[Imaging the brain, from the cell to the organ]. / Imagerie de l'encéphale, de la cellule a l'organe.

Brain imaging has progressed over the centuries, from prehistory (surgical and sculptural empiricism), through the Middle Ages (dissection and drawings), the Renaissance (printing) and the 18th century (Spallanzani and ultrasounds), to the 19th century and the discovery of piezoelectricity by the Curie brothers and X-rays by Röntgen in 1895. The head had finally become transparent! The microscope was used by Ramon Y Cajal for histological and neuropathological brain studies. Marie Curie's discovery of radioisotopes paved the way for advances in in vivo neurophysiology. In the 20th century, technical progress accelerated with the advent of computed tomography. Injected contrast products were initially negative (air for ventriculography and pneumo-encephalography), and subsequently positive (intraventricular then intraarterial iodine, cerebral arteriography, increasingly hyperselective). Neurology and neurosurgery were followed by neuroradiology, stereotaxy, and interventional neuroradiology. G.N. Hounsfield's EMI CT scanner replaced silver salts crystals with computed pixels and voxels. Magnetic resonance imaging (MRI, 1981), which dispenses with the need for X-rays, is evolving at the same pace as computer science itself (Moore's Law) in the form of nanometric biophotonics for example. Diffusion MRI is providing precious information on neuroanatomy (axonal organization of the white matter and neuro-tractography, vascular anatomy), neurochemistry (MRS) and neurophysiology. Functional MRI of sensory activation and resting connectivity, the substrate of thought, is giving fascinating results. Functional stereotactic neurosurgery (for epilepsy, abnormal movements, etc.), stereotactic radiosurgery and endovascular interventional neuroradiology are among the latest approaches.

[Computed tomography and cranial paleoanthropology]. / Scanner à rayons X et paléoanthropologie crânienne.

Since its invention in 1972, computed tomography (C.T.) has significantly evolved. With the advent of multi-slice detectors (500 times more sensitive than conventional radiography) and high-powered computer programs, medical applications have also improved. CT is now contributing to paleoanthropological research. Its non-destructive nature is the biggest advantage for studying fossil skulls. The second advantage is the possibility of image analysis, storage, and transmission. Potential disadvantages include the possible loss of files and the need to keep up with rapid technological advances. Our experience since the late 1970s, and a recent PhD thesis, led us to describe routine applications of this method. The main contributions of CT to cranial paleoanthropology are five-fold: --Numerical anatomy with rapid acquisition and high spatial resolution (helicoidal and multidetector CT) offering digital storage and stereolithography (3D printing). --Numerical biometry (2D and 3D) can be used to create "normograms" such as the 3D craniofacial reference model used in maxillofacial surgery. --Numerical analysis offers thorough characterization of the specimen and its state of conservation and/or restoration. --From "surrealism" to virtual imaging, anatomical structures can be reconstructed, providing access to hidden or dangerous zones. --The time dimension (4D imaging) confers movement and the possibility for endoscopic simulation and internal navigation (see Iconography). New technical developments will focus on data processing and networking. It remains our duty to deal respectfully with human fossils.