Metal nanoshells are a class of nanoparticles with tunable optical resonances. In this article, an application of this technology to thermal ablative therapy for cancer is described. By tuning the nanoshells to strongly absorb light in the near infrared, where optical transmission through tissue is optimal, a distribution of nanoshells at depth in tissue can be used to deliver a therapeutic dose of heat by using moderately low exposures of extracorporeally applied near-infrared (NIR) light. Human breast carcinoma cells incubated with nanoshells in vitro were found to have undergone photothermally induced morbidity on exposure to NIR light (820 nm, 35 W/cm2), as determined by using a fluorescent viability stain. Cells without nanoshells displayed no loss in viability after the same periods and conditions of NIR illumination. Likewise, in vivo studies under magnetic resonance guidance revealed that exposure to low doses of NIR light (820 nm, 4 W/cm2) in solid tumors treated with metal nanoshells reached average maximum temperatures capable of inducing irreversible tissue damage (DeltaT = 37.4 +/- 6.6 degrees C) within 4-6 min. Controls treated without nanoshells demonstrated significantly lower average temperatures on exposure to NIR light (DeltaT < 10 degrees C). These findings demonstrated good correlation with histological findings. Tissues heated above the thermal damage threshold displayed coagulation, cell shrinkage, and loss of nuclear staining, which are indicators of irreversible thermal damage. Control tissues appeared undamaged.

https://www.pnas.org/content/pnas/100/23/13549.full.pdf

Nanoshell-mediated near-infrared thermal therapy of tumors under magnetic resonance guidance

By using a multiple receiving coil composed of receiving coils, an imaging portion of a subject is subjected to a first pulse sequence to create n sensitivity images (701 to 703) fewer than the examination images. When these sensitivity images are created, an NMR signal is measured for only the low-frequency region of the k space. A second pulse sequence from which a phase encode step is removed is conducted to create m (m>n) examination images (704, 705) of the subject by using the receiving coils. When sensitivity distributions (707, 708) of the receiving coils are determined for the sensitivity images (701 to 703), and if there are no sensitivity distributions corresponding to the slice positions of the examination images (704, 705), they are determined by slice interpolation using the sensitivity distributions (701 to 703), and the aliasing artifacts of the examination images (704, 705) are removed by matrix operation by using the sensitivity distributions (707, 708).

Magnetic resonance imaging device

PURPOSE: To determine if focused ultrasound beams can be used to locally open the blood-brain barrier without damage to surrounding brain tissue and if magnetic resonance (MR) imaging can be used to monitor this procedure. MATERIALS AND METHODS: The brains of 18 rabbits were sonicated (pulsed sonication) in four to six locations, with temporal peak acoustic power ranging from 0.2 to 11.5 W. Prior to each sonication, a bolus of ultrasonographic (US) contrast agent was injected into the ear vein of the rabbit. A series of fast or spoiled gradient-echo MR images were obtained during the sonications to monitor the temperature elevation and potential tissue changes. Contrast material–enhanced MR images obtained minutes after sonications and repeated 1–48 hours later were used to depict blood-brain barrier opening. Whole brain histologic evaluation was performed. RESULTS: Opening of the blood-brain barrier was confirmed with detection of MR imaging contrast agent at the targeted locations. The lowest power leve...

Noninvasive MR Imaging-Guided Focal Opening of the Blood-Brain Barrier in Rabbits

A new temperature measurement procedure using phase mapping was developed that makes use of the temperature dependence of the water proton chemical shift. Highly accurate and fast measurements were obtained during phantom and in vivo experiments. In the pure water phantom experiments, an accuracy of more than +/- 0.5 degrees C was obtained within a few seconds/slice using a field echo pulse sequence (TR/TE = 115/13 ms, matrix = 128 x 128, number of slices = 5). The temperature dependence of the water proton chemical shift was found to be almost the same for different materials with a chemical composition similar to living tissues (water, glucide, protein). Using this method, the temperature change inside a cat's brain was obtained with an accuracy of more than +/- 1 degree C and an in-plane resolution of 0.6 x 0.6 mm. The temperature measurement error was affected by several factors in the living system (B0 shifts caused by position shifts of the sample, blood flow, etc.), the position shift effect being the most serious.

A precise and fast temperature mapping using water proton chemical shift.

Provided herein are methods, devices and compositions to conductively or to inductively fix substrates, including tissues, using electromagnetic energy. Also provided is a method of controlling the fixing process via feedback monitoring of a property of the composition and/or of the electromagnetic energy used.

Electromagnetic treatment of tissues and cells

An ultrasonic wave medical treatment apparatus capable of preventing the displacement of the focal point of the ultrasonic waves from the treatment target portion within the patient, eliminating a need for re-positioning of the ultrasonic wave applicator with respect to the patient, and taking MR images to be utilized during the treatment at a high resolution. In this apparatus, the ultrasonic wave applicator can be integrally incorporated within a treatment table for carrying the patient into the MRI gantry for taking the MR images. The surface coil for taking the MR images can be provided on a surface film of a water bag in the ultrasonic wave applicator, or on a body cavity probe on which the ultrasonic transducer is also provided. The mixing rate of the coupling fluid can be adjusted, and the impedance matching between the ultrasonic transducer and the driving circuit can be maintained by minimizing the reflected electric power from the ultrasonic transducer.

Ultrasonic wave medical treatment apparatus suitable for use under guidance of magnetic resonance imaging

This article discusses the applicability to a living animal of the temperature mapping method using the water proton chemical shift obtained with three-dimensional magnetic resonance spectroscopic imaging (3D-MRSI). There are several sources of error in obtaining the spectra with 3D-MRSI: signal noise, limitation in the frequency resolution due to the finite signal length, intravoxel inhomogeneity in the static magnetic field, and variation in the magnetic field due to the eddy current magnetic field. A spectral estimation method called phase deduction complex Lorentzian fitting (PD-CLF) was proposed. Numerical simulations demonstrated that this method reduces the error in the chemical shift to one third of that obtained with the simple frequency subtraction method that uses zero-padded first Fourier transformation (FFT). The temperature images obtained using 3D-MRSI with PD-CLF clearly visualized the changes and distribution of temperature in an anesthetized rat.

Temperature mapping using water proton chemical shift obtained with 3D-MRSI: feasibility in vivo.

An absolute temperature measuring pulse sequence is executed and, subsequently, a relative temperature measuring pulse sequence is repeatedly executed. Since while a relative temperature can be measured from phase information, an absolute temperature requires frequency information, a time required in the relative temperature measuring pulse can be made shorter than that required in the absolute temperature measuring pulse sequence. Since the relative temperature reveals a temperature variation, if an absolute temperature at a given time is known, an absolute temperature at a subsequent time can be calculated from the relative temperature. Thus, a local internal temperature of the subject can be measured, with a shorter temporal resolution, with the use of the absolute temperature and relative temperature.

Temperature monitoring method, temperature monitoring apparatus and magnetic resonance apparatus

A magnetic resonance imaging apparatus capable of measuring a temperature increase due to an application of RF magnetic fields for data acquisition purpose, and notifying an information on the measured temperature increase regularly to an operator, so as to secure the safety of a body to be examined. In this magnetic resonance imaging apparatus, the image data acquisition operation is controlled to acquire a phase information associated with a temperature change in an interior of the body to be examined, by displacing either an observation start timing or a radio frequency magnetic field application timing for a prescribed magnetic resonance signal in the magnetic resonance signal sequence from a normal timing for acquiring image data.

Yasutoshi Ishihara

Papers

A precise and fast temperature mapping using water proton chemical shift.

Ultrasonic wave medical treatment apparatus suitable for use under guidance of magnetic resonance imaging

Temperature mapping using water proton chemical shift obtained with 3D-MRSI: feasibility in vivo.

Temperature monitoring method, temperature monitoring apparatus and magnetic resonance apparatus

Magnetic resonance imaging apparatus with temperature measurement function