Thanasis Loupas

Computer Vision Approach for Ultrasound Doppler Angle Estimation

Doppler ultrasound is an important noninvasive diagnostic tool for cardiovascular diseases. Modern ultrasound imaging systems utilize spectral Doppler techniques for quantitative evaluation of blood flow velocities, and these measurements play a crucial rule in the diagnosis and grading of arterial stenosis. One drawback of Doppler-based blood flow quantification is that the operator has to manually specify the angle between the Doppler ultrasound beam and the vessel orientation, which is called the Doppler angle, in order to calculate flow velocities. In this paper, we will describe a computer vision approach to automate the Doppler angle estimation. Our approach starts with the segmentation of blood vessels in ultrasound color Doppler images. The segmentation step is followed by an estimation technique for the Doppler angle based on a skeleton representation of the segmented vessel. We conducted preliminary clinical experiments to evaluate the agreement between the expert operator’s angle specification and the new automated method. Statistical regression analysis showed strong agreement between the manual and automated methods. We hypothesize that the automation of the Doppler angle will enhance the workflow of the ultrasound Doppler exam and achieve more standardized clinical outcome.

410 RELIABILITY OF MEASURES OF ABDOMINAL MUSCLE THICKNESS DURING ABDOMINAL HOLLOWING, AS ASSESSED WITH M-MODE ULTRASOUND

psychosocial distress measured with the Symptom Checklist-90-Revised (SCL-90-R) and self reported disability measured with the Roland Morris Disability Questionnaire (RMDQ) has not been investigated. Aim of this study is to analyze the relationship between psychosocial distress measured with the SCL-90-R and disability measured with the RMDQ in patients with CLBP. Methods: The study was performed in an outpatient pain rehabilitation setting. The study sample consisted of 152 patients with CLBP admitted for multidisciplinary treatment. All patients completed the SCL-90-R and RMDQ. Results: Pearson’s correlation coefficients between SCL-90-R (Global Severity Index and subscales) and RMDQ ranged from 0.18 to 0.31 (p< 0.05). Conclusion: The relationship between psychosocial distress measured with the SCL-90-R and self reported disability measured with the RMDQ in CLBP patients is weak.

411 TISSUE DOPPLER IMAGING: AN ALTERNATIVE TO FINE-WIRE EMG FOR RECORDING FEED-FORWARD ACTIVITY OF THE ABDOMINAL MUSCLES DURING SUDDEN ARM MOVEMENTS?

Background: During rapid movements of the arm the transversus abdominis muscle (TA) is typically activated before the prime mover (deltoid), to stabilise the spine before the impending postural disturbance. This feedforward activity is compromised in patients with low back pain (LBP), although the phenomenon has not been investigated widely, because of the invasiveness of the assessment technique [fine-wire intramuscular electromyography (iEMG)]; we examined whether ultrasound tissue Doppler imaging (TDI) could represent a non-invasive alternative. Methods: 14 subjects (8M, 6F;23.0±2.0 yrs) performed 10 repetitions each of rapid shoulder flexion, extension and abduction, whilst surface EMG recordings from medial deltoid, and iEMG and M-mode TDI tissuevelocity recordings from the contralateral TA, internal (IO) and external (EO) oblique muscles were made. Muscle onsets were determined by visual inspection of blinded EMG and TDI signals using custom-built software (MATLAB) and expressed relative to the deltoid onset (values −150ms to + 50ms = feed-forward). Results: The TDI-determined onsets were later than those of iEMG by 32.5 (SD 32.8) ms for TA, 17.9 (SD 23.3) ms for IO, and 15.8 (SD 25.3) ms for EO. The methods showed moderately high, significant correlations: r = 0.55 (TA); r = 0.61 (IO); r = 0.56 (EO) (each p< 0.0002). Conclusion: The mean differences between the methods were likely due to electromechanical delay. The SDs of the differences were comparable to those for repeated measurements with either technique. TDI appears to be a valid means of assessing abdominal muscle feed-forward activity, and should allow this phenomenon to be investigated in larger numbers of LBP patients. Support: NFP53–405340–104787/1.