Physiological Imaging - Erik L. Ritman

Micro CT-1

Scan volumes of up to (2.5cm)³ and has resolution down to 5 micro meters. Originally fabricated in 1993 - now being replaced by the Medipix Scanner (MCT5).

X-Ray images are:

Micro CT-2

Schematic of the cryogenic vessel (bottom-left) and photo of vessel (bottom-right). The specimen is enclosed in a double walled beryllium vessel (the walls separated by a vacuum) which is continuously purged with nitrogen gas that has "boiled" off liquid nitrogen. The x-ray beam passes through beryllium windows in the vessels. A seal separates the specimen from the rotational stage so that the specimen remains frozen and no moisture can condense on or in the vessel.

Micro CT-3

MCT 3 is a Micro-CT scanner which has been setup for experimental scanning protocols. It has a variety of motor controlled and manual precision stages which provide precision mounting and motion methods to a variety of versatile componentry. Examples include configurations for evaluation of microSPECT and MicroScatterCT imaging. Unique componentry includes a 25 mm polycapillary parallel x-ray optic (basically an angular filter) for scatter and SPECT work, a copper foil 'fan' collimator for scatter experiments, a fiber optic based columnar CsI(Tl) scintillator fiber optically coupled to a Princeton Instruments 1340X1300 20um pixel CCD camera, a Tb doped fiber optic coupled to the same camera (for high resolution work), and a Varian PAXSCAN 1313, 1024 X 1024, 127um pixel flat panel imager for direct detection of more dynamic (10 fps, with 1x1 binning; 30fps with 2x2 binning) x-ray images.

The x-ray sources for MCT3 are composed of the family of Panalytical's x-ray spectrometry sources, including Cu, Mo, Ag and W targets. The generator operates these tubes at selectable peak kilo voltage settings in the range from 10 to 60 KvP. Tube currents are also selectable and follow the maximum power curves for each of the anode types as a function of KvP. The x-ray spectrum resulting from the Cu, Mo and Ag tubes contains a strong component of the k-alpha characteristic emission with the k-beta emission filtered out by a corresponding metal foil. The W target presents a typical W bremsstrahlung spectrum.

Micro CT-4

MCT 4 has similar capabilities to MCT3 with the exception of the x-ray source. The source in MCT4 is a fixed W target (400 and 1000um focal spot size) with a maximum excitation voltage of 160 KvP.

This unit was obtained for higher energy Micro-CT and scatter experiments. It shares camera and some stage resources with MCT3.

Micro CT-5

The MARS scanner (MCT5), is an innovative multispectral, fast miniCT scanner for specimen and live animal applications. The x-ray source is a 50um focal spot, W based tube (SourceRay SB-80-1k) mounted on a rotating gantry. The tube operates at selectable kilo voltage potentials up to 80 KvP.

The detector is the novel Medipix 2 imager, capable of pixel based spectral imaging. Pixel pitch is 55um. The current detector is 256 X 256 pixels with a 300 um Silicon direct x-ray detection layer bump bonded to the pulse shaping and dual discrimination and counter electronics in the CMOS layer. Upgrades from the Medipix 2 to the Medipix 3 chip with CdTe detection layer are planned.