Monitoring Cell Death in Regorafenib-Treated Experimental Colon Carcinomas Using Annexin-Based Optical Fluorescence Imaging Validated by Perfusion MRI

Objective To investigate annexin-based optical fluorescence imaging (OI) for monitoring regorafenib-induced early cell death in experimental colon carcinomas in rats, validated by perfusion MRI and multiparametric immunohistochemistry. Materials and Methods Subcutaneous human colon carcinomas (HT-29) in athymic rats (n = 16) were imaged before and after a one-week therapy with regorafenib (n = 8) or placebo (n = 8) using annexin-based OI and perfusion MRI at 3 Tesla. Optical signal-to-noise ratio (SNR) and MRI tumor perfusion parameters (plasma flow PF, mL/100mL/min;plasma volume PV,%) were assessed. On day 7, tumors underwent immunohistochemical analysis for tumor cell apoptosis (TUNEL),proliferation (Ki-67),and microvascular density (CD31). Results Apoptosis-targeted OI demonstrated a tumor-specific probe accumulation with a significant increase of tumor SNR under therapy (mean Delta +7.78 +/- 2.95, control: -0.80 +/- 2.48, p = 0.021). MRI detected a significant reduction of tumor perfusion in the therapy group (mean Delta PF -8.17 +/- 2.32 mL/100 mL/min, control -0.11 +/- 3.36 mL/100 mL/min, p = 0.036). Immunohistochemistry showed significantly more apoptosis (TUNEL;11392 +/- 1486 vs. 2921 +/- 334, p = 0.001),significantly less proliferation (Ki-67;1754 +/- 184 vs. 2883 +/- 323, p = 0.012),and significantly lower microvascular density (CD31;107 +/- 10 vs. 182 +/- 22, p = 0.006) in the therapy group. Conclusions Annexin-based OI allowed for the non-invasive monitoring of regorafenib-induced early cell death in experimental colon carcinomas, validated by perfusion MRI and multiparametric immunohistochemistry

Wavelet-Based Angiographic Reconstruction of Computed Tomography Perfusion Data Diagnostic Value in Cerebral Venous Sinus Thrombosis

Objective: The aim of this study was to test the diagnostic value of wavelet-based angiographic reconstruction of CT perfusion data (waveletCTA) to detect cerebral venous sinus thrombosis (CVST) in patients who underwent whole-brain CT perfusion imaging (WB-CTP). Materials and Methods: Datasets were retrospectively selected from an initial cohort of 2863 consecutive patients who had undergone multiparametric CT including WB-CTP. WaveletCTA was reconstructed from WB-CTP: the angiographic signal was generated by voxel-based wavelet transform of time attenuation curves (TACs) from WB-CTP raw data. In a preliminary clinical evaluation, waveletCTA was analyzed by 2 readers with respect to presence and location of CVST. Venous CT and MR angiography (venCTA/venMRA) served as reference standard. Diagnostic confidence for CVST detection and the quality of depiction for venous sections were evaluated on 5-point Likert scales. Thrombus extent was assessed by length measurements. The mean CT attenuation and waveletCTA signal of the thrombus and of flowing blood were quantified. Results: Sixteen patients were included: 10 patients with venCTA-/venMRAconfirmed CVST and 6 patients with arterial single-phase CT angiography (artCTA)-suspected but follow-up-excluded CVST. The reconstruction of waveletCTA was successful in all patients. Among the patients with confirmed CVST, waveletCTA correctly demonstrated presence, location, and extent of the thrombosis in 10/10 cases. In 6 patients with artCTA-suspected but follow-up-excluded CVST, waveletCTA correctly ruled out CVST in 5 patients. Reading waveletCTA in addition to artCTA significantly increased the diagnostic confidence concerning CVST compared with reading artCTA alone (4.4 vs 3.6, P = 0.044). The mean flowing blood-to-thrombus ratio was highest in waveletCTA, followed by venCTA and artCTA (146.2 vs 5.9 vs 2.6, each with P < 0.001). In waveletCTA, the venous sections were depicted better compared with artCTA (4.2 vs 2.6, P < 0.001), and equally well compared with venCTA/venMRA (4.2 vs 4.1, P = 0.374). Conclusions: WaveletCTA was technically feasible in CVST patients and reliably identified CVST in a preliminary clinical evaluation. WaveletCTA might serve as an additional reconstruction to rule out or incidentally detect CVST in patients who undergo WB-CTP

Correlation of Perfusion MRI and F-18-FDG PET Imaging Biomarkers for Monitoring Regorafenib Therapy in Experimental Colon Carcinomas with Immunohistochemical Validation

Objectives To investigate a multimodal, multiparametric perfusion MRI/F-18-fluoro-deoxyglucose (F-18-FDG)-PET imaging protocol for monitoring regorafenib therapy effects on experimental colorectal adenocarcinomas in rats with immunohistochemical validation. Materials and Methods Human colorectal adenocarcinoma xenografts (HT-29) were implanted subcutaneously in n = 17 (n = 10 therapy group;n = 7 control group) female athymic nude rats (Hsd: RH-Foxn1(mu)). Animals were imaged at baseline and after a one-week daily treatment protocol with regorafenib (10 mg/kg bodyweight) using a multimodal, multiparametric perfusion MRI/F-18-FDG-PET imaging protocol. In perfusion MRI, quantitative parameters of plasma flow (PF, mL/100 mL/min), plasma volume (PV,%) and endothelial permeability-surface area product (PS, mL/100 mL/min) were calculated. In F-18-FDG-PET, tumor-to-background-ratio (TTB) was calculated. Perfusion MRI parameters were correlated with TTB and immunohistochemical assessments of tumor microvascular density (CD-31) and cell proliferation (Ki-67). Results Regorafenib significantly (p<0.01) suppressed PF (81.1 +/- 7.5 to 50.6 +/- 16.0 mL/100mL/min), PV (12.1 +/- 3.6 to 7.5 +/- 1.6%) and PS (13.6 +/- 3.2 to 7.9 +/- 2.3 mL/100mL/min) as well as TTB (3.4 +/- 0.6 to 1.9 +/- 1.1) between baseline and day 7. Immunohistochemistry revealed significantly (p<0.03) lower tumor microvascular density (CD-31, 7.0 +/- 2.4 vs. 16.1 +/- 5.9) and tumor cell proliferation (Ki-67, 434.0 +/- 62.9 vs. 663.0 +/- 98.3) in the therapy group. Perfusion MRI parameters Delta PF, Delta PV and Delta PS showed strong and significant (r = 0.67-0.78;p<0.01) correlations to the PET parameter Delta TTB and significant correlations (r = 0.57-0.67;p<0.03) to immunohistochemical Ki-67 as well as to CD-31-stainings (r = 0.49-0.55;p<0.05). Conclusions A multimodal, multiparametric perfusion MRI/PET imaging protocol allowed for non-invasive monitoring of regorafenib therapy effects on experimental colorectal adenocarcinomas in vivo with significant correlations between perfusion MRI parameters and F-18-FDG-PET validated by immunohistochemistry

The transitional phase of multiple sclerosis: Characterization and conceptual framework

The conversion of relapsing-remitting multiple sclerosis (RRMS) to secondary progressive MS (SPMS) cannot be defined by a sharp threshold determined by event-based measures, but rather represents a gradual process. In consequence, there may exist a transitional phase between RRMS and clearly established SPMS. So far, transitional MS has been poorly characterized in terms of patient properties, course of disease and therapeutic interventions that may delay conversion to SPMS. Furthermore, the pathogenesis of transitional MS is incompletely understood, and no definitive imaging or laboratory test informs when exactly a patient has entered the transitional MS phase. Here we review the current knowledge and evidence characterizing the transitional phase of MS and propose potential designs and criteria for a prospective clinical study in patients with transitional MS

Improved fat water separation with water selective inversion pulse for inversion recovery imaging in cardiac MRI

Purpose: To develop an improved chemical shift-based water-fat separation sequence using a water-selective inversion pulse for inversion recovery 3D contrast-enhanced cardiac magnetic resonance imaging (MRI). Materials and Methods: In inversion recovery sequences the fat signal is substantially reduced due to the application of a nonselective inversion pulse. Therefore, for simultaneous visualization of water, fat, and myocardial enhancement in inversion recovery-based sequences such as late gadolinium enhancement imaging, two separate scans are used. To overcome this, the nonselective inversion pulse is replaced with a water-selective inversion pulse. Imaging was performed in phantoms, nine healthy subjects, and nine patients with suspected arrhythmogenic right ventricular cardiomyopathy plus one patient for tumor/mass imaging. In patients, images with conventional turbo-spin echo (TSE) with and without fat saturation were acquired prior to contrast injection for fat assessment. Subjective image scores (1 = poor, 4 = excellent) were used for image assessment. Results: Phantom experiments showed a fat signal-to-noise ratio (SNR) increase between 1.7 to 5.9 times for inversion times of 150 and 300 msec, respectively. The water-selective inversion pulse retains the fat signal in contrast-enhanced cardiac MR, allowing improved visualization of fat in the water-fat separated images of healthy subjects with a score of 3.7 ± 0.6. Patient images acquired with the proposed sequence were scored higher when compared with a TSE sequence (3.5 ± 0.7 vs. 2.2 ± 0.5, P < 0.05). Conclusion: The water-selective inversion pulse retains the fat signal in inversion recovery-based contrast-enhanced cardiac MR, allowing simultaneous visualization of water and fat. J. Magn. Reson. Imaging 2013;37:484–490

Correlation of perfusion MRI and 18F-FDG PET imaging biomarkers for monitoring regorafenib therapy in experimental colon carcinomas with immunohistochemical validation.

OBJECTIVES:To investigate a multimodal, multiparametric perfusion MRI / 18F-fluoro-deoxyglucose-(18F-FDG)-PET imaging protocol for monitoring regorafenib therapy effects on experimental colorectal adenocarcinomas in rats with immunohistochemical validation. MATERIALS AND METHODS:Human colorectal adenocarcinoma xenografts (HT-29) were implanted subcutaneously in n = 17 (n = 10 therapy group; n = 7 control group) female athymic nude rats (Hsd:RH-Foxn1rnu). Animals were imaged at baseline and after a one-week daily treatment protocol with regorafenib (10 mg/kg bodyweight) using a multimodal, multiparametric perfusion MRI/18F-FDG-PET imaging protocol. In perfusion MRI, quantitative parameters of plasma flow (PF, mL/100 mL/min), plasma volume (PV, %) and endothelial permeability-surface area product (PS, mL/100 mL/min) were calculated. In 18F-FDG-PET, tumor-to-background-ratio (TTB) was calculated. Perfusion MRI parameters were correlated with TTB and immunohistochemical assessments of tumor microvascular density (CD-31) and cell proliferation (Ki-67). RESULTS:Regorafenib significantly (p<0.01) suppressed PF (81.1±7.5 to 50.6±16.0 mL/100mL/min), PV (12.1±3.6 to 7.5±1.6%) and PS (13.6±3.2 to 7.9±2.3 mL/100mL/min) as well as TTB (3.4±0.6 to 1.9±1.1) between baseline and day 7. Immunohistochemistry revealed significantly (p<0.03) lower tumor microvascular density (CD-31, 7.0±2.4 vs. 16.1±5.9) and tumor cell proliferation (Ki-67, 434.0 ± 62.9 vs. 663.0 ± 98.3) in the therapy group. Perfusion MRI parameters ΔPF, ΔPV and ΔPS showed strong and significant (r = 0.67-0.78; p<0.01) correlations to the PET parameter ΔTTB and significant correlations (r = 0.57-0.67; p<0.03) to immunohistochemical Ki-67 as well as to CD-31-stainings (r = 0.49-0.55; p<0.05). CONCLUSIONS:A multimodal, multiparametric perfusion MRI/PET imaging protocol allowed for non-invasive monitoring of regorafenib therapy effects on experimental colorectal adenocarcinomas in vivo with significant correlations between perfusion MRI parameters and 18F-FDG-PET validated by immunohistochemistry

Representative immunohistochemical stainings.

<p>Tumor cell apoptosis (TUNEL, A and B), tumor microvascular density (CD31, C and D), and tumor cell proliferation (Ki-67, E and F) in the control (left column; A, C, and E) and the therapy group (right column; B, D, and F). Note the significantly higher apoptosis rate (B vs. A) as well as the significantly lower microvascular density (D vs. C) and proliferation (F vs. E) in the therapy group.</p

Individual OI and MR perfusion values at baseline and follow-up (therapy group).

<p>^abaseline</p><p>^bfollow-up; SE = standard error</p><p>*p < 0.05 (follow-up vs. baseline)</p><p>Note the significant increase of apoptosis-targeted OI signal and the significant plasma flow (PF) reduction in the therapy group (p < 0.05).</p