[Dcmlib] Imager pixel spacing vs Pixel Spacing (Patient)

[Mathieu Malaterre]

Very intersting doc for Imager pixel spacing vs Pixel Spacing (Patient)

http://groups.google.com/group/comp.protocols.dicom/msg/70d66debe4121bbc?hl=en&


Imager pixel spacing was created as an alternative to pixel spacing,
defined as the distanced between adjacent pixels IN THE PATIENT, for
projection radiography. In Imaging Pixel Spacing, the attribute refers
to the distance between pixels on the sensor. In a perfect world,
xrays hitting the imager sensor will be parallel or so close to
parallel so as not to make a significant difference; but with some
technologies, CR in particular, one doesn'
t  really know what the geometry of the x-ray collimater is with the
sensor. So, the attribute is expressed in the dimension of the sensor
(or both the sensor and the image). Your formula is fine but you might
want to note the possibility of distance errors for situations where
the geometry of the imaging context is such that there is a
significant difference between the pixel spacing on the sensor and
distance between pixels in features imaged in the patient.