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Image information content and patient exposure
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1978
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Computed TomographyX-ray FilmEngineeringImage Information ContentSurgeryDiagnostic ImagingImage AnalysisHealth CommunicationCt ScanPhoton-counting Computed TomographyNuclear MedicineCollimationRadiologyMedical ImagingImage Visibility RequirementsRadiographic ImagingHealth DataMedical PrivacyPatient SafetyBiomedical ImagingImage VisibilityClinical ImageMedicineHealth Informatics
Patient exposure and tube kilovoltage are traditionally set by image visibility on film, but image‑processing allows exposure to be based solely on desired information content such as tissue‑density discrimination and spatial resolution. The study derives quantitative relationships between image information content and patient exposure, estimating the minimum exposures needed to detect signals in specific radiological exams. The results show that minimum exposures can be estimated for detecting exam‑specific signals, and for subjects thicker than ~5 cm, optimal single‑kV and filtration settings with image‑enhancement and antiscatter yield maximum information, enabling exposure reduction or information gain.
Presently, patient exposure and x-ray tube kilovoltage are determined by image visibility requirements on x-ray film. With the employment of image-processing techniques, image visibility may be manipulated and the exposure may be determined only by the desired information content, i.e., by the required degree of tissue-density descrimination and spatial resolution. This work gives quantitative relationships between the image information content and the patient exposure, give estimates of the minimum exposures required for the detection of image signals associated with particular radiological exams. Also, for subject thickness larger than approximately 5 cm, the results show that the maximum information content may be obtained at a single kilovoltage and filtration with the simultaneous employment of image-enhancement and antiscatter techniques. This optimization may be used either to reduce the patient exposure or to increase the retrieved information.