Refrigeration – Storage of solidified or liquified gas – With measuring
Reexamination Certificate
2001-05-01
2002-08-13
Donovan, Lincoln (Department: 2832)
Refrigeration
Storage of solidified or liquified gas
With measuring
C600S420000, C604S020000, C604S181000
Reexamination Certificate
active
06430939
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the transport of hyperpolarized gases from one site to another, such as from a production site to a clinical use site. The hyperpolarized gases are particularly suitable for MR imaging and spectroscopy applications.
BACKGROUND OF THE INVENTION
Inert gas imaging (“IGI”) using hyperpolarized noble gases is a promising recent advance in Magnetic Resonance Imaging (MRI) and MR spectroscopy technologies. Conventionally, MRI has been used to produce images by exciting the nuclei of hydrogen molecules (present in water protons) in the human body. However, it has recently been discovered that polarized noble gases can produce improved images of certain areas and regions of the body which have heretofore produced less than satisfactory images in this modality. Polarized Helium-3 (“
3
He”) and Xenon-129 (“
129
Xe”) have been found to be particularly suited for this purpose. Unfortunately, as will be discussed further below, the polarized state of the gases is sensitive to handling and environmental conditions and can, undesirably, decay from the polarized state relatively quickly.
Various methods may be used to artificially enhance the polarization of certain noble gas nuclei (such as
129
Xe or
3
He) over the natural or equilibrium levels, i.e., the Boltzmann polarization. Such an increase is desirable because it enhances and increases the MRI signal intensity, allowing physicians to obtain better images of the substance in the body. See U. S. Pat. No. 5,545,396 to Albert et al., the disclosure of which is hereby incorporated by reference as if recited in full herein.
A “T
1
” decay time constant associated with the longitudinal relaxation of the hyperpolarized gas is often used to characterize the length of time it takes a gas sample to depolarize in a given situation. The handling of the hyperpolarized gas is critical because of the sensitivity of the hyperpolarized state to environmental and handling factors and thus the potential for undesirable decay of the gas from its hyperpolarized state prior to the planned end use, e.g., delivery to a patient for imaging. Processing, transporting, and storing the hyperpolarized gases—as well as delivering the gas to the patient or end user—can expose the hyperpolarized gases to various relaxation mechanisms such as magnetic field gradients, surface-induced relaxation, hyperpolarized gas atom interactions with other nuclei, paramagnetic impurities, and the like.
One way of minimizing the surface-induced decay of the hyperpolarized state is presented in U.S. Pat. No. 5,612,103 to Driehuys et al. entitled “Coatings for Production of Hyperpolarized Noble Gases.” Generally stated, this patent describes the use of a modified polymer as a surface coating on physical systems (such as a Pyrex™ container) which contact the hyperpolarized gas to inhibit the decaying effect of the surface of the collection chamber or storage unit. Other methods for minimizing surface or contact-induced decay are described in co-pending and co-assigned U.S. patent application Ser. No. 09/163,721 to Zollinger et al., entitled “Hyperpolarized Noble Gas Extraction Methods, Masking Methods, and Associated Transport Containers,” and co-pending and co-assigned U.S. patent application identified by Attorney Docket No. 5770-12IP, entitled “Resilient Containers for Hyperpolarized Gases and Associated Methods.” The contents of these applications are hereby incorporated by reference as if recited in full herein.
However, other relaxation mechanisms arise during production, handling, storage, and transport of the hyperpolarized gas. These problems can be particularly troublesome when storing the gases (especially increased quantities) or transporting the hyperpolarized gas from a production site to a (remote) use site. In transit, the hyperpolarized gas can be exposed to many potentially depolarizing influences. In the past, a frozen amount of hyperpolarized
129
Xe (about 300 cc-500 cc's ) was collected in a cold finger and positioned in a metallic coated dewar along with a small yoke of permanent magnets arranged to provide a magnetic holding field therefor. The frozen gas was then taken to an experimental laboratory for delivery to an animal subject. Unfortunately, the permanent magnet yoke provided a relatively small magnetic field region (volume) with a relatively low magnetic homogeneity associated therewith. Further, the thawed sample yielded a relatively small amount of useful hyperpolarized
129
Xe (used for small animal subjects) which would not generally be sufficient for most human sized patients.
There is, therefore, a need to provide improved ways to transport hyperpolarized gases so that the hyperpolarized gas is not unduly exposed to depolarizing effects during transport. Improved storage and transport methods and systems are desired so that the hyperpolarized product can retain sufficient polarization and larger amounts to allow effective imaging at delivery when stored or transported over longer transport distances in various (potentially depolarizing) environmental conditions, and for longer time periods from the initial polarization than has been viable previously.
OBJECTS AND SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a transport system that can protect hyperpolarized gas products from potentially depolarizing environmental exposures during movement of the hyperpolarized gas products from a production site to a remote use site.
It is also an object of the present invention to configure a transport unit to serve alternatively or in addition as a portable storage unit, to hold polarized gases in their polarized state for longer periods including prior to shipment, or prior to delivery even if the gases are not intended to be remotely shipped.
It is also an object of the present invention to provide a portable unit for storing or transporting a quantity of hyperpolarized gas therein, which can substantially protect the hyperpolarized gas from the depolarizing effect of diffusion of the gas atoms through magnetic field gradients.
It is another object of the present invention to provide a portable unit for storing or transporting a quantity of hyperpolarized gas therein, which can substantially protect the hyperpolarized gas from the depolarizing effects of one or more of oscillating magnetic fields, electromagnetic noise, and electromagnetic interference (EMI).
It is another object of the present invention to provide a method of protecting the hyperpolarized gas from the depolarizing effects of undesirable EMI at a predetermined frequency or frequency range.
It is another object of the invention to provide a relatively compact, lightweight, easily transportable device which can provide sufficient protection for the hyperpolarized gas to allow the hyperpolarized gas to be successfully transported (such as in a vehicle) from a production site to a remote use site, such that the hyperpolarized gas retains a sufficient level of polarization at the use site to allow for clinically useful images.
It is another object of the invention to provide a valved hyperpolarized gas chamber configured to inhibit polarization decay (i.e., has relatively long decay times) during transport and/or storage.
It is another object of the invention to configure a transport unit to minimize the external force associated with shock, vibration, and or other mechanical collisions that are input into or transmitted to the hyperpolarized gas container.
It is another object of the invention to provide a protective enclosure for a transport unit which is configured such that the hyperpolarized gas held in an internally disposed hyperpolarized gas chamber may be directed out of or into the transport unit (i.e., the gas chamber may be filled and/or emptied), without the need to remove the gas chamber from its protective housing.
It is another object of the invention to configure a transport unit with an easily accessible means for interrogating the polarized gas held within the gas chamb
Bogorad Paul L.
Hasson Kenton C.
Wheeler Bradley A.
Zollinger David L.
Zollinger Geri T. K.
Donovan Lincoln
Medi--Physics, Inc.
Myers Bigel Sibley & Sajovec P.A.
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