Stock material or miscellaneous articles – Hollow or container type article – Nonself-supporting tubular film or bag
Reexamination Certificate
1999-06-16
2002-07-23
Dye, Rena L. (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Nonself-supporting tubular film or bag
C428S035700, C062S045100, C062S610000, C062S919000, C220S592200, C220S592270, C383S044000
Reexamination Certificate
active
06423387
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to processing, storage, transport and delivery containers for hyperpolarized noble gases.
BACKGROUND OF THE INVENTION
Conventionally, Magnetic Resonance Imaging (“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 are sensitive to handling and environmental conditions and, undesirably, can decay from the polarized state relatively quickly.
Hyperpolarizers are used to produce and accumulate polarized noble gases. Hyperpolarizers 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 herein by reference as if recited in full herein.
In order to produce the hyperpolarized gas, the noble gas is typically blended with optically pumped alkali metal vapors such as rubidium (“Rb”). These optically pumped metal vapors collide with the nuclei of the noble gas and hyperpolarize the noble gas through a phenomenon known as “spin-exchange”. The “optical pumping” of the alkali metal vapor is produced by irradiating the alkali-metal vapor with circularly polarized light at the wavelength of the first principal resonance for the alkali metal (e.g., 795 nm for Rb). Generally stated, the ground state atoms become excited, then subsequently decay back to the ground state. Under a modest magnetic field (10 Gauss), the cycling of atoms between the ground and excited states can yield nearly 100% polarization of the atoms in a few microseconds. This polarization is generally carried by the lone valence electron characteristics of the alkali metal. In the presence of non-zero nuclear spin noble gases, the alkali-metal vapor atoms can collide with the noble gas atoms in a manner in which the polarization of the valence electrons is transferred to the noble-gas nuclei through a mutual spin flip “spin-exchange”.
After the spin-exchange has been completed, the hyperpolarized gas is separated from the alkali metal prior to introduction into a patient to form a non-toxic or sterile composition. Unfortunately, during and after collection, the hyperpolarized gas can deteriorate or decay (lose its hyperpolarized state) relatively quickly and therefore must be handled, collected, transported, and stored carefully. The “T
1
” decay constant associated with the hyperpolarized gas's longitudinal relaxation time is often used to describe the length of time it takes a gas sample to depolarize in a given container. The handling of the hyperpolarized gas is critical, because of the sensitivity of the hyperpolarized state to environmental and handling factors and the potential for undesirable decay of the gas from its hyperpolarized state prior to the planned end use, i.e., delivery to a patient. Processing, transporting, and storing the hyperpolarized gases—as well as delivery of the gas to the patient or end user—can expose the hyperpolarized gases to various relaxation mechanisms such as magnetic gradients, ambient and contact impurities, and the like.
Typically, hyperpolarized gases such as
129
Xe and 3He have been collected in relatively pristine environments and transported in specialty glass containers such as rigid Pyrex™ containers. However, to extract the majority of the gas from these rigid containers, complex gas extraction means are typically necessary. Hyperpolarized gas such as
3
He and
129
Xe has also been temporarily stored in single layer resilient Tedlar® and Teflon® bags. However, these containers have produced relatively short relaxation times.
One way of inhibiting the 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.
However, there remains a need to address and reduce dominant and sub-dominant relaxation mechanisms and to decrease the complexity of physical systems required to deliver the hyperpolarized gas to the desired subject. Minimizing the effect of one or more of these factors can increase the life of the product by increasing the duration of the hyperpolarized state. Such an increase is desired so that the hyperpolarized product can retain sufficient polarization to allow effective imaging at delivery when transported over longer transport distances and/or stored for longer time periods from the initial polarization than has been viable previously.
OBJECTS AND SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the present invention to process and collect hyperpolarized gas in improved resilient containers which are configured to inhibit depolarization in the collected polarized gas and to provide a longer T
1
for
3
He and
129
Xe than has been achieved in the past.
It is another object of the present invention to provide an improved container which can be configured to act as both a transport container and a delivery mechanism to reduce the amount of handling or physical interaction required to deliver the hyperpolarized gas to a subject.
It is a further object of the present invention to provide an improved, relatively non-complex and economical container which can prolong the polarization life of the gas in a container and reduce the amount of polarization lost during storage, transport, and delivery.
It is yet another object of the invention to provide methods, surface materials and containers which will minimize the depolarizing effects of the hyperpolarized state of the gas (especially
3
He) attributed to one or more of paramagnetic impurities, oxygen exposure, and surface relaxation.
It is an additional object of the present invention to provide a method to determine the gas solubility in polymers or liquids with respect to hyperpolarized
129
Xe or
3
He.
These and other objects are satisfied by the present invention which is directed to resilient containers which are configured to reduce surface or contact-induced depolarization by forming an inner contact surface of a first material (of a predetermined thickness) which acts to minimize the associated surface or contact depolarization. In particular, a first aspect of the invention is directed to a container for receiving a quantity of hyperpolarized gas. The container includes at least one wall comprising inner and outer layers configured to define an enclosed chamber for holding a quantity of hyperpolarized gas. The inner layer has a predetermined thickness and an associated relaxivity value which inhibits contact-induced polarization loss of the hyperpolarized gas. The outer layer defines an oxygen shield overlying the inner layer. Of course, the two layers can be integrated into one, if the material chosen acts as a polarization-friendly contact surface and is also resistant to the introduction of oxygen molecules into the chamber of the container. The container also includes a quantity of hyperpolarized noble gas and a port attached to the wall in fluid communication with the chamber for capturing and releasing the hyperpolarized gas therethrough.
Preferably, the container material(s) are selected to result in effective T
1
'
Deaton Daniel M.
Driehuys Bastiaan
Hasson Kenton C.
Zollinger David L.
Dye Rena L.
Medi--Physics, Inc.
Myers Bigel & Sibley & Sajovec
LandOfFree
Resilient containers for hyperpolarized gases and associated... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Resilient containers for hyperpolarized gases and associated..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Resilient containers for hyperpolarized gases and associated... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2816885