Open structure breast coil and support arrangement for interventional MRI

A pair of RF quadrature detection coils are fitted in an open support structure that allows easy diagnostic access to all tissue areas of the human female breast when performing interventional MRI. The open structure dual coil arrangement comprises a flat base and a slightly "V"-shaped bi-planar upper section supported above the lower base section by eight narrow vertical legs. The upper bi-planar section includes two circular openings for accepting the breasts. Four of the support legs are equally spaced at 900 intervals around each breast opening and provide large side-open access areas to the breast tissues via the sides of the support structure. The "V"-shape of the upper portion of the coil support structure increases the gap clearance at both left and right sides of the support structure to further enhance access to the breasts. In a preferred embodiment, two complete MRI quadrature detection coils are supported by the structure and each of the vertical support legs house a pair of conductors forming part of a quadrature detection coil winding. The use of quadrature detection coils increases MRI signal detection efficiency and the open structural support arrangement allows increased accessibility to the breast tissues for efficient interventional MR imaging and easy cleaning after use.

FIELD OF THE INVENTION 
This invention relates to open structure RF receive coils and an associated 
support structure for magnetic resonance imaging (MRI). More specifically, 
it relates to a quadrature type receive coils and associated support 
structures for obtaining MR images of the human breast which allows ample 
access to the breast tissues for permitting interventional MRI procedures. 
BACKGROUND OF THE INVENTION 
Magnetic resonance (MR) images acquired during surgery can assist a surgeon 
to accurately locate tissue malignancies, obtain a biopsy from desired 
locations and ensure successful tissue removal. Interventional MRI is the 
magnetic resonance imaging technique (often involving real-time imaging) 
that allows a surgeon to perform MRI-guided tissue biopsy or surgery. One 
application of interventional MRI is to guide a surgeon during a biopsy or 
surgical operation on one or both of the breasts of female patients 
Interventional MRI procedures typically require that an MR signal detection 
coil have large openings so that a surgeon can have access to the surgical 
site through the coil with biopsy needle or other surgical devices. The 
need for surgical access through an MR signal detection coil is a 
significant constraint on the design of the coil. To meet the tissue 
accessibility requirements of interventional MRI procedures, conventional 
MRI breast coils are often single-channel simple coil windings having a 
structural configuration that limits coil performance. 
One such example of a simplified breast coil configuration used in MRI is a 
conventional flat single-loop surface coil. This type of breast coil is 
typically placed around a breast near the chest wall of the patient. A 
major disadvantage of the simplified breast coil is that it has very poor 
field homogeneity. In other words, it provides very poor received signal 
quality from any tissue that is far away from the loop. Because of these 
disadvantages, for example, a surgeon may not be able to positively 
identify or remove malignancies at certain regions of the breast, 
especially in tissue that is removed from the breast coil. 
The signal detection efficiency of a MRI detection coil is important to 
providing useable tissue images. A higher signal detection efficiency 
means a better quality signal and a cleaner image which allows a surgeon 
to see the subject tissues more clearly and make correct decisions 
regarding the imaged tissues. In this regard, it is known that an RF 
quadrature type detection coil can provide a much improved signal 
detection efficiency over the simple single channel coil typically used 
for interventional MRI surgical procedures. 
In interventional MRI it is crucial that an RF reception coil produce high 
quality, low noise MR signals that will result in good quality high 
resolution images so that a surgeon can accurately identify, locate and 
access the desired tissues. A competing requirement for interventional MRI 
detection coils is that they allow surgical access to the surgical site. 
The difficulty in providing surgical access is especially difficult for 
breasts, due to their sizes and shapes. The compromised performance of 
conventional MRI breast coil arrangements may lead to poor imaging and 
hence false diagnosis or imprecise surgery. In accordance with the present 
invention, a novel MRI breast coil and support arrangement is provided 
that utilizes a highly efficiency quadrature type detection coil 
arrangement and has an open structure for allowing maximum access to 
imaged tissues. 
SUMMARY OF THE INVENTION 
The present invention is directed to a dual receive coil and support 
structure arrangement for interventional MRI that is capable of 
simultaneously accepting two human female breasts. A pair of RF quadrature 
detection coils are fitted in an open support structure that allows easy 
diagnostic and surgical access to tissue areas when performing 
interventional MRI procedures (e.g., tissue biopsy or surgery during 
imaging). 
In accordance with the present invention, an MRI breast coil support 
structure comprises a flat base and a bi-planar upper portion supported 
above the lower base portion by narrow vertical legs that provide large 
between-plane openings for easy surgical access to the breasts by a biopsy 
needle or other diagnostic instruments. The upper portion is slightly 
"V"-shaped (bi-planar) and includes two circular openings for accepting 
the breasts. The slight "V"-shape of the bi-planar upper portion increases 
the clearance at both left and right sides of the coil support structure 
to further enhance accessibility to the breasts from the sides. Eight 
vertical support legs--four equally spaced at 90.degree. intervals around 
each breast opening--provide large open access areas to the breast tissues 
via the sides of the coil support structure. In a preferred embodiment of 
the present invention, two complete pairs of MRI quadrature detection 
coils are supported by the structure. Each of the vertical support legs 
house a pair of conductors to form a portion of a quadrature detection 
coil winding. In particular, the four support legs house the four legs of 
a quadrature-detection coil for each breast. 
The open structure coil support structure of the present invention, 
comprising a "V"-shaped top plane, flat bottom plane and eight connecting 
legs altogether, is easily fitted with either a conventional detection 
coil or a high efficiency quadrature type receive coil, and allows 
increased accessibility to the breast tissues for efficient interventional 
MR imaging. In addition, the open structure of the present invention 
allows for easy cleaning after use. 
Accordingly, one embodiment of the invention is a magnetic resonance 
imaging (MRI) quadrature detection coil and support structure comprising: 
a lower surface; 
an upper surface having an aperture to receive a body part; 
four legs connecting the upper and lower surfaces, wherein the four legs 
are arranged around the aperture; 
an RF quadrature detection coil having conductor windings circumferentially 
around the aperture in the upper surface and conductor windings in each of 
the four legs, and 
an open gap between the upper and lower surfaces to allow access through 
the coil and support structure to the body part. 
Another embodiment of the invention is a dual magnetic resonance imaging 
(MRI) quadrature detection coil and support structure arrangement, 
comprising: 
a bottom portion; 
an upper portion comprising first and second upper sections, where each 
section has an aperture to receive a breast; 
eight leg portions connecting said top and bottom portions, wherein four 
leg portions are arranged around each aperture; 
a first RF quadrature detection coil having conductor winding portions 
positioned circumferencially about the aperture in the first upper section 
and conductor winding portions in each of four leg portions disposed 
around the aperture in the first upper section; and 
a second RF quadrature detection coil having conductor winding portions 
positioned circumferencially about the aperture in the second upper 
section and conductor winding portions in each of four leg portions 
disposed around the aperture in the second upper section. 
A further embodiment of the invention is a magnetic resonance imaging RF 
coil support structure, comprising: 
a flat-planar bottom portion; 
a bi-planar v-shaped upper portion comprising first and second planar 
sections each section having a large circular opening; 
eight leg portions connecting said top and bottom portions, wherein each 
leg portion is disposed perpendicular to said bottom portion and four leg 
portions are arranged around each opening at substantially equal 
90.degree. intervals; and 
a base support housing portion.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENT 
FIG. 1 shows a perspective view of a dual breast MRI receive coil support 
structure 1 comprising a "V"-shaped upper bi-planar portion 2, a bottom 
flat planar section 3, eight vertical leg portions 4 between the upper and 
bottom planar sections, and a base housing portion 5, below the bottom 
planar section. 
The planar upper section 2 comprises left and right planar sections 2a, 2b 
that are mirror symmetrical along center line 11. The slight "V"-shape of 
the bi-planar upper section increases the clearance between the upper and 
bottom sections at both left and right sides of the coil support structure 
1 to enhance accessibility to the breasts from these sides. 
Each of the left and right upper planar sections 2a, 2b has a large central 
circular opening 16a, 16b for accepting a breast. Surrounding the circular 
opening in each upper section, a shallow groove 6 is provided on the top 
surface for housing conductors which form a portion of a supported MR 
signal detection coil. The groove 6 is fitted in the rim of the openings 
16a, 16b of a double-sided printed circuit (PC) board 7 that contains 
printed circuit conductor portions of a quadrature type receive coil 
winding. 
Covering groove 6 is a thin electrically-insulating ring-shape protective 
shield 8 that is closely fitted to seal the groove against moisture and 
fluids. An enlarged drawing of the shield 8 is shown in FIG. 3. The shield 
8 may be formed of a plastic material that does not interfere with or 
diminish RF signals. In addition, the doubled-sided PC board 7 may be an 
annular ring having conductive coil windings mounted on circumferential 
interior 7a and exterior 7b surfaces of the board, or be an annular disk 
having conductive coil windings on upper and lower sides of the PC board, 
as is shown in Ser. No. 09/199,411 to Sunyu Su, entitled "Quadrature 
Detection Coil For Interventional MRI", (attny. dkt. 202-76), which is 
incorporated by reference. 
Sufficient clearance is provided between the bi-planar upper section 2 and 
flat bottom support section 3 to allow easy access to all tissues of the 
breast when performing interventional MRI. For example, a construction 
having a gap (G) sloping from 31/4" at the center line 11 and outward to 
33/4" the left and right sides of the support structure 1. The sloping 
side gaps allow adequate access in most instances for the insertion of a 
biopsy needle. Larger opening spaces are also possible, to the extent that 
the vertical dimension of MRI magnet permits. Upper and lower sections 2 
and 3 are rigidly connected to each other by eight vertical legs 4. Four 
legs are positioned around each breast opening 16a, 16b. The four legs are 
spaced at equal 90.degree. intervals from each other around each opening. 
Each leg is provided with two parallel longitudinal hollow recesses 9 (see 
FIG. 2) or, alternatively, may be a vertical slit for access to the leg's 
interior. These recesses 9 (or slits) allow for the insertion of a 
conductor coil winding portion 13 of a MR signal detection coil. The 
vertical coil winding portions housed within support structure legs 4 
connect with a printed circuit conductor coil winding portions 7 on the 
annulus of the openings in the PC boards 7, and with other coil winding 
conductor portions (see FIG. 4, reference numeral 13) under bottom support 
plane 3 within base support housing 5. Additional longitudinal vertical 
recesses or openings may be provided in each leg to accommodate a more 
complex coil winding. In addition to serving as a housing for lower 
portions of MR signal detection coil windings, the base support 5 may also 
serve as a housing and storage compartment for other related MRI detection 
coil equipment such as LEMO cable 10 and/or, for example, a 
"tune-and-match" PC card. 
FIG. 4 shows schematically an RF quadrature signal detection coil 18, which 
are disclosed in more detail in application Ser. No. 09/199,411 which is 
incorporated by reference. The support structure 1 houses two of these 
quadrature signal detection coils 18. One quadrature detection coil fitted 
to each breast opening 16a, 1b, and its corresponding four support legs 4. 
Each quadrature coil comprises two individual MR receive coils 20a, 20b. 
Output lead connection points 22a, 22b are indicated at ends O-Q and R-L 
of the receive coils. Semicircular portions 12 (arcs F-H, E-G, B-D, A-C) 
of quadrature coil windings are printed on the ring-shaped PC board 7 
Fitted into grooves 6 of upper support section 2. Vertical conductor 
portions of quadrature coil windings 13 are fitted to longitudinal 
recesses 9 in support structure legs 4. The bottom portions of quadrature 
coil windings 14 are housed in base housing 5 beneath the planar support 
bottom 3. Each quadrature coil 18 has its four output lead connection 
points 22a, 22b (O, Q, R, L) from the individual coil windings connected 
to conductors in a multi-conductor LEMO cable 10. 
While the invention has been described in connection with what is presently 
considered to be the most practical and preferred embodiment, it is to be 
understood that the invention is not to be limited to the disclosed 
embodiment, but on the contrary, is intended to cover various 
modifications and equivalent arrangements included within the spirit and 
scope of the appended claims.