D. Kirks: Practical techniques for pediatric computed tomography Table 2. Sedation schedule

1.6 Radiation dose (GE 8800)

Drug

Initial dose

Route of administration

Nembutal (Pentobarbital)

6 mg/kg of body weight for children up to 15 kg 5 mg/kg of body weight

I.M. 20-30 min before exam

Valium (Diazepam) CMB Demerol 25 mg/ml (Pethidine) Largactil 6.25 mg/ml (Chlorpromazine) Phenergan 6.25 mg/ml (Promethazine)

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Supplementary dose

1 h later if initial dose not effective, 2 mg/kg for children up to 15 kg, 25 mg/kg for children greater than 15 kg 0.2-0.4 mg/kg I.V. slowly 5 % h later if initial of body weight to 10min dose not effective maximum of before exam 0.2 mg/kg 12 mg 0.1 ml/kg up I.M. 30-60 A supplementary to a maximum min before dose is not given of 2 ml exam

1.5 Examination

A. Head rest modifications may be needed B. Positions: semiaxial - routine; coronal - orbits, suprasellar, temporal lobes, face, surface masses, anomalies; clival-perpendicular - posterior fossa, tentorium; and clival-parallel - brain stem, 4th ventricle C. Section thickness: 10 mm - s t a n d a r d ; 5 mm - s u s p i c i o u s areas, posterior fossa, face, orbits; 5 m m with 2 mm overlap - optic nerves, suprasellar; 1.5 m m - suprasellar, optic nerves (motion limitations, grainy) D. Reconstructions: coronal - when true coronal not possible, 5 mm axial slices required; sagittal - midline abnormalities; oblique - optic nerves, off axis pathology E. Data reprocessing (review): bone or high contrast for bone, orbits, metrizamide; and soft tissue - limited value F. Examination time: normal (slower time) best resolution; dynamic (short interslice delay) may use routinely for children

A. Average: (1) premature 0.6-0.Brad; (2) infant 1.0-1.5 rad; (3) child 2.0-2.5 rad: B High dose - thin sections 4 - 6 rads: C. Low dose - facial and bone 70 rads References

1. Byrd SE, Harwood-Nash DC, Barry JF, Fitz CR, Boldt DW (1977) Coronal computed tomography of the skull and brain in infants and children, part 1: Technique and results. Radiology 124:705 2. Byrd SE, Harwood-Nash DC, Barry JF, Fitz CR, Boldt DW (1977) Coronal computed tomography of the skull and brain in infants and children, part II: Clinical value. Radiology 124: 710 3. Fitz CR, Harwood-Nash DC, Resjo M, Chuang S (1978) The clival-perpendicular or modified water's view in computed tomography. Neuroradiology 16: 15 4. Byrd SE, Harwood-Nash DC, Fitz CR, Barry JF, Rogovitz DM (1978) Two projection computed tomography: the axial and Towne projections. Radiology 128:512 5. Kramer RA, Janetos GP, Perlstein G (1975) An approach to contrast enhancement in computed tomography of the brain. Radiology 116: 641 6. Norman D, Enzmann DR, Newton TH (1978) Comparative efficacy of contrast agents in computed tomography scanning of the brain. J Comput Assist Tomogr 2:319 7. Mass S, Norman D, Newton TH (1978) Coronal computed tomography: indications and accuracy. Am J Roentgenol 131 : 875 8. Messina AV, Potts G, Rottenberg D, Patterson RH (1976) Computed tomography: demonstration of contrast medium with cystic tumours. Radiology 120:345 9. Penn RD, Trinko B, Baldwin L (1980) Brain maturation followed by computed tomography. J Comput Assist Tomogr 4: 614 10. Trefler M, Haughton VM (1981) Patient dose and image quality in computed tomography. AJNR 2:269 11. Rhodes ML, Glenn WV, Azzawi YM (1980) Extracting oblique planes from serial CT sections. J Comput Assist Tomogr 4:649 12. Roberson GH, Taveras JM, Tadmor R, Kleefield J, Ellis G (1977) Computed tomography in metrizamide cisternography - importance of coronal and axial views. J Comput Assist Tomogr 1 : 241 13. Traupe H, Heiss WD, H0effken W, Zulch KJ (1980) Perfusion patterns in CT transit studies. Neuroradiology 19:181

2. CT of the spine and cord Derek C. H a r w o o d - N a s h Department of Radiology Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8 2.1 Choice of CT modality

A. Advantages: (1) Geography (a) anatomical detail: cord, nerves and vessels; subarachnoid space; extradurat space; bone; paravertebral structures; and occipitocervical junction; (b) orientation: digital 'Scoutview'; axial; coronal; sagittal; oblique; and montage; 2. Character: vascular enhancement; cyst; bone distortion; distribution of Metriz-

amide; and 3. Diagnostic protocol: 'Package deal', most information from few examinations; greater detail; greater sensitivity and specificity; quick; and often with less radiation

B. Disadvantages: expense (maybe less); lumbar puncture for Metrizamide; possible anesthesia; sedation; and intravenous contrast

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D. Kirks: Practical techniques for pediatric computed tomography

2.2 Potential indications

1 cm collimation (if reformatting required - 5 mm contiguous or with 2 mm overlap); angle gantry to axis of spine e. g. lmnbar and sacral regions in particular; include occipitocervial junction in all congenital lesions; keep head flexed to prevent intracranial entrance of contrast; use direct coronal when possible B. Specific:with General Electric 8800 (kVp - 120 kVp mA 160-500mA) also low dose technique for preliminary slices at 20 to 40 maS; time - 9.6 sec; field of View - 25 cm; thickness - 10 mm or 5 ram; mandatory to use high resolution imaging techniques (review)

A. General: identify cause of neural abnormality; characterize congenital abnormality; detail of destruction or displacement of vertebra; clarify abnormality on nuclear medicine, radiographs; or tomograms; preoperative 'road map'; mass; bony involvement; and intraspinal extension or vice versa: and B. Specific: (1) Spine: local plane; straight back; scoliosis; cutaneous blemishes; overt or covert cord involvement; t r a u m a _ cord involvement; and primary or secondary neoplasia. (2) Occipitocervical junction: distortion, displacement, bone and cord; and presence of tonsils. (3) Cord and roots: any neurological abnormality; bone or paravertebral mass with intraspinal involvement; congenital abnormalities (e.g. tethered cord) diastematomyelia; meningocele or myelomeningocele associated anomalies; and cutaneous abnormalities, hairy tuft, lipomas. (4) Disc: protrusion or apophyseal avulsion 2.3 Patient preparation A. Review of clinical history, laboratory data, conventional chest radiograph, and any supplementary imaging modalities, especially nuclear medicine and tomography B. Withold feedings for 4 h C. Sedation is required in Primary CTMM (4-6years maybe, 6 + rarely, 0-4 G. A.); and Secondary CTMM (4-6 maybe, 6-10 rarely, 0-4 G.A.). Drug Intramuscular Nembutal (1) Initial dose (a) Less than 15 kg patient weight 6 mg/kg (b) Greater than 15 kg patient weight - 5 mg/kg; maximum - 200 mg; and with (c) onset in 20-30 rain with (2) repeat dose: may repeat after 1-2 h and supplementary dose is % to 89 original dose and (3) General Anesthesia needed in (a) In primary C T M M (0-4 years, 4-6 maybe, 6 + rarely); and (b) In secondary C T M M (0-6 years) D. Contrast agents. (1) Intravenous contrast medium for spinal or paraspinal mass or bone destruction; intraspinal vascular lesion; and mass lesion in cord, neoplasm: Dosage - Hypaque 60-3 cc/kg maximum 200 cc bolus injection. (2) CSF contrast agent: lumbar puncture 21-22 gauge needle and off center if low cord suspected and, less common lateral cervical puncture but beware of lesions. Using primary CTMM 2-6 cc's of isotonic contrast; and secondary C T M M 1-4 h after standard myelogram

2.4 Techniqueof scanning A. General: scan time 9.6s; supine position; Scoutview; pre-planning of sections; sections at least into a normal vertebra on either side of suspect lesion; 1 cm intervals at

2.5 CT images need to be closely monitored by physician; sections - high window levels and wide window width not usually necessary to reverse colour display; reformatting, sagittal/coronal sections (often most useful) need at least 3 cm of contiguous slices 5 mm w i d e _ overlap

2.6 Unique problems A. Examination: excess of subarachnoid space iodine; often many CT sections - increase time; and 5-12 h followup scans in hydromyelia; and B. Pediatric patient: features for consideration are - complexity of congenital abnormalities; preliminary standard myelogram often needed; not noninvasive; sedation; immobilization; alteration of environment; intravenous contrast medium; radiation exposure; and subarachnoid space contrast medium 2.7 Radiation dose A. General Electric 8800: peak single section skin dose 1.5 rads; complete spine 2-3 rads; and with low dose technique, 50-100 mr.

References 1. Resjo [Met al (1979) Normal cord in infants and children examined with computed tomographic metrizamide myelography. Radiology 130:691 2. Resjo IM et al (1979) CT metfizamide myelography for intraand paraspinal neoplasms in infants and children. AJR 132: 367 3. Post MJD (1980) CT update: impact of time metrizamide and high resolution on diagnosis of spinal pathology. In: Post MJD (ed) Radiologic evaluation of the spine. Masson, New York, pp 259-294 4. Post MJD (1980) Radiologic evaluation of the spine. Masson, New York 5. James HE, Oliff M (1977) Computed tomography in spinal dysraphism. JCAT 1 : 391 6. Harwood-Nash DC (1981) Computed tomography of the pediatric spine: a protocol for the 1980s. Rad Clin N Am 19:479

3. Chest computedtomography Donald R. Kirks Department of Radiology, Duke University Medical Center, Durham, NC 27710, USA 3.1 Choice of CT modality

A. Advantages: greater detail - inherent sensitivity of system and transverse cross-sectional anatomic display;

greater sensitivity - density of abnormality; anatomic regions - mediastinum, parenchyma, chest wall; and C T M M - extradural extension; and B. Disadvantages: expensive; time-consuming; ionizing