of sufficient quality and quantity

of sufficient quality and quantity

The patient s body attenuates the beam as it passes though the body More energy is deposited in organs located near the entry of the beam than near the exit of the beam Exposure-to-dose conversion factor for breasts is 14X higher for AP vs. PA Chest view (Tables 23-24, HHS Pub 89-8031) Wolbarst Physics of Radiology 2 nd Edition

Exposure-to-dose conversion factor for breasts is 14X higher for AP vs. PA Chest view (Tables 23-24, HHS Pub 89-8031) The field of view (FOV) affects patient dose in two ways Organs within the FOV are irradiated unless shielded The larger the FOV, the more scatter is produced increasing the depth dose for the same entrance exposure About 10% higher for 35x35cm vs. 15x15cm (Table B.8 NCRP 102) Wolbarst Physics of Radiology 2 nd Edition

Dense objects (mandible, hardware, shields)=>loss of contrast Too much uncovered area (under-collimation, boundary not detected)=>loss of contrast Effective dose for image on right is more than 2 x higher! Centering, multiple FOV s, boundaries of FOV

Rotating polygon mirror Analog-to-Digital Converter Laser fast scan Photomultiplier tube Digital Image Light guide Amplifier Latent Image slow scan Imaging plate

conversion layer (courtesy J. A. Rowlands and Wei Zhao)

This correction is only as good as the uniformity of the x-ray field during calibration and the present condition of the scanner and imaging plate.

This correction is only as good as the uniformity of the x-ray field during calibration and the present condition of the scanner and imaging plate.

In DR, corrections must be applied for differences in gain and offset among individual detector elements (dels) and amplifiers as well as corrections for nonfunctional ( dead ) dels.

These corrections are applied in two dimensions.

These corrections are applied in two dimensions. Like CR, the correction is only as good as the uniformity of the x-ray field during calibration and the present condition of the detector.

Like CR, the correction is only as good as the uniformity of the x-ray field during calibration and the present condition of the detector.

Courtesy Laurence Parr, Naval Medical Center Portsmouth, VA Like CR, the correction is only as good as the uniformity of the x-ray field during calibration and the present condition of the detector.

Like CR, the correction is only as good as the uniformity of the x-ray field during calibration and the present condition of the detector.

Like CR, the correction is only as good as the uniformity of the x-ray field during calibration and the present condition of the detector.

Like CR, the correction is only as good as the uniformity of the x-ray field during calibration and the present condition of the detector.

Courtesy Eric Gingold, Thomas Jefferson University Hospital

Courtesy Eric Gingold, Thomas Jefferson University Hospital

Hamlet Previous CR Chest image modified by non-linear LUT and edge enhanced

Hamlet

Hamlet AP 110 kvp 5.8 mas AP 120 kvp 3.1 mas PA 100 kvp 17.3 mas Technique chart calls for PA 115 kvp 2.5 mas (180 cm SID w/ non-removable grid)

Only enough SNR is needed to visualize important clinical features Agfa Fuji Kodak/CSH Konica/Minolta GE Philips Canon Swissray IDC lgm S# EI S# DEI EI_S REX DI F#

The variety and inconsistency of traditional Exposure Indicators created a problem for technologists who work with different CR and DR systems. Specific target values have yet to be established

The objective data is there for you to establish your own local standards for target values and action levels

Beware segmentation errors! DI = - 0.4 DI = - 18.2

plus Even when the display is properly GSDF calibrated, the PACS may not display the image so that it looks the same as it did to the technologist. Acquisition Station PACS Display

plus Even when the display is properly GSDF calibrated, the PACS may not display the image so that it looks the same as it did to the technologist. The PACS may not display all of the information that is necessary to understand how the image was acquired.

plus Even when the display is properly GSDF calibrated, the PACS may not display the image so that it looks the same as it did to the technologist. The PACS may not display all of the information that is necessary to understand how the image was acquired.

Processed Unprocessed

Take-away points from all this chaos CR, DR, and PACS are wonderful technologies fully capable of acquiring high quality radiographic projection images and displaying them for primary interpretation. In order to evaluate interval change in a patient, the radiologist may need to look beyond the visual appearance of the image and consider how comparison images were acquired or digitally processed. CR, DR, and PACS vendors have made great strides in providing objective information about how each image was acquired and processed for technologist feedback, radiologist oversight, medical physicist troubleshooting, and for incorporation into a QI Program. SPR was instrumental in catalyzing improvements in CR, DR, and PACS technology, especially for managing patient radiation dose. This is not a solved problem. Marvin s responses (the manically depressed robot) CR, DR, and PACS are fully capable of producing inconsistent and nondiagnostic radiographic projection images with unnecessary radiation doses to patients. Here I am, brain the size of a planet, and they ask me to pick up a piece of paper. I ve seen it. It s rubbish. Well I wish you d just tell me rather than try to engage my enthusiasm. I d give you advice, but you wouldn t listen. No one ever does. The highest level of quality that the medical physicist and the imaging operation is going to be able to provide is the lowest level of quality that the radiologist is willing to accept. I m not getting you down at all am I?