysis of grain development in two spring wheat varieties under drought stress

Two spring wheat varieties Ningchun 4 and Chinese Spring with good and poor resistance to abiotic stress, respectively, were used to investigate proteomic changes in the developing grains under drought stress by a comparative proteomics approach. A total of 152 protein spots showed at least twofold differences in abundance on two-dimensional electrophoresis (2-DE) maps, of which 28 and 68 protein spots were identified by MALDI-TOF and MALDI-TOF/TOF mass spectrometry, respectively. Of the 96 identified protein spots, six different expression patterns were found and they were involved in stress/defense/detoxification, carbohydrate metabolism, photosynthesis, nitrogen metabolism, storage proteins and some other important functions. Comparative proteomic analysis revealed that under the drought conditions the decreased degree of ascorbate peroxidases was more significant in Chinese Spring than in Ningchun 4 during grain development whereas translationally controlled tumor protein, which was significantly upregulated at 14 DAF, was present in Ningchun 4 and absent in Chinese Spring. The Rubisco large subunit displayed an upregulated expression pattern in Ningchun 4. In addition, two drought-tolerant proteins, triosephosphate isomerase and oxygen-evolving complex showed B and F type expression patterns in Chinese Spring, but D and B types in Ningchun 4, respectively. These differentially expressed proteins might be responsible for the stronger drought resistance of Ningchun 4 compared to Chinese Spring.

Optimization of complex conditions by response surface methodology for APAM-oil/water emulsion removal from aqua solutions using nano-sized TiO2/Al2O3 PVDF ultrafiltration membrane

This paper studies the cumulative effect of various parameters, namely anionic polyacrylamide (APAM) concentration, oil concentration, pH, trans-membrane pressure (TMP), and total dissolved solid (TDS), and obtains optimal parameters for the minimum relative flux (J/J(0)) declining in aqueous solutions with response surface methodology (RSM). In order to analyze the mutual interaction and optimal values of parameters affecting ultrafiltration, a central composite rotatable design (CCRD), one method of RSM, was employed. The analysis of variance (ANOVA) of the cubic polynomial model demonstrated that this model was highly significant and reliable. The results show that the effect of APAM and oil on J/J(0) has an inverse trend with pH value increasing. Moreover, the mutual interaction of initial APAM (oil) concentration (C(APAM(oil))) and pH (TMP) were negligible, while the mutual interaction of C(APAM) and C(oil) has an obvious effect, i.e. the effect of initial feed C(APAM) became more important at higher values of initial feed C(oil), and the J/J(0) was only about 4%. The favorable operate conditions in this ultrafiltration process were at low C(APAM), C(oil), pH, and TMP, which agreed with the conclusions of many authors, while considering water production, C(APAM) and C(oil) < 50 mg/L, pH < 4, and TMP < 0.075 MPa could be accepted.

In vivo responses of cutaneous C-mechanosensitive neurons in mouse to punctate chemical stimuli that elicit itch and nociceptive sensations in humans

Native cowhage spicules, and heat-inactivated spicules containing histamine or capsaicin, evoke similar sensations of itch and nociceptive sensations in humans. In ongoing studies of the peripheral neural mechanisms of chemical itch and pain in the mouse, extracellular electrophysiological recordings were obtained, in vivo, from the cell bodies of mechanosensitive nociceptive neurons in response to spicule stimuli delivered to their cutaneous receptive fields (RFs) on the distal hindlimb. A total of 43 mechanosensitive, cutaneous, nociceptive neurons with axonal conduction velocities in the C-fiber range (C-nociceptors) were classified as CM if responsive to noxious mechanical stimuli, such as pinch, or CMH if responsive to noxious mechanical and heat stimuli (51°C, 5 s). The tips of native cowhage spicules, or heat-inactivated spicules containing histamine or capsaicin, were applied to the RF. Heat-inactivated spicules containing no chemical produced only a transient response occurring during insertion. Of the 43 mechanosensitive nociceptors recorded, 20 of the 25 CMHs responded to capsaicin, and of these, 13 also responded to cowhage and/or histamine. In contrast, none of the 18 CMs responded to any of the chemical stimuli. The time course of the mean discharge rate of CMHs was similar in response to each type of spicule and generally similar, although reaching a peak earlier, to the temporal profiles of itch and nociceptive sensations evoked by the same stimuli in humans. These findings are consistent with the hypothesis that the itch and nociceptive sensations evoked by these punctuate chemical stimuli are mediated at least in part by the activity of mechanoheat-sensitive C-nociceptors. In contrast, activity in mechanosensitive C-nociceptors that do not respond to heat or to pruritic chemicals is hypothesized as contributing to pain but not to itch.