Real-Time Adaptive Correction for Varying Source-To-Image-Distance (SID) for a Novel Region of Interest (ROI) Fluoroscopy Dose Reduction Technique Involving Spatially Different Temporal Filtering
S Setlur Nagesh*, A Panse, A Jain, P Sharma, C Ionita, A Titus, A Cartwright, D Bednarek, S Rudin, Univ. at Buffalo (SUNY) School of Med., Buffalo, NYSU-C-218-2 Sunday 1:30:00 PM - 2:15:00 PM Room: 218
Purpose: A technique is presented to adjust the ROI fluoroscopy equalization mask for changes in the SID and thus to provide boundary-artifact-free brightness and noise equalized images.
Methods: Patient dose reduction during x-ray guided interventions can be achieved by using a combination of ROI fluoroscopy and spatially-different temporal filtering. ROI fluoroscopy reduces the dose to the patient in the peripheral regions, thus resulting in an image with differential brightness and noise regions. The brightness can be equalized by subtracting a pre-acquired mask image of the attenuation filter, resulting in an image noisier in the periphery (due to fewer quanta reaching the detector) as compared to the non-attenuated region. The noise in the periphery region can be reduced by choosing a higher temporal-filtering weight using this mask as a reference. However, as source-to-imager-distance (SID) changes, the mask also needs to be changed due to magnification changes of the ROI-attenuation filter. To correct for changes in the SID during a procedure, different pre-acquired masks are used at different SIDs. The SID information is obtained in real-time from a digital bus on the x-ray system and, whenever the SID changes, the corresponding mask in the memory is chosen. Although memory inefficient, this implementation is computationally efficient.
Results: The technique was implemented and brightness and noise equalized images were obtained without the introduction of boundary artifacts as the SID was changed. The corrections are performed in real-time without interruption to the interventional procedure.
Conclusions: With correction for the change in SID implemented in real-time, the technique involving the combination of ROI fluoroscopy and spatially-different temporal filtering can be used in a clinical environment and thus significant patient integral-dose reduction can be realized during x-ray guided interventional procedures.