Tumour T1 changes in vivo are highly predictive of response to chemotherapy and reflect the number of viable tumour cells – a preclinical MR study in mice

BACKGROUND: Effective chemotherapy rapidly reduces the spin–lattice relaxation of water protons (T(1)) in solid tumours and this change (ΔT(1)) often precedes and strongly correlates with the eventual change in tumour volume (TVol). To understand the biological nature of ΔT(1), we have performed studies in vivo and ex vivo with the allosteric mTOR inhibitor, everolimus. METHODS: Mice bearing RIF-1 tumours were studied by magnetic resonance imaging (MRI) to determine TVol and T(1), and MR spectroscopy (MRS) to determine levels of the proliferation marker choline and levels of lipid apoptosis markers, prior to and 5 days (endpoint) after daily treatment with vehicle or everolimus (10 mg/kg). At the endpoint, tumours were ablated and an entire section analysed for cellular and necrotic quantification and staining for the proliferation antigen Ki67 and cleaved-caspase-3 as a measure of apoptosis. The number of blood-vessels (BV) was evaluated by CD31 staining. Mice bearing B16/BL6 melanoma tumours were studied by MRI to determine T(1) under similar everolimus treatment. At the endpoint, cell bioluminescence of the tumours was measured ex vivo. RESULTS: Everolimus blocked RIF-1 tumour growth and significantly reduced tumour T(1) and total choline (Cho) levels, and increased polyunsaturated fatty-acids which are markers of apoptosis. Immunohistochemistry showed that everolimus reduced the %Ki67(+) cells but did not affect caspase-3 apoptosis, necrosis, BV-number or cell density. The change in T(1) (ΔT(1)) correlated strongly with the changes in TVol and Cho and %Ki67(+). In B16/BL6 tumours, everolimus also decreased T(1) and this correlated with cell bioluminescence; another marker of cell viability. Receiver-operating-characteristic curves (ROC) for everolimus on RIF-1 tumours showed that ΔT(1) had very high levels of sensitivity and specificity (ROC(AUC) = 0.84) and this was confirmed for the cytotoxic patupilone in the same tumour model (ROC(AUC) = 0.97). CONCLUSION: These studies suggest that ΔT(1) is not a measure of cell density but reflects the decreased number of remaining viable and proliferating tumour cells due to perhaps cell and tissue destruction releasing proteins and/or metals that cause T(1) relaxation. ΔT(1) is a highly sensitive and specific predictor of response. This MRI method provides the opportunity to stratify a patient population during tumour therapy in the clinic

Physicochemical and MRI characterization of Gd3+-loaded polyamidoamine and hyperbranched dendrimers

Generation 4 polyamidoamine (PAMAM) and, for the first time, hyperbranched poly(ethylene imine) or polyglycerol dendrimers have been loaded with Gd3+ chelates, and the macromolecular adducts have been studied in vitro and in vivo with regard to MRI contrast agent applications. The Gd3+ chelator was either a tetraazatetracarboxylate DOTA-pBn4− or a tetraazatricarboxylate monoamide DO3A-MA3− unit. The water exchange rate was determined from a 17O NMR and 1H Nuclear Magnetic Relaxation Dispersion study for the corresponding monomer analogues [Gd(DO3A-AEM)(H2O)] and [Gd(DOTA-pBn-NH2)(H2O)]− (k ex 298 =3.4 and 6.6×106s−1, respectively), where H3DO3A-AEM is {4-[(2-acetylaminoethylcarbamoyl)methyl]-7,10-bis(carboxymethyl-1,4,7,10-tetraazacyclododec-1-yl)}-acetic acid and H4DOTA-pBn-NH2 is 2-(4-aminobenzyl)-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid. For the macromolecular complexes, variable-field proton relaxivities have been measured and analyzed in terms of local and global motional dynamics by using the Lipari-Szabo approach. At frequencies below 100MHz, the proton relaxivities are twice as high for the dendrimers loaded with the negatively charged Gd(DOTA-pBn)− in comparison with the analogous molecule bearing the neutral Gd(DO3A-MA). We explained this difference by the different rotational dynamics: the much slower motion of Gd(DOTA-pBn)−-loaded dendrimers is likely related to the negative charge of the chelate which creates more rigidity and increases the overall size of the macromolecule compared with dendrimers loaded with the neutral Gd(DO3A-MA). Attachment of poly(ethylene glycol) chains to the dendrimers does not influence relaxivity. Both hyperbranched structures were found to be as good scaffolds as regular PAMAM dendrimers in terms of the proton relaxivity of the Gd3+ complexes. The in vivo MRI studies on tumor-bearing mice at 4.7T proved that all dendrimeric complexes are suitable for angiography and for the study of vasculature parameters like blood volume and permeability of tumor vessel

The Non-Affected Muscle Volume Compensates for the Partial Loss of Strength after Injection of Botulinum Toxin A

Local botulinum toxin (BTX-A, Botox®) injection in overactive muscles is a standard treatment in patients with cerebral palsy. The effect is markedly reduced in children above the age of 6 to 7. One possible reason for this is the muscle volume affected by the drug. Nine patients (aged 11.5; 8.7–14.5 years) with cerebral palsy GMFCS I were treated with BTX-A for equinus gait at the gastrocnemii and soleus muscles. BTX-A was administered at one or two injection sites per muscle belly and with a maximum of 50 U per injection site. Physical examination, instrumented gait analysis, and musculoskeletal modelling were used to assess standard muscle parameters, kinematics, and kinetics during gait. Magnetic resonance imaging (MRI) was used to detect the affected muscle volume. All the measurements were carried out pre-, 6 weeks post-, and 12 weeks post-BTX-A. Between 9 and 15% of the muscle volume was affected by BTX-A. There was no effect on gait kinematics and kinetics after BTX-A injection, indicating that the overall kinetic demand placed on the plantar flexor muscles remained unchanged. BTX-A is an effective drug for inducing muscle weakness. However, in our patient cohort, the volume of the affected muscle section was limited, and the remaining non-affected parts were able to compensate for the weakened part of the muscle by taking over the kinetic demands associated with gait, thus not enabling a net functional effect in older children. We recommend distributing the drug over the whole muscle belly through multiple injection sites

Deep Anatomical Federated Network (Dafne): an open client/server framework for the continuous collaborative improvement of deep-learning-based medical image segmentation

Semantic segmentation is a crucial step to extract quantitative information from medical (and, specifically, radiological) images to aid the diagnostic process, clinical follow-up. and to generate biomarkers for clinical research. In recent years, machine learning algorithms have become the primary tool for this task. However, its real-world performance is heavily reliant on the comprehensiveness of training data. Dafne is the first decentralized, collaborative solution that implements continuously evolving deep learning models exploiting the collective knowledge of the users of the system. In the Dafne workflow, the result of each automated segmentation is refined by the user through an integrated interface, so that the new information is used to continuously expand the training pool via federated incremental learning. The models deployed through Dafne are able to improve their performance over time and to generalize to data types not seen in the training sets, thus becoming a viable and practical solution for real-life medical segmentation tasks.Comment: 10 pages (main body), 5 figures. Work partially presented at the 2021 RSNA conference and at the 2023 ISMRM conference In this new version: added author and change in the acknowledgmen

Preclinical Models for Neuroblastoma: Establishing a Baseline for Treatment

Preclinical models of pediatric cancers are essential for testing new chemotherapeutic combinations for clinical trials. The most widely used genetic model for preclinical testing of neuroblastoma is the TH-MYCN mouse. This neuroblastoma-prone mouse recapitulates many of the features of human neuroblastoma. Limitations of this model include the low frequency of bone marrow metastasis, the lack of information on whether the gene expression patterns in this system parallels human neuroblastomas, the relatively slow rate of tumor formation and variability in tumor penetrance on different genetic backgrounds. As an alternative, preclinical studies are frequently performed using human cell lines xenografted into immunocompromised mice, either as flank implant or orthtotopically. Drawbacks of this system include the use of cell lines that have been in culture for years, the inappropriate microenvironment of the flank or difficult, time consuming surgery for orthotopic transplants and the absence of an intact immune system.Here we characterize and optimize both systems to increase their utility for preclinical studies. We show that TH-MYCN mice develop tumors in the paraspinal ganglia, but not in the adrenal, with cellular and gene expression patterns similar to human NB. In addition, we present a new ultrasound guided, minimally invasive orthotopic xenograft method. This injection technique is rapid, provides accurate targeting of the injected cells and leads to efficient engraftment. We also demonstrate that tumors can be detected, monitored and quantified prior to visualization using ultrasound, MRI and bioluminescence. Finally we develop and test a "standard of care" chemotherapy regimen. This protocol, which is based on current treatments for neuroblastoma, provides a baseline for comparison of new therapeutic agents.The studies suggest that use of both the TH-NMYC model of neuroblastoma and the orthotopic xenograft model provide the optimal combination for testing new chemotherapies for this devastating childhood cancer

Open Science: Principles and Practices for Better Research

Material for journal club/seminar series at University of Basel

Quantitative dynamic contrast-enhanced MRI in tumor-bearing rats and mice with inversion recovery TrueFISP and two contrast agents at 4.7 T.

PURPOSE: To characterize tumor vascularization by dynamic-contrast enhanced (DCE) MRI using low and medium molecular weight paramagnetic contrast agents (CA) and inversion recovery (IR) true fast imaging with steady state precession (TrueFISP) in tumor-bearing rats and mice. MATERIALS AND METHODS: T(1) mapping was performed using IR True FISP in phantoms and in vivo at 4.7 T and validated with a segmented IR gradient-echo (IR GE) method. CA concentration in DCE-MRI studies in vivo was calculated from time-series T(1) maps using the CAs GdDOTA and P792 (low and medium molecular weight, respectively). Standard vascular input functions (VIFs) were measured in the jugular veins and were used for modeling of the CA kinetics with a two-compartment model. In rat breast tumors, vascular permeability (transfer constant K(trans)), fractional plasma volume v(p), and fractional leakage space v(e) were quantified and parametric maps were generated. RESULTS: The IR TrueFISP T(1) was slightly underestimated in phantoms and overestimated in vivo (10%) with respect to IR GE. VIFs showed only small interindividual variation. Mean K(trans) values were 0.062 +/- 0.017 min(-1) for GdDOTA and 0.015 +/- 0.005 min(-1) for P792 (N = 12). Mean v(e) and v(p) values were 0.15 +/- 0.04 (0.09 +/- 0.03) and 0.04 +/- 0.01 (0.03 +/- 0.01) for GdDOTA (P792). CONCLUSION: DCE-MRI with IR TrueFISP provided absolute values for K(trans), v(p), and v(e). Direct comparison between GdDOTA and P792 revealed significant differences in the VIF, model-fit-quality, permeability, leakage space, and plasma volume. The larger molecular weight CA P792 appears to be better for measuring tumor vascular parameters

Tumour T1 changes in vivo are highly predictive of response to chemotherapy and reflect the number of viable tumour cells

We have shown that chemotherapy rapidly reduces the spin-lattice relaxation of water protons (T1) in solid tumours and this change (T1) often precedes and strongly correlates with the eventual change in tumour volume [McSheehy et al 2010]. To understand the biological nature of T1, we have performed further studies in vivo and ex vivo with the allosteric mTOR inhibitor, everolimus. Mice bearing RIF-1 tumours were studied by magnetic resonance imaging (MRI) to determine TVol and T1, and MR spectroscopy (MRS) to determine levels of the proliferation marker choline and levels of lipid apoptosis markers, prior to and 5 days (endpoint) after daily treatment with vehicle or everolimus (10 mg/kg). At the endpoint, tumours were ablated and an entire section analyzed to permit full cellular and necrotic quantification as well staining for the proliferation antigen Ki67 and cleaved-caspase-3 as a measure of apoptosis. The number of blood-vessels per slice was evaluated by haematoxyline-eosin staining. Everolimus blocked tumour growth and significantly reduced the tumour T1 and total choline (Cho) levels, and increased polyunsaturated fattyacids (PUFA) which are markers of apoptosis. Histology and IHC showed that everolimus reduced the %Ki67+ cells and number of blood vessels but did not affect caspase-3 apoptosis, necrosis or cell density. The change in T1 (T1) strongly correlated with the TVol and also the Cho and the endpoint Ki67. In murine B16/BL6 melanoma tumours, everolimus also decreased T1 and this correlated with cell bioluminescence; another marker of cell viability. These studies suggest that T1 is not a measure of cell density but reflects the number of viable and proliferating tumour cells because cell and tissue destruction release factors that cause T1 relaxation. Receiver-operator-curves for everolimus on RIF-1 tumours showed that T1 had very high levels of sensitivity and specificity (AUC=0.91) and this was confirmed for the cytotoxic patupilone in the same tumour model (AUC=0.95)

Stability of real-time MR temperature mapping in healthy and diseased human liver

Purpose: To determine the stability and quality of MR temperature mapping using the proton resonance frequency (PRF) method in the liver of hepatic tumor patients.Material and Methods: The standard deviation of a series of temperature maps was determined in 30 patients (21 cirrhotic livers with carcinoma, 9 non-cirrhotic livers with metastasis or angioma) and in 5 volunteers at normal body temperature under free breathing. A respiratory-gated segmented EPI sequence (3 slices in 1 expiration phase) was performed with SENSE acceleration on a 1.5 T scanner. Motion corrupted images were identified by calculation of the cross-correlation coefficient and discarded.Results: A T 2* range of 10-33 ms was found with especially low values in advanced cirrhotic livers. The mean temperature standard deviation in patients was 2.3°C (range 1.5-5.0°C). The stability in healthy livers was slightly better than that in cirrhotic livers, and it was higher in the right than in the left liver. The gaiting failed in 4 % of the images when the respiratory cycle was irregular, leading to motion artifacts and errors in the temperature maps.Conclusion: The achieved temperature stability and image quality makes real-time quantitative monitoring of thermal ablation of liver tumors feasible on a clinical scanner