Книги по МРТ КТ на английском языке / Functional Neuroimaging in Child Psychiatry Ernst 1 ed 2000

414 Glossary

1H nucleus is 1/2, and when placed in a magnetic Weld, it can exist in only two energy states.

Readout gradient Refers to the ªG-frequency-encodeº because the actual NMR data collection takes place when this gradient is in use.

Radiofrequency (rf) Wave frequency group intermediate between auditor and infrared range. The rf used in NMR studies is commonly in the megahertz (MHz) range. The principal eVect of rf magnetic Welds on the body is power deposition in the form of heating, mainly at the surface; this is the main area of concern for safety limits.

Radiofrequency pulse A short burst of radiofrequency (rf) electromagnetic radiation. Rotation of the magnetization vector can be caused by controlling the duration and amplitude of the rf pulse.

Radionuclide A nuclide of artiWcial or natural origin that exhibits radioactivity. For example, 131I is a radionuclide, whereas 127I is a stable nuclide. Radionuclides are radioactive nuclides.

Receiver coil Coil, or antenna, positioned within the magnet bore to detect the NMR signal: sometimes also used for excitation.

Reconstruction image An image representing a twodimensional slice of a structure; reconstructed from data obtained by means of any of the tomographic techniques.

Recovery time The time, following detection of a pulse, that must elapse before a second pulse can be detected. Also called resolving time or coincidence time.

Reference region A region of the brain that is assumed to be devoid ± or nearly devoid ± of receptors. Taken together with receptor-rich regions, the reference region data can often be used to analyze dynamic receptor±ligand data without the need for an arterial input function.

Region of interest (ROI) Outlined area on a computerprocessed image deWned automatically or manually to obtain the accepted events (e.g., radioactive counts in PET) in that area. Time activity curves result when the ROI is sequentially measured in multiple images of a study. Sometimes ROI is used informally to indicate a subset of voxels in a three-dimensional data set. In NMRS, a volume of interest in single voxel acquisition is usually 1 to 12ml, and a single spectrum from that region takes 2±10min to be obtained (in contrast to spectroscopic imaging).

Relaxation rates These are inversions of relaxation times (NMR): spin-lattice relaxation rate R1 5 1/T1. Spin-spin relaxation rate R2 5 1/T2.

Relaxation times After excitation, nuclei tend to return to

their equilibrium distribution in which the longitudinal magnetization is at its maximum value and oriented in the direction of the static magnetic Weld, the value of the transverse magnetization being zero. On cessation of the radiofrequency (rf) excitation pulse, the longitudinal magnetization Mz returns toward the equilibrium value M0 at a rate characterized by the time constant T1; any transverse magnetization decays towards zero with a time constant T2 (or T2* in the real situation) (NMR).

Repeated free induction decay Another term for saturation recovery (qv). A sequence in which 90° pulses are repeated for excitation and measurement. It results in partial saturation if the period between the 90° pulses is of the order of T1 or less and gives a T1-weighted signal. Generally the term is only applied where the signal is detected as a free induction decay (and not as an echo) (NMR).

Repetition time (TR) See time to repetition.

Rephasing gradient Gradient magnetic Weld applied for a brief period after a selective excitation pulse, in the opposite direction to the gradient used for the selective excitation. The result of the gradient reversal is a rephasing of the spins (which will have become out of phase with each other along the direction of the selection gradient), forming an echo by ªtime reversalº, and improving the sensitivity of imaging after the selective excitation process (NMR).

rf coils Coils that transmit the radiofrequency (rf) electro-

magnetic energy used to Xip Mlongitudinal into Mtransverse and to receive the NMR signal generated by the rf pulse.

Transmission and reception can be obtained by either a single coil or two separate coils. The reason to use separate coils is that the requirements are diVerent. A transmitter coil needs to be able to send its rf energy uniformly anywhere in the body. The receiver coil may only need to pick up signal from a small portion of the body in some cases. For example, a ªsurface coilº is sometimes used to receive the signal. It has better signal-to-noise near its center than a receiver coil designed to detect signals uniformly throughout a larger portion of the body.

Run In the context of functional MRI, a run refers to a single, continuous collection of images.

Sagittal plane Passes longitudinally through the body from front to back, dividing it into right and left halves.

Saturation After exposure to a single radiofrequency pulse, if T2 is much shorter than T1, then the net transverse magnetization will disappear before signiWcant repolarization of the spins occurs. During this time the sample is said to be saturated (NMR).

Saturation recovery The repeated free induction decay in

NMR sequence using images for which the pixel values are proportional to nuclear density and have a T1 dependence that varies with the repetition time of the sequence.

Sequence delay time The time between the last pulse of a pulse sequence and the beginning of the next identical pulse sequence. It is the time allowed for the nuclear spin system to recover its magnetization and is equal to the sum of the acquisition delay time, data acquisition time, and the waiting time (NMR).

Sequence repetition time This is the time between the beginning of a pulse sequence and the beginning of the succeeding identical pulse sequence.

Shim coils Coils carrying a relatively small current that are used to provide auxiliary magnetic Welds to compensate for inhomogeneities in the main magnetic Weld of an NMR system.

Shimming Correction of inhomogeneity of the magnetic Weld over a volume of interest. Inhomogeneity is produced by imperfections in the NMR magnet or the presence of external ferromagnetic objects. Shimming may involve changing the conWguration of the magnet, adding shim coils, or adding small pieces of steel.

Signal averaging Technique to improve signal-to-noise ratio (SNR) (sensitivity of the NMR experiment) by averaging repeated scans over a few minutes through the same region of interest. The noise tends to decrease because of its random nature, whereas the signal reinforces itself.

Slice selection The region whose electromagnetic vector will be Xipped can be limited to a slice by applying a gradient in the longitudinal direction while the initial saturation radiofrequency pulse is presented.

Smoothing The purpose of smoothing is to enhance an image by reducing high-frequency phenomena, such as statistical noise, while preserving the overall form of the data. However, since edges within an image or large gradients in a curve are dominated by high-frequency components, the eVect of smoothing is to reduce or ªaverage outº such features. Smoothing can be applied successfully to both images (spatial representation) and curves (temporal representation) from radionuclide images. For example, in many ªdynamicº studies, temporal (i.e., between corresponding pixels in several frames) or spatial (i.e., between adjacent pixels within a frame) smoothing is usually implemented prior to viewing the data in cine mode. It is important to understand that if the image data have been smoothed, then subsequent data extraction or display may be modiWed by the smoothing algorithm.

Glossary 415

Spatial frequency Wltering Technique for eliminating in an image the higher spatial frequencies, assumed to be noise; employs Fourier transform analysis (qv).

Spatial resolution The ability of an instrument to image two separate line or point sources of radioactivity as separate entities. The smaller the distance between the two sources, the better the spatial resolution. A measure of spatial resolution is the point spread function (PSF) or the line spread function (LSF) and the derived system transfer function (STF).

SPECT Single photon emission computed tomography. Spectroscopic imaging Acquisition of NMR spectra from

multiple volumes simultaneously (each contiguous volume of 1±2ml each); takes typically about 20 to 40min to complete.

Spin coupling The diVusion of magnetic moments owing to actual movement of the associated molecule and/or chemical exchange.

Spin density The density of resonating spins in a given region in SI units of molecules per cubic meter. For water, there are about 1.1!105 mol/m3 hydrogen, or 0.11 mol/cm3. True spin density is not imaged directly but is calculated from signals received with diVerent interpulse times.

Spin echo The reappearance of an NMR signal arising from refocusing or rephasing the various components of magnetization in the x, y plane. This usually results from the application of the 180° pulse after decay of the initial free induction decay. It can be used to determine T2 without contamination from inhomogenous eVects of the magnetic Weld (e.g., time to repetition (TR) spin-echo sequence 1800 to 2500ms; time to echo (TE) 80 to 120ms). Most 1H MRS uses a spin echo with a long TE ($100ms), which permits the measurement of three to four compounds present in the brain at relatively high concentrations (e.g., N-acetylaspartate (NAA), creatine (Cr) and phosphocreatine (PCr)). Short TE (#20ms) permits the observation and quantiWcation of other metabolies (e.g., glucose, myo-inositol, glutamate, glutamine, gamma-aminobutyric acid (GABA)).

Spin-lattice relaxation time See longitudinal relaxation time.

Spin-spin broadening Increased line width of the NMR spectra caused by interactions between neighboring dipoles. The line width of a peak from its intrinsic T2 time is typically #1Hz, whereas the line width from Weld inhomogeneity may be from 5 to 10Hz. The term T2* refers to the combined eVect of the intrinsic T2 of the peak and the magnetic Weld inhomogeneity that aVects the Weld width (NMR).

416Glossary

Spin-spin relaxation time See transverse relaxation time. Spin-spin splitting Splitting in the lines of an NMR spectrum arises from the interaction of the nuclear magnetic

moment with those of neighboring nuclei.

Surface coil NMR A simple, Xat, radiofrequency receiver coil placed over a region of interest will have an eVective selectivity for a volume approximately subtended by the coil circumference and one radius deep from the coil center. Such a coil can be used for simple localization of sites for measurement of chemical shift spectra, especially of phosphorus, and blood Xow studies. Some additional spatial selectivity can be achieved with gradient magnetic Welds.

T1 See longitudinal relaxation time. T2 See transverse relaxation time.

T2* (ªT.two-starº) The characteristic time constant for loss of phase coherence among spins oriented at an angle to

the static magnetic Weld inhomogeneities, %B, and spin-spin transverse relaxation with a resultant more rapid loss in transverse magnetization and NMR signal. NMR signal can still be recovered as a spin echo in times

less than or of the order of T2 (1/T2* 5 1/T2 1 %4/2; %45

)%B).

T1-weighted MRI An MR image generated using imaging parameters that cause contrast to be primarily based on

diVerences in T1 times for diVerent tissues. (Short time to repetition (TR) and time to echo (TE) are used for T1 weighting, e.g., TR 400±600ms, TE 10±30ms.) Tissues

with short T1 times are bright in T1 weighted images. The T1 contrast is best to delineate anatomic structures, diVerentiate white and gray matter, and detect subacute

hemorrhage.

T2-weighted MRI An MR image generated using imaging parameters that cause contrast to be primarily based on

diVerences in T2 times for diVerent tissues. (Long time to repetition (TR) and time to echo (TE) are used for T2 weighting, e.g., TR 1800±2500ms, TE 80±120ms.) Tissues

with long T2 times are bright in T2-weighted images. These images have strong contrast between normal

brain tissue and areas with high water content, for example cerebrospinal Xuid and pathologic tissue (i.e., tumors, inXammation, cysts, demyelinating processes).

High iron content decreases MR signal, especially on T2- weighted images. Gradient-echo sequences do not allow

true T2 weighting to be obtained (because of the absence of a refocusing radiofrequency pulse); rather a T2 contrast is obtained that corresponds to spontaneous signal

decay along the xy plane and depends on magnetic Weld

inhomogeneities. The T2* contrast is widely used in functional MRI.

Talairach coordinates A system for specifying locations in individual brains. It yields three coordinates (x, y, z) based on a rigid rotation of the brain to an orientation speciWed by anatomic landmarks and followed by a piecewise linear transformation of the brain in six sections that preserve continuity. It is the most widely used system for comparing brains between individuals. (It was Wrst developed and presented by J. Talairach in 1967.)

Time to echo (TE) The time (milliseconds) between presentation of the saturating radiofrequency pulse that

Xips Mlongitudinal by 90° and the time that an echo is detected (because of a refocusing pulse.) The total echo

time (TE) aVects the peak's intensity as a function of T2.

Time to inversion (inversion time, TI) The time (milliseconds) between the center of the Wrst inversion pulse and the middle of the saturating (90°) pulse in an inversion recovery pulse sequence.

Time to repetition (TR) The time (milliseconds) between presentation of the radiofrequency pulse that Xips

Mlongitudinal and the start of the succeeding sequence (NMR signal). It aVects a peak's intensity as a function of

T1.

Tesla The preferred (SI) unit of magnetic Xux density or Weld strength. One tesla (1 T) is equal to 10000 Gauss.

Time-activity curve A histogram of the change in the count rate as a function of time.

Transmission scan Detection of radiation transmitted through the body from a source on one side of the body to the detector on the opposite side; it provides an image of body absorption densities much like a radiograph but generally lacking the detailed resolution and produces data to be used in the calculation of attenuation correction (PET).

Transverse magnetization (Mtransverse) Component (Mxy) of the net magnetization vector orthogonal to the direction

of the main Weld (longitudinal, B0), whose precession, at the Larmor frequency, generates the NMR response signal. In the absence of externally applied radiofrequency energy, Mxy decays to zero with a characteristic time constant T2, or more strictly T2*.

Transverse relaxation time T2 (spin-spin relaxation time)

The exponential time constant that characterizes the decay of conWnement of magnetization to perpendicular to the external Weld. It is the rate at which nuclei reach equilibrium (go out of phase, lose phase coherence, with each other) and measures the gradual loss of magnetization in the plane perpendicular to the external magnetic Weld (B0). Starting from a nonzero value of the magnetization in the xy plane, the xy magnetization will decay so

that it loses 63% of its initial value in a time T2. Protons attached to large macromolecules have short T2 values and are observed as broad, short peaks, whereas protons attached to small metabolites have longer T2 values and are observed as narrow, tall peaks in the proton spectrum. See also T2*.

Transverse (transaxial) plane Passes horizontally through the body at right angles to the median sagittal

Glossary 417

plane and divides the body into upper and lower portions.

iReferencesi

Iturralde, M. P. (1990). Dictionary and Handbook of Nuclear

Medicine and Clinical Imaging. Boca Raton, FL: CRC Press.

phobias 234

social phobia 234±5 post-traumatic stress disorder 235±7

functional neuroimaging study 235±6 structural imaging studies 235

simulation training for anxiety reduction 225 see also obsessive-compulsive disorder

Asperger's syndrome 171, 342±3, 344 attention

cancellation tests of 291 development of 139±41

attention-de®cit hyperactivity disorder (ADHD) 41±2, 194, 195±6, 278±93, 398±9, 401

dopaminergic hypothesis 287 dyslexia and 268±9 epidemiology 278

future directions 292 neuroanatomic studies 280±7

anterior cingulate 285±6 caudate nuclei 283±4 cerebellum 286

corpus callosum 286±7 globus pallidus 285

hemispheric asymmetries 286±7 prefrontal cortex 281±3 putamen 284±5

neurobehavioral probes 288±92 cancellation tests of attention 291 Continuous Performance Tasks 288 impulsivity 291±2

response inhibition tasks 292 task development 288

working memory/short-term memory 288±91 phenomenology 278

subtypes 278

theoretical perspectives 278±80 diagnostic labels 278±9 functional neuroanatomy 279±80

attentional set-formation and shifting 373, 383±4 attenuation 409

attenuation correction, PET 4±5, 409 auditory evoked magnetic ®elds (AEF) 89±91

children 90±1 fetus 89±90

auditory processing, autism and 345 autism 171±84, 342±4, 401

de®nition 171 diagnosis 171

functional imaging studies 175±81, 342±4

blood ¯ow changes during performance of tasks 177 brain blood ¯ow 176±7

brain glucose metabolism changes 175±6 brain metabolite diVerences 177±8 neurotransmission alterations 178±81 sample size 343

spatial normalization 344 studying outcome 343±4 undirected hypothesizing 343

future study problems 181±3 brain functional changes 181±2

control subjects or comparison groups 182±3

heterogeneity in etiology 175

top-down and bottom-up approaches 344±8 axial resolution 409

basal ganglia, role in obsessive-compulsive disorder 226 behavior, evolution of 126

behavioral facilitory system (BFS) 207 behavioral inhibitory system (BIS) 207 bene®cence see ethical issues bene®t±risk ratio 99±104

assessment of 104 see also ethical issues

benzodiazepine, generalized anxiety disorder and 231±2 binding potential (BP) 29±30, 409

bipolar disorders 205, 210, 217 natural history 207 prevalence 206

see also mood disorders BOLD eVect 409

bolus-plus-infusion method 32±3 brain development 113±31, 335±42

autism and 181±2 cell death 118

cellular proliferation 117±18 cellular migration 118

eVects of early structural lesions 336±42 animal studies 336±7

compensation and vulnerability 340±2, 351 human neuropsychologic studies 337±9 neuroimaging studies 339±40

embryogenesis 114±17 focal lesions 393±4 growth 118±22

cortical gyri and sulci 121 myelinogenesis 121±2

need for normative models 400 neurotransmitters and hormones 122±5

brain evolution 125±6 lateralization 129±30 prolongation of maturation 128±9

brainstem, Tourette's syndrome and 248 bulimia nervosa 299±300

comorbidity 300 diagnosis 299 PET studies 305±6

see also eating disorders

California Verbal Learning Test (CVLT-C) 291

Cambridge Neuropsychological Test Automated Battery (CANTAB)

366±75, 379±95

clinical validation of 388±95

adolescents with phenylketonuria 388±90 children with early deprivation 392±3

children with histories of neonatal neurologic injury 390±2 focal brain lesions 393±4

strategies for 394±5 developmental ®ndings 386±8

frontal lobe function assessment 380±5 attentional set-formation and shifting 373, 383±4 planning ability 368±71, 384±5

spatial working memory 371±2, 381±3

420 Index

Cambridge Neuropsychological Test Automated Battery (CANTAB)

(cont.)

future directions 374±5 motor screening task 385

rapid visual information processing 372±3 spatial span task 385

use of in pediatric populations 380 visual recognition memory 373±4, 385±6

Canavan's disease 72

caudate nuclei, attention-de®cit hyperactivity disorder and 283±4 cell adhesion molecule (CAM) gene mutations 349

central nervous system development cell death 118

cellular proliferation 117±18 embryogenesis 114±17

see also brain development central programming 126±7

cerebellum, attention-de®cit hyperactivity disorder and 286 cerebral blood ¯ow (CBF) 409

anxiety disorders 237

attention-de®cit hyperactivity disorder 281, 283±5 autism 176±7

changes during performance of tasks 177 dyslexia 273±4

eating disorders 306±7

early-onset anorexia nervosa 307±8 interpretation of changes 18±20 mood disorders 208±9, 212±16, 217 PET studies 12±13

schizophrenia 190, 193 SPECT studies 15

Tourette's syndrome 249±54, 260 cerebral blood volume (CBV) 11±12

cerebral glucose metabolism (CMRGlu) 9±11, 409 anorexia nervosa 303±5

attention-de®cit hyperactivity disorder 281±5 autism 175±6, 181±2

bulimia nervosa 305±6 interpretation of changes 18±20 mood disorders 208±9 schizophrenia 190, 193±6 Tourette's syndrome 248±54, 260

cerebral oxygen metabolism (CMRO2) 13 interpretation of changes 18±20

chemical shift 409

chemical shift imaging (CSI) 61, 63 childhood-onset schizophrenia 189±99, 399

etiology 189±90

functional brain imaging 193±8 cerebral blood ¯ow 193

cerebral glucose metabolism 193±6 proton MRS 196±8

future directions 198±9 magnetoencephalography applications 92 MRS studies 67±9

neurobiology 192 phenomenology 192 structural brain imaging 192±3

choline acetyltransferase (ChAT) 125 choline (Cho) 59, 64

autism and 177±8

depression and 69±70 neurologic conditions and 71±2

schizophrenia and 68±9, 191, 196±8 social phobia and 234±5

see also magnetic resonance spectroscopy cingulate cortex

attention-de®cit hyperactivity disorder 285±6 obsessive-compulsive disorder 227±8 Tourette's syndrome and 247±8

clinical setting as stressor 102 coincidence (PET) 409

coincidence loss 410

columnar organization 113±14, 125 compensation 340±2, 351

compensatory plasticity 335, 338±42 determination of 340±2

in developmental disorders 354±6 complex disorders 317±19 computed tomography (CT) 101, 410

eating disorders 302

emission computed tomography (ECT) 410

see also single photon emission computed tomography (SPECT) Concentration Endurance Test 291

con®dentiality issue 102±3 consent issues see ethical issues

Continuous Performance Test/Task (CPT) 140, 190, 194, 232 attention-de®cit hyperactivity disorder 281, 288

convolution 410

coronal (frontal) plane 410 corpus callosum

in attention-de®cit hyperactivity disorder 286±7 in obsessive-compulsive disorder 226±7

cortex

frontal cortex role in obsessive-compulsive disorder 226±7 gyri 121

organization 125 sulci 121

see also prefrontal cortex cortico±striato±thalamo±cortical (CSTC) pathways

attention-de®cit hyperactivity disorder 279 Tourette's syndrome and 245±6, 247, 258±60

cortisol, depression and 208 count rate 410

creatine 59, 64, 125 autism and 178 depression and 69

neurologic conditions and 71±2 schizophrenia and 68±9, 191, 196±8 social phobia and 234±5

dead time 410

dead time losses, PET 5 decay 410

delayed-matching-to-sample (DMTS) test/task 366, 373, 385, 394±5 delayed-nonmatching-to-sample (DNMTS) test/task 374, 394±5 dephasing 410

depression 206 activation studies 216

facial expression recognition 211±12

major depressive disorder 205±7, 209, 216±17 MRS studies 69±70

neuroendocrine studies 207±8 neurotransmitter studies 207 see also mood disorders

development

brain see brain development CANTAB ®ndings 386±8 cognitive development 137±50

attention 139±41 executive functions 141±3 language 146±9

memory 143±6

motor and visuomotor functions 150 Piaget's theory 138±9

visuospatial skills 149±50 consent and 105

fMRI studies 155±66 paradigms for use 155±9

prefrontal cortical functioning 159±64 future directions 400±1

genetic studies and 332±3 developmental disorders 342±51

Asperger's syndrome 171, 342±3, 344 of language 348±51

perspectives 351±6

compensation in developmental disorders 354±6 pleiotropy and multiple brain-behavior impairments

351±4

top-down and bottom-up approaches 344±8

see also attention-de®cit hyperactivity disorder; autism; dyslexia; fragile X

diencephalon 116, 117 disintegration 410 distribution volume (DV) 410 DNA sample collection 323±4 dopamine

attention-de®cit hyperactivity disorder and 279, 287 autism and 178

depression and 207 eating disorders and 301

obsessive-compulsive disorder 229 schizophrenia and 191

Tourette's syndrome and 247, 255±8 dosimetry 410

dual center hypothesis of eating control 301 dyslexia 266±75, 348±9, 350

future directions 274±5 anatomic model tests 275

genetic or behavioral subtypes 275 longitudinal studies 275 subtraction methodology 275

genetic studies 319 magnetoencephalography applications 92 models of cognitive de®cits 266±8

anatomic model 267±8 modular cognitive model 266±7

neuroimaging studies 273±4 progress and problems 269±72

converging pathway paradigm 270 strong heterogeneity paradigm 270 tautology paradigm 271

psychiatric comorbidity 268±9

studies of normal language and reading 272 dysphagia 300

early lesion 335, 351

see also brain development eating disorders 298±309

epidemiology 300 etiology 300±2

brain structures implicated 301 genetics 301±2 neuroendocrine aspects 301 neuropsychology 302 neurotransmitter system 301

food avoidance emotional disorder 300 functional dysphagia 300

functional neuroimaging studies 303±8 methodologic limitations 303

PET studies of anorexia nervosa 303±5

PET studies of bulimia nervosa 305±6

SPECT studies 306±8

future directions 308±9 pervasive refusal syndrome 300 selective eating 300

structural neuroimaging studies 302±3 see also anorexia nervosa; bulimia nervosa

echo 410

echo planar imaging (EPI) 410

Ekman facial recognition paradigm 210±12 electroencephalography (EEG)

comparison with magnetoencephalography 86±9 diVerences in recorded signal 86±9

potential for source localization 89 panic disorder abnormalities 233 Tourette's syndrome 247

electromagnetic ®eld exposure 101±2 embryogenesis, brain 114±17

emission computed tomography (ECT) 410 epilepsy, magnetoencephalography applications 92 epoch 410

Ernst angle 410 ethical issues 99±108

bene®cence 99±104

bene®t±risk ratio assessment 104 con®dentiality issue 102±3 de®nition of minimal risk 100 electromagnetic ®eld exposure 101±2 hospital/clinic setting as stressor 102 protections 99±100

radiation exposure 101 risk and aversiveness 100±3 risk minimization 103±4

risks of neuroimaging 100±1 sedation/anesthesia 102

informed assent/consent 104±7 clinician's role 106±7

developmentally sensitive consent 105 inducements 105±6

motivation 105 selection of subjects 107±8

patients versus healthy controls 107 socioeconomic status and ethnic issues 107±8

422 Index

evolution behavior 126 brain 125±6

lateralization 129±30

nervous system reorganization 126±8, 129±30 prolonged maturation process 128±9

executive functions, development of 141±3 expansion mutations 316

facial expressions, recognition of 210±12 facial recognition, activation studies 212 ®eld of view (FOV) 410

®ltering 410 ¯exures 116±17 ¯ip angle 410

fMRI see functional magnetic resonance imaging focal brain lesions 393±4

food avoidance emotional disorder 300 Fourier transform analysis 411

fragile X syndrome 316

free induction decay (FID) 411 frequency encoding 411 functional dysphagia 300

functional magnetic resonance imaging (fMRI) 45±56, 405, 411 activation studies of facial recognition 212

attention-de®cit hyperactivity disorder 283, 284, 286 data acquisition 47±52

acoustic interference 49±51 event-related fMRI 52 minimization of head motion 49 monitoring subject responses 49

practical issues when scanning children 48 rate-related eVects 51±2

subject exclusion 48 subject preparation 48±9

data analysis 52±5

data interpretation 55

global and local signal variation 54 image artifacts 53

motion detection and correction 53±4 pediatric language study example 55 rigid-body and parenchymal motion 53 statistical map generation 54 structure±function correlation 54±5

depression 216 developmental studies 155±66

paradigms for use 155±9

prefrontal cortical functioning 159±64 future direction 55±6

technologic advances 402±3 pediatric studies 46±7 physiologic basis of 45±6 safety considerations 46 sources of equipment 56

Tourette's syndrome 255, 260, 261

see also magnetic resonance spectroscopy (MRS) functional neuroimaging

contributions of in child psychiatry 398±9 critical needs in pediatric neuroimaging 399±402

forays into new areas 401 integrative models 401±2

nature of process under study 400±1

normative models 400

primary versus secondary role of de®cits 401 priorities in research questions 400

future directions 405±6

image analysis developments 404±5 research design developments 404±5 technological advances 402±3

enhancements of existing technology 402±3 new techniques 403

see also speci®c forms of imaging

gamma-aminobutyric acid (GABA) obsessive-compulsive disorder and 230 Tourette's syndrome and 246, 258

see also magnetic resonance spectroscopy generalized anxiety disorder 231±2

benzodiazepine cerebral eVects 231±2 neurochemical brain imaging studies 232

genetics 315±26, 328±33 developmental aspects 332±3 dyslexia 275

eating disorders 301±2 future directions 324±5, 333

genetic methods in neuroimaging studies 323±4 Mendelian genetics 315±17

imprinting 317

trinucleotide repeat expansion 316 methodologic approaches 331 multiple gene interactions 317±19 nongenetic risk factors 331±2 phenotype assessment 330±1 phenotype delineation 328±9

phenotypes of known genetic disorders 329±30

study design for complex traits in neuroimaging 319±23 population association design 322±3

sib-pair designs 320

transmission disequilibrium test 320±2 whole genome scans 323

Tourette's syndrome 242±3

globus pallidus, attention-de®cit hyperactivity disorder and 285, 286 gradient 411

magnetic gradient 412 readout gradient 414 rephasing gradient 415

gradient coils 411

growth hormone, depression and 208 gyromagnetic ratio 411

Hann ®lter 411 homogeneity 411 hormones

mood disorders and 207±8

role in brain development 122±5 hospital setting as stressor 102 Huntington's disease 316 hypofrontality 190, 193±5, 399 hypothalamus, eating disorders and 301

hypoxanthine-guanine phosphoribosyl transferase (HPRT), gene for 316

image noise, PET 5

image resolution see spatial resolution

imprinting 317

impulsivity, attention-de®cit hyperactivity disorder and 291±2 inducements for research participation 105±6

informed assent/consent see ethical issues instrumentation, PET 6

interpulse time 411 inversion 411 inversion recovery 411

inversion recovery sequence 411 inversion time 411

Kennard principle 336±7

Landau±KleVner syndrome (LKS) 92 language

development of 146±9 developmental disorders of 348±51 evolution of 129±30

studies of 272 see also dyslexia

Larmor equation 411 Larmor frequency 411±12 lateralization 129±30

Lesch±Nyhan disease 316, 330 linkage studies see genetics Logan-plot analysis 38 long-term memory 143±4 longitudinal relaxation 412 longitudinal relaxation time 412 lumped constant 412

magnetic gradient 412 magnetic resonance 412

magnetic resonance spectroscopy (MRS) 59±73 autism and 176, 177±8

eating disorders 302±3 electromagnetic ®eld exposure 101±2 limitations of 61, 62±3

metabolites measured 63±7 phosphorus 64

protons 64±7 methods 59±62

mood disorders 208, 209, 216±17 depression 69±70

neurologic conditions 71±2 obsessive-compulsive disorder 69 schizophrenia 67±9, 191, 192±3, 399

see also functional magnetic resonance imaging; proton MRS magnetic susceptibility 412

magnetoencephalography (MEG) 77±93 comparison with electroencephalography 86±9

diVerences in recorded signal 86±9 potential for source localization 89

data analysis 82±5

magnetic source imaging 85 signal averaging 82

source analysis 82±5 instrumentation 79±82

recording environment 79 sensor arrays 81±2 sensor geometries 80±1

Index 423

superconducting quantum interference device (SQUID) 80 neuroanatomic considerations 79

neurophysiologic basis of 78 pediatric clinical applications 92 pediatric research applications 89±92

auditory evoked magnetic ®elds in children 90±1 auditory evoked magnetic ®elds of the human fetus 89±90 childhood-onset schizophrenia 91

dyslexia 92

future research directions 91 rationale 77±8

magnocellular system 350

major depressive disorder (MDD) 205±7, 209, 216±17 maturation process prolongation 128±9

memory

attention-de®cit hyperactivity disorder and 288±91 CANTAB assessment

spatial working memory 371±2, 381±3 visual recognition memory 373±4

development of 143±6 mesencephalon 116, 117

a-[11C]-methyl-l-tryptophan ([11C]-AMT) and autism 178±81 metencephalon 116, 117

mood disorders 205±19 comorbidity 206 epidemiology 205±6 future directions 217±19 natural course 206±7 neurobiology of 207±8

neuroendocrine studies 207±8 neurotransmitter studies 207

neuroimaging studies 208±17

activation studies of adult mood disorders 216 activation studies of facial recognition in normal

adults/adolescents 212

mood induction paradigms in normal adults 212±16 neurobehavioral probes 210±12

in pediatric mood disorders 216±17

single-state studies of adults with mood disorders 208±9 structural studies of adults with mood disorders 210

signs and symptoms 206 see also depression

motivation for research participation 105 motor screening task 385

motor skill development 150

MRS see magnetic resonance spectroscopy myelencephalon 116, 117 myelinogenesis 121±2

neural tube development 115±16, 117 neuromodulatory synaptic transmission detection 40±1 neurotransmitter activation studies 39±40 neurotransmitter changes 31±3

autism 178±81

dopaminergic dysfunction 178 serotonergic dysfunction 178±81

eating disorders 301 mood disorders 207

obsessive-compulsive disorder 229±30 glutamatergic neurotransmitter 230 serotonin 229±30

role in brain development 122±5