36M-pixel synchrotron radiation micro-CT for whole secondary pulmonary lobule visualization from a large human lung specimen

A micro-CT system was developed using a 36M-pixel digital single-lens reflex camera as a cost-effective mode for large human lung specimen imaging. Scientific grade cameras used for biomedical x-ray imaging are much more expensive than consumer-grade cameras. During the past decade, advances in image sensor technology for consumer appliances have spurred the development of biomedical x-ray imaging systems using commercial digital single-lens reflex cameras fitted with high megapixel CMOS image sensors. This micro-CT system is highly specialized for visualizing whole secondary pulmonary lobules in a large human lung specimen. The secondary pulmonary lobule, a fundamental unit of the lung structure, reproduces the lung in miniature. The lung specimen is set in an acrylic cylindrical case of 36 mm diameter and 40 mm height. A field of view (FOV) of the micro-CT is 40.6 mm wide × 15.1 mm high with 3.07 μm pixel size using offset CT scanning for enlargement of the FOV. We constructed a 13,220 × 13,220 × 4912 voxel image with 3.07 μm isotropic voxel size for three-dimensional visualization of the whole secondary pulmonary lobule. Furthermore, synchrotron radiation has proved to be a powerful high-resolution imaging tool. This micro-CT system using a single-lens reflex camera and synchrotron radiation provides practical benefits of high-resolution and wide-field performance, but at low cost.

Investigation on the resolution of a micro cone beam CT scanner scintillating detector using Monte Carlo methods

The impact of several physical quantities on the spatial resolution of an X-ray scintillating pixel detector for a micro cone beam CT (µCBCT) is investigated and discussed. The XtremeCT from SCANCO Medical AG was simulated using the EGSnrc/EGS++ Monte Carlo (MC) framework and extensively benchmarked in a previous work. The resolution of the detector was determined by simulating a titanium knife-edge to obtain the edge spread function (ESF) and the modulation transfer function (MTF). Propagation of the scintillation light through the scintillator and its coupling into the fiber optics system was taken into account. The contribution of particles scattered in the main scanner components to the detector signal is very low and does not affect the spatial resolution of the detector. The resolution obtained from the energy deposition in the scintillator without any blurring due to the propagation of the scintillation light into the fiber optics array was 31 µm. By assuming isotropic light propagation in the scintillator, the resolution degraded to 360 µm. A simple light propagation model taking into account the impact of the scintillator's columnar microstructures was developed and compared with the MANTIS Monte Carlo simulation package. By reducing the width of the model's light propagation kernel by a factor of 2 compared to the isotropic case, the detector resolution can be improved to 83 µm, which corresponds well to the measured resolution of 86 µm. The resolution of the detector is limited mainly by the propagation of the scintillation light through the scintillator layer. It offers the greatest potential to improve the resolution of the µCBCT imaging system.