Grapefruit USA Inc (GPFT)

[goldcoastoh]

mr. sano --- getting back to "what is conebeam ct" it probably best just to repost this... i can tell you that as far as which generation conventional CT scanners are most typical, most typical are the 3rd generation scanners. it was good to go through this again...


http://investorshub.advfn.com/boards/read_msg.aspx?message_id=42630231

read the first article, title, "Conebeam CT of the Head and Neck, Part 1: Physical Principles."

"Data acquisition in conventional CT imaging has evolved through 4 generations of acquisition geometries. First-generation scanners used parallel pencil beams of x-rays and required both translation and rotation of the source and a single-detector apparatus. Second-generation scanners introduced fan-beam x-ray geometry and used a single-detector linear array. In third-generation scanners, the single-detector arc was introduced in conjunction with fan-beam x-ray geometry. Fourth-generation scanners used a fan-beam of x-rays and a circular detector array. In current practice, multidetector helical CT (MDCT) scanning is most frequently used, answering the call for reduced acquisition times. MDCT is loosely based on third-generation geometry, though the detector array has multiple rows of detectors."


--- okay, here's the basic concept of a conebeam...per the same article (see figure 2) to see a picture/drawing comparing fan-beam to cone-beam.

"Data Acquisition
In CBCT systems, the x-ray beam forms a conical geometry between the source (apex) and the detector (base) (Fig 2). This is in contrast to conventional fan-beam geometry (Fig 2), in which the collimator restricts the x-ray beam to approximately 2D geometry. In a fan-beam single-detector arc geometry, data acquisition requires both rotation and z-direction translation of the gantry to eventually construct an image set composed of multiple axial sections. In CBCT systems using a 2D FPD, however, an entire volumetric dataset can be acquired with a single rotation of the gantry. Incident photons on multiple-row detectors in MDCT actually fall on a 2D area of detectors, as with flat-panel detection; indeed, with increasing numbers of rows in MDCT detector arrays, the acquisition geometry actually approximates that of a conebeam system."


--- okay, also make sure you look what can be viewed as a typical non-3d post processed CBCT image... it's figure 3 in the same article. it's really pretty much similar to any non-3d post processed 3d CT image.


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here's a picture of a third generation scanner from my fav cyclopedia...not wiki...

http://www.medcyclopaedia.com/library/radiology/chapter04/4_2.aspx

here's a picture of a fourth generation gantry...

http://radiographics.rsna.org/content/22/4/949/F7.expansion


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i highly encourage you to take a look at these animation clips...it'll paint a picture of the third generation MDCT... in particular the "detector plate" clip.

http://investorshub.advfn.com/boards/read_msg.aspx?message_id=43836146


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from my reading it appears as CT manufacturers are attempting to move toward flat planel detectors...meaning perhaps the fourth generation gantry won't really become the norm.