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Multimodality Pet-Ct Imaging PowerPoint Presentation

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Description : Check out this medical PowerPoint presentation titled "Multimodality PET/CT Imaging” by Paul Kinahan.

This medical PowerPoint presentation is about multimodality PET/CT imaging, a medical imaging technique that combines two types of scans: positron emission tomography (PET) and computed tomography (CT). PET is a nuclear medicine imaging technique that uses radioactive tracers to visualize metabolic processes in the body, while CT is a diagnostic imaging technique that uses X-rays to produce detailed images of the bodys internal structures.

In a PET/CT scan, the patient is first injected with a small amount of a radioactive tracer, which is taken up by the bodys tissues and organs. The PET scanner then detects the gamma rays emitted by the tracer to create a three-dimensional image of the metabolic activity of the body. The CT scanner, on the other hand, produces detailed images of the bodys anatomy using X-rays.

The images produced by PET and CT scans are then combined to create a more comprehensive picture of the patients condition. This allows physicians to more accurately identify and locate abnormalities such as tumors, and to assess the extent of disease in the body.

Multimodality PET/CT imaging is particularly useful in oncology, where it is used to detect and stage various types of cancer, and to monitor the effectiveness of treatment. It is also used in cardiology, neurology, and other fields of medicine to diagnose and manage a wide range of diseases and conditions.

Tags : Multimodality PET/CT Imaging, medical imaging, positron emission tomography (PET), computed tomography (CT), Nuclear Medicine, Nuclear Medicine PowerPoint presentation

Published on : Jun 20, 2023 | Views : 1196 | Downloads : 1

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Slide 1-

Multimodality PET/CT Imaging Paul Kinahan Imaging Research Laboratory Director, PET/CT Physics Department of Radiology
Slide 2-

Types of Images René Magritte The Treachery of Images 1928
Slide 3-

Types of Images: Projection Imaging
Slide 4-

Types of Images: Tomography Imaging basilar tip aneurysm tomographic acquisition reconstruction of multiple images form image volume image processing simple sophisticated transaxial or axial view coronal view sagittal view
Slide 5-

Two Types of Tomography ‘Tomo’ + ‘graphy’ = Greek: ‘slice’ + ‘picture’ PET: Emission CT: Transmission source detector
Slide 6-

radiofrequency micro-wave TV FM AM IR UV Optical (not to scale) X-ray gamma -ray cosmic -ray The Electromagnetic Spectrum Transmission through 10cm of tissue (i.e. water) 0.0 1.0 longer wavelength higher energy low resolution region (long wavelength) high resolution region Physics of PET and CT Imaging
Slide 7-

Modality Resolution (mm) TX or EM* Mode X-ray 0.1 – 1.0 TX Projection Nuclear 10 – 20 EM ProjectionMedicine X-ray CT 0.5 TX Tomographic Ultrasound 0.3 TX (sound) Tomographic MRI 1 EM (RF) Tomographic SPECT 10 EM Tomographic PET 5 EM Tomographic *(TX = transmission, EM = emission) Major Medical Imaging Modalities
Slide 8-

How it works: Positron Emission Radioactive decay decays to stable form by converting a proton to a neutron and ejects a 'positron' to conserve electric charge positron annihilates with an electron, releasing two anti-colinear high-energy photons detection system is ~1-5% efficient, and can be made quantitative n p n p n p n p n p n p n p p p n p n p n p n p n n p n p n p n p n p n p n p n p n p n p n p n p n ~2 mm 18F 18O ~180 deg E = mc2 = 511 keV + e-
Slide 9-

How it works: Scintillation high energy 511 keV photon optical photons (~ 1eV) scintillator (e.g. BGO Dense yet transparent) current pulse for each UV photon detected photomultiplier tubes (PMTs) gain of ~ 106
Slide 10-

PET Detector Block Reflective light sealing tape Two dual photocathode PMTs PET scanners are assembled in block modules Each block uses a limited number of PMTs to decode an array of scintillation crystals gamma rays scintillation light signal out to processing
Slide 11-

Typical PET Scanner Detector Ring
Slide 12-

Block matrix: BGO crystals 6 x 8 crystals (axial by transaxial) Each crystal: 6.3 mm axial 4.7 mm transaxial Scanner construction Axial: 4 blocks axially = 24 rings 15.7 cm axial extent Transaxial: 70 blocks around = 560 crystals 88 cm BGO ring diameter 70 cm patient port 13,440 individual crystals Inside GE Discovery STE PET/CT
Slide 13-

How it works: Timing coincidence Dt < 10 ns? detector A detector B record positron decay event scanner FOV b+ + e- annihilation reconstruct image of tracer uptake
Slide 14-

PET Image Formation Workflow Primary Detection Decoding Detector corrections Coincidence Processing Data Binning Data Corrections Image Reconstruction
Slide 15-

Quantitative errors in measurement Lost (attenuated) event Scattered coincidence event Random coincidence event incorrectly determined LORs Compton scatter no LOR
Slide 16-

Effects of Attenuation: Patient Study PET: without attenuation correction PET: with attenuation correction (accurate) CT image (accurate) Enhanced skin uptake reduced mediastinal uptake Non-uniform liver 'hot' lungs Errors in attenuation correction can dominate image quality
Slide 17-

CT images are also used for attenuation correction (CTAC) of the PET data Note that images are not really fused, but are displayed as fused or side-by-side with linked cursors PET/CT Scanner Physiology
Slide 18-

Basic PET/CT Architecture
Slide 19-

Commercial/Clinical PET/CT Scanner PET detector blocks thermal barrier rotating CT system
Slide 20-

x-ray tube patient couch detector array rotating gantry with tube and detectors attached x-ray fan beam How it works: CT Scan Concept
Slide 21-

CT Scanner in Operation 64-slice CT, weight ~ 1 ton, speed 0.33 sec (180 rpm)
Slide 22-

X-ray CT Tubes Rotating anode tube (dissipates heat to allow higher beam currents)
Slide 23-

Modern X-Ray Tube Large Patient Large Patient Electron Collector: reduce off-focal radiation Lower patient dose High Peak-Power Target & Bearings High peak-mA for fast rotation kVp mA Small Spot mA Large Spot 80 10-300 305-675 100 10-310 315-770 120 10-335 340-800 140 10-335 340-715
Slide 24-

What are we looking at?
Slide 25-

Molecular Imaging: Glu Metabolism FDG-6-PO4 is ‘trapped’ and is a marker for glucose metabolic rates* gylcolysis (anaerobic, inefficient) TCA (oxidative, efficient) HOCH2 H 18 F H OH H HO H OH H radioactive fluorine O [18F]fluorodeoxyglucose (FDG) what we see X
Slide 26-

Imaging FDG uptake (PET) & anatomical localization (CT) Function Function+Anatomy and CT-based attenuation correction Anatomy
Slide 27-

Diagnostic Accuracy of PET/CT exceeds CT or PET only Weber et al. Nature Reviews Clinical Oncology 2008
Slide 28-

PET with 18F-FDG is used for cancer imaging Currently ~ 92% of all PET/CT studies are for diagnosis and staging in oncology imaging About 5000 scanners world wide 2.5 millions scans done annually in US everything else Cancer diagnosis and staging Neuro Cardiac Therapy planning Therapy development
Slide 29-

Castell and Cook, British J Cancer 2008 Pre therapy 1 wk imatinib therapy CT PET/CT Response to therapy of liver met gastric GIST No morphological change in the metastasis
Slide 30-

What are the advantages of PET/CT?
Slide 31-

Meikle PMB 2005 Sensitivity
Slide 32-

Quantitation MR CT PET US What do the image values represent? Linear with position and tracer concentration
Slide 33-

Quantitation MR CT PET CT What do the image values represent? Linear with position Linear with position and tracer concentration
Slide 34-

Improvements and/or Artifacts
Slide 35-

Modified NEMA NU-2 Image Quality Phantom (30 cm x 23 cm cross section) Sphere diameters:1.0, 1.3, 1.7, 2.2, 2.8, 3.7 cm 4:1 target:background ratio and typical patient activity RC = measured / true Resolution Effects
Slide 36-

2 cm sphere 5 cm sphere 33 cm profile Resolution Effects
Slide 37-

Image Reconstruction: Modeling Detector Blurring Inter-crystal scattering Parallax error true LOR variable depth of interaction assigned line of response (LOR) Shape of detector blurring point spread function (PSF) Radially variant Asymmetric in transaxial direction Two-fold symmetric about FOV center crystal thickness true event crystal assigned event crystal due to scattering scintillation (Compton scatter) light collection annihilation photon
Slide 38-

Spatially-Variant Image Resolution standard OSEM OSEM with detector blurring modeled
Slide 39-

Including improved physics modeling in image reconstruction In principle can remove detector blurring
Slide 40-

Phantom measurements: ringing artifact Bai, 2010 IEEE MIC conf record real?
Slide 41-

Patient shifting Large change in attenuation going from spine to lung ?
Slide 42-

Breathing Artifacts: Propagation of CT breathing artifacts via CT-based attenuation correction Attenuation artifacts from CT can dominate true PET tracer uptake values
Slide 43-

Image Smoothing: Noise vs. Resolution Always a trade-off in noise vs. resolution The choice of the best filter to use with the reconstruction algorithm depends on the clinical task There are no standards for choice of smoothing
Slide 44-

Effect of changing smoothing 10 mm smoothing 4 mm smoothing 7 mm smoothing RC for 1 cm spheres 0.85 0.92 0.52 0.80 0.40 0.72 SNM Chest phantom: True RC is 1.0
Slide 45-

Image Quality
Slide 46-

Image Quality Image quality, for the purposes of medical imaging, can be defined as the ability to extract desired information from an image - Harrison H. Barrett PNAS, 1993
Slide 47-

Traditional measures: Resolution Point-spread function (PSF): Narrower is better Modulation transfer function (MTF), which is the absolute value of the frequency-space version of the PSF: Wider is better FWHM, FWTM, FW100M, etc - but these can only approximate the PSF Bias is related to the PSF, but in a non-trivial way FWHM
Slide 48-

Traditional measures: Noise Sensitivity: response to very low activity levels More counts -> lower noise -> Better SNR Noise Power Spectrum: noise power at each frequency Note that apparent noise in a single image, is not necessarily the same as true noise measured from multiple images.
Slide 49-

Law of conservation of difficulty There are always trade-offs: In this case usually noise vs. resolution or bias looking at the range of values is important to be fair looking at the operating point may be the most important, but can be difficult to determine
Slide 50-

How do you compare images? define task detection localization estimation (quantitation) shape discrimination combinations of the above, etc. measure (quantitate) task performance these are often time consuming studies and can be difficult to perform properly we can in some cases use computer models of human performance -- so called ‘model’ or ‘computational’ observers -- that are based on the human perceptual system
Slide 51-

Noiseless lesion:background 1 : 1.2 : 1.5 : 2 100 kcounts 10 kcounts 2 kcounts Detectability: Is it there?
Slide 52-

Decreased resolution Noiseless 100 kcounts 10 kcounts 2 kcounts
Slide 53-

Correlated Noise Introduced by Image Reconstruction Correlated Uncorrelated 1M Counts 0.1M Counts No Noise (reconstructed) True Object
Slide 54-

Human abdomen simulation with 2cm diam. lesion 2:1 contrast Resolution Effect of Smoothing vs. Noise more counts (less noise) less smoothing (more noise)
Slide 55-

Image Quality Image quality, for the purposes of medical imaging, can be defined as the ability to extract desired information from an image - Harrison H. Barrett PNAS, 1993
Slide 56-

Diagnostic Accuracy of PET/CT exceeds CT or PET only Weber et al. Nature Reviews Clinical Oncology 2008
Slide 57-

Acknowledgements UW Imaging Research Laboratory