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“Time-of-Flight” takes off in PET/CT October 5, 2007

Posted by tomography in CT, Nuclear Medicine, PET, Tomography, Uncategorized.

TOF or time-of-flight reconstruction is actually not a recent invention in tomography as its application in diagnostics was first proposed in the 1980s, but only recent technological improvements allowed its use in scanners. In a diagnostic scan improvement means better image quality, and less tracer dose for the patient.
In a PET scan when a positron collides with an electron, two gamma rays are generated in the annihilation process. The detector ring is looking for two, almost “simultaneous” rays, which is then noted as an event and is stored as data. Naturally, only those two rays are simultaneous, that traveled the same distance. Therefore using the time difference (fraction of a second) between the gamma rays, the scanner can pinpoint the original location of the positron-electron annihilation.tofschematic


To best understand it, you need to look at conventional PET imaging, which involves the injection of a decaying radioactive agent into a patient. As each nucleus decays, a positron is released that immediately collides with an electron, creating an annihilation that releases a pair of photons, or gamma rays. These two photons travel away from the collision point at 180° from each other. After detecting the photons, the PET scanner’s computer uses that information to calculate where the radioactive agent is concentrated and produce an image localizing the affected area. TOF makes it possible for point of origination of annihilation to be more accurately predicted, which leads to more accurate imaging. Improved event localization reduces noise in image data, resulting in higher image quality, shorter imaging times, and lower dose to the patient

A time-of-flight mass spectrometer uses the differences in transit time through a drift region to separate ions of different masses. It operates in a pulsed mode so ions must be produced or extracted in pulses. An electric field accelerates all ions into a field-free drift region with a kinetic energy of qV, where q is the ion charge and V is the applied voltage. Since the ion kinetic energy is 0.5mv2, lighter ions have a higher velocity than heavier ions and reach the detector at the end of the drift region sooner.

TOF is especially useful in examining overweight patients who have been traditionally difficult to image.


Must click links! October 4, 2007

Posted by tomography in Blogroll, Cancer, Nuclear Medicine, Uncategorized.
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1. You may download toll free and use in your own presentations the ppt.-s and lectures that are posted on this website on breast cancer .

2. Have you ever needed hard facts on cancer statistics? You may find a wealth of information on the National Cancer Institute’s website including state cancer profiles, population, morbidity and mortality data from the 70’s up to the latest.

3. This English website has many layers of information not only for public but also for professional use that’d be too much to list here. Apart from the latest news in cancer research, it deals with public policy, health awareness campaigns, and even reports on scientific competitions for the youth. If teachers needed educational resources, they will find it here!

4. Here is an interactive animation that explains all you have ever wanted to know on the origins of cancer, its progression, treatment, and drugs’ sideeffects.

5. Ever wondered how new technology in nuclear medicine is tested before human applications are done? The answers are mice and rats, of course! As in other fields of science, small mammals are used to try out new protocol to determine weather they are fit for human use. Follow this link to check out a couple sizzling images on SPECT/CT fusion technology:

BL tomography October 3, 2007

Posted by tomography in Bioluminescence, Nuclear Medicine, Tomography, Uncategorized.
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What is bioluminescence? Bioluminescence is the production and emission of light by a living organism the result of a chemical reaction during which chemical energy is converted to light energy. Its name is a hybrid word, originating from the greek bios for “living” and the latin lumen “light”. Bioluminescence(BL) may be generated by symbiotic organisms carried within a larger organism. It is generated by an enzyme-catalyzed chemoluminescence reaction, wherein the pigment luciferin is oxidised by the enzyme luciferase.


Milky seas from space! (http://www.lifesci.ucsb.edu/~biolum/organism/milkysea.html)

„Molecular imaging using bioluminescence imaging(BLI) requires expression of an enzyme known as luciferase that is responsible for making some insects, jellyfish, and bacteria glow. The gene for this enzyme is incorporated into DNA of cells, micro-organism, or animal models of diease. If an appropriate substrate is available for the enzyme to act upon, the result is a reaction that emits a subtle glow of visible light called bioluminescence that can be used to monitor cellular and genetic activity of every cell that expresses the luciferase.”

„The peak wavelength of that glow for naturally occuring firefly luciferase eg. is at ~560nm; for bacterial luciferase is at ~490nm. Recently, luciferase genes isolated from insects and sea organism havebeen genetically modified to be efficiently expressed in mammalian cells.”

„In contrast, radionuclides of interest emit high-energy photons of very specific energies and the photons are emitted essentially one at a time (for SPECT) or in acoincident pair (for PET) as a result of decay of a single atomic nucleus. Thus, in radionuclide imaging, photons are detected and processed one at a time, buti n BLI, a continuous current of photons is collected (integrated) and processed in a single or multiple exposures of the optical camera sensor.”


„BL tomography? Unlike in PET and SPECT, the field of BLI up to now has mainly used single view, non-tomographic, planar-imaging to estimate the luciferase producing cell distribution within a mouse. Limitations of planar compared with tomographic imaging are: (1) planar images are superpositions of emission from all depths; (2)lack of precise depth localization; (3)strong depth-dependent resolution blurring; (4)lack of quantification due to significant photon attenuation. 3D BLI is needed because there are applications for which the BL surface radiance signal is weak from certain views, but stronger from others, and it is simply important to sample the signal from different projection angels.” – from the European Journal of Nuclear Medicine

Stop the spread of cancer…



Bioluminescence Genes Found Through Metagenomic Study Of Deep Mediterranean



Luciferase systems are widely used in the field of genetic engineering as reporter genes. Luciferase systems have also been harnessed for biomedical research using bioluminescence imaging.

Solution to Picture of the week #3, and this week’s image. October 2, 2007

Posted by tomography in Picture of the week, Uncategorized.
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Take a look at the following image, that will help you better visualize the way SPECT images are taken. Therefor, if you go back to last week’s image, which as zslog pointed out was taken after the so-called dobutamine stress test, you may easily identify the parts with poor perfusion. (Scroll down for the solution to last week’s image).


Solution to image of the week # 3:

  • From the HLA – horizontal long axis view – you can tell, that the septum has perfusion defect, and
  • From the SA – short axis view – and the VLA – vertical long axis view – you can tell that the apex of the heart is hypo-oxygenated.

And here is this week’s image:


  • What kind of image is this?
  • Identify 3 abnormalities on it.
  • What could have caused this trauma?

Must Click Links! October 1, 2007

Posted by tomography in Blogroll, Radiology, Tomography, Uncategorized.
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Every now and then, you will find a short detail of certain websites we found useful and interesting, and therefor welcome you to check out for yourself. Certainly, you may recommend some of your own!

1. Here is a great MRI teaching website, where you can scan the whole body, and learn to identify its parts and their physiological configuration:

2. You will find a couple interesting cases here like lymphomas, breast, colon, and lung cancer. Since only the PET images can be viewed here, it may be a great challenge for you to try and locate the “hot spots” for yourself:

3. Art and medicine has always been very closely intertwined. Illustrations can help our understanding of medical concepts a great deal, and sometimes they are just pleasant to look at:

4. This site is an interesting and strinking example of how web 2.0 can help science evolve. Beyond topics like “picture of the week,” it has helpful mnemonics, staging information, a study guide, helpful study techniques, and even a textbook section!

5. Need help figuring out what is on that X-ray? On this website you will find loads of chest x-rays, with clear explanations. Great tool for students!

September 28, 2007

Posted by tomography in Uncategorized.
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Hello there!

Of course we continue adding new posts -we’re on to find always some interesting themes-, and pics.

If you have any questions (besides comments) or wishes we should deal with, please feel free and disturb us 🙂

Thank you


Természetesen továbbra is próbálunk érdekes témákkal szolgálni, folytatva újabb cikkek és képek hozzáadását.

Ha bármilyen kérdés (a commenteken kívül) vagy kívánság felmerül bennetek, ami részletesebben, komolyabban érdekel, szívesen fogadunk zaklató hozzászólásokat 🙂


Picture of the week #3 September 25, 2007

Posted by tomography in Picture of the week, Uncategorized.

Thoracic pain is a quite common and freightening symptom that can be caused by various reasons. Based on this SPECT image, what is the origin of pain in this case?

Solution to the picture of the week – Megfejtés a 7Képe feladványra September 25, 2007

Posted by tomography in Picture of the week, Uncategorized.
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Hello! So, another week has passed, and we are through our 600th hit 🙂 ! Thanks for that, Everybody! Here I am going to give you two hints for last week’s picture puzzle. Hints, because some of You found the solution, others were partially right with their answers, and for the Latter a little help will stear them to the correct answer:

(Picture from: http://www.e-radiography.net)

(Picture from: http://www.loogoo.de/images/piercing/breast.jpg)

Yep’! Look back on the original image, and You will find both of these “abnormalities” on that x-ray 🙂 So, You got the urge to swallow swords, or get some of your own piercings? You may find more information on these three sites:

And check out this video I found on You Tube where the whole swallowing process can be followed through x-ray!



Egy újabb hét eltelt, és már a 600-dik oldalletöltésen is túl vagyunk, aminek nagyon örülünk. Köszönjük mindenkinek, aki ellátogatott hozzánk! A múlt heti feladványhoz inkább csak egy kis segítséget nyújtanánk, mert páran kitaláltak, hogy mik is az “elváltozások,” akik pedig csak félig, azok a két puska alapján már biztosan összerakják a képet 🙂 Ha ezek után bárkinek kedve támadna a kardnyelés művészetéről olvasgatni, vagy netán egy újabb piercinggel gazdagítaná gyűjteményét, akkor a linkekre kattintva többet is megtudhat. A videón pedig nyomon követhetjük a kard útját a szájüregtől egészen… amíg ér ! 🙂 Jó szórakozást hozzá!