Biomedical subjects

Empar Rollano-Hijarrubia

Publications and source records attributed to Empar Rollano-Hijarrubia.

3 recordsLinked to original sources

PubMed2007

Histogram-based selective deblurring to improve computed tomography imaging of calcifications.

OBJECTIVES: Computed tomography (CT) imaging of small high-density structures, eg, calcifications, is hampered by image blur. This study aims to deconvolve calcifications in the transverse and longitudinal directions while avoiding noise amplification and edge-ringing artifacts in the surrounding low-density structures. MATERIALS AND METHODS: A method referred to as histogram-based selective deblurring (HiSD) has been developed to generate a restored image by combining the low-intensity (ie, Hounsfield Units) information of the original image with the high-intensity information of the deconvolved image. HiSD is evaluated on phantom and in vitro atherosclerotic plaque CT images by comparing the original and restored images with their corresponding reference micro-CT images both qualitatively and quantitatively. RESULTS: HiSD reduces calcification blur in the transverse and longitudinal directions without introducing noise and ringing-artifacts in the surrounding tissues. Calcification area and volume measurements are significantly improved in the restored images (reducing on average overestimation by 32% and 83%, respectively). CONCLUSIONS: HiSD significantly improves CT visualization and quantification of small high-density structures imaged in vitro.

Algorithms↗

PubMed2006

Imaging of small high-density structures in CT A phantom study.

RATIONALE AND OBJECTIVES: The aim of this work is to study how the limited spatial resolution of a computed tomographic (CT) system affects the imaging of small high-density structures. This knowledge is relevant not only to understand and interpret clinical data, but also to apply and develop quantification methods for calcifications and stented vessels. MATERIALS AND METHODS: A dedicated phantom containing small differently sized aluminum cylinders was imaged on a 64-slice multidetector row CT (MDCT) while varying acquisition and reconstruction parameters from a high-resolution protocol. In addition, a bead phantom was imaged to estimate the point spread function (PSF) for the different parameter settings. The accuracy in determining object density and size was established for various imaging protocols and compared with simulations based on the estimated PSF. RESULTS: Attenuation values and size measurements were accurate for objects larger than two times the size of the system PSF at the full-width-at-half-maximum. For smaller objects, attenuation values were increasingly underestimated and size was increasingly overestimated. The convolution kernel had the most influence on object signal and size. Use of edge-enhancing kernels yielded more accurate size measurements and higher signal for small objects. However, their application was constrained by noise amplification and edge-ringing artifacts, which led to lower signal-to-noise ratio, degrading the visualization of low densities and small high-density objects. CONCLUSION: Results presented in this report provide insight into limitations in the quantification of small high-density structures and their effect on the visualization of surrounding tissues with recently developed MDCT systems.

Calcinosis↗

PubMed2006

Accuracy comparison of a 16 and 64 multidetector-row computed tomography scanner to image small high-density structures.

OBJECTIVES: The accuracy in imaging small high-density structures is compared for 16 and 64 multidetector-row computed tomography (MDCT) scanners. MATERIALS AND METHODS: Phantom experiments and different quantification methods are used to establish size measurement accuracy, object signal, and image noise, for both MDCT systems. RESULTS: At similar scanning doses, image noise is larger ( approximately 55%) for the 64 MDCT compared with the 16 MDCT, leading to lower signal-to-noise ratios ( approximately 28% for objects <2 mm). Object spread in the xy-plane is similar for both systems; while it is reduced along the z-axis (by approximately 0.18 mm) for the 64 MDCT. Measurement accuracy of the 64 MDCT is not significantly higher (P < 0.05) compared with the 16 MDCT when using a relative-threshold corresponding to 50% of the object maximum attenuation value. However, when using a fixed-threshold, interscanner and interprotocol measurement differences are statistically significant (eg, volume relative errors are reduced by approximately 17% on average for the 64 MDCT). CONCLUSIONS: Measurement accuracy of the 16 and 64 MDCT scanners is not significantly different when using a 50% relative threshold. However, image noise is significantly larger for the 64 MDCT. Compared with a fixed-threshold based method, the 50% relative-threshold strongly reduces interscanner and interprotocol measurement dependency and improves accuracy.

Image Enhancement↗