Speculation about the physical and neuroanatomical aspects of criminal behaviour began with Franz Joseph Gall at the end of the 18th century. His observations evolved into phrenology, a theory that assigns specific mental functions to topographical regions of the skull (1). Until recently, EEG was one of our main methods of looking at brain abnormalities in cases of aggressive behaviour, but the nonspecific and relatively unlocalized nature of the findings limited its interpretation. Now, more than 2 centuries after Gall, neuroimaging technologies promise to greatly enhance our understanding of the biological underpinnings and substrates of antisocial behaviour in a way that Gall could not even imagine. Structural techniques, such as CT or magnetic resonance imaging (MRI), look at brain architecture, detailing size, shape, and location of tissue damage. Functional approaches, such as positron emission tomography (PET) or functional MRI, add the dimension of live neural activity. This paper reviews imaging technology as applied to the study of antisocial behaviour. Each approach is summarized and followed by relevant clinical studies.

Manuscript received March 2001, revised and accepted July 2001.
¹Lecturer, University of Toronto; Staff Psychiatrist and Head, Young Offender Team, Child Psychiatry Program, Centre for Addiction and Mental Health, Toronto, Ontario.
Address for correspondence: Dr L Bassarath, Centre for Addiction and Mental Health, 250 College St., Toronto, ON M5T 1R8
lindley_bassarath@camh.net

For a more detailed discussion of the technical aspects of neuroimaging assessment, the reader is referred elsewhere (2,3).

The earliest imaging method involved X-rays, discovered in 1895. A form of electromagnetic radiation, X-rays provide contrast as they attenuate differently, depending on tissue density. The soft tissues of the brain proved to be a barrier to use, however, except for gross pathology due to brain displacement. In 1918, the next development was pneumoencephalography (4). Here, air was injected into the subarachnoid space, followed by delineation of ventricles. In 1927, an emerging functional technique, cerebral arteriography, was developed (5). The next milestone was Wada’s injections of sodium amytal into the carotid artery to assess language laterality (6). The pre-CT era was largely dominated by angiography.

Computerized Tomography (CT)

Tomographic imaging refers to X-ray images of specific planes within the body. The digital computer revolution of the late 1960s made CT possible. Also known as computerized axial tomography (CAT), CT was developed in the early 1970s by Godfrey Hounsfield of Great Britain and Allen Cormack of the US. Narrow beams of X-rays sweep sequentially across the head, resulting in a series of electrical impulses recorded by a radiation detector. Sophisticated computer software integrates the data, using the radiation absorption figures to assess tissue density and create 2-dimensional slices of the brain.