X-Ray probe sheath apparatus

Details X-Ray probe sheath apparatus X-Ray probe sheath apparatus

1998-12-10

2001-06-12

Seidel, Richard K. (Department: 3763)

Surgery

Means for introducing or removing material from body for...

Treating material introduced into or removed from body...

C604S162000, C604S171000, C604S174000

Reexamination Certificate

active

06245047

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
Not Applicable
REFERENCE TO MICROFICHE APPENDIX
Not Applicable
BACKGROUND OF THE INVENTION
This invention relates to a miniaturized, programmable radiation source having an x-ray emitting probe for use in delivering substantially constant or intermittent levels of x-rays to a specified region and, more particularly, to a biocompatible sheath, for covering the probe during treatment, or a biocompatible sheath and probe treatment kit.
In the field of medicine, radiation is used for diagnostic, therapeutic and palliative treatment of patients. The conventional medical radiation sources used for these treatments include large fixed position machines as well as small, transportable radiation generating probes. The current state of the art treatment systems utilize computers to generate complex treatment plans for treating complex geometric volumes.
Typically, these systems apply doses of radiation in order to inhibit the growth of new tissue because it is known that radiation affects dividing cells more than the mature cells found in non-growing tissue. Thus, the regrowth of cancerous tissue in the site of an excised tumor can be treated with radiation to prevent the recurrence of cancer. Alternatively, radiation can be applied to other areas of the body to inhibit tissue growth, for example the growth of new blood vessels inside the eye that can cause macular degeneration.
Conventional radiation treatments systems, such as the LINAC used for medical treatment, utilize a high power remote radiation source and direct a beam of radiation at a target area, such as tumor inside the body of a patient. This type of treatment is referred to as teletherapy because the radiation source is located at a predefined distance, typically on the order of one meter, from the target. This treatment suffers from the disadvantage that tissue disposed between the radiation source and the target is exposed to radiation.
An alternative treatment system utilizing a point source of radiation is disclosed in U.S. Pat. No. 5,153,900 ('900 patent) issued to Nomikos et al., owned by the assignee of the present application, which is hereby incorporated by reference. As shown in
FIG. 1
, the system
10
includes an x-ray source
12
and a miniaturized insertable probe assembly
14
capable of producing low power radiation in predefined dose geometries or profiles disposed about a predetermined location. The probe assembly
14
includes a shoulder
16
which provides a rigid surface by which the system
10
may be secured to another element, such as a stereotactic frame used in the treatment of brain tumors. The probe assembly
14
also includes an X-ray emitting tube
18
, or “probe”, rigidly secured to shoulder
16
. This type of treatment is referred to as brachytherapy because the X-ray source is located close to or in some cases within the area receiving treatment. One advantage of brachytherapy is that the radiation is applied primarily to treat a predefined tissue volume, without significantly affecting the tissue in adjacent volumes.
Typical radiation therapy treatment involves positioning the insertable probe
18
into the tumor or the site where the tumor or a portion of the tumor was removed to treat the tissue adjacent to the site with a “local boost” of radiation. In order to facilitate controlled treatment of the site, it is desirable to support the tissue portions to be treated at a predefined distance from the radiation source. Alternatively, where the treatment involves the treatment of surface tissue or the surface of an organ, it is desirable to control the shape of the surface as well as the shape of the radiation field applied to the surface.
The treatment can involve the application of radiation, either continuously or intermittently, over an extended period of time. Therefore, in some cases, the insertable probe
18
is adjustably supported in a compliant manner to accurately position the radiation source with respect to the treated site and accommodate normal minor movements of the patient, such as movements associated with breathing.
It is typically considered essential that the interface between the patient and the probe
18
be biocompatible. However, the probes are not always made from such material. Rather, as disclosed in the '900 patent and shown in probe assembly
14
of
FIG. 2A
, the probe
18
is usually a hollow, evacuated cylinder made of a beryllium (Be) cap
24
at one end, a molybdenum-rhenium (Mo—Re), molybdenum (Mo) or mu-metal tubular body
22
, and a probe shoulder
16
opposite the Be cap
24
. The tubular body
22
is rigidly secured to the probe shoulder
16
using bushing element
20
. A target assembly
26
is located inside the Be Cap
24
of probe
18
and emits x-rays in response to an incident electron beam produced from the x-ray source
12
of FIG.
1
. The target assembly includes an x-ray emission element consisting, typically, of a small beryllium (Be) target element
26
located within the cap
24
and coated on side exposed to the incident electron beam with a thin film or layer of a high-Z element, such as tungsten (W), uranium (U) or gold (Au). A typical probe of this type is 10-16 cm in length and has an inner diameter of about 2 mm and an outer diameter of about 3 mm.
Probe
18
is comprised of materials which maximize the x-ray emitting characteristics of the device, rather than materials which concern themselves with biocompatibility. Therefore, a biocompatible sheath
50
, shown in
FIG. 2B
, is typically used to encase the probe
18
during patient treatments. Such sheaths
50
are usually comprised of an elongated and cylindrical (assuming the probe to be cylindrical) body
52
, very closely mimicking the dimensions of the probe
18
. Additionally, a sheath
50
has a smooth hollow interior cavity defined by an inner surface of the sheath body
52
and a closed end
58
of the sheath
50
. The diameter of the inner surface of the sheath is about 3.3 mm, and accommodates insertion of a probe having an outer diameter of about 3 mm, as described above. Opposite the closed end
58
, is an open end
56
, which accommodates insertion of the probe
18
within the sheath
50
. Near the open end
56
of the sheath is a flange
54
and an annular ring
62
, as shown in FIG.
2
C. The circumferential outer surface of annular ring
62
is integral with the inner surface of sheath
50
and oriented within or near flange
54
. The probe opening formed within annular ring
62
is about 2.9 mm, which accommodates insertion of a probe body
22
of diameter of about 3 mm into the sheath
50
, in the direction of arrow
30
. Annular ring
62
ultimately comes to rest, at the terminus of the probe's
18
insertion into the sheath
50
, near the probe shoulder
16
, thereby removably securing the sheath
50
to the probe
18
. Because the diameter of the annular ring is less than the diameter of the probe body
22
, annular ring
62
is made to be compliant relative to probe body
22
. The compliance of the annular ring
62
causes the sheath
50
to securely grip probe
18
, so that sheath
50
does not become easily removed from the probe
18
during use. To achieve the desired advantages of biocompatibility and a compressible securing assembly, sheath
50
is typically made out of an aliphatic thermoplastic material, for example, “Tecoflex®” (supplied by Thermedics Inc. of Waltham, Mass.).
A problem with typical sheaths is that as a result of the smaller inner diameter of annular ring
62
, relative to the probe's outer diameter, and the location of the ring
62
at or near flange
54
of the sheath
50
, air becomes trapped within the region between the sheath
50
and probe
18
, as the probe
18
is inserted into the sheath
50
, as shown in FIG.
2
C. Therefore, it can be difficult to insert the probe within the sheath without exerting an undesirable amount of force on the probe and sheath combination, which could lead to bending of t

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