Quantitative assessment of the normal adult spinal canal at the fourth lumbar vertebra by computed tomography

We reviewed the computed tomographic (CT) studies of 105 adults with various complaints. Spinal canal diameters were measured by CT using both the conventional and Jones-Thomson (JT) techniques at the level of the fourth lumbar vertebra. The data were statistically assessed in an attempt to define spinal stenosis.     

Quantitative analysis of the cervical spinal canal by computed tomography

Summary Computed tomography measurements of the AP diameter, width, and cross-sectional area of the bony cervical canal were derived from cervical spine examinations of fifty-two normal adults. These quantitative parameters were then used to evaluate 80 patients with various cervical abnormalities to determine the clinical usefulness of the measurements. With the exception of spinal stenosis, quantitative cervical canal analysis was found to be of limited usefulness since normal measurements frequently occurred in the presence of significant cervical pathology.Protions of this material was presented at the Annual Meeting of the Radiological Society of North America Chicago, Illinois, November 14–18, 1983     

Quantitative computed tomography for spinal mineral assessment: current status

Quantitative CT (QCT) is an established method for the noninvasive assessment of bone mineral content in the vertebral spongiosum and other anatomic locations. The potential strengths of QCT relative to dual photon absorptiometry (DPA) are its capability for precise three-dimensional anatomic localization providing a direct density measurement and its capability for spatial separation of highly responsive cancellous bone from less responsive cortical bone. The extraction of this quantitative information from the CT image, however, requires sophisticated calibration and positioning techniques and careful technical monitoring.     

Quantitative computed tomography in assessment of osteoporosis

Computed tomography (CT) has been widely investigated and applied in recent years as a means for noninvasive quantitative bone mineral determination. The usefulness of computed tomography for measurement of bone mineral lies in its ability to provide a quantitative image and, thereby, measure trabecular, cortical, or integral bone, centrally or peripherally. For measuring the spine, the potential advantages of quantitative computed tomography (QCT) over dual-photon absorptiometry (DPA) are its capability for precise three-dimensional anatomic localization providing a direct density measurement, and its capability for spatial separation of highly responsive cancellous bone from less responsive compact bone. Currently, QCT vertebral mineral determination has been implemented at over 800 sites encompassing a wide geographic distribution and a wide array of commercial scanners. With a world-wide distribution of approximately 8,000 advanced CT body scanners, the capability now exists for widespread application of vertebral bone mineral determination by quantitative computed tomography. These QCT techniques for vertebral mineral determination have been used to study skeletal changes in osteoporosis and other metabolic bone diseases. Longitudinal and cross-sectional bone mass measurements have been obtained at the University of California at San Francisco (UCSF) in over 3,000 patients seen clinically or on research protocols. The results presented here illustrate the use of QCT spinal mineral measurement in the delineation of normal age-related bone loss, in the evaluation of estrogen effects on bone, in the assessment of fracture threshold and risk, and in the study of the effects of various exercise regimens on bone mineral and the determination of relationships to other techniques of bone mineral measurement. The laboratory and clinical results presented herein indicate that QCT provides a reliable means to evaluate and monitor the many forms of osteoporosis and the various interventions aimed at ameliorating this condition. The greatest advantages of spinal QCT for noninvasive bone mineral measurement lie in the high precision of the technique, the high sensitivity of the vertebral trabecular measurement site, and the potential for widespread application.     

Quantitative computed tomography

Quantitative computed tomography (QCT) is an established technique for measuring bone mineral density (BMD) in the axial spine and peripheral skeleton (forearm, tibia). QCT can determine in three dimensions the true volumetric density (mg/cm 3) of trabecular or cortical bone at any skeletal site. However, because of the high responsiveness of spinal trabecular bone and its importance for vertebral strength, QCT has been principally employed to determine trabecular BMD in the vertebral body. QCT has been used for assessment of vertebral fracture risk, measurement of age-related bone loss, and follow-up of osteoporosis and other metabolic bone diseases. This article reviews the current capabilities of QCT at different skeletal sites and the recent technical developments, including volumetric acquisition.     

Quantitative computed tomography

Quantitative computed tomography (QCT) was introduced in the mid 1970s. The technique is most commonly applied to 2D slices in the lumbar spine to measure trabecular bone mineral density (BMD; mg/cm³). Although not as widely utilized as dual-energy X-ray absortiometry (DXA) QCT has some advantages when studying the skeleton (separate measures of cortical and trabecular BMD; measurement of volumetric, as opposed to ‘areal’ DXA-BMDa, so not size dependent; geometric and structural parameters obtained which contribute to bone strength). A limitation is that the World Health Organisation (WHO) definition of osteoporosis in terms of bone densitometry (T score ?2.5 or below using DXA) is not applicable. QCT can be performed on conventional body CT scanners, or at peripheral sites (radius, tibia) using smaller, less expensive dedicated peripheral CT scanners (pQCT). Although the ionising radiation dose of spinal QCT is higher than for DXA, the dose compares favorably with those of other radiographic procedures (spinal radiographs) performed in patients suspected of having osteoporosis. The radiation dose from peripheral QCT scanners is negligible. Technical developments in CT (spiral multi-detector CT; improved spatial resolution) allow rapid acquisition of 3D volume images which enable QCT to be applied to the clinically important site of the proximal femur, more sophisticated analysis of cortical and trabecular bone, the imaging of trabecular structure and the application of finite element analysis (FEA). Such research studies contribute importantly to the understanding of bone growth and development, the effect of disease and treatment on the skeleton and the biomechanics of bone strength and fracture.     

Sonographic determination of spinal canal width. Comparison of computed tomography, myelography and conventional roentgen study of the lumbar spine

Sonographic evaluation of the width of the spinal canal is inferior compared to CT or myelography, concerning accuracy and especially quantity of information received. The advantage of sonography is the lacking of X-ray exposure, the non-invasive procedure and the low cost of apparatus and operational time. For these reasons sonography is favoured as a screening method in detecting spinal canal stenosis in a group whose handicap was largely occupational or sport-related.     

Quantitative assessment of the superior sagittal sinus on unenhanced computed tomography

Purpose

To determine the relationship between hemoglobin levels and attenuation measurements of the superior sagittal sinus (SSS) on unenhanced computed tomography (UECT). Secondly, to determine if SSS attenuation values are normally distributed such that measurements below and above certain thresholds are suggestive of pathology, such as anemia or acute venous thrombosis respectively.

Methods

Institutional review board approval was obtained for retrospective review of adult patients having both an UECT head examination and a complete blood count within 24 h of the scan. A cohort of 151 consecutive patients formed the study sample (76 males and 75 females, 17-91 years of age with a mean of 61). The dorsal aspect of the SSS was divided into upper, middle and lower segments. Using freehand and circle region of interest (ROI) techniques, a total of six attenuation measurements were obtained from each patient. Next, statistical analyses were preformed to assess the correlation between Hgb levels and attenuation values, and distribution curves were plotted to assess the normal range of SSS attenuation measurements.

Results

There is a moderate, yet statistically significant (p < 0.001), correlation between Hgb levels and attenuation values in upper, middle and lower segments of the SSS (r = 0.487, 0.497 and 0.533 respectively). Based on the calculated mean, median and mode, the attenuation values are normally distributed. When using the freehand ROI technique, the mean value is 50 Hounsfield Units (HU) with a standard deviation (SD) of 7.5. Attenuation values less than 2 SDs (35 HU) are highly suggestive of anemia (specificity and PPV = 100%).

Conclusion

There is a moderate, yet statistically significant, correlation between Hgb levels and attenuation of the SSS on UECT. Furthermore, attenuation measurements of the SSS are normally distributed with a mean of 50 HU and a SD of 7.5. Therefore, quantitative assessment of the SSS may prove useful in the clinical practice of a radiologist; namely, in the diagnosis of anemia and acute venous thrombosis.     

Quantitative assessment of classic anteroinferior bony Bankart lesions by radiography and computed tomography

BACKGROUND: An anteroinferior osseous defect of the glenoid rim is sometimes encountered in patients with recurrent anterior dislocations of the shoulder. A defect of more than 21% of the glenoid length is reported to cause instability after Bankart repair. HYPOTHESIS: We can estimate the critical size of glenoid defects by using radiography or computed tomography. STUDY DESIGN: A controlled laboratory study. METHODS: Osseous defects of 0%, 9%, 21%, 34%, and 46% of the glenoid length were created stepwise in 12 cadaveric scapulae, and plain radiographs simulating the axillary and West Point views and computed tomographic images were obtained. The maximum width of the remnant glenoid was measured under each condition and expressed as a percentage of the width of the intact glenoid. RESULTS: A 21% defect appeared to be 18.6% of the intact glenoid on the West Point view. With computed tomography, a 21% defect resulted in loss of 50% of the width on a single slice across the lower one-fourth of the glenoid. CONCLUSIONS: We can estimate the size of a glenoid defect by using the West Point radiographic view or computed tomogram. CLINICAL RELEVANCE: These images gave decisive information as to whether an osseous glenoid defect required bone grafting to achieve stability after Bankart repair.     

Quantitative computed tomography for spinal density measurement. Factors affecting precision

Quantitative computed tomography (QCT) was performed in duplicate on 84 patients to test the short-term precision of the technique. Statistical analysis of the data revealed that precision was not a function of spinal density. It appeared to be worse in osteopenic individuals only when expressed as a percentage. Precision was slightly better in male than in female patients. There is a 90% likelihood that a duplicate measurement will fall within 20 CT units of the first determination in female patients and within ten units in male patients.     

Quantitative computed tomography assessment of spinal trabecular bone. I. Age-related regression in normal men and women

Computed tomography, utilized in conjunction with a calibrated phantom containing a set of reference densities (K₂HP0₄ and water), is capable of determining the mineral content of the trabecular bone of the spine with an accuracy of about 6% of the ash weight of the vertebrae scanned (specimen studies). Other modalities measure a composite of cortical and trabecular bone. Computed tomography is capable of exclusively measuring the mineral content of the trabecular bone of the spine, where the earliest and most pronounced changes of spinal osteoporosis occur. Quantitative computed tomography measurements are useful for a precise and objective assessment of the spinal mineral content and its changes with age, disease, and drugs.     

Quantitative assessment of lung damage due to bleomycin using computed tomography

Visual assessment and density measurements of the lung using computed tomography (CT) were made in 18 patients undergoing treatment with bleomycin for malignant teratoma of the testis. The results of both visual assessment and density measurements were compared with changes in gas transfer per unit lung volume (KCO). Visual assessment of severity of damage to the lungs caused by bleomycin is unrelated to changes in KCO but is characteristic of bleomycin damage and allows a confident diagnosis to be made. Quantitative density measurement by CT, however, is inversely related to changes in KCO and may therefore be used to monitor the physiological effect on the patient. Examination of the lung by CT in these patients can not only characterise and define the extent of lung damage due to bleomycin but can be used to give a quantitative measurement on which to monitor treatment.     

Stenotic spinal canal models derived from computed tomography data: a preliminary investigation

The feasibility of creating plastic models of the spinal canal derived from computed tomography data was investigated in six patients with suspected spinal stenosis. The plastic models correlated well with the information provided on the axial scans and with documented stenosis of the central canal or neural foramina in four of the six patients.