Quantitative Imaging in Oncology

The Special Issue of Tomography is a collection of articles focused on the quantitative imaging methods in clinical oncology [...

Analysis of Hydraulic Fracturing Efficiency Considering the Principal Stress in Brushy Canyon Formation of the Permian Basin

The purpose of this study is to investigate the effect of principal stress direction on the efficiency of hydraulic fracturing treatment. There are two different drilling scenarios: 1. Four horizontal wells drilled in four orthogonal directions regardless of in-situ stress condition (“Actual”). 2. Three horizontal wells drilled equivalent to “Actual” case by considering the direction of principal stress (“Proposed”). The hydraulic fracturing modeling was carried out based on well logging data and completion reports of Brushy Canyon formation, Permian Basin. In the results of “Actual” case, transverse fractures were generated in two horizontal wells drilled parallel to σhmin-dir (direction of σhmin), similar to “Proposed” case. Meanwhile, for two other wells drilled perpendicular to σhmin-dir, longitudinal fractures were generated. These obliquely deviated fractures significantly decreased the fracture spacing between the stages up to 26%. This induced great stress shadow, however, the fractures propagated straight due to the large stress anisotropy of 2000 psi (σHmax/σhmin = 1.4). Therefore, it was found that due to the different direction of fracture propagation in “Actual” case, “Proposed” case was 14.6% of stimulated reservoir volume (SRV) higher. In conclusion, for successful hydraulic fracturing treatment, the direction of horizontal well must be determined in consideration of the principal stress direction as well as stress anisotropy

Efficiency of enhanced oil recovery by injection of low-salinity water in barium-containing carbonate reservoirs

Abstract When low-salinity water containing sulfate ions is injected into carbonate reservoirs, rock dissolution and in situ precipitation occur, altering rock permeability and wettability. Particularly, when barium ions are present in formation water, they react chemically with $${\text{SO}}_{4}^{2 - }$$ SO42- , and BaSO4 is precipitated. These reactions can cause a serious impact on the efficiency of enhanced oil recovery (EOR). Therefore, the main purpose of this study was to identify EOR efficiency induced by low-salinity waterflooding (LSWF) when Ba2+ is present in carbonate reservoirs. From the experimental results, it was confirmed that the permeability calculated by the measured pressure difference was improved because of rock dissolution predominating over in situ precipitation for the case of low Ba2+ concentrations. In the analysis of wettability alteration through the measurements of relative permeabilities before and after LSWF, the higher Ba2+ concentration case consumed more $${\text{SO}}_{4}^{2 - }$$ SO42- in precipitating the BaSO4, resulting in weaker wettability alteration due to the reduction of sulfate activity. These phenomena ultimately influenced EOR efficiency, i.e., the oil recovery was greater for the lower Ba2+ concentration

Evaluation of Sustained BMP-2 Release Profiles Using a Novel Fluorescence-Based Retention Assay.

The purpose of this study was to develop and characterize a novel fluorescence-based retention assay for the evaluation of the release profile of bone morphogenetic protein-2 (BMP-2) released from bone graft carrier. In this study, we evaluated the binding, release kinetics, and delivery efficacies of BMP-2 incorporated into hydroxyapatite (HA) bone grafts. The evaluation of the release profile of BMP-2 from HA bone grafts using a fluorescence-based retention assay revealed initial burst releases from the HA bone grafts followed by long sustained releases up to 14 weeks. The sustained biological activity of the released BMP-2 from HA bone grafts over the full 14-week period supports a long sustained mechanism via fluorescence-based retention assay. Thus, the results from this study show that BMP-2 could be incorporated into HA bone grafts for sustained release over a prolonged period of time with retention of bioactivity and our fluorescence-based retention assay, which is principally detecting the retention profile of BMP-2 in HA bone grafts, is more accurate than conventionally collecting the released BMP-2 for evaluation of BMP-2 release profiles

Ipsilateral Recurrence of DCIS in Relation to Radiomics Features on Contrast Enhanced Breast MRI

The purpose of this retrospective study was to investigate the association between ipsilateral recurrence of ductal carcinoma in situ (DCIS) and radiomics features from DCIS and contralateral normal breast on contrast enhanced breast MR imaging. A total of 163 patients with DCIS who underwent preoperative MR imaging between January 2010 and December 2014 were included (training cohort; n = 117, validation cohort; n = 46). Radiomics features were extracted from whole tumor volume of DCIS on early dynamic T1-subtraction images and from the contralateral normal breast on precontrast T1 and early dynamic T1-subtraction images. After feature selection, a Rad-score was established by LASSO Cox regression model. Performance of Rad-score was evaluated by the receiver operating characteristic (ROC) curve and Kaplan Meier curve with log rank test. The Rad-score was significantly associated with ipsilateral recurrence free survival (RFS). The low-risk group with a low Rad-score showed higher ipsilateral RFS than the high-risk group with a high Rad-score in both training and validation cohorts (p < 0.01). The Rad-score based on radiomics features from DCIS and contralateral normal breast on breast MR imaging showed the potential for prediction of ipsilateral RFS of DCIS

A Mathematical Model for Predicting Patient Responses to Combined Radiotherapy with CTLA-4 Immune Checkpoint Inhibitors

The purpose of this study was to develop a cell–cell interaction model that could predict a tumor’s response to radiotherapy (RT) combined with CTLA-4 immune checkpoint inhibition (ICI) in patients with hepatocellular carcinoma (HCC). The previously developed model was extended by adding a new term representing tremelimumab, an inhibitor of CTLA-4. The distribution of the new immune activation term was derived from the results of a clinical trial for tremelimumab monotherapy (NCT01008358). The proposed model successfully reproduced longitudinal tumor diameter changes in HCC patients treated with tremelimumab (complete response = 0%, partial response = 17.6%, stable disease = 58.8%, and progressive disease = 23.6%). For the non-irradiated tumor control group, adding ICI to RT increased the clinical benefit rate from 8% to 32%. The simulation predicts that it is beneficial to start CTLA-4 blockade before RT in terms of treatment sequences. We developed a mathematical model that can predict the response of patients to the combined CTLA-4 blockade with radiation therapy. We anticipate that the developed model will be helpful for designing clinical trials with the ultimate aim of maximizing the efficacy of ICI-RT combination therapy

Determining the Radiation Enhancement Effects of Gold Nanoparticles in Cells in a Combined Treatment with Cisplatin and Radiation at Therapeutic Megavoltage Energies

Combined use of chemotherapy and radiation therapy is commonly used in cancer treatment, but the toxic effects on normal tissue are a major limitation. This study assesses the potential to improve radiation therapy when combining gold nanoparticle (GNP) mediated radiation sensitization with chemoradiation compared to chemoradiation alone. Incorporation of GNPs with 2 Gy, 6 MV (megavoltage) radiation resulted in a 19 ± 6% decrease in survival of MDA-MB-231 cells. Monte-Carlo simulations were performed to assess dosimetric differences in the presence of GNPs in radiation. The results show that physics dosimetry represents a small fraction of the observed effect. The survival fraction of the cells exposed to GNPs, cisplatin, and radiation was 0.16 ± 0.007, while cells treated with cisplatin and radiation only was 0.23 ± 0.011. The presence of GNPs resulted in a 30 ± 6% decrease in the survival, having an additive effect. The concentration of the GNPs and free drug used for this study was 0.3 and 435 nM, respectively. These concentrations are relatively lower and achievable in an in vivo setting. Hence, the results of our study would accelerate the incorporation of GNP-mediated chemoradiation into current cancer therapeutic protocols in the near future