Molecular Imaging with PET and SPECT Physics of Nuclear Medicine(RAD 311) Presentation-2009 Done by: Shatha Jamal Al-Mushait 1 KSU,CAMS,Raidiological Sciences Department
KSU,CAMS,Raidiological Sciences Department 2 | The OUTLINE
|INTRODUCTION 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 imagingcame out as an important step in the diagnostic and prognostic assessment of patients using nuclear, magnetic resonance and ultrasonic techniques. More recently the importance of molecular targets for diagnosis and therapy has been recognized and MOLECULAR IMAGING(MI) introduced to visualize and measure these target structures.
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|WHAT is The MOLECULAR IMAGING ? > 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. 4 KSU,CAMS,Raidiological Sciences Department
| PRINCIPLE of MI In order to visualize molecular events non-invasively, imaging agents (radiotracers) need to be designed that interact specifically with appropriate molecular targets involved in the pathophysiology of 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 and processed using computer systems. 5 KSU,CAMS,Raidiological Sciences Department
| Uses of MI in Biomedical and clinical medicine Has two basic applications: 1.diagnostic imaging 2.therapy
Diagnostic imaging, to determine the location and extent of targeted molecules for the disease being studied. Abnormalities may be detected very early, often before medical problems can be detected by other diagnostic tests and even before symptoms occur. Such early detection allows a disease to be treated early when there may be a more successful outcome.
Therapy, to treat specific disease-target molecules by adding a therapeutic agent 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. 7 KSU,CAMS,Raidiological Sciences Department
8 In 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 MODALITIES There 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. 9 PET SPECT KSU,CAMS,Raidiological Sciences Department
SPECT 10 PET/CT Single Photon Emission Computed Tomography Positron Emission Tomography KSU,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. In PET, positron emitting radioisotope is used. Then, these positrons annihilate with nearby electrons, emitting two opposite direction photons. These photons are then detected 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) SPECT is often chosen over PET simply as a cost issue, for less equipment is involved and fewer staff is required to perform the tests. KSU,CAMS,Raidiological Sciences Department
12 Maximum intensity projection (MIP) of a typical F-18 FDG whole body PET acquisition SPECT image (bone tracer) of a mouse KSU,CAMS,Raidiological Sciences Department
13 |Conclusion The field is still in its infancy and strong efforts need to continue. But it is becoming increasingly clear that it will bring a new perspective to our understanding of diseases biology and their relevance in the planning of radiation treatments. KSU,CAMS,Raidiological Sciences Department
14 |References Handbook of Experimental Pharmacology - Molecular Imaging II (Springer, 2008) http://www.answers.com/topic/molecular-imaging http://www.iop.org/EJ/abstract/0031-9155/50/22/R01 http://medicalphysicsweb.org/cws/article/opinion/33601 http://www.molecularimagingcenter.org http://www.karolinska.se/templates/DepartmentPage____67570.aspx?epslanguage=EN EmissiionTomography: The Fundamentals of PET and SPECT By Miles N. Wernick, John N. Aarsvold http://rheumatology.oxfordjournals.org/cgi/content/full/44/11/1341/FIG1 http://radiology.rsnajnls.org/cgi/content/full/219/2/316 KSU,CAMS,Raidiological Sciences Department