LASER POINTER DEVICE TO LOCALIZE SITE OF RADIOACTIVITY IN THE BODY

DISPOSITIF DE POINTAGE LASER POUR LA LOCALISATION D'UN SITE DE RADIOACTIVITE DANS UN CORPS

English Abstract

A laser localizer may include a laser pointer on handle to be placed co-
parallel against the surface of a detector head of a gamma camera and a mirror
angled to direct the laser beam normal with respect to the detector head
surface. The source of radiation may be a button containing Co-57 or other
radioactive material placed under the mirror. When the image of the
radioactive material in the laser localizer is superimposed on an image of a
source of radioactive uptake in the patient on a system monitor, the laser
beam will automatically point to the source within the body.

French Abstract

La présente invention a trait à un appareil de localisation par laser pouvant comporter un pointeur laser monté sur une poignée destiné à être disposé mutuellement en parallèle contre la surface d'une tête de détection d'une caméra gamma et un miroir incliné pour orienter le faisceau laser perpendiculairement par rapport à la surface de la tête de détection. La source de rayonnement peut être un bouton contenant du cobalt 57 ou autre matériau radioactif disposé sous le miroir. Lors de la superposition de l'image du matériau radioactif dans l'appareil de localisation par laser sur une image d'une source d'apport radioactif chez le patient sur un moniteur du système, le faisceau laser effectuera automatiquement un pointage vers la source au sein du corps.

Claims

CLAIMS
1. An apparatus comprising:
a laser source to generate a laser beam;
means for directing the laser beam at an angle normal to
the surface of a detector head at a first location; and
means for indicating on a monitor a second location
corresponding to the first location on the detector head
surface.
2. The apparatus of claim 1, wherein the means for
directing the laser beam comprises a mirror.
3. The apparatus of claim 2, wherein the means for
indicating comprises a radioactive material.
4. The apparatus of claim 3, wherein the radioactive
material is placed under the mirror such that the radioactive
material is between the mirror and the detector head surface
when the apparatus is in an operating position.
5. The apparatus of claim 1, wherein the means for
indicating comprises a pressure sensitive device.
6. The apparatus of claim 1, further comprising a
handle connected to the laser source and adapted to be placed
against the detector head surface.
7. The apparatus of claim 1, further comprising a base
to maintain the laser beam at an angle normal to the detector
head surface.
8. A method comprising:
imaging a body with a gamma camera;
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identifying an image corresponding to a source of
radioactive uptake in a body on a camera monitor;
placing a localizer including an indicator on a
detector head surface;
positioning the indicator in the localizer on the
detector head surface such that an image representative
of the indicator is superimposed on the image of the
source of radioactive uptake; and
directing a laser beam at an angle normal to the
detector head surface at the position of the radioactive
material on the detector head surface.
9. The method of claim 8, wherein the indicator
comprises a radioactive material.
10. The method of claim 8, wherein the laser beam
directed at an angle normal to the detector head surface
is directed to the source of radioactive uptake in the
body when the image representative of the indicator is
superimposed on the image of the source of radioactive
uptake.
11. A laser localizer to localize a site of
radioactivity in a body, the laser localizer comprising:
a handle to be placed against a surface of a
detector head;
a laser pointer connected to the handle and oriented
to generate a laser beam parallel to the detector head
surface;
a mirror in the path of the laser beam and tilted to
direct the laser beam 90 degrees from the detector head
surface; and
a holder positioned under the mirror, the holder
adapted to hold a radioactive material.
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12. The laser localizes of claim 11, further
comprising a base having a flat surface positioned under
the mirror.

Description

CA 02478686 2004-09-07
WO 03/076004 PCT/US03/07020
LASER POINTER DEVICE TO LOCALIZE SITE OF
RADIOACTIVITY IN THE BODY
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S.
Provisional Patent Application Serial No. 60/362,673, filed on
March 8, 2002, the disclosure of which is considered part of
(and is incorporated by reference in) the disclosure of this
application.
BACKGROUND
[0002] Localization of gamma photon-emitting radioactive
accumulations in the body is commonly performed by using a
gamma camera to produce an image of the distribution of
radioactivity in the body. It may be relatively easy to
relate the source of radioactivity to surrounding structures
if there are adjacent anatomical references, e.g., other
radioactivity, but it is difficult to precisely localize
single sources. This is particularly true when, for example,
a surgeon wants to biopsy a specific site indicated by focal
radioactive uptake. This is made even more difficult when the
procedure is performed in the operating room under sterile
conditions.
SUMMARY
[0003] The invention permits the precise localization of a
gamma emitting source of radioactivity in the body as viewed
by a nuclear gamma camera or similar radioisotope imaging
device. The radioactivity within the body is caused by a
radioactive chemical having been administered by intravenous
injection, orally, or by surgical implantation. Using a gamma
camera or similar planar (2-D) imager plus a laser pointer
that slides over the face of the camera, the operator can
locate the source of radioactivity in the body from the

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location of the laser beam on the surface of the patient.
This is accomplished by having a second, small point source of
radioactivity located coaxially with respect to the laser beam
so that both the radioactive source in the body and the
radioactive point source on the laser pointing device can be
observed on the monitor display of the gamma imager. When
these images superimpose, the laser beam will automatically
point to the source within the body.
[0004] The laser localizer may include a laser pointer on a
handle adapted to be placed co-parallel against the surface of
a detector head of the gamma camera and a mirror angled to
direct the laser beam normal with respect to the detector
head surface. The source of radiation may be a button
containing cobalt-57 (Co-57) or other radioactive material
such as technetium-99m (Tc-99m) positioned to be coaxial with
the laser beam.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] Figure 1 illustrates images of radioactive sources
shown on a gamma camera monitor.
[0006] Figure 2 is a side view of a laser localizer in an
operating position.
[0007] Figure 3 is a flowchart describing a real-time
laser-guide localization technique.
[0008] Figure 4 is a perspective view of the laser
localizer in use.
[0009] Figure 5 is a perspective view of a laser localizer
according to an alternative implementation.
[0010] Figure 6 illustrates images of radioactive sources,
including that from the laser localizer, on the gamma camera
monitor.
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DETAINED DESCRIPTION
[0011] In nuclear medicine imaging, very low-level
radioactive chemicals (called radionuclides,
radiopharmaceuticals, or radiotracers) are introduced into the
body. The radioactive chemicals may be introduced orally,
intravenously, or by surgical implantation. The radioactive
chemicals may be taken up by the organs in the body and then
emit gamma rays the spatial distribution of which are measured
by a gamma camera.
[0012] A gamma camera has one or more crystal detector(s),
called scintillation crystal(s). These crystals detect the
emitted gamma rays and convert the energy of the gamma ray
into optical photons . The intensity and spatial location of
these photons are then converted to electric signals, which
are digitized and are reconstructed into an image by a
computer. Other types of gamma cameras may have detectors
that directly convert the gamma ray energy into an electric
signal. Regardless of the method of conversion, the resulting
image is viewed on a system monitor.
[0013] It may be difficult to translate the position on the
system monitor to the location of a single source of
radioactive uptake in the body. Reference sources may be used
to relate the position of a source of radioactive uptake shown
on the monitor to a position on the patient's body. For
example, a calibrated radiation source may be placed on the
skin, an image 105 of which shows up on the system monitor
100, as shown in Figure 1. The source of radioactive uptake
110, e.g., a sentinel lymph node, may be identified by its
relative position to the injection site 115 and the calibrated
source on the patient's skin.
[0014] In an embodiment, a laser localizes device is used
to precisely localize sources of radioactive uptake in the
patient. Figure 2 shows an exemplary laser localizes 200.
The laser localizes may include a laser pointer 205 on a
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handle 210 and a mirror 215 angled to reflect a laser beam 220
from the laser pointer at a 90 degree angle to the plane of
the handle. A source of radiation 225 is positioned under the
mirror 215. The source of radiation may be, e.g., a removable
button containing the cobalt-57 (Co-57) radioactive isotope.
[0015] Figure 3 is a flowchart describing a real-time
laser-guided localization operation 300 according to an
embodiment. A radioactive material is introduced into the
patient (block 305). The patient is imaged with a gamma
camera (block 310), and a source of radioactive uptake is
identified on the system monitor (block 315). The laser
localizer 200 is placed flat against the detector head 405 of
the camera (block 320), which has a flat, two-dimensional
surface 410, as shown in Figure 4. The laser pointer 205 may
then be activated (block 325). The laser pointer on the
handle 210, and hence the laser beam exiting the laser source,
are parallel to the plane of the detector head surface 410.
The mirror 215 bends the laser beam so that it is normal to
the detector head surface 410. A large, flat base 505 may
also be provided on the laser localizer under the mirror to
help keep the device flat and the laser,beam perpendicular to
the detector head surface 410, as shown in Figure 5. The
laser beam illuminates a spot 250 on the patient's body 255
corresponding to the position of the radioactive button 225 on
the detector head surface 410.
[0016] The radioactive button (Tc-99m is shown) appears as
a hot spot 600 on the monitor, as shown in Figure 6. The
operator slides the laser localizer over the surface of the
detector until the image of the radioactive button 600 is
superimposed over the image of the radioactive uptake source
605 shown on the system monitor (block 330). Superimposition
of the images as viewed on the monitor indicates that the
laser beam is pointing directly at the site of radioactive
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uptake (block 335), which may be beneath the surface of the
skin or other tissue.
[0017] It may be desirable to mark the position of the
source on the monitor itself because the intensity of the
image of the radioactive material in the button may be much
greater than that of the radioactive uptake source in the
patient's body.
[0018] The localization technique may be used for a variety
of imaging applications. For example, the laser localizes may
be used to identify sentinel lymph nodes when screening for
breast cancer. Sentinel node localization and skin marking
can be performed outside of the operating room as long as the
correct position of the patient is maintained. Alternatively,
the node localization may be performed in the operating room.
Furthermore, imaging immediately following surgical removal of
the sentinel nodes can provide assurance that all nodes were
removed.
[0019] The real-time laser-guided localization technique
may be advantageous in instances when marking the patient's
skin prior to surgery is impractical, e.g., when screening for
colorectal cancer where the skin and tissue over the source of
radioactive uptake needs to be moved or removed.
[0020] In alternative implementations, other tracking
technologies may be applied, which may eliminate the need for
the radioactive button on the laser localizes. For example, a
pressure-sensitive, radiation-transparent (at least to
radiation of interest) tablet may be placed over the detector
head surface and a tip placed under the mirror. The tablet
may translate the position of the tip on the tablet, and hence
on the detector head surface, to a position on the system
monitor.
[0021] A number of embodiments have been described.
Nevertheless, it will be understood that various modifications
may be made without departing from the spirit and scope of the

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invention. For example, blocks in the flowchart may be
skipped or performed out of order and still produce desirable
results. Accordingly, other embodiments are within the scope
of the following claims.
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