"Photon Counting Medical X-ray Imaging from Mammography to - - PowerPoint PPT Presentation

▶
photon counting medical x ray imaging from mammography to
SMART_READER_LITE
LIVE PREVIEW

"Photon Counting Medical X-ray Imaging from Mammography to - - PowerPoint PPT Presentation

Oct 19, 2023 320 likes •951 views

The Art of Experiment, Berkeley, CA , May 2-3, 2014 "Photon Counting Medical X-ray Imaging from Mammography to CT" Mats Danielsson KTH Royal Institute of Technology, Stockholm, Sweden Sponsors for the Project The Erling-Persson

slide-1
SLIDE 1

"Photon Counting Medical X-ray Imaging from Mammography to CT"

Mats Danielsson KTH – Royal Institute of Technology, Stockholm, Sweden

The Art of Experiment, Berkeley, CA , May 2-3, 2014

slide-2
SLIDE 2

The Erling-Persson Family Foundation

Sponsors for the Project

CT Gantry

slide-3
SLIDE 3
slide-4
SLIDE 4

4

slide-5
SLIDE 5
slide-6
SLIDE 6

Who Counted Photons First?

What was that? Maybe a photon

slide-7
SLIDE 7

1 Energy

To Count Photons – What does it mean?

  • Number of X-rays
  • Pulse height give the

energy for each X-ray

  • No electronic noise

Result

X-ray photons Threshold 1 Threshold 2 Threshold 3 Electronic noise 1 2 3 Time

7

slide-8
SLIDE 8

X-ray photons Energy Time

Integrating Current: Today’s praxis in X-ray Imaging

  • Area of
  • Indirect estimate of

number of photons

Result

8

slide-9
SLIDE 9

Photon Counting or Integrating – Two Ways of Eating the Smorgasbord

Mix everything before you eat and try to guess the ingredients The normal way (one dish at a time)

slide-10
SLIDE 10

Example of Clinical use Today: Mammography

slide-11
SLIDE 11
slide-12
SLIDE 12

Photon Counting Mammography

slide-13
SLIDE 13

Spiculated mass

2D

slide-14
SLIDE 14

Crystalline Silicon Detector

slide-15
SLIDE 15
slide-16
SLIDE 16
slide-17
SLIDE 17
slide-18
SLIDE 18

DQE at Zero Spatial Frequency

Monnin et al. Med. Phys., vol. 34 (3), pp. 906-914, 2007

DQE(0) PHILIPS Micro Dose Photon Counting

18

slide-19
SLIDE 19

Clinical Example: Experience from Breast Check, the Irish Breast Screening Program

  • 4 static & 16 mobile

screening units

  • Equipment:

– 11 CsI scintillator – 10 a-Se – 7 Photon counting

19

slide-20
SLIDE 20

Ireland Breast Screening Program Cancer Detection Rates

Mccullagh et al. The British Institute of Radiology (2011), doi: 10.1259/bjr/29747759

20

slide-21
SLIDE 21

Ireland Breast Screening Program Radiation Dose

P Baldelli et. al., “Comprehensive Dose Survey Of Breast Screening In Ireland”, Radiation Protection Dosimetry , Vol. 145, No. 1, pp. 52–60, 2010

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 mGy

Average Mean Glandular Dose

Philips MicroDose* GE Essential Hologic Selenia

21

slide-22
SLIDE 22

Visualization of Iodine Contrast Agent

  • 35 mm invasive lobular

carcinoma

  • Difficult to detect in 2D
  • Difficult to detect in

tomosynthesis

  • Energy subtraction –

clear improvement in this case

Courtesy Dr. Felix Diekmann

22

slide-23
SLIDE 23

Differentiation of Cysts from Cancer

23

slide-24
SLIDE 24

CONFIDENTIAL

2

On the photo you can tell what is what…

Acrylic Aluminum Aluminum Acrylic Acrylic

slide-25
SLIDE 25

CONFIDENTIAL

2

But on the X-ray image, can you tell what is what?

slide-26
SLIDE 26

Spectral image of acrylic Spectral image of Aluminium

On photon counting spectral you can!

All acrylic removed Aluminum removed Al Al

slide-27
SLIDE 27
slide-28
SLIDE 28
slide-29
SLIDE 29

Measuring breast tissue attenuation

Björn Cederström, Erik Fredenberg Philips, Solna, Sweden Matthew G. Wallis, Paula Willsher,

Cambridge Breast Unit and NIHR Cambridge Biomed. Research Centre, U.K.

David R. Dance, Kenneth C. Young,

NCCPM, Royal Surrey County Hospital, U.K.

Setup:

– cyst samples in 1-cm cuvettes – PMMA + Al step wedge Method: – Map cyst fluid directly into (PMMA, Al)-space

  • E. Fredenberg et al. “Measurement of breast-tissue x-ray attenuation by

spectral mammography: first results on cyst fluid”, Phys. Med. Biol. 58 (2013) 8609–8620

slide-30
SLIDE 30

Measurement of solid tumor attenuation

  • Published data on tumor

composition/attenuation scarce

  • Different experimental condition
  • Use same setup as for cyst fluid
  • Tailored sample holder
slide-31
SLIDE 31

Clinical use in the Future: Computed Tomography

slide-32
SLIDE 32
slide-33
SLIDE 33

Overview of detector

  • Detector element size: 0.4 × 0.5

mm2

  • Depth segmentation:

16 segments along incident direction

  • 8 thresholds for each channel
slide-34
SLIDE 34

ASIC – Developed for Silicon Spectral CT

slide-35
SLIDE 35

Detector Materials

slide-36
SLIDE 36

Detector Materials for Spectral Photon Counting

Material Signal (20 keV X-ray) Fano- factor Speed (ns) 70% Absorption Depth (mm)

20 keV 100 keV Silicon 5500 0.1 10 1 28 Gas (Krypton) 770 0.2 10 12 900 (Xe 200) CdTe/CZT 2000 0.1 10 0.1 1.3

36

slide-37
SLIDE 37

Compton Scattering versus Photo-effect

Silicon CdZnTe

37

slide-38
SLIDE 38

Compton scattering?

H Bornefalk and M Danielsson, “Photon-counting spectral computed tomography using silicon strip detectors: A feasibility study,” Phys. Med. Biol., vol. 55, no. 7, pp. 1999– 2022, Apr. 2010

slide-39
SLIDE 39

Front-end Electronics

  • very similar to high

energy physics

slide-40
SLIDE 40
  • Fast
  • Small Signals
  • Low noise
  • Massive parallel processing
  • Small channel to channel

variation

  • Low power
  • Temperature stable
  • Digital readout not inducing

noise

40

slide-41
SLIDE 41

Electronics for Photon Counting

Multi-level Comparators and Counters Memory Pre amp Shaper

41

slide-42
SLIDE 42

Problems: Pile-up and charge sharing

slide-43
SLIDE 43
  • 120 kVp polychromatic x-ray

spectrum

  • 33 ns deadtime per x-ray

detection

  • Linear relation up to 200

Mcps/mm2

Are we fast enough?

X-ray count rate (Mcps/mm2)

Maximum clinical count-rate 160 320 480 640 800

43

slide-44
SLIDE 44

Measurement of Energy Resolution - Example

𝑔 𝑦; 𝜈, 𝜏, Α, Β = 1 2 erfc (𝑦 − 𝜈 √2𝜏 )(𝐵 𝑦 − 𝜈 + 𝐶)

44

slide-45
SLIDE 45

Measurement of Energy Resolution - Example

45

slide-46
SLIDE 46

Normalization

slide-47
SLIDE 47

Threshold off-set

47

slide-48
SLIDE 48

48

slide-49
SLIDE 49

Clinical Benefit Example: Bone versus Iodine

Calcium Iodine - Concentration

matching Calcium attenuation

Voxels with different materials can appear the same in image

49

slide-50
SLIDE 50

50

slide-51
SLIDE 51

51

slide-52
SLIDE 52

52

slide-53
SLIDE 53

53

slide-54
SLIDE 54

54

slide-55
SLIDE 55

Wear in Knee Replacements

Image Courtesy of Dr L. Wiedenhielm, Karolinska Hospital, Stockholm Hospital

slide-56
SLIDE 56

Silicon CT segmented image

slide-57
SLIDE 57

State-of-the-art Karolinska Hospital

slide-58
SLIDE 58

Clinical trial focusing on stroke planned for 2015

slide-59
SLIDE 59
slide-60
SLIDE 60
slide-61
SLIDE 61
slide-62
SLIDE 62

X-rays have color