Opportunistic Screening Techniques for Analysis of CT Scans

Abstract

Purpose of Review Opportunistic screening is a combination of techniques to identify subjects of high risk for osteoporotic fracture using routine clinical CT scans prescribed for diagnoses unrelated to osteoporosis. The two main components are automated detection of vertebral fractures and measurement of bone mineral density (BMD) in CT scans, in which a phantom for calibration of CT to BMD values is not used. This review describes the particular challenges of opportunistic screening and provides an overview and comparison of current techniques used for opportunistic screening. The review further outlines the performance of opportunistic screening. Recent Findings A wide range of technologies for the automatic detection of vertebral fractures have been developed and successfully validated. Most of them are based on artificial intelligence algorithms. The automated differentiation of osteoporotic from traumatic fractures and vertebral deformities unrelated to osteoporosis, the grading of vertebral fracture severity, and the detection of mild vertebral fractures is still problematic. The accuracy of automated fracture detection compared to classical radiological semi-quantitative Genant scoring is about 80%. Accuracy errors of alternative BMD calibration methods compared to simultaneous phantom-based calibration used in standard quantitative CT (QCT) range from below 5% to about 10%. The impact of contrast agents, frequently administered in clinical CT on the determination of BMD and on fracture risk determination is still controversial. Summary Opportunistic screening, the identification of vertebral fracture and the measurement of BMD using clinical routine CT scans, is feasible but corresponding techniques still need to be integrated into the clinical workflow and further validated with respect to the prediction of fracture risk.

Messtechnische Verfahren im Kontext der DVO Leitlinie – neue Entwicklungen

“…Ein neuer vielversprechender Ansatz zur effizienten Identifikation von Patienten mit hohem Frakturrisiko ist das sogenannte opportunistic screening (OS). In Bezug auf Osteoporose beschreibt OS ein Konglomerat von Methoden, um CT Datensätze aus der klinischen Routine sowohl zur automatischen Detektion von Wirbelkörperfrakturen als auch zur Bestimmung der Knochendichte zu benutzen [27]. Damit ließen sich zwei häufige und starke Risikofaktoren quasi umsonst und ohne zusätzlich Strahlenexposition aus Routine CT Datensätzen der Lunge, des Abdomens oder des Beckens extrahieren.…”

Opportunistic Computed Tomography Screening for Osteoporosis and Fracture

“…6 Although most studies on opportunistic screening have used results from a single vertebra, most often L1, an average of at least two nonfractured vertebrae, typically L1 and L2, is recommended to increase accuracy. 10…”

“…Quantitative computed tomography (QCT) is challenging in BMD opportunistic screening because it uses an in-scan calibration to convert CT to BMD values, and acquisition and reconstruction parameters are highly standardized. 10…”

Bone density of the axis (C2) measured using Hounsfield units of computed tomography

“…This method separates patient investigation and phantom scan. The calibration phantom can be scanned once weekly or once monthly[ 18 ]. The internal density calibration eliminates the need of a calibration phantom for opportunistic CT screening.…”

“…A calibration is not performed, making this method surely the easiest to use. The direct use of HU requires a CT scanner produced by the same manufacturer or ideally the same scanner [ 18 , 20 ]. Determination of HU is associated with no additional cost or additional radiation because a CT scan is usually already available after trauma or before spinal instrumentation [ 3 ].…”