Radiology

Depuis quelques années, des progrès importants ont été effectués dans le diagnostic, le traitement et le suivi des patients atteints de cancer notamment grâce au formidable essor de l’imagerie médicale. Cette spécialité médicale utilise à la fois des méthodes irradiantes telles que la radiologie conventionnelle, le CT scanner, l’angiographie, la fluoroscopie, et des techniques non irradiantes telles que l’échographie et la résonance magnétique nucléaire. Chacune de ces modalités d'imagerie possède ses caractéristiques avec ses avantages et inconvénients que le radiologue et le clinicien connaissent et choisissent en fonction du contexte clinique, de l'organe à imager ou du type de tumeur à évaluer.

The use of X-rays must be carried out in an appropriate way, given that their abuse can exert a deleterious effect on the organs examined. In this context, major technological advances have been made in recent years designed to improve the quality of images produced in radiology and to reduce the time of exposure to X-rays. The immediate consequences of these advances are a significant shortening of the image acquisition time on the one hand, and access to high resolution (great detail) on the other. As the patient must suspend his breathing during the examination, these improvements render it possible to examine a much larger area than previously with a reduced time of respiratory arrest. Thus, with the computer tomography (CT) scanner, which is a method using X-rays, it is possible to image the entire thorax in a few seconds with slices of less than 1mm thickness. Just 10 years ago, it took about 30 seconds to image the same area with slices of about 5mm thickness.

Non-irradiating imaging methods have their advantages and disadvantages. Ultrasound is perfectly harmless, but the quality of the image and diagnosis depends strongly on the experience of the physician who performs it. Magnetic resonance imaging (MRI), unlike ultrasound, provides global images in cross-section of the organ studied, thus facilitating its examination. Acquisitions are made in different space planes in order to specify certain anomalies. The major advantage of this technique compared to the CT scanner, which also gives cross-sectional images, is to distinguish certain tissues, such as fat for example. MRI can be used repeatedly with complete safety for the patient. However, patients with ferromagnetic objects, such as pacemakers or certain bone fixation materials, cannot undergo this examination. It must be noted that the cost of this type of examination is relatively high..

A new technique, which is called PET-CT, has recently been introduced into the medical imaging arsenal. It is a scanner combining two medical imaging techniques: X-rays (CT) and positron emission tomography (PET). This new technology allows for providing in a single examination an idea of the functioning of the organs and their morphology. It is a successful combination that allows for a better diagnosis of certain diseases thanks to extremely precise images.

Medical imaging techniques are multiple and each one has its advantages and limitations. Yet, all of them contribute, depending on the case, to the diagnosis or treatment planning of cancers.

The decision to use a particular radiological technique to establish a diagnosis depends on the type of cancer. The procedure to be followed is determined in particular by the body area to be explored.

For example, to look for a lung lesion in a smoker, the pulmonologist examines the smoker and then orders a standard chest x-ray. If there is an abnormality, he or she will need to undergo a CT scan to determine if the lesion is benign or malignant. The CT scan will similarly reveal if there are any associated abnormalities such as damaged lymph nodes and bone abnormalities. In most cases, he will ask for a puncture guided by fluoroscopy, ultrasound, endoscopy or CT scan to determine the type of cancer to treat. He will also determine the extent of the tumor using different imaging modalities.

In order to provide the high level of expertise and performance required by the multidisciplinary team caring for patients, we have a well-equipped technical platform with state-of-the-art equipment. The group of imaging specialists working in this entity is constantly updating themselves as knowledge and techniques evolve very rapidly. It is also relevant to understand that we have an image archiving system containing the entire patient history, rendering it is possible to draw comparisons between images taken at different times of the disease, such as to evaluate the effects of treatment.

For radiologists, as for all other medical specialties confronted with cancer, high competence and collaboration within a multidisciplinary team are an absolute necessity. Each radiologist is a specialist in a particular organ, of which she or he has a particularly acute knowledge and to which he devotes most of his activity.

Data from MRI, CT, or PET scans can be applied to plan radiotherapy treatments. Indeed, these examinations provide an idea of the size of the tumor, its contours, and the nodes that may be invaded. Radiotherapists can then make dose profiles to better target the lesion to be treated.

Radiology can also be employed as a means of guidance for radiofrequency, a technique based on the introduction of a probe into the affected organ in order to eradicate the tumor lesion.