Background Osteoporosis is a prevalent but underdiagnosed condition. Objective To evaluate computed tomography (CT)-derived bone mineral density (BMD) assessment compared with dual-energy x-ray absorptiometry (DXA) measures for identifying osteoporosis by using CT scans performed for other clinical indications. Design Cross-sectional study. Setting Single academic health center. Patients 1867 adults undergoing CT and DXA (n = 2067 pairs) within a 6-month period over 10 years. Measurements CT-attenuation values (in Hounsfield units [HU]) of trabecular bone between the T12 and L5 vertebral levels, with an emphasis on L1 measures (study test); DXA BMD measures (reference standard). Sagittal CT images assessed for moderate-to-severe vertebral fractures. Results CT-attenuation values were significantly lower at all vertebral levels for patients with DXA-defined osteoporosis (P < 0.001). An L1 CT-attenuation threshold of 160 HU or less was 90% sensitive and a threshold of 110 HU was more than 90% specific for distinguishing osteoporosis from osteopenia and normal BMD. Positive predictive values for osteoporosis were 68% or greater at L1 CT-attenuation thresholds less than 100 HU; negative predictive values were 99% at thresholds greater than 200 HU. Among 119 patients with at least 1 moderate-to-severe vertebral fracture, 62 (52.1%) had nonosteoporotic T-scores (DXA false-negative results), and most (97%) had L1 or mean T12 to L5 vertebral attenuation of 145 HU or less. Similar performance was seen at all vertebral levels. Intravenous contrast did not affect CT performance. Limitation The potential benefits and costs of using the various CT-attenuation thresholds identified were not formally assessed. Conclusion Abdominal CT images obtained for other reasons that include the lumbar spine can be used to identify patients with osteoporosis or normal BMD without additional radiation exposure or cost. Primary Funding Source National Institutes of Health.

Purpose To evaluate the utility of lumbar spine attenuation measurement for bone mineral density (BMD) assessment at screening CT colonography (CTC), using central dual-energy x-ray absorptiometry (DXA) as the reference standard. Material and Methods 252 adults (240 women, 12 men; mean age, 58.9 years) underwent CTC screening and central DXA BMD measurement within 2 months (mean interval, 25.0 days). The lowest DXA T-score between the spine and hip served as the reference standard, with low BMD defined per WHO as osteoporosis (DXA T-score ≤-2.5) or osteopenia (DXA T-score between −1.0 and −2.4). Both phantomless QCT and simple non-angled ROI MDCT attenuation measurements were applied to T12-L5 levels. Ability to predict osteoporosis and low BMD (osteoporosis or osteopenia) by DXA was assessed. Results A BMD cut-off of 90 mg/cc at phantomless QCT yielded 100% sensitivity for osteoporosis (29/29) and specificity of 63.8% (143/224); 87.2% (96/110) below this threshold had low BMD and 49.6% (69/139) above this threshold had normal BMD at DXA. At L1, a trabecular ROI attenuation cut-off of 160 HU was 100% sensitive for osteoporosis (29/29), with a specificity of 46.4% (104/224); 83.9% (125/149) below this threshold had low BMD and 57.5% (59/103) above had normal BMD at DXA. ROI performance was similar at all individual T12-L5 levels. At ROC analysis, AUC for osteoporosis was 0.888 for phantomless QCT (95% CI: 0.780–0.946) and ranged from 0.825–0.853 using trabecular ROIs at single lumbar levels (0.864 [0.752–0.930] at multivariate analysis). Supine-prone reproducibility was better with simple ROI method compared with QCT. Conclusion Both phantomless QCT and simple ROI attenuation measurements of the lumbar spine are effective for BMD screening at CTC, with high sensitivity for osteoporosis as defined by the DXA T-score.

Background The natural history of small colorectal polyps is an important area for which major evidence gaps persist. We report the results of a prospective trial assessing the behavior of small (6-9 mm) colorectal polyps through in vivo growth rates at longitudinal CT colonography (CTC) evaluation. Methods In vivo CTC surveillance was performed on 306 small (6-9 mm) polyps initially detected at screening CTC in 243 consenting asymptomatic adults (mean interval, 2.3 years; range, 1-7 years). Volumetric and linear polyp measurements at initial and surveillance CTC were correlated with histologic subgroups. Histology was established in 132 lesions at post-CTC colonoscopy. The trial is registered (ClinicalTrials.gov Identifier: NCT00204867) Findings Applying a polyp volume threshold of ±20% change per year to categorize growth, 22% (68/306) of all polyps progressed, 50% (153/306) were stable, and 28% (85/306) regressed, including apparent resolution in 10% (32/306). 91% (21/23) of proven advanced adenomas progressed, compared with 37% (31/84) of proven non-advanced adenomas, and 8% (15/198) of all other lesions (p<0.0001). Odds ratio for a growing polyp at CTC surveillance to represent an advanced adenoma was 15.6 (95%CI, 7.6-31.7) compared with 6-9 mm polyps detected and removed at initial CTC screening (without surveillance). Mean polyp volume change was +77%/year for proven advanced adenomas (n=23), +16%/year for proven non-advanced adenomas (n=84), and -13%/year for all proven non-neoplastic or unresected polyps (p<0.0001). An absolute polyp volume >180 mm3 at surveillance CTC identified proven advanced neoplasia with a sensitivity of 92% (22/24), specificity of 94% (266/282), PPV of 58% (22/38), and NPV of 99% (266/268). In general, volume changes amplified small or absent linear size changes, as only sixteen 6-9 mm polyps (6%) exceeded 10 mm at follow-up. Interpretation Volumetric growth assessment of small colorectal polyps represents a powerful biomarker for determining clinical importance. Advanced adenomas demonstrate more rapid growth than non-advanced adenomas, whereas most other small polyps remain stable or regress over time. These findings may allow for less invasive surveillance strategies, reserving polypectomy for lesions that demonstrate significant growth. Ongoing research will eventually provide more information regarding the ultimate fate of unresected small polyps without significant growth.

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Contrast-enhanced CT shows an average increase of 11 HU over the unenhanced series for L1 trabecular attenuation. The overall performance for predicting osteoporosis is similar between the enhanced and unenhanced scans, thus either can be employed for initial opportunistic screening.