Quantitative X-ray imaging of rodent bone by Faxitron.

This chapter describes the use of digital micro-radiography with the Faxitron machine as a means of imaging and quantitating bone mineral content in mice and rats.

Tomography versus computed tomography for assessing step off in intraarticular distal radial fractures.

Computed tomography scans have supplanted conventional tomography for many applications and often are considered the imaging study of choice for assessing intraarticular distal radial fractures. Concern about cost containment in healthcare delivery prompts the question of whether the two studies provide comparable information and at what cost. Common intraarticular distal radial fractures were created in 12 lightly embalmed cadaveric specimens. The fractures were fixed with radiolucent Kirschner wires. Articular step off was measured with a caliper. Plain radiographs, computed tomography scans, and trispiral tomograms were obtained of each specimen. Maximal step off was measured blindly by two musculoskeletal radiologists and four hand surgeons. The radiographic measurements were compared with the actual step off and expressed as a positive or negative deviation from the actual value. There was no statistically significant difference between computed tomography scans and tomograms in predicting step off. In addition, the difference between actual and radiographic measurements was insignificant in tomogram readings and different in one of the computed tomography measurements. In the authors' institution, a tomogram costs $200, and a computed tomography scan costs $562. Trispiral tomography is more accurate and cost effective than computed tomography, and thus when available should be considered the imaging modality of choice for assessing articular step off in distal radius fractures.

Dosimetry and cost of imaging osseointegrated implants with film-based and computed tomography.

Thermoluminescent dosimeters were used to measure radiation doses at craniofacial sites in a tissue-equivalent phantom during film-based multidirectional tomography with the Tomax Ultrascan (Incubation Industries, Ivyland, Pa.) and during computed tomography with the Elscint Excel 2400 (Elscint Corp., Tel Aviv, Israel). Mean absorbed doses for presurgical mandibular and maxillary canine and molar implant assessments were converted to equivalent doses, which were then multiplied by published weighting factors and summed to give effective doses. The computed tomography device consistently delivered higher doses than the Tomax Ultrascan to all anatomic locations; the differences were most pronounced when only one or two implant sites were evaluated. The reasons for the dose disparities are considered both anatomically and procedurally. A survey of examination cost revealed film-based multidirectional tomography to be less expensive than computed tomography.

A new method for assessing the temporomandibular joint quantitatively by dental scan.

The objective of this study was to assess the applicability of a multiplanar reformatting program (dental scan) for delineation and quantitative evaluation of the temporomandibular joint (TMJ) in the sagittal and coronal planes using the data of axial computed tomography. The resulting images were compared with standardized linear tomograms and direct sagittal and frontal computed tomography. Standardized linear tomograms and computed tomography of the TMJ in axial, frontal and sagittal planes were obtained in 11 patients. The axial computed tomography slices were then reconstructed in oblique frontal and sagittal planes according to the horizontal condylar angle of the TMJ by dental scan software. For each patient and each of the three imaging methods, 14 measurements were undertaken and 24 qualitative characterizations were assessed. Axial computed tomograms in combination with their corresponding coronal and sagittal reconstructions were more accurate than conventional tomograms. Direct coronal and sagittal scans gave the most detailed images, but required additional radiation dose, time and cost. Reconstructions of axial computed tomography slices of the TMJ using the dental scan software show several advantages over linear tomograms. They allow qualitative as well as quantitative evaluation of the TMJ.

Intravenous urography in children: is routine tomography useful?

We have evaluated the usefulness of routine nephrotomography in pediatric uroradiology. We reviewed all of the intravenous urograms done on children under 12 years of age, over a period of 18 months. In only 13 of 81 examinations (16%) was additional information obtained from tomography. It made no difference whether the patient could or could not cooperate during the study. In view of the cost of the extra films and the increase in radiation exposure, we therefore concluded that routine nephrotomography in pediatric intravenous urography is not indicated.

Radiographic evaluation of thoracolumbar fractures.

The data presented in this report support the selection of computerized body tomography to augment standard films in the assessment of thoracolumbar fractures when a more definitive assessment of the posterior elements of the spine or the neural canal is desired. The advantages of computerized axial tomography include (1) accuracy in assessing the integrity of the neural canal; (2) determination of injuries to other organ systems; (3) accuracy in determining the mechanism of injury and the degree of instability; and (4) the ability to obtain a tomograph while the patient is in the supine position in less and with ten times less radiation than is required for conventional tomography.

Radiological techniques for small acoustic tumors--a re-evaluation.

Small acoustic neuromas are not detected on conventional, computed tomography (CT) brain scans. Eighteen patients with proven acoustic tumors and negative CT brain scans were studied retrospectively to re-evaluate current radiological techniques. We found that the conventional mastoid plain film or thin section tomography is an accurate, cost effective, screening test for acoustic tumors. When these screening studies are positive and agree with the clinical and audiometric examinations, a CT brain scan should then be performed. If the latter is negative, Pantopaque myelography or air-CT should follow. The decision to proceed to invasive studies has been helped by such tests as brain stem audiometry. Since no single, noninvasive X-ray test currently exists to diagnose the small acoustic tumor, screening X-ray studies are indicated before the use of invasive, expensive studies. A protocol for the radiological work-up of small acoustic tumors is suggested.