Radiant energy – Invisible radiant energy responsive electric signalling – With or including a luminophor
Reexamination Certificate
2001-12-21
2003-08-05
Porta, David (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
With or including a luminophor
C250S363020, C250S363040
Reexamination Certificate
active
06603124
ABSTRACT:
The invention relates to an apparatus for detecting and locating a radioactive source emitting gamma rays. It also relates to the use of the apparatus.
In the rest of the description, the detection apparatus of the invention applies more particularly, but not exclusively, to the detection of lymph nodes, some of which by fixing an in situ injected radioactive substance are capable of characterizing the extension of a tumor, especially in the case of breast cancer or skin cancer (melanoma).
However, other applications of the apparatus may be envisaged, such as the search for lost radioactive sources, the drilling of a material based on information available on its other face and, more widely, the detection and location of an almost point-like radioactive source through a medium that does not completely absorb the gamma rays that it emits, without this being restrictive.
Primary cancers firstly exhibit a local stage followed somewhat later by secondary sites. The extension process starts even before the clinical manifestations of dissemination are detectable. The first anatomical structures attacked outside the primary tumor are generally the lymph nodes. Thus, one cancer treatment consists in ablating the lymph nodes of the region in question. The purpose of such an operation is not only to remove possible secondary sites but also to diagnose possible metastasic dissemination, thus making it possible to propose the indication of a complementary medical treatment.
In the Particular case of breast cancer, the surgical treatment consists, apart from removing the primary tumor, in also removing the lymph nodes located in the axillary hollow, this operation being called “lymph node curage”, and then in carrying out a histological analysis of the lymph nodes removed.
Such an operation is a major source of functional sequela for the patient. First of all, the lymphatic engorgement resulting from removal of the lymphatic system draining the major part of the upper limb generates a pathology called lymphoedema or “fat arm” syndrome causing as much a functional impediment as unsightliness. Furthermore, it turns out that during curage the branches of the first intercostal nerves present in the axillary region are cut, thus leading to the appearance of sensitive disorders. Motor disorders of the shoulder also appear.
Furthermore, and above all, it turns out -hat the lymph nodes removed during axillary curage do not always prove, by histological analysis, to be invaded. It should be noted, in particular, that in the case of tumors less than or equal to 10 mm in size, only 6% of the lymph nodes removed are invaded. In other words, 95% of curages carried out are in fact unnecessary.
This is the reason why a number of techniques have been developed to try to detect preoperatively and/or preoperatively, and then to remove, only the lymph node or nodes likely to be attacked during the secondary extension of a primary tumor.
Thus, in a case of the treatment of a melanoma, it has been found that the first, relay node draining the melanoma (called the sentinel node) is capable of fixing a dye, particularly patent blue.
It has been demonstrated that the absence of invasion of the sentinel node corresponds in almost 100% of cases to the absence of invasion of the other nodes. It therefore becomes possible, by carrying out an extemporaneous analysis of the sentinel node, once identified and then removed, to decide during intervention whether or not to continue the lymph node curage.
However, according to this technique, since identifying the sentinel node is strictly visual, it is necessary to dissect the tissues in the region where it is assumed the sentinel node is. However, since the sentinel node has no perfectly defined location from the anatomical standpoint, this search is not simple and may prove to be lengthy and relatively impairing.
To solve this problem, it has been proposed to replace the dye with a radioactive substance. Detection of the sentinel node is then performed by one of two techniques, respectively:
either by scintigraphic imaging (lymphoscinti-graphy) using a scintillation camera;
or using a peroperative detection probe.
It turns out that scintigraphic imaging of lymph nodes, although validated in the display of nodes in non-cancerous pathology, is poorly suited to the specific detection of the sentinel node.
This is because, owing to its imposing weight (more than 1 tonne), the imaging apparatus is not transportable, so that the examination has to be performed preoperatively and elsewhere than in the room where said operation is being carried out, thus complicating the planning organization for the various parties involved.
Moreover, and above all, locating is performed by means of skin marking guided by a radioactive source brought into correspondence with the hyperfixing area on the image. Consequently, this mark is necessarily imprecise since;
firstly, it depends on how the head of the camera is angled;
secondly, it is often difficult to mark the skin accurately in a soft and not easily accessible region;
and finally, the surgeon cannot check in real time the well-foundedness of the skin mark.
At the same time, the angle of incidence of the incision may be different from that of the imaging, resulting in a location error which is all the greater the deeper the node.
In other words, the scintillation camera allows only coarse pre-locating of the position of the node during the preoperative stage.
On the other hand, the detection probe is a small piece of equipment, which can therefore be manipulated manually. This probe detects the gamma photons emitted by a radioactive source and allows audible location of said source placed within the beam angle of its collimator.
Technically, the detection probe includes a collimator consisting of a single hole, a scintillating crystal, a photomultiplier with a single anode, and associated electronic means for assessing, by a displayed numerical value or an audible signal, the intensity of the signal detected. However, this detection probe can only be used to assess the amount of radioactivity present in the field of view of its collimator, without being capable of specifying the precise direction in which the radioactive source lies.
In addition, it is very tricky to locate the node because of the very restricted angle of observation of the system and the large number of degrees of freedom in positioning. Moreover, because of the variability in the angle of incidence, and therefore in the thickness of the tissues through which the radiation emanating from the node passes, together with the inconstancy of the positioning, since the probe is hand-held, locating the nodes requites a great deal of time and sometimes proves to be fruitless.
In other words, the problem that the invention aims to solve is to provide an apparatus which allows preoperative and above all peroperative detection and precise location of a radioactive source, thus making it possible, for example in the case of the detection of lymph nodes, to avoid any unnecessary impairment in view of or during the surgical operation.
To solve this problem, the invention proposes an apparatus for detecting and locating a radioactive source emitting gamma rays.
This apparatus is characterized in that it comprises:
first means for determining the direction of the gamma-ray-emitting source with respect to the center of the detector;
a second means capable of pin-pointing the radioactive emission source.
In other words, the invention consists of a detection system making it possible during a surgical intervention to identify and precisely locate organs or tissues, and especially lymph nodes fixing a radioactive source emitting gamma rays.
Contrary to the technique of imaging using a scintillation camera, the objective is not to form a faithful image of the tissue or organ fixing the radicactive source, but to identify in which direction with respect to the center of the detector said source lies, so as to control the movement of the detector for the purpose of bringing this source oppos
Cardona, Esq. Victor A.
Heslin Rothenberg Farley & & Mesiti P.C.
Porta David
Sung Christine
LandOfFree
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