Magnetic resonance imaging in cancer research

Selective bioimaging of cancer cells and detection of HSA with indomethacin-based fluorescent probes

Two fluorescent probes were designed by connecting indomethacin to coumarin through different linkers. The introduction of indomethacin quenched the fluorescence of coumarin-based probes with apparent red-shifts in the absorption and emission maxima, probably due to the photoinduced electron transfer (PET) from the indomethacin to the fluorophore and the formation of folding conformation. The addition of human serum albumin (HSA) triggered about 40-fold fluorescence enhancements of ADC-IMC-2 and ADC-IMC-6 with 85 nm blue-shifts. The probe with longer spacer ADC-IMC-6 exhibited ratiometric fluorescent response toward HSA, and that with shorter linker showed "off-on" fluorescence response to HSA. However, insignificant spectral changes of the reference compounds (ADC-6 and ADC-2) initiated by HSA implied that indomethacin played critical role in the identification of HSA. The competitive assays and molecular docking results reveal that the indomethacin in ADC-IMC-6 could tightly combine at drug site I of HSA. Fluorescence bio-imaging experiments show that both probes could distinguish cancer cells from normal cells.

Dual-input tracer kinetic modeling of dynamic contrast-enhanced MRI in thoracic malignancies

Pulmonary perfusion with dynamic contrast‐enhanced (DCE‐) MRI is typically assessed using a single‐input tracer kinetic model. Preliminary studies based on perfusion CT are indicating that dual‐input perfusion modeling of lung tumors may be clinically valuable as lung tumors have a dual blood supply from the pulmonary and aortic system. This study aimed to investigate the feasibility of fitting dual‐input tracer kinetic models to DCE‐MRI datasets of thoracic malignancies, including malignant pleural mesothelioma (MPM) and nonsmall cell lung cancer (NSCLC), by comparing them to single‐input (pulmonary or systemic arterial input) tracer kinetic models for the voxel‐level analysis within the tumor with respect to goodness‐of‐fit statistics. Fifteen patients (five MPM, ten NSCLC) underwent DCE‐MRI prior to radiotherapy. DCE‐MRI data were analyzed using five different single‐ or dual‐input tracer kinetic models: Tofts‐Kety (TK), extended TK (ETK), two compartment exchange (2CX), adiabatic approximation to the tissue homogeneity (AATH) and distributed parameter (DP) models. The pulmonary blood flow (BF), blood volume (BV), mean transit time (MTT), permeability‐surface area product (PS), fractional interstitial volume (v_I), and volume transfer constant (K^Trans) were calculated for both single‐ and dual‐input models. The pulmonary arterial flow fraction (γ), pulmonary arterial blood flow (BF_PA) and systemic arterial blood flow (BF_A) were additionally calculated for only dual‐input models. The competing models were ranked and their Akaike weights were calculated for each voxel according to corrected Akaike information criterion (cAIC). The optimal model was chosen based on the lowest cAIC value. In both types of tumors, all five dual‐input models yielded lower cAIC values than their corresponding single‐input models. The 2CX model was the best‐fitted model and most optimal in describing tracer kinetic behavior to assess microvascular properties in both MPM and NSCLC. The dual‐input 2CX‐model‐derived BF_A was the most significant parameter in differentiating adenocarcinoma from squamous cell carcinoma histology for NSCLC patients.

Differentiation between glioma and radiation necrosis using molecular magnetic resonance imaging of endogenous proteins and peptides

It remains difficult to distinguish tumor recurrence from radiation necrosis after brain tumor therapy. Here we show that these lesions can be distinguished using the amide proton transfer (APT) magnetic resonance imaging (MRI) signals of endogenous cellular proteins and peptides as an imaging biomarker. When comparing two models of orthotopic glioma (SF188/V+ glioma and 9L gliosarcoma) with a model of radiation necrosis in rats, we could clearly differentiate viable glioma (hyperintense) from radiation necrosis (hypointense to isointense) by APT MRI. When we irradiated rats with U87MG gliomas, the APT signals in the irradiated tumors had decreased substantially by 3 d and 6 d after radiation. The amide protons that can be detected by APT provide a unique and noninvasive MRI biomarker for distinguishing viable malignancy from radiation necrosis and predicting tumor response to therapy.

Novel molecular imaging platform for monitoring oncological kinases

Recent advances in oncology have lead to identification of a plethora of alterations in signaling pathways that are critical to oncogenesis and propagation of malignancy. Among the biomarkers identified, dysregulated kinases and associated changes in signaling cascade received the lion's share of scientific attention and have been under extensive investigations with goal of targeting them for anti-cancer therapy. Discovery of new drugs is immensely facilitated by molecular imaging technology which enables non-invasive, real time, dynamic imaging and quantification of kinase activity. Here, we review recent development of novel kinase reporters based on conformation dependent complementation of firefly luciferase to monitor kinase activity. Such reporter system provides unique insights into the pharmacokinetics and pharmacodynamics of drugs that modulate kinase signaling and have a huge potential in drug discovery, validation, and drug-target interactions.

Exogenous Molecular Probes for Targeted Imaging in Cancer: Focus on Multi-modal Imaging

Cancer is one of the major causes of mortality and morbidity in our health care system. Molecular imaging is an emerging methodology for the early detection of cancer, and the development of exogenous molecular probes that can be labeled for multi-modality imaging is critical to this process. Today, molecular imaging is at crossroad, and new targeted imaging agents are expected to broadly expand our ability to detect pre-malignant lesions. This integrated imaging strategy will permit clinicians to not only localize lesions within the body, but also to visualize the expression and activity of specific molecules. This information is expected to have a major impact on diagnosis, therapy, drug development and understanding of basic cancer biology. At this time, a number of molecular probes have been developed by conjugating various labels to affinity ligands for targeting in different imaging modalities. This review will describe the current status of exogenous molecular probes for optical, nuclear and MRI imaging platforms. Furthermore, we will also shed light on how these techniques can be used synergistically in multi-modal platforms and how these techniques are being employed in current research.

Unresectable hepatocellular carcinoma: serial early vascular and cellular changes after transarterial chemoembolization as detected with MR imaging

PURPOSE

To prospectively assess serial changes in contrast material-enhanced and diffusion-weighted (DW) magnetic resonance (MR) imaging values within 1 month after transarterial chemoembolization (TACE) in patients with unresectable hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Institutional review board approval was obtained for this prospective HIPAA-compliant study. MR imaging was performed before and within 24 hours after TACE in 24 patients with HCC (21 male, three female; mean age, 59 years and 62 years, respectively). Serial MR imaging was subsequently performed 1, 2, 3, and 4 weeks after therapy. The imaging protocol included fast spin-echo T2-weighted MR imaging, breath-hold DW echo-planar MR imaging, and breath-hold unenhanced and contrast-enhanced T1-weighted three-dimensional fat-suppressed gradient-recalled-echo MR imaging in the arterial and portal venous phases. Tumor size, enhancement, and apparent diffusion coefficient (ADC) values were recorded before and sequentially after treatment. Regression models for the correlated data were used to assess changes in these parameters over time after TACE.

RESULTS

Mean tumor size was 7.5 cm and was unchanged up to 4 weeks after therapy. Reduction in tumor enhancement in the arterial phase occurred immediately after TACE, with a consistent reduction occurring 1-3 weeks after therapy (P = .001). Reduction in tumor enhancement in the portal venous phase also occurred immediately after TACE, with a consistent reduction occurring 1-3 weeks after therapy (P = .0003). The increase in tumor ADC value was significant 1-2 weeks after therapy (P = .004), borderline significant 3 weeks after therapy, and insignificant 24 hours and 4 weeks after therapy.

CONCLUSION

Significant reduction in tumor enhancement occurred within 24 hours after TACE and persisted up to 4 weeks after TACE. Lesser changes in the ADC value appeared 1 week after TACE, persisted through 2 weeks after TACE, and became less apparent 3 and 4 weeks after TACE. No change in tumor size was recorded during the follow-up period.

Dynamic contrast-enhanced and T2-weighted magnetic resonance imaging study of the correlation between tumour angiogenesis and growth kinetics

Accumulating evidence indicates that tumour growth is angiogenesis-dependent. Non-invasive assessment of the relationship between tumour growth and associated angiogenesis is essential for diagnosis and for therapeutic interventions. We utilized a combination of high-resolution T2-weighted and dynamic contrast-enhanced magnetic resonance imaging to investigate the dynamics of angiogenesis during tumour growth in a mouse tumour model expressing Epstein-Barr virus-encoded latent membrane protein 1 isolated from a nasopharyngeal carcinoma in Taiwan. Serial imaging acquisitions were performed starting on the third day after subcutaneous implantation of tumours, through day 28. We observed a progressive increase in tumour volume until day 14, followed by rapid and exponential growth. The volume transfer constant, K(trans), also increased significantly on day 14, and then gradually decreased, suggesting that the angiogenic switching occurs prior to significant tumour growth. At the initial stage, the K(trans) values were significantly higher in the tumour peripheral region than in the tumour core, but, during tumour growth, the K(trans) values in the region between the tumour periphery and core gradually increased, becoming larger than those of the periphery. These results demonstrate that the ability to perform repeated measurements assessing the correlation between tumour growth kinetics and tumour angiogenesis makes it possible to determine the critical time of angiogenic switching prior to rapid tumour growth, as well as suggesting the timing of therapy.

Assessment of metastatic breast cancer response to chemoembolization with contrast agent enhanced and diffusion-weighted MR imaging

PURPOSE

To assess the value of functional magnetic resonance (MR) imaging in the evaluation of early tumor response after transarterial chemoembolization (TACE) for metastatic breast cancer and to compare tumor response based on functional MR imaging versus traditional assessment based on iodized oil deposition, tumor size, and tumor enhancement.

MATERIALS AND METHODS

For 14 patients with metastatic breast cancer, MR imaging studies before and after TACE were evaluated. Diffusion and contrast medium-enhanced MR imaging was performed on a 1.5-T unit. Parameters evaluated included change in tumor size, enhancement, and apparent diffusion coefficient (ADC) values. Median survival was also calculated in the entire cohort.

RESULTS

A total number of 27 lesions were evaluated, with a mean diameter of 5.5 cm. Although mean tumor size decreased by 18% after treatment, no tumors met the Response Evaluation Criteria In Solid Tumors (RECIST) for complete response (ie, complete disappearance of target lesions) and only seven of 27 met RECIST for partial response (ie, >30% decrease in target lesion size). After treatment, decrease of tumor enhancement in the arterial (32%) and portal venous (39%) phases was statistically significant (P < .0001). Mean tumor ADC increased by 27% (P < .0001) after TACE, whereas ADC remained unchanged in nontumorous liver, spleen, and kidney. Median survival was 25 months for the entire cohort.

CONCLUSION

In patients with breast cancer and liver metastases who were treated with TACE, although changes in tumor size were small, significant early changes in the treated lesions occurred on contrast medium-enhanced and functional MR imaging. These include decrease in tumor enhancement and increase in tumor ADC value, which suggest increasing tumor necrosis and cell death.

Magnetic resonance imaging determination of tumor grade and early response to temozolomide in a genetically engineered mouse model of glioma

PURPOSE

The median survival for patients diagnosed with glioblastoma multiforme, the most common type of brain tumor, is less than 1 year. Animal glioma models that are more predictive of therapeutic response in human patients than traditional models and that are genetically and histologically accurate are an unmet need. The nestin tv-a (Ntv-a) genetically engineered mouse spontaneously develops glioma when infected with ALV-A expressing platelet-derived growth factor, resulting in autocrine platelet-derived growth factor signaling.

EXPERIMENTAL DESIGN

In the Ntv-a genetically engineered mouse model, T2-weighted and T1-weighted, contrast-enhanced magnetic resonance images were correlated with histology, glioma grade (high or low), and survival. Magnetic resonance imaging (MRI) was therefore used to enroll mice with high-grade gliomas into a second study that tested efficacy of the current standard of care for glioma, temozolomide (100 mg/kg qdx5 i.p., n=13).

RESULTS

The Ntv-a model generated a heterogeneous group of gliomas, some with high-grade growth rate and histologic characteristics and others with characteristics of lower-grade gliomas. We showed that MRI could be used to predict tumor grade and survival. Temozolomide treatment of high-grade tv-a gliomas provided a 14-day growth delay compared with vehicle controls. Diffusion MRI measurement of the apparent diffusion coefficient showed an early decrease in cellularity with temozolomide, similar to that observed in humans.

CONCLUSIONS

The use of MRI in the Ntv-a model allows determination of glioma grade and survival prediction, distribution of mice with specific tumor types into preclinical trials, and efficacy determination both by tumor growth and early apparent diffusion coefficient response.

Proton and sodium MRI assessment of emerging tumor chemotherapeutic resistance

The ultimate goal of any cancer therapy is to target the elimination of neoplastic cells. Although newer therapeutic strategies are in constant development, therapeutic assessment has been hampered by the inability to assess, rapidly and quantitatively, efficacy in vivo. Diffusion imaging and, more recently, sodium MRI have demonstrated their distinct abilities to detect therapy-induced alterations in tumor cellularity, which has been demonstrated to be indicative of therapeutic efficacy. More importantly, both imaging modalities detect tumor response much earlier than traditional methodologies that rely on macroscopic volumetric changes. In this study, the correlation between tumor sodium and diffusion was further tested to demonstrate the sensitivity of sodium imaging to gauge tumor response to therapy by using a 9L rat gliosarcoma treated with varying doses of BCNU [1,3-bis(2-chloroethyl)-1-nitrosourea]. This orthotopic model has been demonstrated to display variability in response to BCNU therapy where initial insult has been shown to lead to drug-resistance. In brief, a single 26.6 mg/kg BCNU dose yielded dramatic responses in both diffusion and sodium MRI. However, a second equivalent BCNU dose yielded a much smaller change in diffusion and sodium, suggesting a drop in tumor sensitivity to BCNU. The MRI responses of animals treated with 13.3 mg/kg BCNU were much lower and similar responses were observed after the initial and secondary applications of BCNU. Furthermore, these results were further validated using volumetric measurements of the tumor and also ex vivo determination of tumor sensitivity to BCNU. Overall, these experiments demonstrate the sensitivity and applicability of sodium and diffusion MRI as tools for dynamic assessment of tumor response to therapy.

The functional diffusion map: an imaging biomarker for the early prediction of cancer treatment outcome

Functional diffusion map (fDM) has been recently reported as an early and quantitative biomarker of clinical brain tumor treatment outcome. This approach spatially maps and quantifies treatment-induced changes in tumor water diffusion values resulting from alterations in cell density/cell membrane function and microenvironment. This current study was designed to evaluate the capability of fDM for preclinical evaluation of dose escalation studies and to determine if these changes were correlated with outcome measures (cell kill and overall survival). Serial T2-weighted were carried out on rodents with orthotopically implanted 9L brain tumors receiving three doses of 1,3-bis(2-chloroethyl)-1-nitrosourea (6.65, 13.3, and 26.6 mg/kg, i.p.). All images were coregistered to baseline T2-weighted images for fDM analysis. Analysis of tumor fDM data on day 4 posttreatment detected dose-dependent changes in tumor diffusion values, which were also found to be spatially dependent. Histologic analysis of treated tumors confirmed spatial changes in cellularity as observed by fDM. Early changes in tumor diffusion values were found to be highly correlative with drug dose and independent biologic outcome measures (cell kill and survival). Therefore, The fDM imaging biomarker for early prediction of treatment efficacy can be used in the drug development process.

The role of functional MR imaging in the assessment of tumor response after chemoembolization in patients with hepatocellular carcinoma

PURPOSE

To assess treatment response of hepatocellular carcinoma (HCC) after transarterial chemoembolization (TACE) with use of diffusion and dynamic contrast medium-enhanced magnetic resonance (MR) imaging.

MATERIALS AND METHODS

MR imaging studies before and after TACE in 38 patients with HCC (33 male patients and five female patients) were evaluated. Diffusion and dynamic contrast medium-enhanced MR imaging was performed on a 1.5-T unit. The imaging protocol included T2-weighted fast spin-echo, breath-hold diffusion-weighted echoplanar, and breath-hold unenhanced and contrast medium-enhanced T1-weighted three-dimensional fat-saturation gradient-recalled echo imaging in the arterial and portal venous phases. Tumor size, percent enhancement, and apparent diffusion coefficient (ADC) values were recorded before and after treatment. Survival analysis was also performed.

RESULTS

The study included 38 lesions with a mean diameter of 8.0 cm. Mean reduction in tumor diameter was 8 mm after treatment (t test; P = .0005), which did not fulfill Response Evaluation Criteria in Solid Tumors for complete or partial response. Reduction in tumor enhancement in the arterial (30%) and venous (47%) phases was statistically significant (signed-rank test; P = .0003 and P < 0.00005, respectively). Tumor ADC value increased from 0.0015 mm(2)/sec to 0.0018 mm(2)/sec after treatment (t test; P = .026), whereas the ADC values for the liver, spleen, and muscle remained unchanged. Median patient survival was 19 months.

CONCLUSIONS

After TACE, tumors demonstrated decreased size and enhancement with increases in ADC values. In this cohort, diffusion and dynamic contrast medium-enhanced MR imaging parameters were significantly altered after TACE, and these could be useful tools in the assessment of tumor response.

Advanced neuroimaging of pediatric brain tumors: MR diffusion, MR perfusion, and MR spectroscopy

This article highlights the MR imaging techniques of MR perfusion, MR diffusion, and MR spectroscopy in the evaluation of the child with a pediatric brain tumor. These techniques are complementary to conventional MR imaging in providing tumor physiologic information useful for diagnosis and therapy.

Noninvasive Bioluminescence Imaging of Luciferase Expressing Intracranial U87 Xenografts: Correlation with Magnetic Resonance Imaging Determined Tumor Volume and Longitudinal Use in Assessing Tumor Growth and Antiangiogenic Treatment Effect

OBJECTIVE

Outcome studies in rodent tumor models rely on both histological and noninvasive study end points. Intracranial models require special tools to observe tumor growth over time noninvasively, such as magnetic resonance imaging (MRI), computed tomographic scanning, or cranial window techniques. These techniques share disadvantages in terms of cost, technical expertise required, and overall animal throughput for analysis. In this report, we sought to validate the use of the relatively newer technique of bioluminescence imaging (BLI) of intracranial glioblastoma xenograft growth by comparing it with gadolinium-enhanced MRI.

METHODS

U87MG glioma cell lines genetically engineered to express the firefly luciferase gene were stereotactically injected into nude mice in the left frontal lobe. Weekly BLI and MRI were performed after the inoculation of tumor cells. For BLI, tumor growth was assessed as the peak BLI after systemic injection of luciferin substrate. MRI-based growth curves were created by three-dimensional volumetric reconstruction of axial gadolinium-enhanced MRI data covering the whole brain. In a separate experiment, mice were treated with adenoviruses encoding antiangiogenic soluble vascular endothelial growth factor receptors, and treatment effect was monitored by BLI.

RESULTS

Untreated tumor growth was readily detected and observed over time by serial BLI measurements. Furthermore, tumor-derived light emission was highly correlated with volume of tumor as assessed by MRI. Furthermore, the tested antiangiogenic treatment effect was readily detected using this technique, suggesting the power of the technique for sensitive monitoring of novel therapeutics.

CONCLUSION

BLI offers a simple and rapid technique for assessing intracranial glioblastoma growth in rodent models noninvasively, which correlates well with MRI. The speed of the BLI technique can increase experimental throughput, allows for targeted histological analysis in animals showing the greatest treatment effects, and provides new insights into the kinetics of intracranial tumor growth in the setting of different treatments.

Application of 23Na MRI to monitor chemotherapeutic response in RIF-1 tumors

Effects of an alkylating anticancer drug, cyclophosphamide (Cp), on 23Na signal intensity (23Na SI) and water apparent diffusion coefficient (ADC) were examined in subcutaneously-implanted radiation-induced fibrosarcoma (RIF-1) tumors by 23Na and 1H magnetic resonance imaging (MRI). MRI experiments were performed on untreated control (n = 5) and Cp-treated (n = 6) C3H mice, once before Cp injection (300 mg/kg) then daily for 3 days after treatment. Tumor volumes were significantly lower in treated animals 2 and 3 days posttreatment. At the same time points, in vivo MRI experiments showed an increase in both 23Na SI and water ADC in treated tumors, whereas control tumors did not show any significant changes. The correlation between 23Na SI and water ADC changes was dramatically increased in the Cp-treated group, suggesting that the observed increases in 23Na SI and water ADC were caused by the same mechanism. Histologic sections showed decreased cell density in the regions of increased 23Na and water ADC SI. Destructive chemical analysis showed that Cp treatment increased the relative extracellular space and tumor [Na+]. We conclude that the changes in water ADC and 23Na SI were largely due to an increase in extracellular space. 23Na MRI and 1H water ADC measurements may provide valuable noninvasive techniques for monitoring chemotherapeutic responses.

Molecular MR imaging in oncology

The implementation and integration of systems biology approaches with the emerging nanosciences and microchip technology will revolutionize profoundly molecular imaging and fuel the drive toward a more predictive and individualized health care. In combination with informatics platforms, key gene and protein targets will be identified, and serve as more effective targets for diagnostic and therapeutic interventions. Drug development also will be expedited by the judicious selection of more appropriate molecular biomarkers that will serve as objective end points of treatment efficacy, in addition to facilitating the development of new target-specific therapeutics. Finally, with the more widespread proliferation of high-field magnets and advancements in imaging hardware; acquisition methods; and novel,"smart" MR agents, the ability to achieve higher resolution analyses of tumor biology, cell track-ing, and gene expression will be realized more fully. Although radiologists will continue to serve as diagnostic consultants and assist in management decisions, the contributions from new developments in the biologic and molecular sciences will significantly alter the scope of our profession. Radiologists will be required to participate more actively in the individualized care of the patient and cultivate a deeper understanding of the underlying molecular basis of disease and molecular pharmacology for facilitating selection of the most appropriate combination of imaging studies that address biologically relevant questions. These radical changes in our profession will necessitate the re-education and emergence of a small cadre of professionals that is educated broadly in multiple scientific disciplines, and demonstrate expertise in clinical care and the basic sciences. The optimistic view is that this already is happening.

Application of a macromolecular contrast agent for detection of alterations of tumor vessel permeability induced by radiation

Permeability of tumor vasculature can be a major barrier to successful drug delivery, particularly for high molecular weight agents such as monoclonal antibodies and their diagnostic or therapeutic conjugates. In this study, changes in permeability of SCCVII tumor vessels after radiation treatment were evaluated by dynamic magnetic resonance imaging as a function of time after irradiation using a generation-8 polyamidoamine dendrimer (G8-Gd-D)-based magnetic resonance imaging contrast agent shown previously to be confined to tumor blood vessels. Tumor irradiation consisted of either single doses (2-15 Gy) or various daily fractionated doses (5 days). A single radiation dose of 15 Gy resulted in significant transient image enhancement of the tumor tissue with a maximum occurring between 7 and 24 hours after radiation treatment. No observable enhancement was recorded for fractionated radiation doses. Use of dynamic magnetic resonance imaging coupled with G8-Gd-D provides an exquisite methodology capable of defining the timing of enhanced permeability of macromolecules in tumors after irradiation. Such information might be applied to optimize the efficacy of subsequent or concurrent therapies including radiolabeled antibodies or other anticancer agents in combination with external beam therapies.

Diffusion imaging for evaluation of tumor therapies in preclinical animal models

The increasing development of novel targeted therapies for treating solid tumors has necessitated the development of technology to determine their efficacy in preclinical animal models. One such technology that can non-invasively quantify early changes in tumor cellularity as a result of an efficacious therapy is diffusion MRI. In this overview we present some theories as to the origin of diffusion changes as a result of tumor therapy, a robust methodology for acquisition of apparent diffusion coefficient maps and some applications of determining therapeutic efficacy in a variety therapeutic regimens and animal models.

A dual function fusion protein of Herpes simplex virus type 1 thymidine kinase and firefly luciferase for noninvasive in vivo imaging of gene therapy in malignant glioma

Background

Suicide gene therapy employing the prodrug activating system Herpes simplex virus type 1 thymidine kinase (HSV-TK)/ ganciclovir (GCV) has proven to be effective in killing experimental brain tumors. In contrast, glioma patients treated with HSV-TK/ GCV did not show significant treatment benefit, most likely due to insufficient transgene delivery to tumor cells. Therefore, this study aimed at developing a strategy for real-time noninvasive in vivo monitoring of the activity of a therapeutic gene in brain tumor cells.

Methods

The HSV-TK gene was fused to the firefly luciferase (Luc) gene and the fusion construct HSV-TK-Luc was expressed in U87MG human malignant glioma cells. Nude mice with subcutaneous gliomas stably expressing HSV-TK-Luc were subjected to GCV treatment and tumor response to therapy was monitored in vivo by serial bioluminescence imaging. Bioluminescent signals over time were compared with tumor volumes determined by caliper.

Results

Transient and stable expression of the HSV-TK-Luc fusion protein in U87MG glioma cells demonstrated close correlation of both enzyme activities. Serial optical imaging of tumor bearing mice detected in all cases GCV induced death of tumor cells expressing the fusion protein and proved that bioluminescence can be reliably used for repetitive and noninvasive quantification of HSV-TK/ GCV mediated cell kill in vivo.

Conclusion

This approach may represent a valuable tool for the in vivo evaluation of gene therapy strategies for treatment of malignant disease.

Microdensitometry of T2-weighted magnetic resonance (MR) images from patients with advanced neoplasias in a phase I clinical trial of an infrared pulsed laser device (IPLD)

BACKGROUND AND OBJECTIVE

The aim of this study was to determine whether an infrared pulsed laser device (IPLD)-induced pathophysiologic changes could be identified before measurable modifications in tumor volume.

STUDY DESIGN/PATIENTS AND METHODS

Pre-and post-IPLD treatment magnetic resonance (MR) images of tumor heterogeneities and peritumoral tissues were digitized and a linear transformation was performed to convert images to 256 intensity levels. Data were analyzed by using the Student's t-test and the Kolmogorov-Sminov test (alpha = 0.05).

RESULTS

The post-treatment mean intensity values of tumor heterogeneities increased significantly (P < 0.001) for all of the seven patients (n = 7) evaluated. For peritumoral tissues, a significant increase (P < 0.001) was measured in four patients (n = 4). The Kolmogorov-Sminov test showed significant values for the tumor tissue of six (n = 6) patients.

CONCLUSION

This is the first study of early evidence of anti-cancer activity of a novel IPLD showing a significant increase in the water content of tumor heterogeneities before measurable changes in tumor volume.

Magnetic resonance imaging in experimental models of brain disorders

This review gives an overview of the application of magnetic resonance imaging (MRI) in experimental models of brain disorders. MRI is a noninvasive and versatile imaging modality that allows longitudinal and three-dimensional assessment of tissue morphology, metabolism, physiology, and function. MRI can be sensitized to proton density, T1, T2, susceptibility contrast, magnetization transfer, diffusion, perfusion, and flow. The combination of different MRI approaches (e.g., diffusion-weighted MRI, perfusion MRI, functional MRI, cell-specific MRI, and molecular MRI) allows in vivo multiparametric assessment of the pathophysiology, recovery mechanisms, and treatment strategies in experimental models of stroke, brain tumors, multiple sclerosis, neurodegenerative diseases, traumatic brain injury, epilepsy, and other brain disorders. This report reviews established MRI methods as well as promising developments in MRI research that have advanced and continue to improve our understanding of neurologic diseases and that are believed to contribute to the development of recovery improving strategies.