At the interface between oncology and physics, current technological advances which improve the management of cancer are mainly based on developing novel physical methods for screening, diagnosis and clinical therapy.  Of these, medical imaging techniques based on the use of radioactive tumor tracers have seen major growth, thanks to the development of new and specific compounds.  This multidisciplinary research goes beyond instrumentation, also addressing clinical aspects and aiming to establish appropriate methodologies to evaluate the usefulness of this device in patients.  It is in this context that scientists in the IMNC laboratory have initiated an inter-disciplinary research group with physicians at Hôpital Tenon (Paris), whose work has enabled the development of a Hospital Program for Clinical Research (PHRC), a national project which includes the clinical evaluation of POCI imaging in 200 female patients.

POCI, a novel medical imaging system

In the surgical treatment of cancer, probes acting as radioactivity counters have been introduced into the operating room to provide real-time guidance to surgeons during the ablation of previously radio-labeled tumors.  This radio guidance technique enables access to the precise location of tumor tissues, and their complete ablation.  It was to enhance this technique that the "Imagerie et Modélisation en Cancérologie" team at the IMNC undertook to develop a new generation of miniaturized gamma cameras to assist in the surgical treatment of cancer, called POCI. This is a particularly novel application of the recently developed instruments used in fundamental physics.  With a field of view of 13 cm² and reduced dimensions(5), this imaging device has been designed so that it can easily be positioned on the surgical wound in order to locate radio-labeled tumor lesions during the surgical procedure (see Figure 1).

The POCI imaging device is currently being assessed in the context of a "sentinel lymph node"(6) protocol in breast cancers.  In practice, the cancer is detected by injecting a radioactive solution around the tumor.  Lymphoscintigraphy(7) can then count the lymph nodes and situate them precisely.  Finally, a biopsy(8) is usually performed in the operating room using the radioactive counter probe, which allows the surgeon to check the position of the "sentinel lymph node" prior to making an incision, in order to identify it in the surgical wound and then, after ablation, to confirm the absence of any residual radioactivity.

Clinical evaluation of the POCI camera, which for the first time is bringing together researchers from IN2P3-CNRS and AP-HP(9), is based on a double study: firstly, to prove its equivalence compared with standard gamma cameras, and secondly to confirm its value in the operating room regarding the identification of "sentinel lymph nodes" which are not detected by standard probes.  Initiated in January 2006 with the agreement of the Ethics Committee (Comité consultatif de protection des personnes dans la recherche biomédicale, CCPPRB) and the French Agency for the Safety of Healthcare Products (Agence française de sécurité sanitaire des produits de santé, AFSSAPS), this clinical trial includes 200 female patients.  After the examination of some 100 patients using the POCI camera, in both the Nuclear Medicine Department and the operating room, the initial results are extremely encouraging (see Figure 2). 

Several research groups, particularly in North America, Japan and Italy, have turned towards the development of portable gamma cameras(10) designed specifically for peroperative screening.  It is in this context of strong international competition that the IMNC team is the only one at present to have evaluated the miniaturized imaging system as an aid to the surgical treatment of cancer, both in the operating room and in a significant number of patients.

 

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© camera IMNC / CNRS 2007 (this picture is available from the CNRS photo library, phototheque@cnrs-bellevue.fr)

Figure 1: Use of the POCI

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© IMNC / CNRS 2007 (this picture is available from the CNRS photo library, phototheque@cnrs-bellevue.fr)

Figure 2: Lymphoscintigraphic image obtained using:
A)a standard gamma camera which reveals a radioactively-labeled "sentinel lymph node"
B)the POCI camera which reveals three, radioactively-labeled "sentinel lymph nodes"

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How was the POCI camera born?

The team started the POCI project in 1996 at the Institut de physique nucléaire d'Orsay (IN2P3-CNRS, Université Paris-Sud): two years later, their results enabled the development and characterization of the first feasibility prototype, which offered a field of view of 25 mm in diameter.  In 1999, the POCI camera was the first miniaturized gamma camera to be introduced into the operating room, in the context of a protocol to detect "sentinel lymph nodes" in patients presenting with a melanoma or breast cancer.  During successive stages of the development and clinical evaluation of the POCI system, the team has succeeded in generating a prototype which was validated by the AFSSAPS.  This scientific success has also made a marked contribution to the creation of an interdisciplinary laboratory, IMNC, where today, multimodal peroperative imaging constitutes a major area of research.

 

Notes:

1) "Imagerie et modélisation en neurobiologie et cancérologie" laboratory (IMNC, IN2P3-CNRS / University Denis Diderot Paris 7 / University Paris-Sud 11). IN2P3 is CNRS' National Institute for Nuclear and Particle Physics
2) POCI for Peroperative Compact Imager refers to the gamma camera developed by the "Imagerie et Modélisation en Cancérologie" team at the IMNC.
3) This camera is a scintigraphic system which detects gamma rays and thus reflects their spatial distribution.
4) Per-operative imaging performed during surgery, in the operating room.
5) The imaging device measures 9.5 x 9.5 × 9 cm, and weighs 1.2 kg.
6) The sentinel lymph node is the first lymph node into which fluid drains from the area containing the tumor (in this case, breast tissue). Because of its anatomical position, it is theoretically the lymph node most likely to contain metastases if the cancer cells have spread.
7) Lymphoscintigraphy is an investigation of the lymph nodes using a standard gamma camera after administration in the patient of a radioactive tracer which enables the external detection of certain structures in the body (this in vivo functional imaging is based on detecting gamma radiation emissions).
8) A biopsy is a medical examination which consists in sampling pathological tissue with a view to histological analysis.
9) Paris Public Hospitals AP-HP) is the sponsor of this study. In addition, exploitation of the clinical results has been the subject of an initial collaborative contract between AP-HP and CNRS-IN2P3.
10) These are systems which weighing less than 2 kg and thus do not require the use of an additional articulated arm.

References:

For further information:
Since that time, other research teams have become interested in the field of peroperative imaging, and particularly the IN2P3 (LPC Clermont-Ferrand, IPHC Strasbourg).
- « L'imagerie nucléaire miniaturisée pour le traitement chirurgical du cancer » (CNRS Info n°400, mars 2002) :
View web site
- « Electronique d'acquisition d'une gamma-caméra » (2005) : View web site
- « Cancer du sein : des outils pour localiser les ganglions potentiellement métastasés » (2005) : View web site

Contact information:

Researcher
Stéphanie Pitre
T 01 69 15 71 90
pitre@imnc.in2p3.fr

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Priscilla Dacher
T 01 44 96 4606

IN2P3-CNRS communications
Christina Cantrel
T 01 44 96 47 60