molecular imaging with PET & SPECT

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Molecular Imaging with PET and SPECT

Physics of Nuclear Medicine(RAD 311) Presentation-2009Done by: Shatha Jamal Al-Mushait 1KSU,CAMS,Raidiological Sciences Department

1Molecular Imaging with PET & SPECT

KSU,CAMS,Raidiological Sciences Department2| The OUTLINE

Imaging has witnessed a rapid growth in recent decades. This successful development was mainly driven by notable technical advances in structural Imaging (i.e. CT and MRI).In parallel, functional imaging came out as an important step in the diagnostic and prognostic assessment of patients using nuclear,magnetic resonance and ultrasonic techniques. More recently theimportance of molecular targets for diagnosis and therapy has been recognized and MOLECULAR IMAGING(MI) introduced to visualize and measure these target structures.

| INTRODUCTION3KSU,CAMS,Raidiological Sciences Department

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Molecular Imaging with PET & SPECT

> is the in vivo and non-invasive imaging of biological processes(functions) at the molecular and cellular level. In vivo inside a living organism.Non-invasive doesn't require an (invasive) incision into the body or the removal of biological tissue. SO, it is different from microscopy, which can also produce images at the molecular level, in that microscopy is used on sample that have been removed from the body.Also different from other technologies in that it primarily provides information about functions while others image physical structure (anatomy).> Uses biomarkers to help image various targets. | WHAT is The MOLECULAR IMAGING ?4KSU,CAMS,Raidiological Sciences Department

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In order to visualize molecular events non-invasively, imagingagents (radiotracers) need to be designed that interact specificallywith appropriate molecular targets involved in the pathophysiologyof disease. Once a suitable target has been defined, a ligand(tracer) that binds to the target with high affinity and specificity needs to be designed. Depending on the imaging modality, a label(radioisotope)has to be linked to the ligand, facilitating the sensitive detection of the imaging agent in a clinical setting. Finally, the acquired images need to be reconstructed andprocessed using computer systems.| PRINCIPLE of MI5KSU,CAMS,Raidiological Sciences Department

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Has two basic applications:

1.diagnostic imaging 2.therapyDiagnostic imaging, to determine the location and extent of targeted moleculesfor the disease being studied. Abnormalities may be detected very early, oftenbefore medical problems can be detected by other diagnostic tests and evenbefore symptoms occur. Such early detection allows a disease to be treatedearly when there may be a more successful outcome.Therapy, to treat specific disease-target molecules by adding a therapeuticagent onto the radiotracer. Also contributes to improving the treatment of diseases such as cancer, neurological and cardiovascular diseases by optimizing the pre-clinical and clinical tests of new medication.

| Uses of MI in Biomedical and clinical medicine7KSU,CAMS,Raidiological Sciences Department

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8In the field of Cancer, for example, molecular imaging is playing an increasing role, in particular for drug discovery and assessment of therapeutic response. So, instead of waiting months to determine if a treatment is working, we are watching the performance of our cancer drugs virtually in real time. This technology is designed to say is your tumor growing or is it going away?! KSU,CAMS,Raidiological Sciences Department

| IMAGING MODALITIESThere are different modalities such as the CT, and , as well as other methods that can be used for molecular imaging. Each have their different strengths and weaknesses. The choice of imaging modality for molecular imaging depends on the kind and location of the molecular event that needs to be monitored, as well as the biological questions that need to be answered.

> This technology has its roots in nuclear medicine.> PET & SPECT are currently considered as the foundation of nuclear medicine. 9PET SPECT KSU,CAMS,Raidiological Sciences Department

shathoy (s) - The imaging methods differ with respect to spatial resolution, the ability to produce 3-dimensional images, depth limit, sensitivity, the possibility of quantification, the availability of imaging agents, the potential to gather information at the anatomical, physiological, cellular and molecular levels, costs and effort.SPECT10

PET/CT

Positron Emission TomographySingle Photon Emission Computed TomographyKSU,CAMS,Raidiological Sciences Department


11| Mechanism of PET & SPECT Both measures emissions from radiotracers and uses the data gathered by the sensors to produce multicolored two or three-dimensional images of the distribution of the chemicals throughout the target.

KSU,CAMS,Raidiological Sciences DepartmentSPECT is often chosen over PET simply as a cost issue, for less equipment is involved and fewer staff is required to perform the tests.

In PET, positron emitting radioisotope is used. Then, these positrons annihilate with nearby electrons, emitting two opposite direction photons. These photons are thendetected by the scanner.(higher resolution)In SPECT, Gamma rays emitting radioisotope is used. Then, the Gamma camera rotates around the interested area and detect gamma rays.(lower resolution)

12KSU,CAMS,Raidiological Sciences DepartmentMaximum intensity projection (MIP) of a typical F-18 FDG whole body PET acquisition

SPECT image (bone tracer) of a mouse

13The field is still in its infancy and strong efforts need to continue. But it is becoming increasingly clear that itwill bring a new perspective to our understanding of diseases biology and their relevance in the planning ofradiation treatments.

KSU,CAMS,Raidiological Sciences Department| Conclusion


14Handbook of Experimental Pharmacology - Molecular Imaging II (Springer, 2008)http://www.answers.com/topic/molecular-imaginghttp://www.iop.org/EJ/abstract/0031-9155/50/22/R01http://medicalphysicsweb.org/cws/article/opinion/33601http://www.molecularimagingcenter.orghttp://www.karolinska.se/templates/DepartmentPage____67570.aspx?epslanguage=ENEmissiionTomography: The Fundamentals of PET and SPECT By Miles N. Wernick, John N. Aarsvoldhttp://rheumatology.oxfordjournals.org/cgi/content/full/44/11/1341/FIG1http://radiology.rsnajnls.org/cgi/content/full/219/2/316| References KSU,CAMS,Raidiological Sciences Department

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molecular imaging with PET & SPECT