Intrinsic susceptibility MR imaging of chemically induced rat mammary tumors: relationship to histologic assessment of hypoxia and fibrosis

Caliper, contrast enhanced-ultrasound or laser speckle contrast imaging: Techniques to follow mice melanoma growth

Due to morphological characteristics, metastatic melanoma is a cancer for which vascularization is not a diagnostic criterion. Laser speckle contrast imaging (LSCI) and contrast enhanced ultrasound (CEUS) are two imaging techniques that will be explored in this study, which aims to confirm these two techniques for monitoring tumor vascularization. B16F10 cells were xenografted to C57BL/6 mice treated with anti-PD1 or 0.9% NaCl. Tumor volume was measured daily while CEUS and LSCI were performed weekly. LSCI and CEUS analyses showed a decrease in tumor perfusion in both groups of mice. Although both CEUS and LSCI are useful for measuring tumor volume, LSCI appears to be more robust and effective for monitoring tumor microcirculation. Non-invasive investigations are needed to better predict tumor vascularization: CEUS and LSCI have a good applicability in a mice model.

Hyperoxic BOLD-MRI-Based Characterization of Breast Cancer Molecular Subtypes Is Independent of the Supplied Amount of Oxygen: A Preclinical Study

Hyperoxic BOLD-MRI targeting tumor hypoxia may provide imaging biomarkers that represent breast cancer molecular subtypes without the use of injected contrast agents. However, the diagnostic performance of hyperoxic BOLD-MRI using different levels of oxygen remains unclear. We hypothesized that molecular subtype characterization with hyperoxic BOLD-MRI is feasible independently of the amount of oxygen. Twenty-three nude mice that were inoculated into the flank with luminal A (n = 9), Her2+ (n = 5), and triple-negative (n = 9) human breast cancer cells were imaged using a 9.4 T Bruker BioSpin system. During BOLD-MRI, anesthesia was supplemented with four different levels of oxygen (normoxic: 21%; hyperoxic: 41%, 71%, 100%). The change in the spin-spin relaxation rate in relation to the normoxic state, ΔR2*, dependent on the amount of erythrocyte-bound oxygen, was calculated using in-house MATLAB code. ΔR2* was significantly different between luminal A and Her2+ as well as between luminal A and triple-negative breast cancer, reflective of the less aggressive luminal A breast cancer's ability to better deliver oxygen-rich hemoglobin to its tissue. Differences in ΔR2* between subtypes were independent of the amount of oxygen, with robust distinction already achieved with 41% oxygen. In conclusion, hyperoxic BOLD-MRI may be used as a biomarker for luminal A breast cancer identification without the use of exogenous contrast agents.

Chemical Shift-Encoded Sequence (IDEAL-IQ) and Amide Proton Transfer (APT) MRI for Prediction of Histopathological Factors of Rectal Cancer

To investigate whether parameters from IDEAL-IQ/amide proton transfer MRI (APTWI) could help predict histopathological factors of rectal cancer. Preoperative IDEAL-IQ and APTWI sequences of 67 patients with rectal cancer were retrospectively analyzed. The intra-tumoral proton density fat fraction (PDFF), R2* and magnetization transfer ratio asymmetry (MTRasym (3.5 ppm)) were measured according to the histopathological factors of rectal cancer. The relationship between MR parameters and histopathological factors were analyzed, along with diagnostic performance of MR parameters. PDFF, R2* and MTRasym (3.5 ppm) were statistically different between T1+T2/T3+T4 stages, non-metastatic/metastatic lymph nodes, lower/higher tumor grade and negative/positive status of MRF and EMVI (p < 0.001 for PDFF, p = 0.000-0.015 for R2* and p = 0.000-0.006 for MTRasym (3.5 ppm)). There were positive correlations between the above parameters and the histopathological features of rectal cancer (r = 0.464-0.723 for PDFF (p < 0.001), 0.299-0.651 for R2* (p = 0.000-0.014), and 0.337-0.667 for MTRasym (3.5 ppm) (p = 0.000-0.005)). MTRasym (3.5 ppm) correlated moderately and mildly with PDFF (r = 0.563, p < 0.001) and R2* (r = 0.335, p = 0.006), respectively. PDFF provided a significantly higher diagnostic ability than MTRasym (3.5 ppm) for distinguishing metastatic from non-metastatic lymph nodes (z = 2.407, p = 0.0161). No significant differences were found in MR parameters for distinguishing other histopathological features (p > 0.05). IDEAL-IQ and APTWI were associated with histopathological factors of rectal cancer, and might serve as non-invasive biomarkers for characterizing rectal cancer.

Acupotomy Improves Synovial Hypoxia, Synovitis and Angiogenesis in KOA Rabbits

Purpose

Knee osteoarthritis (KOA) is a chronic inflammatory disease highly associated with intra-articular hypertension, hypoxia and angiogenesis of synovial tissue. Our previous studies showed that acupotomy could treat KOA in a variety of ways, including reducing cartilage deterioration and enhancing biomechanical qualities. However, the mechanism of hypoxia and angiogenesis induced by acupotomy in KOA synovium remains unclear. This study looked for the benign intervention of acupotomy in synovial pathology.

Methods

The rabbits were divided into 3 groups, Normal group, KOA group, and KOA + Acupotomy (Apo) group, with 11 rabbits in each group. The KOA rabbit model was established by the modified Videman method with six weeks. The KOA + Apo group performed the intervention. The tendon insertion of vastus medialis, vastus lateralis, rectus femoris, biceps femoris, and anserine bursa were selected as treatment points in rabbits. Rabbits were treated once every 7 days for 3 weeks. We observed the intra-articular pressure and oxygen partial pressure (BOLD MRI). The synovial morphology was monitored by Hematoxylin-Eosin Staining (HE Staining). The expression of hypoxia-inducible transcription factor-1α (HIF-1α), vascular endothelial growth factor (VEGF), interleukin-1β (IL-1β) and tumour necrosis factor-α (TNF-α) was detected using Immunohistochemical (IHC), Western Blot and Enzyme-Linked Immunosorbent Assay (ELISA).

Results

Acupotomy reduced intra-articular hypertension and improved the synovial oxygen situation, synovial inflammatory and angiogenesis. HIF-1α, VEGF, IL-1β and TNF-α expression were downregulated by acupotomy.

Conclusion

Acupotomy may reduce inflammation and angiogenesis in KOA rabbit by reducing abnormally elevated intra-articular pressure and improving synovial oxygen environment. The above may provide a new theoretical foundation for acupotomy treatment of KOA.

The Role of Imaging Biomarkers to Guide Pharmacological Interventions Targeting Tumor Hypoxia

Hypoxia is a common feature of solid tumors that contributes to angiogenesis, invasiveness, metastasis, altered metabolism and genomic instability. As hypoxia is a major actor in tumor progression and resistance to radiotherapy, chemotherapy and immunotherapy, multiple approaches have emerged to target tumor hypoxia. It includes among others pharmacological interventions designed to alleviate tumor hypoxia at the time of radiation therapy, prodrugs that are selectively activated in hypoxic cells or inhibitors of molecular targets involved in hypoxic cell survival (i.e., hypoxia inducible factors HIFs, PI3K/AKT/mTOR pathway, unfolded protein response). While numerous strategies were successful in pre-clinical models, their translation in the clinical practice has been disappointing so far. This therapeutic failure often results from the absence of appropriate stratification of patients that could benefit from targeted interventions. Companion diagnostics may help at different levels of the research and development, and in matching a patient to a specific intervention targeting hypoxia. In this review, we discuss the relative merits of the existing hypoxia biomarkers, their current status and the challenges for their future validation as companion diagnostics adapted to the nature of the intervention.

Oxygen-Challenge Blood Oxygen Level-Dependent Magnetic Resonance Imaging for Evaluation of Early Change of Hepatocellular Carcinoma to Chemoembolization: A Feasibility Study

RATIONALE AND OBJECTIVES

To investigate the feasibility of oxygen-challenge blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) at 3T for evaluating the early change of blood oxygenation before and after transcatheter arterial embolization (TACE) in patients with hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Thirty HCC patients with cirrhosis (HCC group, n = 30) and 30 healthy volunteers (control group, n = 30) were included in this study. Patients in the HCC group underwent BOLD before and 1 month after TACE. Oxygen was administered via a mask. Differences between pre- and post-O₂ T₂* values were evaluated using a pairwise t-test. Analysis of variance was performed to assess the statistical differences in the T₂* values measured in HCC group pre-TACE and post-TACE and in healthy volunteers.

RESULTS

In the HCC group, the pre- and post-O₂ T₂* values of the cancerous area before TACE were 26.03 ± 3.30 and 26.84 ± 3.42 msec, respectively, and both decreased significantly to 8.67 ± 1.76 and 8.82 ± 1.80 msec, respectively, at 1 month after TACE (p < 0.001). The respective pre- and post-O₂ T₂* values of the noncancerous area increased significantly from 14.96 ± 2.32 and 15.33 ± 2.28 msec at baseline to 16.38 ± 2.22 and 16.89 ± 2.24 msec at 1 month after TACE (p < 0.001). No significant response to BOLD was observed in the control group (p = 0.059).

CONCLUSION

Oxygen-challenge BOLD MRI is feasible to assess post-TACE changes in HCC patients.

C(3)1-TAg in C57BL/6 J background as a model to study mammary tumor development

Diagnosis and prognosis of breast cancer is based on disease staging identified through histopathological and molecular biology techniques. Animal models are used to gain mechanistic insights into the development of breast cancer. C(3)1-TAg is a genetically engineered mouse model that develops mammary cancer. However, carcinogenesis caused by this transgene was characterized in the Friend Virus B (FVB) background. As most genetic studies are done in mice with C57BL/6 J background, we aimed to define the histological alterations in C3(1)-TAg C57BL/6 J animals. Our results showed that C3(1)-TAg animals with C57BL/6 J background develop solid-basaloid adenoid cystic carcinomas with increased fibrosis, decreased area of adipocytes, and a high proliferative index, which are triple-negative for progesterone, estrogen, and human epidermal growth factor receptor 2 (HER2) receptors. Our results also revealed that tumor development is slower in the C57BL/6 J background when compared with the FVB strain, providing a better model to study the different stages in breast cancer progression.

Blood Oxygenation Level Dependent Magnetic Resonance Imaging (MRI), Dynamic Contrast Enhanced MRI, and Diffusion Weighted MRI for Benign and Malignant Breast Cancer Discrimination: A Preliminary Experience

Simple Summary

The aim of the study is to combine blood oxygenation level dependent magnetic resonance imaging (BOLD-MRI), dynamic contrast enhanced MRI (DCE-MRI), and diffusion weighted MRI (DW-MRI) in differentiation of benign and malignant breast lesions. The results suggest that the combined use of DCE-MRI, DW-MRI and/or BOLD-MRI does not provide a dramatic improvement compared to the use of DCE-MRI features alone, in the classification of breast lesions. However, an interesting result was the negative correlation between R₂* and D.

Abstract

Purpose. To combine blood oxygenation level dependent magnetic resonance imaging (BOLD-MRI), dynamic contrast enhanced MRI (DCE-MRI), and diffusion weighted MRI (DW-MRI) in differentiation of benign and malignant breast lesions. Methods. Thirty-seven breast lesions (11 benign and 21 malignant lesions) pathologically proven were included in this retrospective preliminary study. Pharmaco-kinetic parameters including K^trans, k^ep, v_e, and v_p were extracted by DCE-MRI; BOLD parameters were estimated by basal signal S0 and the relaxation rate R₂*; and diffusion and perfusion parameters were derived by DW-MRI (pseudo-diffusion coefficient (D_p), perfusion fraction (f_p), and tissue diffusivity (D_t)). The correlation coefficient, Wilcoxon-Mann-Whitney U-test, and receiver operating characteristic (ROC) analysis were calculated and area under the ROC curve (AUC) was obtained. Moreover, pattern recognition approaches (linear discrimination analysis and decision tree) with balancing technique and leave one out cross validation approach were considered. Results. R₂* and D had a significant negative correlation (−0.57). The mean value, standard deviation, Skewness and Kurtosis values of R₂* did not show a statistical significance between benign and malignant lesions (p > 0.05) confirmed by the ‘poor’ diagnostic value of ROC analysis. For DW-MRI derived parameters, the univariate analysis, standard deviation of D, Skewness and Kurtosis values of D* had a significant result to discriminate benign and malignant lesions and the best result at the univariate analysis in the discrimination of benign and malignant lesions was obtained by the Skewness of D* with an AUC of 82.9% (p-value = 0.02). Significant results for the mean value of K^trans, mean value, standard deviation value and Skewness of k_ep, mean value, Skewness and Kurtosis of v_e were obtained and the best AUC among DCE-MRI extracted parameters was reached by the mean value of k_ep and was equal to 80.0%. The best diagnostic performance in the discrimination of benign and malignant lesions was obtained at the multivariate analysis considering the DCE-MRI parameters alone with an AUC = 0.91 when the balancing technique was considered. Conclusions. Our results suggest that the combined use of DCE-MRI, DW-MRI and/or BOLD-MRI does not provide a dramatic improvement compared to the use of DCE-MRI features alone, in the classification of breast lesions. However, an interesting result was the negative correlation between R₂* and D.

Markers of human endometrial hypoxia can be detected in vivo and ex vivo during physiological menstruation

STUDY QUESTION

Can markers of human endometrial hypoxia be detected at menstruation in vivo?

SUMMARY ANSWER

Our in vivo data support the presence of hypoxia in menstrual endometrium of women during physiological menstruation.

WHAT IS KNOWN ALREADY

Current evidence from animal models and human in vitro studies suggests endometrial hypoxia is present at menstruation and drives endometrial repair post menses. However, detection of human endometrial hypoxia in vivo remains elusive.

STUDY DESIGN, SIZE, DURATION

We performed a prospective case study of 16 women with normal menstrual bleeding.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Reproductively aged female participants with a regular menstrual cycle underwent objective measurement of their menstrual blood loss using the alkaline haematin method to confirm a loss of <80 ml per cycle. Exclusion criteria were exogenous hormone use, an intrauterine device, endometriosis or fibroids >3 cm. Participants attended for two MRI scans; during days 1-3 of menstruation and the early/mid-secretory phase of their cycle. The MRI protocol included dynamic contrast-enhanced MRI and T2* quantification. At each visit, an endometrial sample was also collected and hypoxia-regulated repair factor mRNA levels (ADM, VEGFA, CXCR4) were quantified by RT-qPCR.

MAIN RESULTS AND THE ROLE OF CHANCE

Women had reduced T2* during menstrual scans versus non-menstrual scans (P = 0.005), consistent with menstrual hypoxia. Plasma flow (Fp) was increased at menstruation compared to the non-menstrual phase (P = 0.0005). Laboratory findings revealed increased ADM, VEGF-A and CXCR4 at menstruation on examination of paired endometrial biopsies from the menstrual and non-menstrual phase (P = 0.008; P = 0.03; P = 0.009). There was a significant correlation between T2* and these ex vivo hypoxic markers (P < 0.05).

LIMITATIONS, REASONS FOR CAUTION

This study examined the in vivo detection of endometrial hypoxic markers at specific timepoints in the menstrual cycle in women with a menstrual blood loss <80 ml/cycle and without significant uterine structural abnormalities. Further research is required to determine the presence of endometrial hypoxia in those experiencing abnormal uterine bleeding with and without fibroids/adenomyosis.

WIDER IMPLICATIONS OF THE FINDINGS

Heavy menstrual bleeding (HMB) is a common, debilitating condition. Understanding menstrual physiology may improve therapeutics. To our knowledge, this is the first in vivo data supporting the presence of menstrual hypoxia in the endometrium of women with normal menstrual bleeding. If aberrant in those with HMB, these non-invasive tests may aid diagnosis and facilitate personalized treatments for HMB.

STUDY FUNDING/COMPETING INTEREST(S)

This work was funded by Wellbeing of Women grant RG1820, Wellcome Trust Fellowship 209589/Z/17/Z and undertaken in the MRC Centre for Reproductive Health, funded by grants G1002033 and MR/N022556/1. H.O.D.C. has clinical research support for laboratory consumables and staff from Bayer AG and provides consultancy advice (but with no personal remuneration) for Bayer AG, PregLem SA, Gedeon Richter, Vifor Pharma UK Ltd, AbbVie Inc; Myovant Sciences GmbH. H.O.D.C. receives royalties from UpToDate for articles on abnormal uterine bleeding.

TRIAL REGISTRATION NUMBER

N/A.

An optimized and highly repeatable MRI acquisition and processing pipeline for quantitative susceptibility mapping in the head-and-neck region

PURPOSE

Quantitative Susceptibility Mapping (QSM) is an emerging technique sensitive to disease-related changes including oxygenation. It is extensively used in brain studies and has increasing clinical applications outside the brain. Here we present the first MRI acquisition protocol and QSM pipeline optimized for the head-and-neck region together with a repeatability analysis performed in healthy volunteers.

METHODS

We investigated both the intrasession and the intersession repeatability of the optimized method in 10 subjects. We also implemented two, Tikhonov-regularisation-based susceptibility calculation techniques that were found to have higher contrast-to-noise than existing methods in the head-and-neck region. Repeatability was evaluated by calculating the distributions of susceptibility differences between repeated scans and the corresponding minimum detectable effect sizes (MDEs).

RESULTS

Deep brain regions had higher QSM repeatability than neck regions. As expected, intrasession repeatability was generally better than intersession repeatability. Susceptibility maps calculated using projection onto dipole fields for background field removal were more repeatable than using the Laplacian boundary value method in the head-and-neck region. Small (short-axis diameter <5 mm) lymph nodes had the lowest repeatability (MDE = 0.27 ppm) as imperfect segmentation included some of the surrounding paramagnetic fatty fascia, highlighting the importance of accurate region delineation. MDEs in the larger lymph nodes (0.16 ppm), submandibular glands (0.10 ppm), and especially the parotid glands (0.06 ppm) were much lower, comparable to those of the brain regions.

CONCLUSIONS

The high repeatability of the acquisition and pipeline optimized for QSM will facilitate clinical studies in the head-and-neck region.

Stromal markers of activated tumor associated fibroblasts predict poor survival and are associated with necrosis in non-small cell lung cancer

OBJECTIVES

Tumor associated fibroblasts (TAFs) are essential contributors of the progression of non-small cell lung cancer (NSCLC). Most lung TAFs exhibit an activated phenotype characterized by the expression of α-SMA and fibrillar collagens. However, the prognostic value of these activation markers in NSCLC remains unclear.

MATERIAL AND METHODS

We conducted a quantitative image analysis of α-SMA immunostaining and picrosirius red staining of fibrillar collagens imaged by bright-field and polarized microscopy, respectively, using tissue microarrays with samples from 220 surgical patients, which elicited a percentage of positive staining area for each marker and patient.

RESULTS

Kaplan-Meier curves showed that all TAF activation markers were significantly associated with poor survival, and their prognostic value was independent of TNM staging as revealed by multivariate analysis, which elicited an adjusted increased risk of death after 3 years of 129% and 94% for fibrillar collagens imaged with bright-field (p = 0.004) and polarized light (p = 0.003), respectively, and of 89% for α-SMA (p = 0.009). We also found a significant association between all TAF activation markers and tumor necrosis, which is often indicative of hypoxia, supporting a pathologic link between tumor desmoplasia and necrosis/hypoxia.

CONCLUSIONS

Our findings identify patients with large histologic coverage of fibrillar collagens and α-SMA + TAFs to be at higher risk of recurrence and death, supporting that they could be considered for adjuvant therapy.

Dependency of the blood oxygen level dependent-response to hyperoxic challenges on the order of gas administration in intracranial malignancies

PURPOSE

Literature reports contradicting results on the response of brain tumors to vascular stimuli measured in T2*-weighted MRI. Here, we analyzed the potential dependency of the MRI-response to (hypercapnic) hyperoxia on the order of the gas administration.

METHODS

T2* values were quantified at 3 Tesla in eight consenting patients at rest and during inhalation of hyperoxic/hypercapnic gas mixtures. Patients were randomly divided into two groups undergoing different gas administration protocols (group A: medical air-pure oxygen-carbogen; group B: medical air-carbogen-pure oxygen). Mann-Whitney U test and Wilcoxon signed rank test have been used to proof differences in T2* regarding respiratory challenge or different groups, respectively.

RESULTS

T2* values at rest for gray and white matter were 50.3 ± 2.6 ms and 46.1 ± 2.0 ms, respectively, and slightly increased during challenge. In tumor areas, T2* at rest were: necrosis = 74.1 ± 10.1 ms; edema = 60.3 ± 17.6 ms; contrast-enhancing lesions = 48.6 ± 20.7 ms; and solid T2-hyperintense lesions = 45.0 ± 3.0 ms. Contrast-enhancing lesions strongly responded to oxygen (+ 20.7%) regardless on the gas protocol (p = 0.482). However, the response to carbogen significantly depended on the order of gas administration (group A, + 18.6%; group B, - 6.4%, p = 0.042). In edemas, a different trend between group was found when breathing oxygen (group A, - 9.9%; group B, + 19.5%, p = 0.057).

CONCLUSION

Preliminary results show a dependency of the T2* response of contrast-enhancing brain tumor lesions on the order of the gas administration. The gas administration protocol is an important factor in the interpretation of the T2*-response in areas of abnormal vascular growth.

Imaging tumour hypoxia with oxygen-enhanced MRI and BOLD MRI

Hypoxia is known to be a poor prognostic indicator for nearly all solid tumours and also is predictive of treatment failure for radiotherapy, chemotherapy, surgery and targeted therapies. Imaging has potential to identify, spatially map and quantify tumour hypoxia prior to therapy, as well as track changes in hypoxia on treatment. At present no hypoxia imaging methods are available for routine clinical use. Research has largely focused on positron emission tomography (PET)-based techniques, but there is gathering evidence that MRI techniques may provide a practical and more readily translational alternative. In this review we focus on the potential for imaging hypoxia by measuring changes in longitudinal relaxation [R1; termed oxygen-enhanced MRI or tumour oxygenation level dependent (TOLD) MRI] and effective transverse relaxation [R2*; termed blood oxygenation level dependent (BOLD) MRI], induced by inhalation of either 100% oxygen or the radiosensitising hyperoxic gas carbogen. We explain the scientific principles behind oxygen-enhanced MRI and BOLD and discuss significant studies and their limitations. All imaging biomarkers require rigorous validation in order to translate into clinical use and the steps required to further develop oxygen-enhanced MRI and BOLD MRI into decision-making tools are discussed.

Correlation between tumor glucose metabolism and multiparametric functional MRI (IVIM and R2*) metrics in cervical carcinoma: Evidence from integrated 18 F-FDG PET/MR

BACKGROUND

Multiparameter, multimodality ¹⁸ F-FDG PET/MRI holds great potential for the diagnosis of cervical cancer based on the correlation between tumor glucose metabolism and imaging parameters.

PURPOSE

To characterize the heterogeneity of tumor glucose metabolism by evaluating the correlation between ¹⁸ F-FDG uptake parameters and multiparametric functional MRI metrics in cervical carcinoma.

STUDY TYPE

Retrospective.

POPULATION

Fifty-four patients with cervical carcinoma.

FIELD STRENGTH/SEQUENCE

Hybrid PET/MR (3T), multi-b DWI, and R2* mapping.

ASSESSMENT

The maximum and mean standardized uptake values (SUV_max and SUV_mean , respectively) from PET and functional MRI metrics (D, D*, f, and R2*) were obtained. Cervical carcinoma tissues also underwent HIF-1α, VEGF, and GLUT-1 immunohistochemical staining.

STATISTICAL TESTS

Single-factor Spearman rank and Pearson correlation analysis and multiple linear regression (MLR) analysis were applied.

RESULTS

R2*, D, and f have different degrees of correlation (moderate, weak, moderately strong correlation, respectively) with SUV_max and SUV_mean (r = 0.530 and 0.527, and P < 0.001 for R2*; r = -0.292 and -0.291, and P < 0.05 for D; r = 0.539 and 0.520, and P < 0.001 for f, respectively). Immunohistochemical staining showed that HIF-1α expression has a moderate degree of correlation with R2* (r = 0.491; P < 0.001); GLUT-1 expression was significantly correlated with SUV_max and SUV_mean (r = 0.633 and 0.622; P < 0.001), and VEGF expression had a moderately strong correlation with f (r = 0.457; P = 0.001). If SUV_max is the dependent variable, MLR yields an R-squared value after adjustment (adjusted R-squared) = 0.358, and F = 10.833 (P < 0.001), and the fitting linear equation is Y (SUV_max ) = 9.184 + 0.161X1 (R2*)+50.343X2 (f)-4.780 (D). Otherwise, MLR yields the adjusted R-squared = 0.342, and F = 10.187 (P < 0.001), and the linear regression equation is Y (SUV_mean ) = 5.925 + 0.102X1 (R2*)+28.029X2 (f)-2.907X3 (D).

DATA CONCLUSION

The functional MRI sequence parameters R2*, f, and D can provide information on the hypoxic condition, blood perfusion, and molecular diffusion of the tumor. ¹⁸ F-FDG PET/MR multi-imaging technique can be adopted to evaluate the heterogeneity of glucose metabolism in cervical carcinoma.

LEVEL OF EVIDENCE

3 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2019;49:1704-1712.

Pre-treatment functional MRI of breast cancer: T2* evaluation at 3 T and relationship to dynamic contrast-enhanced and diffusion-weighted imaging

PURPOSE

Baseline T2* relaxation time has been proposed as an imaging biomarker in cancer, in addition to Dynamic Contrast-Enhanced (DCE) MRI and diffusion-weighted imaging (DWI) parameters. The purpose of the current work is to investigate sources of error in T2* measurements and the relationship between T2* and DCE and DWI functional parameters in breast cancer.

METHODS

Five female volunteers and thirty-two women with biopsy proven breast cancer were scanned at 3 T, with Research Ethics Committee approval. T2* values of the normal breast were acquired from high-resolution, low-resolution and fat-suppressed gradient-echo sequences in volunteers, and compared. In breast cancer patients, pre-treatment T2*, DCE MRI and DWI were performed at baseline. Pathologically complete responders at surgery and non-responders were identified and compared. Principal component analysis (PCA) and cluster analysis (CA) were performed.

RESULTS

There were no significant differences between T2* values from high-resolution, low-resolution and fat-suppressed datasets (p > 0.05). There were not significant differences between baseline functional parameters in responders and non-responders (p > 0.05). However, there were differences in the relationship between T2* and contrast-agent uptake in responders and non-responders. Voxels of similar characteristics were grouped in 5 clusters, and large intra-tumoural variations of all parameters were demonstrated.

CONCLUSION

Breast T2* measurements at 3 T are robust, but spatial resolution should be carefully considered. T2* of breast tumours at baseline is unrelated to DCE and DWI parameters and contribute towards describing functional heterogeneity of breast tumours.

Mapping Hypoxia in Renal Carcinoma with Oxygen-enhanced MRI: Comparison with Intrinsic Susceptibility MRI and Pathology

Purpose To cross-validate T1-weighted oxygen-enhanced (OE) MRI measurements of tumor hypoxia with intrinsic susceptibility MRI measurements and to demonstrate the feasibility of translation of the technique for patients. Materials and Methods Preclinical studies in nine 786-0-R renal cell carcinoma (RCC) xenografts and prospective clinical studies in eight patients with RCC were performed. Longitudinal relaxation rate changes (∆R1) after 100% oxygen inhalation were quantified, reflecting the paramagnetic effect on tissue protons because of the presence of molecular oxygen. Native transverse relaxation rate (R2*) and oxygen-induced R2* change (∆R2*) were measured, reflecting presence of deoxygenated hemoglobin molecules. Median and voxel-wise values of ∆R1 were compared with values of R2* and ∆R2*. Tumor regions with dynamic contrast agent-enhanced MRI perfusion, refractory to signal change at OE MRI (referred to as perfused Oxy-R), were distinguished from perfused oxygen-enhancing (perfused Oxy-E) and nonperfused regions. R2* and ∆R2* values in each tumor subregion were compared by using one-way analysis of variance. Results Tumor-wise and voxel-wise ∆R1 and ∆R2* comparisons did not show correlative relationships. In xenografts, parcellation analysis revealed that perfused Oxy-R regions had faster native R2* (102.4 sec-1 vs 81.7 sec-1) and greater negative ∆R2* (-22.9 sec-1 vs -5.4 sec-1), compared with perfused Oxy-E and nonperfused subregions (all P < .001), respectively. Similar findings were present in human tumors (P < .001). Further, perfused Oxy-R helped identify tumor hypoxia, measured at pathologic analysis, in both xenografts (P = .002) and human tumors (P = .003). Conclusion Intrinsic susceptibility biomarkers provide cross validation of the OE MRI biomarker perfused Oxy-R. Consistent relationship to pathologic analyses was found in xenografts and human tumors, demonstrating biomarker translation. Published under a CC BY 4.0 license. Online supplemental material is available for this article.

Characterisation of fibrosis in chemically-induced rat mammary carcinomas using multi-modal endogenous contrast MRI on a 1.5T clinical platform

OBJECTIVES

To determine the ability of multi-parametric, endogenous contrast MRI to detect and quantify fibrosis in a chemically-induced rat model of mammary carcinoma.

METHODS

Female Sprague-Dawley rats (n=18) were administered with N-methyl-N-nitrosourea; resulting mammary carcinomas underwent nine-b-value diffusion-weighted (DWI), ultrashort-echo (UTE) and magnetisation transfer (MT) magnetic resonance imaging (MRI) on a clinical 1.5T platform, and associated quantitative MR parameters were calculated. Excised tumours were histologically assessed for degree of necrosis, collagen, hypoxia and microvessel density. Significance level adjusted for multiple comparisons was p=0.0125.

RESULTS

Significant correlations were found between MT parameters and degree of picrosirius red staining (r > 0.85, p < 0.0002 for ka and δ, r < -0.75, p < 0.001 for T1 and T1s, Pearson), indicating that MT is sensitive to collagen content in mammary carcinoma. Picrosirius red also correlated with the DWI parameter fD* (r=0.801, p=0.0004) and conventional gradient-echo T2* (r=-0.660, p=0.0055). Percentage necrosis correlated moderately with ultrashort/conventional-echo signal ratio (r=0.620, p=0.0105). Pimonidazole adduct (hypoxia) and CD31 (microvessel density) staining did not correlate with any MR parameter assessed.

CONCLUSIONS

Magnetisation transfer MRI successfully detects collagen content in mammary carcinoma, supporting inclusion of MT imaging to identify fibrosis, a prognostic marker, in clinical breast MRI examinations.

KEY POINTS

• Magnetisation transfer imaging is sensitive to collagen content in mammary carcinoma. • Magnetisation transfer imaging to detect fibrosis in mammary carcinoma fibrosis is feasible. • IVIM diffusion does not correlate with microvessel density in preclinical mammary carcinoma.

Genetically modified lentiviruses that preserve microvascular function protect against late radiation damage in normal tissues

Improvements in cancer survival mean that long-term toxicities, which contribute to the morbidity of cancer survivorship, are being increasingly recognized. Late adverse effects (LAEs) in normal tissues after radiotherapy (RT) are characterized by vascular dysfunction and fibrosis causing volume loss and tissue contracture, for example, in the free flaps used for immediate breast reconstruction after mastectomy. We evaluated the efficacy of lentivirally delivered superoxide dismutase 2 (SOD2) overexpression and connective tissue growth factor (CTGF) knockdown by short hairpin RNA in reducing the severity of LAEs in an animal model of free flap LAEs. Vectors were delivered by intra-arterial injection, ex vivo, to target the vascular compartment. LVSOD2 and LVshCTGF monotherapy before irradiation resulted in preservation of flap volume or reduction in skin contracture, respectively. Flaps transduced with combination therapy experienced improvements in both volume loss and skin contracture. Both therapies reduced the fibrotic burden after irradiation. LAEs were associated with impaired vascular perfusion, loss of endothelial permeability, and stromal hypoxia, which were all reversed in the treatment model. Using a tumor recurrence model, we showed that SOD2 overexpression in normal tissues did not compromise the efficacy of RT against tumor cells but appeared to enhance it. LVSOD2 and LVshCTGF combination therapy by targeted, intravascular delivery reduced LAE severities in normal tissues without compromising the efficacy of RT and warrants translational evaluation as a free flap-targeted gene therapy.

Cancer Metabolism and Tumor Heterogeneity: Imaging Perspectives Using MR Imaging and Spectroscopy

Cancer cells reprogram their metabolism to maintain viability via genetic mutations and epigenetic alterations, expressing overall dynamic heterogeneity. The complex relaxation mechanisms of nuclear spins provide unique and convertible tissue contrasts, making magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) pertinent imaging tools in both clinics and research. In this review, we summarized MR methods that visualize tumor characteristics and its metabolic phenotypes on an anatomical, microvascular, microstructural, microenvironmental, and metabolomics scale. The review will progress from the utilities of basic spin-relaxation contrasts in cancer imaging to more advanced imaging methods that measure tumor-distinctive parameters such as perfusion, water diffusion, magnetic susceptibility, oxygenation, acidosis, redox state, and cell death. Analytical methods to assess tumor heterogeneity are also reviewed in brief. Although the clinical utility of tumor heterogeneity from imaging is debatable, the quantification of tumor heterogeneity using functional and metabolic MR images with development of robust analytical methods and improved MR methods may offer more critical roles of tumor heterogeneity data in clinics. MRI/MRS can also provide insightful information on pharmacometabolomics, biomarker discovery, disease diagnosis and prognosis, and treatment response. With these future directions in mind, we anticipate the widespread utilization of these MR-based techniques in studying in vivo cancer biology to better address significant clinical needs.

Evaluation of the R2* value in invasive ductal carcinoma with respect to hypoxic-related prognostic factors using iterative decomposition of water and fat with echo asymmetry and least-squares emission (IDEAL)

OBJECTIVE

To correlate the R2* value obtained by iterative decomposition of water and fat with echo asymmetry and least-squares emission (IDEAL) with fibrotic focus (FF), microvessel density and hypoxic biomarker (HIF-1α) in breast carcinoma.

METHODS

Forty-two patients who were diagnosed with invasive ductal carcinoma (IDC) of the breast underwent breast MRI including IDEAL before surgery. The entire region of interest (ROI) was delineated on the R2* map, and average tumour R2* value was calculated for each ROI. Histological specimens were evaluated for the presence of FF, the microvessel density (the average microvessel density and the ratio of peripheral to central microvessel density), and the grading of HIF-1α.

RESULTS

FF was identified in 47.6% (20/42) of IDCs. Average R2* value for IDC with FF (42.4±13.2 Hz) was significantly higher than that without FF (28.5±13.9 Hz) (P = 0.01). Spearman rank correlation suggested that the average R2* value correlated with the grade of HIF-1α and the ratio of peripheral to central microvessel density for IDCs (P < 0.001).

CONCLUSION

Quantification of tumour R2* using IDEAL is associated with the presence of FF and the overexpression of HIF-1α, and may therefore be useful in predicting hypoxia of breast carcinoma.

KEY POINTS

• R2* value obtained by IDEAL correlates with the overexpression of HIF-1α. • R2* value obtained by IDEAL is associated with fibrotic focus. • R2* quantification may be useful in predicting hypoxia of breast carcinoma.

Blood Oxygenation Level-dependent Magnetic Resonance Imaging of Breast Cancer: Correlation with Carbonic Anhydrase IX and Vascular Endothelial Growth Factor

Background:

Blood oxygenation level-dependent magnetic resonance imaging (BOLD-MRI) is a functional MRI technique which involves using the paramagnetic properties of deoxyhemoglobin to image the local tissue oxygen concentration. The purpose of this study was to investigate whether BOLD-MRI could evaluate hypoxia and angiogenesis of breast invasive ductal carcinoma (IDC).

Methods:

Ninety-eight female patients with IDC were retrospectively included in this research. All patients underwent breast BOLD-MRI at 3.0 T before surgery. R2* values of BOLD-MRI were measured. The expression of carbonic anhydrase IX (CA IX) and vascular endothelial growth factor (VEGF) was analyzed by immunohistochemistry. Spearman's correlation analysis was used to correlate R2* value with CA IX and VEGF levels.

Results:

Heterogeneous intensity on BOLD-MRI images was the main finding of IDCs. The mean R2* value was 52.8 ± 18.6 Hz. The R2* values in patients with axillary lymph node metastasis were significantly higher than the R2* values in patients without axillary lymph node metastasis (t = 2.882, P = 0.005). R2* values increased with CA IX level and positively correlated with the level of CA IX (r = 0.616, P < 0.001); however, R2* value had no significantly correlation with the level of VEGF (r = 0.110, P = 0.281).

Conclusion:

BOLD-MRI could noninvasively evaluate chronic hypoxia of IDC, but not angiogenesis.

Assessing Tumor Oxygenation for Predicting Outcome in Radiation Oncology: A Review of Studies Correlating Tumor Hypoxic Status and Outcome in the Preclinical and Clinical Settings

Tumor hypoxia is recognized as a limiting factor for the efficacy of radiotherapy, because it enhances tumor radioresistance. It is strongly suggested that assessing tumor oxygenation could help to predict the outcome of cancer patients undergoing radiation therapy. Strategies have also been developed to alleviate tumor hypoxia in order to radiosensitize tumors. In addition, oxygen mapping is critically needed for intensity modulated radiation therapy (IMRT), in which the most hypoxic regions require higher radiation doses and the most oxygenated regions require lower radiation doses. However, the assessment of tumor oxygenation is not yet included in day-to-day clinical practice. This is due to the lack of a method for the quantitative and non-invasive mapping of tumor oxygenation. To fully integrate tumor hypoxia parameters into effective improvements of the individually tailored radiation therapy protocols in cancer patients, methods allowing non-invasively repeated, safe, and robust mapping of changes in tissue oxygenation are required. In this review, non-invasive methods dedicated to assessing tumor oxygenation with the ultimate goal of predicting outcome in radiation oncology are presented, including positron emission tomography used with nitroimidazole tracers, magnetic resonance methods using endogenous contrasts (R₁ and R2*-based methods), and electron paramagnetic resonance oximetry; the goal is to highlight results of studies establishing correlations between tumor hypoxic status and patients’ outcome in the preclinical and clinical settings.

Estimation of T2* Relaxation Time of Breast Cancer: Correlation with Clinical, Imaging and Pathological Features

OBJECTIVE

The purpose of this study was to estimate the T2* relaxation time in breast cancer, and to evaluate the association between the T2* value with clinical-imaging-pathological features of breast cancer.

MATERIALS AND METHODS

Between January 2011 and July 2013, 107 consecutive women with 107 breast cancers underwent multi-echo T2*-weighted imaging on a 3T clinical magnetic resonance imaging system. The Student's t test and one-way analysis of variance were used to compare the T2* values of cancer for different groups, based on the clinical-imaging-pathological features. In addition, multiple linear regression analysis was performed to find independent predictive factors associated with the T2* values.

RESULTS

Of the 107 breast cancers, 92 were invasive and 15 were ductal carcinoma in situ (DCIS). The mean T2* value of invasive cancers was significantly longer than that of DCIS (p = 0.029). Signal intensity on T2-weighted imaging (T2WI) and histologic grade of invasive breast cancers showed significant correlation with T2* relaxation time in univariate and multivariate analysis. Breast cancer groups with higher signal intensity on T2WI showed longer T2* relaxation time (p = 0.005). Cancer groups with higher histologic grade showed longer T2* relaxation time (p = 0.017).

CONCLUSION

The T2* value is significantly longer in invasive cancer than in DCIS. In invasive cancers, T2* relaxation time is significantly longer in higher histologic grades and high signal intensity on T2WI. Based on these preliminary data, quantitative T2* mapping has the potential to be useful in the characterization of breast cancer.

Modulation of renal oxygenation and perfusion in rat kidney monitored by quantitative diffusion and blood oxygen level dependent magnetic resonance imaging on a clinical 1.5T platform

BACKGROUND

To investigate the combined use of intravoxel incoherent motion (IVIM) diffusion-weighted (DW) and blood oxygen level dependent (BOLD) magnetic resonance imaging (MRI) to assess rat renal function using a 1.5T clinical platform.

METHODS

Multiple b-value DW and BOLD MR images were acquired from adult rats using a parallel clinical coil arrangement, enabling quantitation of the apparent diffusion coefficient (ADC), IVIM-derived diffusion coefficient (D), pseudodiffusion coefficient (D*) and perfusion fraction (f), and the transverse relaxation time T2*, for whole kidney, renal cortex, and medulla. Following the acquisition of two baseline datasets to assess measurement repeatability, images were acquired following i.v. administration of hydralazine, furosemide, or angiotensin II for up to 40 min.

RESULTS

Excellent repeatability (CoV <10 %) was observed for ADC, D, f and T2* measured over the whole kidney. Hydralazine induced a marked and significant (p < 0.05) reduction in whole kidney ADC, D, and T2*, and a significant (p < 0.05) increase in D* and f. Furosemide significantly (p < 0.05) increased whole kidney ADC, D, and T2*. A more variable response to angiotensin II was determined, with a significant (p < 0.05) increase in medulla D* and significant (p < 0.05) reduction in whole kidney T2* established.

CONCLUSIONS

Multiparametric MRI, incorporating quantitation of IVIM DWI and BOLD biomarkers and performed on a clinical platform, can be used to monitor the acute effects of vascular and tubular modulating drugs on rat kidney function in vivo. Clinical adoption of such functional imaging biomarkers can potentially inform on treatment effects in patients with renal dysfunction.

Investigating the Vascular Phenotype of Subcutaneously and Orthotopically Propagated PC3 Prostate Cancer Xenografts Using Combined Carbogen Ultrasmall Superparamagnetic Iron Oxide MRI

The aim of this study was to use the combined carbogen-ultrasmall superparamagnetic iron oxide (CUSPIO) magnetic resonance imaging (MRI) method, which uses spatial correlations in independent susceptibility imaging biomarkers, to investigate and compare the impact of tumor size and anatomical site on vascular structure and function in vivo. Mice bearing either subcutaneous or orthotopic PC3 LN3 prostate tumors were imaged at 7 T, using a multi-gradient echo sequence to quantify R2, before and during carbogen (95% O2/5% CO2) breathing, and subsequently following intravenous administration of USPIO particles. Carbogen and USPIO-induced changes in R2 were used to inform on hemodynamic vasculature and fractional blood volume (%), respectively. The CUSPIO imaging data were also segmented to identify and assess five categories of R2 response. Small and large subcutaneous and orthotopic tumor cohorts all exhibited significantly (P < 0.05) different median baseline R2, ΔR2carbogen, and fractional blood volume. CUSPIO imaging showed that small subcutaneous tumors predominantly exhibited a negative ΔR2carbogen followed by a positive ΔR2USPIO, consistent with a well perfused tumor vasculature. Large subcutaneous tumors exhibited a small positive ΔR2carbogen and relatively low fractional blood volume, suggesting less functional vasculature. Orthotopic tumors revealed a large, positive ΔR2carbogen, consistent with vascular steal, and which may indicate that vascular function is more dependent on site of implantation than tumor size. Regions exhibiting significant ΔR2carbogen, but no significant ΔR2USPIO, suggesting transient vascular shutdown over the experimental timecourse, were apparent in all 3 cohorts. CUSPIO imaging can inform on efficient drug delivery via functional vasculature in vivo, and on appropriate tumor model selection for pre-clinical therapy trials.

Prognostic Significance of Transverse Relaxation Rate (R2*) in Blood Oxygenation Level-Dependent Magnetic Resonance Imaging in Patients with Invasive Breast Cancer

Objective

To examine the relationship between magnetic resonance transverse relaxation rate (R2*) and prognostic factors.

Materials and Methods

A total of 159 women with invasive ductal carcinomas (IDCs) underwent breast magnetic resonance imaging (MRI) including blood oxygenation level-dependent (BOLD) sequence at 3 T. The distribution of the measured R2* values were analyzed, and the correlation between R2* and various prognostic factors (age, tumor size, histologic grade, lymphovascular invasion, and axillary lymph node status, as well as expression of estrogen receptor, progesterone receptor, human epidermal growth factor receptor 2, p53, and Ki-67) were retrospectively assessed using patient medical records.

Results

The baseline R2* values of the IDCs were very heterogeneous with wide range among the patients. The mean R2* value was (32.8 ± 14.0) Hz with a median of 29.3 Hz (range 13.5–109.4 Hz). In multivariate analysis, older age was associated with decreased R2* value (P = 0.011) and IDCs with p53-overexpression showed higher R2* values than those without p53-overexpression group (P = 0.031). Other prognostic factors were not significantly correlated with R2* value.

Conclusion

In this study, R2* values were significantly correlated with age and expression of p53. Further studies are necessary to determine the prognostic value of BOLD-MRI.

Repeatability and sensitivity of T2* measurements in patients with head and neck squamous cell carcinoma at 3T

PURPOSE

To determine whether quantitation of T2* is sufficiently repeatable and sensitive to detect clinically relevant oxygenation levels in head and neck squamous cell carcinoma (HNSCC) at 3T.

MATERIALS AND METHODS

Ten patients with newly diagnosed locally advanced HNSCC underwent two magnetic resonance imaging (MRI) scans between 24 and 168 hours apart prior to chemoradiotherapy treatment. A multiple gradient echo sequence was used to calculate T2* maps. A quadratic function was used to model the blood transverse relaxation rate as a function of blood oxygenation. A set of published coefficients measured at 3T were incorporated to account for tissue hematocrit levels and used to plot the dependence of fractional blood oxygenation (Y) on T2* values, together with the corresponding repeatability range. Repeatability of T2* using Bland-Altman analysis, and calculation of limits of agreement (LoA), was used to assess the sensitivity, defined as the minimum difference in fractional blood oxygenation that can be confidently detected.

RESULTS

T2* LoA for 22 outlined tumor volumes were 13%. The T2* dependence of fractional blood oxygenation increases monotonically, resulting in increasing sensitivity of the method with increasing blood oxygenation. For fractional blood oxygenation values above 0.11, changes in T2* were sufficient to detect differences in blood oxygenation greater than 10% (Δ T2* > LoA for ΔY > 0.1).

CONCLUSION

Quantitation of T2* at 3T can detect clinically relevant changes in tumor oxygenation within a wide range of blood volumes and oxygen tensions, including levels reported in HNSCC. J. Magn. Reson. Imaging 2016;44:72-80.

Characterizing Heterogeneity within Head and Neck Lesions Using Cluster Analysis of Multi-Parametric MRI Data

PURPOSE

To describe a methodology, based on cluster analysis, to partition multi-parametric functional imaging data into groups (or clusters) of similar functional characteristics, with the aim of characterizing functional heterogeneity within head and neck tumour volumes. To evaluate the performance of the proposed approach on a set of longitudinal MRI data, analysing the evolution of the obtained sub-sets with treatment.

MATERIAL AND METHODS

The cluster analysis workflow was applied to a combination of dynamic contrast-enhanced and diffusion-weighted imaging MRI data from a cohort of squamous cell carcinoma of the head and neck patients. Cumulative distributions of voxels, containing pre and post-treatment data and including both primary tumours and lymph nodes, were partitioned into k clusters (k = 2, 3 or 4). Principal component analysis and cluster validation were employed to investigate data composition and to independently determine the optimal number of clusters. The evolution of the resulting sub-regions with induction chemotherapy treatment was assessed relative to the number of clusters.

RESULTS

The clustering algorithm was able to separate clusters which significantly reduced in voxel number following induction chemotherapy from clusters with a non-significant reduction. Partitioning with the optimal number of clusters (k = 4), determined with cluster validation, produced the best separation between reducing and non-reducing clusters.

CONCLUSION

The proposed methodology was able to identify tumour sub-regions with distinct functional properties, independently separating clusters which were affected differently by treatment. This work demonstrates that unsupervised cluster analysis, with no prior knowledge of the data, can be employed to provide a multi-parametric characterization of functional heterogeneity within tumour volumes.

Dynamic oxygen challenge evaluated by NMR T1 and T2*--insights into tumor oxygenation

There is intense interest in developing non-invasive prognostic biomarkers of tumor response to therapy, particularly with regard to hypoxia. It has been suggested that oxygen sensitive MRI, notably blood oxygen level-dependent (BOLD) and tissue oxygen level-dependent (TOLD) contrast, may provide relevant measurements. This study examined the feasibility of interleaved T2*- and T1-weighted oxygen sensitive MRI, as well as R2* and R1 maps, of rat tumors to assess the relative sensitivity to changes in oxygenation. Investigations used cohorts of Dunning prostate R3327-AT1 and R3327-HI tumors, which are reported to exhibit distinct size-dependent levels of hypoxia and response to hyperoxic gas breathing. Proton MRI R1 and R2* maps were obtained for tumors of anesthetized rats (isoflurane/air) at 4.7 T. Then, interleaved gradient echo T2*- and T1-weighted images were acquired during air breathing and a 10 min challenge with carbogen (95% O2 -5% CO2). Signals were stable during air breathing, and each type of tumor showed a distinct signal response to carbogen. T2* (BOLD) response preceded T1 (TOLD) responses, as expected. Smaller HI tumors (reported to be well oxygenated) showed the largest BOLD and TOLD responses. Larger AT1 tumors (reported to be hypoxic and resist modulation by gas breathing) showed the smallest response. There was a strong correlation between BOLD and TOLD signal responses, but ΔR2* and ΔR1 were only correlated for the HI tumors. The magnitude of BOLD and TOLD signal responses to carbogen breathing reflected expected hypoxic fractions and oxygen dynamics, suggesting potential value of this test as a prognostic biomarker of tumor hypoxia.

Prospective, longitudinal, multi-modal functional imaging for radical chemo-IMRT treatment of locally advanced head and neck cancer: the INSIGHT study

BACKGROUND

Radical chemo-radiotherapy (CRT) is an effective organ-sparing treatment option for patients with locally advanced head and neck cancer (LAHNC). Despite advances in treatment for LAHNC, a significant minority of these patients continue to fail to achieve complete response with standard CRT. By constructing a multi-modality functional imaging (FI) predictive biomarker for CRT outcome for patients with LAHNC we hope to be able to reliably identify those patients at high risk of failing standard CRT. Such a biomarker would in future enable CRT to be tailored to the specific biological characteristics of each patients' tumour, potentially leading to improved treatment outcomes.

METHODS/DESIGN

The INSIGHT study is a single-centre, prospective, longitudinal multi-modality imaging study using functional MRI and FDG-PET/CT for patients with LAHNC squamous cell carcinomas receiving radical CRT. Two cohorts of patients are being recruited: one treated with, and another treated without, induction chemotherapy. All patients receive radical intensity modulated radiotherapy with concurrent chemotherapy. Patients undergo functional imaging before, during and 3 months after completion of radiotherapy, as well as at the time of relapse, should that occur within the first two years after treatment. Serum samples are collected from patients at the same time points as the FI scans for analysis of a panel of serum markers of tumour hypoxia.

DISCUSSION

The primary aim of the INSIGHT study is to acquire a prospective multi-parametric longitudinal data set comprising functional MRI, FDG PET/CT, and serum biomarker data from patients with LAHNC undergoing primary radical CRT. This data set will be used to construct a predictive imaging biomarker for outcome after CRT for LAHNC. This predictive imaging biomarker will be used in future studies of functional imaging based treatment stratification for patients with LAHNC. Additional objectives are: defining the reproducibility of FI parameters; determining robust methods for defining FI based biological target volumes for IMRT planning; creation of a searchable database of functional imaging data for data mining. The INSIGHT study will help to establish the role of FI in the clinical management of LAHNC.

TRIAL REGISTRATION

NCRI H&N CSG ID 13860.

Feasibility of blood oxygenation level-dependent MRI at 3T in the characterization of hepatic tumors

PURPOSE

To determine the feasibility of using blood oxygenation level-dependent (BOLD) MRI in the characterization of hepatic tumors.

METHODS

A total of 100 patients with 43 hepatocellular carcinomas (HCCs), 36 metastases, 17 cholangiocarcinomas, and 23 hemangiomas underwent gadoxetic acid-enhanced and BOLD MRI at 3T. BOLD MRI was performed using a multiple fast-field echo sequence (TR/TE, 290/10-28; slice thickness 5 mm) to generate 20 T2*-weighted images. The T2* value of each tumor were calculated. On a color-coded T2* map, tumors were classified into five categories of high signal intensity (strong, moderate, rim, mild) and iso-intensity, which was correlated with the enhancement pattern on dynamic phases by two observers.

RESULTS

The mean T2* value (ms) of hemangiomas (97.3 ± 20.2) was the highest, followed by HCCs (48.4 ± 12.7), metastases (37.1 ± 10.5), and cholangiocarcinomas (36.6 ± 11.1). These values were significantly different (hemangioma vs. others tumors and HCC vs. metastasis or cholangiocarcinoma) (P ≤ 0.001). The agreement between the T2* color map and dynamic images was moderate for all tumors (k = 0.544), good for tumors >2.0 cm (k = 0.666), and fair for tumors ≤2.0 cm (k = 0.334). With the gadoxetic acid-enhanced MRI used as a reference, the sensitivities of BOLD MRI (T2* color map) for displaying hypervascularity of HCC (categories of 1-3) were 81.0 % (n = 34/42) and 78.6 % (n = 33/42) for both observers.

CONCLUSION

Liver BOLD MRI has a potential to predict the vascular pattern of hepatic tumors.

Functional MRI and CT biomarkers in oncology

Imaging biomarkers derived from MRI or CT describe functional properties of tumours and normal tissues. They are finding increasing numbers of applications in diagnosis, monitoring of response to treatment and assessment of progression or recurrence. Imaging biomarkers also provide scope for assessment of heterogeneity within and between lesions. A wide variety of functional parameters have been investigated for use as biomarkers in oncology. Some imaging techniques are used routinely in clinical applications while others are currently restricted to clinical trials or preclinical studies. Apparent diffusion coefficient, magnetization transfer ratio and native T1 relaxation time provide information about structure and organization of tissues. Vascular properties may be described using parameters derived from dynamic contrast-enhanced MRI, dynamic contrast-enhanced CT, transverse relaxation rate (R2*), vessel size index and relative blood volume, while magnetic resonance spectroscopy may be used to probe the metabolic profile of tumours. This review describes the mechanisms of contrast underpinning each technique and the technical requirements for robust and reproducible imaging. The current status of each biomarker is described in terms of its validation, qualification and clinical applications, followed by a discussion of the current limitations and future perspectives.

Transmembrane voltage potential of somatic cells controls oncogene-mediated tumorigenesis at long-range

The microenvironment is increasingly recognized as a crucial aspect of cancer. In contrast and complement to the field's focus on biochemical factors and extracellular matrix, we characterize a novel aspect of host:tumor interaction - endogenous bioelectric signals among non-excitable somatic cells. Extending prior work focused on the bioelectric state of cancer cells themselves, we show for the first time that the resting potentials of distant cells are critical for oncogene-dependent tumorigenesis. In the Xenopus laevis tadpole model, we used human oncogenes such as mutant KRAS to drive formation of tumor-like structures that exhibited overproliferation, increased nuclear size, hypoxia, acidity, and leukocyte attraction. Remarkably, misexpression of hyperpolarizing ion channels at distant sites within the tadpole significantly reduced the incidence of these tumors. The suppression of tumorigenesis could also be achieved by hyperpolarization using native CLIC1 chloride channels, suggesting a treatment modality not requiring gene therapy. Using a dominant negative approach, we implicate HDAC1 as the mechanism by which resting potential changes affect downstream cell behaviors. Based on published data on the voltage-mediated changes of butyrate flux through the SLC5A8 transporter, we present a model linking resting potentials of host cells to the ability of oncogenes to initiate tumorigenesis. Antibiotic data suggest that the relevant butyrate is generated by a native bacterial species, identifying a novel link between the microbiome and cancer that is mediated by alterations in bioelectric signaling.

Effectiveness of additional diagnostic parameters in magnetic resonance mammography: a comparative study with the BI-RADS classification and scoring system

OBJECTIVE

This study aims to evaluate the strength of magnetic resonance (MR) lesion descriptors for malignancy and to determine the effectiveness of a scoring system that combines BI-RADS parameters with additional criteria.

MATERIALS AND METHODS

Three hundred thirty-nine histopathologically proven lesions that had undergone MR imaging were analyzed retrospectively. Based on the Fischer scoring system, an optimal cutoff value was calculated for combined parameters. Sensitivity, specificity, positive predictive value, and negative predictive value were calculated for all lesions with MR BI-RADS classification without using additional parameters. Finally, the results of the scoring system and MR BI-RADS classification were compared.

RESULTS

The optimal cutoff value according to the total score was calculated as 5. The sensitivity and the specificity of BI-RADS classification were calculated to be 94.20% and 56.12%, respectively. The scoring system using a cutoff value of 5 resulted in a little loss of sensitivity (89.86%) but resulted in a reasonable increase in the specificity (88.49%).

CONCLUSIONS

Additional parameters can improve the specificity of MR imaging. T2-weighted signal features, adjacent vessel sign, unilateral-focal edema, and hook sign were considered as effective parameters.

Intrinsic susceptibility MRI identifies tumors with ALKF1174L mutation in genetically-engineered murine models of high-risk neuroblastoma

The early identification of children presenting ALK(F1174L)-mutated neuroblastoma, which are associated with resistance to the promising ALK inhibitor crizotinib and a marked poorer prognosis, has become a clinical priority. In comparing the radiology of the novel Th-ALK(F1174L)/Th-MYCN and the well-established Th-MYCN genetically-engineered murine models of neuroblastoma using MRI, we have identified a marked ALK(F1174L)-driven vascular phenotype. We demonstrate that quantitation of the transverse relaxation rate R2* (s(-1)) using intrinsic susceptibility-MRI under baseline conditions and during hyperoxia, can robustly discriminate this differential vascular phenotype, and identify MYCN-driven tumors harboring the ALK(F1174L) mutation with high specificity and selectivity. Intrinsic susceptibility-MRI could thus potentially provide a non-invasive and clinically-exploitable method to help identifying children with MYCN-driven neuroblastoma harboring the ALK(F1174L) mutation at the time of diagnosis.

Estimation of rat mammary tumor volume using caliper and ultrasonography measurements

Mammary tumors similar to those observed in women can be induced in rats by intraperitoneal administration of N-methyl-N-nitrosourea. Determining tumor volume is a useful and quantitative way to monitor tumor progression. In this study, the authors measured dimensions of rat mammary tumors using a caliper and using real-time compound B-mode ultrasonography. They then used different formulas to calculate tumor volume from these tumor measurements and compared the calculated tumor volumes with the real tumor volume to identify the formulas that gave the most accurate volume calculations. They found that caliper and ultrasonography measurements were significantly correlated but that tumor volumes calculated using different formulas varied substantially. Mammary tumors seemed to take on an oblate spheroid geometry. The most accurate volume calculations were obtained using the formula V = (W(2) × L)/2 for caliper measurements and the formula V = (4/3) × π × (L/2) × (L/2) × (D/2) for ultrasonography measurements, where V is tumor volume, W is tumor width, L is tumor length and D is tumor depth.

Evaluation and immunohistochemical qualification of carbogen-induced ΔR₂ as a noninvasive imaging biomarker of improved tumor oxygenation

PURPOSE

To evaluate and histologically qualify carbogen-induced ΔR2 as a noninvasive magnetic resonance imaging biomarker of improved tumor oxygenation using a double 2-nitroimidazole hypoxia marker approach.

METHODS AND MATERIALS

Multigradient echo images were acquired from mice bearing GH3 prolactinomas, preadministered with the hypoxia marker CCI-103F, to quantify tumor R2 during air breathing. With the mouse remaining positioned within the magnet bore, the gas supply was switched to carbogen (95% O2, 5% CO2), during which a second hypoxia marker, pimonidazole, was administered via an intraperitoneal line, and an additional set of identical multigradient echo images acquired to quantify any changes in tumor R2. Hypoxic fraction was quantified histologically using immunofluorescence detection of CCI-103F and pimonidazole adduct formation from the same whole tumor section. Carbogen-induced changes in tumor pO2 were further validated using the Oxylite fiberoptic probe.

RESULTS

Carbogen challenge significantly reduced mean tumor R2 from 116 ± 13 s(-1) to 97 ± 9 s(-1) (P<.05). This was associated with a significantly lower pimonidazole adduct area (2.3 ± 1%), compared with CCI-103F (6.3 ± 2%) (P<.05). A significant correlation was observed between ΔR2 and Δhypoxic fraction (r=0.55, P<.01). Mean tumor pO2 during carbogen breathing significantly increased from 6.3 ± 2.2 mm Hg to 36.0 ± 7.5 mm Hg (P<.01).

CONCLUSIONS

The combined use of intrinsic susceptibility magnetic resonance imaging with a double hypoxia marker approach corroborates carbogen-induced ΔR2 as a noninvasive imaging biomarker of increased tumor oxygenation.

Exploring ΔR(2) * and ΔR(1) as imaging biomarkers of tumor oxygenation

PURPOSE

To investigate the combined use of hyperoxia-inducedΔR(2) * and ΔR(1) as a noninvasive imaging biomarker of tumor hypoxia.

MATERIALS AND METHODS

MRI was performed on rat GH3 prolactinomas (n = 6) and human PC3 prostate xenografts (n = 6) propagated in nude mice. multiple gradient echo and inversion recovery truefisp images were acquired from identical transverse slices to quantify tumor R(2) * and R(1)before and during carbogen (95% O2 /5% CO2 ) challenge, and correlates of ΔR(2) * and ΔR(1) assessed.

RESULTS

Mean baseline R(2) * and R(1) were 119 ± 7 s(-1) and 0.6 ± 0.03 s(-1) for GH3 prolactinomas and 77 ± 12 s(-1) and 0.7 ± 0.02 s(-1) for PC3 xenografts, respectively. During carbogen breathing, mean ΔR(2) * and ΔR(1) were -20 ± 8 s(-1) and 0.08 ± 0.03 s(-1) for GH3 and -0.5 ± 1 s(-1) and 0.2 ± 0.08 s(-1) for the PC3 tumors, respectively. A pronounced relationship betweenΔR(2) * and ΔR(1) was revealed.

CONCLUSION

Considering the blood oxygen-hemoglobin dissociation curve, fast R2 * suggested that GH3 prolactinomas were more hypoxic at baseline, and their carbogen response dominated by increased hemoglobin oxygenation, evidenced by highly negative ΔR(2) *. PC3 tumors were less hypoxic at baseline, and their response to carbogen dominated by increased dissolved oxygen, evidenced by highly positive ΔR(1) . Because the two biomarkers are sensitive to different oxygenation ranges, the combination of ΔR(2) * and ΔR(1) may better characterize tumor hypoxia than each alone.

BOLD-MRI of breast invasive ductal carcinoma: correlation of R2* value and the expression of HIF-1α

OBJECTIVE

To explore the reliability and feasibility of blood oxygenation level-dependent-based functional magnetic resonance imaging (BOLD-fMRI) to depict hypoxia in breast invasive ductal carcinoma.

METHODS

A total of 103 women with 104 invasive ductal carcinomas (IDCs) underwent breast BOLD-fMRI at 3.0 T. Histological specimens were analysed for tumour size, grade, axillary lymph nodes and expression of oestrogen receptors, progesterone receptors, human epidermal growth factor receptor 2, p53, Ki-67 and hypoxia inducible factor 1α (HIF-1α). The distribution and reliability of R2* were analysed. Correlations of the R2* value with the prognostic factors and HIF-1α were respectively analysed.

RESULTS

The R2* map of IDC demonstrated a relatively heterogeneous signal. The mean R2* value was (53.4 ± 18.2) Hz. The Shapiro-Wilk test (W = 0.971, P = 0.020) suggested that the sample did not follow a normal distribution. The inter-rater and intrarater correlation coefficient was 0.967 and 0.959, respectively. The R2* values of IDCs were significantly lower in patients without axillary lymph nodes metastasis. The R2* value had a weak correlation with Ki67 expression (r = 0.208, P = 0.038). The mean R2* value correlated moderately with the level of HIF-1α (r = 0.516, P = 0.000).

CONCLUSION

BOLD-fMRI is a simple and non-invasive technique that yields hypoxia information on breast invasive ductal carcinomas.

Correlations of noninvasive BOLD and TOLD MRI with pO2 and relevance to tumor radiation response

PURPOSE

To examine the potential use of blood oxygenation level dependent (BOLD) and tissue oxygenation level dependent (TOLD) contrast MRI to assess tumor oxygenation and predict radiation response.

METHODS

BOLD and TOLD MRI were performed on Dunning R3327-AT1 rat prostate tumors during hyperoxic gas breathing challenge at 4.7 T. Animals were divided into two groups. In Group 1 (n = 9), subsequent (19) F MRI based on spin lattice relaxation of hexafluorobenzene reporter molecule provided quantitative oximetry for comparison. For Group 2 rats (n = 13) growth delay following a single dose of 30 Gy was compared with preirradiation BOLD and TOLD assessments.

RESULTS

Oxygen (100%O2 ) and carbogen (95%O2 /5%CO2 ) challenge elicited similar BOLD, TOLD and pO2 responses. Strong correlations were observed between BOLD or R2* response and quantitative (19) F pO2 measurements. TOLD response showed a general trend with weaker correlation. Irradiation caused a significant tumor growth delay and tumors with larger changes in TOLD and R1 values upon oxygen breathing exhibited significantly increased tumor growth delay.

CONCLUSION

These results provide further insight into the relationships between oxygen sensitive (BOLD/TOLD) MRI and tumor pO2 . Moreover, a larger increase in R1 response to hyperoxic gas challenge coincided with greater tumor growth delay following irradiation.

Magnetic resonance imaging features in triple-negative breast cancer: comparison with luminal and HER2-overexpressing tumors

BACKGROUND

It has been ascertained that triple-negative (TN) breast cancer is characterized by an aggressive clinical course and a poor prognosis. The purpose of our study was to compare the magnetic resonance imaging (MRI) features of the 3 major different breast cancer subtypes (TN, luminal, and human epidermal growth factor receptor 2 [HER2]-overexpressing) and to suggest the criteria that might predict TN phenotype.

MATERIALS AND METHODS

From October 2007 to April 2011, we studied 77 patients with histologically confirmed TN breast cancer who underwent breast MRI. We randomly included 148 patients with non-TN breast cancer (110 luminal and 38 HER-overexpressing) as a control group. We evaluated the clinicopathologic data, the MRI morphologic and kinetic features, the signal intensity on T2-weighted images, and the apparent diffusion coefficient (ADC).

RESULTS

Our results confirmed that TN tumors are more aggressive, are usually diagnosed at a younger age compared with the other study groups, and show benign morphologic features with MRI. Backward stepwise logistic regression identified some parameters as independent predictors of TN-type lesions: age, size, shape, presence of edema, and infiltrative characteristics. The receiver operating characteristic (ROC) curve, built with 4 of 5 these factors as criteria to predict TN status, showed a 0.664 area under the curve (AUC) value (sensitivity 58.4%, specificity 73.2%). The inclusion of the fifth criterion showed a 0.699 AUC value (sensitivity, 49.4%; specificity, 89.4%).

CONCLUSION

We identified the clinicoradiologic parameters that are independent predictors of TN breast lesions, which might be helpful for earlier prediction of the TN status of a breast lesion.

Oxygenation in cervical cancer and normal uterine cervix assessed using blood oxygenation level-dependent (BOLD) MRI at 3T

Hypoxia is reported to be a biomarker for poor prognosis in cervical cancer. However, a practical noninvasive method is needed for the routine clinical evaluation of tumor hypoxia. This study examined the potential use of blood oxygenation level-dependent (BOLD) contrast MRI as a noninvasive technique to assess tumor vascular oxygenation at 3T. Following Institutional Review Board-approved informed consent and in compliance with the Health Insurance Portability and Accountability Act, successful results were achieved in nine patients with locally advanced cervical cancer [International Federation of Gynecology and Obstetrics (FIGO) stage IIA to IVA] and three normal volunteers. In the first four patients, dynamic T₂*-weighted MRI was performed in the transaxial plane using a multi-shot echo planar imaging sequence whilst patients breathed room air followed by oxygen (15 dm³/min). Later, a multi-echo gradient echo examination was added to provide quantitative R₂* measurements. The baseline T₂*-weighted signal intensity was quite stable, but increased to various extents in tumors on initiation of oxygen breathing. The signal in normal uterus increased significantly, whereas that in the iliacus muscle did not change. R₂* responded significantly in healthy uterus, cervix and eight cervical tumors. This preliminary study demonstrates that BOLD MRI of cervical cancer at 3T is feasible. However, more patients must be evaluated and followed clinically before any prognostic value can be determined.

Reproducibility and biological basis of in vivo T(2)* magnetic resonance imaging of liver metastasis of colorectal cancer

In this study, the reproducibility of T2* MR imaging in colorectal liver metastases was assessed and T2* values were correlated with the expression of the hypoxia-related markers GLUT-1 and CA-IX as well as the relative vascular area, and the vessel density in resected tumors. The reproducibility of T2* was analyzed in 18 patients with in total 22 colorectal liver metastases using the Bland and Altman method for the 16th, 50th, and 84th percentile values. Immunohistochemical staining was performed on 17 resected tumors obtained from 16 patients. The median T2* of all liver metastases was 25.0 ± 5.6 ms vs. 23.0 ± 4.1 ms (median ± st.dev.) in normal liver. The coefficient of repeatability was 11.2 ms and the limits of agreement were -13.2 ms and 9.1 ms for median T2* values. On average, T2* showed fair reproducibility. No correlations between T2* values, hypoxia- and vascularity-related markers were observed.