MOD 9 - Photon Counting CT

PCCT

major advance of CT, regarding the detectors which have the unique ability to measure each and every individual photon interaction → precise attenuation measurements, multiple energy discrimination, and vastly improved increased spatial resolution

Scintillation Dectectors (EID)

• earlier CT detector models were made of Gadolinium Oxisulphide or Cadmium Tungstate, with fused photodiodes

• photon absored → light emitted → light converted to electrical signals, this two step process alloed electronic noise to enter

Septa

walls between scintillation detectors to block light/signal spread into adjacent detectors, taking up precious surface area and thus creating dose inefficiencies

Photon Counting Detector

• relies on a solid (non-pixelated, silicone, cadmium zinc telluride) semiconductor material for the direct conversion of photons into electrical signal

• no septa = increased SA, and no light spread

• challenge: significant heat generation combined with heat-sensitive detector materials

MultiEnergy CT with PCD

• elimination of low-energy ‘noise” photons

• no need to preemtively select dual energy protocols

Advantages of PCD Technology

• Dose reduction

• Increased Spatial Resolution

• Inherent Spectral Acquisition

• Elimination of Electronic Noise

Dose Reduction

since more photons are measured with increased SA, less photons are required to generate an equivalent image to EID CT

Inherent Spectral Data

• inherently generates spectral data making it available with all acquisitions, allowing to gain information about the elemental composition of an object

• elimination of high attenuation/ beam hardening artifacts hen used in conjunction with adapted reconstruction algorithms

PCD Direct Conversion Impact and Application

PCD Elimination of Septa Impact and Application

Disadvantages of PCD / PCCT

• additional recons which take time

• cost of equipment