Peter Bendel

Photodynamic therapy with Pd-Bacteriopheophorbide (TOOKAD): successful in vivo treatment of human prostatic small cell carcinoma xenografts.

Small cell carcinoma of the prostate (SCCP), although relatively rare, is the most aggressive variant of prostate cancer, currently with no successful treatment. It was therefore tempting to evaluate the response of this violent malignancy and its bone lesions to Pd‐Bacteriopheophorbide (TOOKAD)‐based photodynamic therapy (PDT), already proven by us to efficiently eradicate other aggressive non‐epithelial solid tumors. TOOKAD is a novel bacteriochlorophyll‐derived, second‐generation photosensitizer recently, developed by us for the treatment of bulky tumors. This photosensitizer is endowed with strong light absorbance (ϵ0 ∼ 105 mol−1 cm−1) in the near infrared region (λ=763nm), allowing deep tissue penetration. The TOOKAD‐PDT protocol targets the tumor vasculature leading to inflammation, hypoxia, necrosis and tumor eradication. The sensitizer clears rapidly from the circulation within a few hours and does not accumulate in tissues, which is compatible with the treatment of localized tumor and isolated metastases. Briefly, male CD1‐nude mice were grafted with the human SCCP (WISH‐PC2) in 3 relevant anatomic locations: subcutaneous (representing tumor mass), intraosseous (representing bone metastases) and orthotopically within the murine prostate microenvironment. The PDT protocol consisted of i.v. administration of TOOKAD (4 mg/kg), followed by immediate illumination (650–800 nm) from a xenon light source or a diode laser emitting at 770 nm. Controls included untreated animals or animals treated with light or TOOKAD alone. Tumor volume, human plasma chromogranin A levels, animal well being and survival were used as end points. In addition, histopathology and immunohistochemistry were used to define the tumor response. Subcutaneous tumors exhibited complete healing within 28–40 days, reaching an overall long‐term cure rate of 69%, followed for 90 days after PDT. Intratibial WISH‐PC2 lesions responded with complete tumor elimination in 50% of the treated mice at 70–90 days after PDT as documented histologically. The response of the orthotopic model was also analyzed histologically with similar results. The study with this model suggests that TOOKAD‐based PDT can reach large tumors and is a feasible, efficient and well‐tolerated approach for minimally invasive treatment of local and disseminated SCCP.

Boron analysis and boron imaging in biological materials for Boron Neutron Capture Therapy (BNCT)

Boron Neutron Capture Therapy (BNCT) is based on the ability of the stable isotope 10B to capture neutrons, which leads to a nuclear reaction producing an alpha- and a 7Li-particle, both having a high biological effectiveness and a very short range in tissue, being limited to approximately one cell diameter. This opens the possibility for a highly selective cancer therapy. BNCT strongly depends on the selective uptake of 10B in tumor cells and on its distribution inside the cells. The chemical properties of boron and the need to discriminate different isotopes make the investigation of the concentration and distribution of 10B a challenging task. The most advanced techniques to measure and image boron are described, both invasive and non-invasive. The most promising approach for further investigation will be the complementary use of the different techniques to obtain the information that is mandatory for the future of this innovative treatment modality.

Antivascular Treatment of Solid Melanoma Tumors with Bacteriochlorophyll–serine-based Photodynamic Therapy¶

We describe here a strategy for photodynamic eradication of solid melanoma tumors that is based on photoinduced vascular destruction. The suggested protocol relies on synchronizing illumination with maximal circulating drug concentration in the tumor vasculature attained within the first minute after administrating the sensitizer. This differs from conventional photodynamic therapy (PDT) of tumors where illumination coincides with a maximal concentration differential of sensitizer in favor of the tumor, relative to the normal surrounding tissue. This time window is often achieved after a delay (3–48 h) following sensitizer administration. We used a novel photosensitizer, bacteriochlorophyll–serine (Bchl–Ser), which is water soluble, highly toxic upon illumination in the near‐infrared (λmax 765–780 nm) and clears from the circulation in less than 24 h. Nude CD1 mice bearing malignant M2R melanotic melanoma xenografts (76–212 mm3) received a single complete treatment session. Massive vascular damage was already apparent 1 h after treatment. Changes in vascular permeability were observed in vivo using contrast‐enhanced magnetic resonance imaging (MRI), with the contrast reagent Gd‐DTPA, by shortening spin–spin relaxation time because of hemorrhage formation and by determination of vascular macromolecular leakage. Twenty‐four hours after treatment a complete arrest of vascular perfusion was observed by Gd‐DTPA–enhanced MRI. Histopathology performed at the same time confirmed primary vascular damage with occlusive thrombi, hemorrhage and tumor necrosis. The success rate of cure of over 80% with Bchl–Ser indicates the benefits of the short and effective treatment protocol. Combining the sensitizer administration and illumination steps into one treatment session (30 min) suggests a clear advantage for future PDT of solid tumors.

Spin-echo attenuation by diffusion in nonuniform field gradients

Abstract The diffusion-dependent decay of spin-echo signals from samples distributed over non-uniform field gradients is analyzed. This decay deviates from the linear semilogarithmic dependencies on t 3 or t obtained, respectively, in Hahn spin-echo or Carr-Purcell echo trains from spins in constant field gradients. It is demonstrated here that when the average diffusion distance is small compared to the spatial variation of the gradient, the spin-echo decay can be modeled by a simple superposition of signals from a large number of microdomains, each characterized by a different gradient. This is illustrated by two examples, a water sample in a deliberately created quadratic variation of the external field, and a saturated water/ sand mixture with large internal field gradients.

Quantitation of ventricular size in normal and spontaneously hypertensive rats by magnetic resonance imaging

Magnetic resonance imaging (MRI) performed at high field (4.7 Tesla), and high spatial resolution (0.6 mm slice thickness, 0.18 mm inplane) enabled noninvasive quantitative measurement of the ventricular vol. in live rats. Comparing the results for 15 male Wistar-Kyoto (WKY) rats, aged 2.5-10 months, with those from 17 spontaneously hypertensive rats (SHR), clearly confirmed the previously reported elevated ventricular vols. in the SHR strain. A significant difference in ventricular vol. between the two strains was detected above the age of 3 months. For mature animals above the age of 6 months the mean vol. in the SHR strain was elevated by about a factor of two compared to the WKY control animals.

Tamoxifen induced changes in MCF7 human breast cancer: In vitro and in vivo studies using nuclear magnetic resonance spectroscopy and imaging

The effects of 17 beta-estradiol versus tamoxifen on the growth and metabolism of MCF7 human breast cancer cells, in culture and in tumors implanted in nude mice, were studied by 31P and 13C nuclear magnetic resonance spectroscopy and by proton magnetic resonance imaging. In culture, the content of the phosphate metabolites including nucleoside triphosphates (NTP), phosphomonoesters, phosphodiesters and inorganic phosphate (Pi) were not affected by tamoxifen treatment. However, in the presence of estrogen the rate of glucose consumption and lactate production via glycolysis (270 and 280 fmol/cell.h, respectively) were twice that of tamoxifen treated cells. Estrogen rescue of tamoxifen treated cells indicated that glycolysis induction occurs at the early stages of the hormonal response. The in vivo studies included recording of proton images that provided an accurate measure of tumor size and distribution of tumor cells, necrotic regions and stromal tissue. Tamoxifen caused enhanced necrosis extending from the center of the tumor during the first two days of treatment (12 h to 6 days). This was followed by growth of reparative tissue along with tumor regression. Tamoxifen also modified the content of the phosphate metabolites, increasing markedly (P less than 0.0002) the ratio of NTP to Pi from 0.41 before treatment to 1.75 9-19 days after treatment. This change was attributed to the enhanced growth of repair tissue. The results provide new information regarding the response of human breast cancer to hormonal treatment and suggest a mechanism for the induction of tumor regression by tamoxifen.

The role of boron MRI in boron neutron capture therapy

Boron magnetic resonance imaging (MRI) and spectroscopy (MRS)are being developed for use in boron neutroncapture therapy (BNCT). With continued development, boron MRImay be used to locate BNCT agents invivo, evaluate the pharmacokinetics of BNCT agents, andaid in treatment planning.

Major mouse placental compartments revealed by diffusion-weighted MRI, contrast-enhanced MRI, and fluorescence imaging.

Significance Fluid motion measurements can provide valuable insight regarding the structure and function of developing placentas. This study presents to our knowledge the first MRI characterization of multicompartmental diffusion and incoherent flow in pregnant mice at different gestation stages, made possible by methods herein introduced for the single-scan acquisition of diffusion-encoded images in the challenging environment associated with in vivo embryonic studies. These methods were combined with a customized contrast agent to reveal a freely diffusive maternal blood pool, a strongly perfused fetal blood flow, and an intermediate behavior for the trophoblastic labyrinth cell layer. Structural features associated with these dynamics were corroborated with ex vivo fluorescence microscopy and are discussed within the context of the anatomical structure of developing mouse placentas. Mammalian models, and mouse studies in particular, play a central role in our understanding of placental development. Magnetic resonance imaging (MRI) could be a valuable tool to further these studies, providing both structural and functional information. As fluid dynamics throughout the placenta are driven by a variety of flow and diffusion processes, diffusion-weighted MRI could enhance our understanding of the exchange properties of maternal and fetal blood pools—and thereby of placental function. These studies, however, have so far been hindered by the small sizes, the unavoidable motions, and the challenging air/water/fat heterogeneities, associated with mouse placental environments. The present study demonstrates that emerging methods based on the spatiotemporal encoding (SPEN) of the MRI information can robustly overcome these obstacles. Using SPEN MRI in combination with albumin-based contrast agents, we analyzed the diffusion behavior of developing placentas in a cohort of mice. These studies successfully discriminated the maternal from the fetal blood flows; the two orders of magnitude differences measured in these fluids’ apparent diffusion coefficients suggest a nearly free diffusion behavior for the former and a strong flow-based component for the latter. An intermediate behavior was observed by these methods for a third compartment that, based on maternal albumin endocytosis, was associated with trophoblastic cells in the interphase labyrinth. Structural features associated with these dynamic measurements were consistent with independent intravital and ex vivo fluorescence microscopy studies and are discussed within the context of the anatomy of developing mouse placentas.

Nuclear Magnetic Resonance Imaging of Miscible Fingering in Porous Media

Nuclear Magnetic Resonance Imaging (MRI) can noninvasively map the spatial distribution of Nuclear Magnetic Resonance (NMR)-sensitive nuclei. This can be utilized to investigate the transport of fluids (and solute molecules) in three-dimensional model systems. In this study, MRI was applied to the buoyancy-driven transport of aqueous solutions, across an unstable interface in a three-dimensional box model in the limit of a small Péclet number (Pe<0.4). It is demonstrated that MRI is capable of distinguishing between convective transport (‘fingering’) and molecular diffusion and is able to quantify these processes. The results indicate that for homogeneous porous media, the total fluid volume displaced through the interface and the amplitude of the fastest growing finger are linearly correlated with time. These linear relations yielded mean and maximal displacement velocities which are related by a constant dimensionless value (2.4±0.1). The mean displacement velocity (U) allows us to calculate the media permeability which was consistent between experiments (1.4±0.1×10−7cm2).U is linearly correlated with the initial density gradient, as predicted by theory. An extrapolation of the density gradient to zero velocity enables an approximate determination of the critical density gradient for the onset of instability in our system (0.9±0.3×10−3 g/cm3), a value consistent with the value predicted by a calculation based upon the modified Rayleigh number. These results suggest that MRI can be used to study complex fluid patterns in three-dimensional box models, offering a greater flexibility for the simulation of natural conditions than conventional experimental modelling methods.

Method to eliminate the effects of magnetic field inhomogeneities in NMR imaging and apparatus therefor

NMR imaging apparatus comprising apparatus for applying a linear magnetic field gradient to a sample, apparatus for varying the magnetic field gradient in a predetermined manner, apparatus for obtaining an NMR signal based on the linear magnetic field gradient, apparatus for storing the NMR signal, apparatus for reconstructing an NMR image from the stored NMR signal, and display apparatus for displaying the reconstructed NMR image, and wherein the apparatus for obtaining an NMR signal includes apparatus for obtaining the NMR signal at times when cancellation of the signal component dependent on magnetic field inhomogeneities occurs. There is also provided a technique for NMR imaging using the above apparatus.