A square root analog to digital converter to optimally convert photonic signals for computed tomography

The arrival of photons at a given location is a Poisson process with an associated shot noise which rises with the square root of the number of photons received. An analog-to-digital converter (ADC) with a square root transfer function can quantize photonic signals with LSB size kept constant with respect to the photon shot noise. In imaging applications, this can greatly reduce the number of bits needed to characterize a signal compared to a linear ADC without detrimental effects to image quality. Such a device, based on the Analogic MuSIC chip, was designed and tested for the needs of a medical computed tomography (CT) device. The experimental setup increases the MuSIC sampling frequency from 3kHz to 7kHz, while reducing the amount of data necessary for reconstruction. A constant quantization noise to photon shot noise ratio acceptable for CT is maintained by sizing each LSB to be one half the rms noise level. Results show an INL of 2.5 LSB, which is reduced to 0.27 LSB after a correction scheme.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2010

Author dc:creator

• Bieniosek, Matthew (Matthew F.)

Advisor dc:contributor.advisor

• Charles G. Sodini and Martin Choquette.

• Electrical Engineering and Computer Science.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/62309

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/62309