Image processing for photographing scintigram of subject on X-ray film at optimum density

Claim 1

A diagnostic nuclear medical apparatus comprising: a digital scintillation camera unit including a two-dimensional radiation detector for detecting radiation from the inside of a subject with radioisotope dosed for each of pixels arranged in a two-dimensional array to provide detection data, representing counts of detection of radiation, in the form of a digital signal; data processing means coupled to said digital scintillation camera unit for converting the radiation detection digital signal into an analog video information signal; and video imaging means coupled to data processing means for visually displaying a scintigram image representing the radioisotope distribution of said subject, the scintigram image displayed by said video imaging means being photographed on a photographic film, and the photographic density of the film after a developing process being a function of the amplitude of the analog video information signal; said data processing means being arranged to convert the digital signal into the analog information signal such that a substantially linear characteristic of conversion of radiation detection level to photographic density is obtained on a developed film.

Claim 7

A method of photographing a scintillation image of a subject on a film at a density best suited for diagnosis and for use in a diagnostic nuclear medical apparatus, said developed film image having a maximum photographic density, comprising a digital scintillation camera unit including a two-dimensional radiation detector for detecting radiation dosed for each of pixels arranged in a two-dimensional array to provide detection data, representing counts of detection of radiation, in the form of a digital signal; data processing means coupled to said digital scintillation camera unit for converting the radiation detection digital data into an analog video information signal; and video imaging means coupled to data processing means for visually displaying a scintigram image representing the radioisotope distribution of said subject, the scintigram image displayed by said video imaging means being photographed on a photographic film; said method comprising the steps of: measuring a characteristic of conversion of a video signal to photographic density on a developed film by supplying a test pattern video signal to said video imaging means; preparing a first conversion table showing the measured characteristic of conversion of video signal to photographic density in said data processing means; displaying a scintigram image of the subject by counting radiation emitted from the subject in said video imaging means; setting a region-of -interest in the scintigram image of the subject; computing an average value AV and standard deviation value SD of the radiation detection count per pixel in the region-of-interest in said data processing means; computing in said data processing means an upper count level WU from the average value AV and standard deviation value SD as follows: WU=AV+a×SD where a is a constant; preparing a second conversion table representing a linear characteristic of conversion of count to photographic density such that the upper count level WU is displayed at said maximum photographic density on the film in said data processing means; preparing, in said data processing means, by referring to said first and second conversion tables a third conversion table showing a characteristic of conversion of count to gray scale such that the upper count level WU is displayed the said maximum photographic density of the film; converting detection data representing a scintigram of the subject into data signals having gray levels according to said third conversion table in said data processing means; converting the data signals having gray levels into video signals according to a linear characteristic of conversion of gray scale to amplitude level in said data processing means; and photographing the scintigram image of the subject on the film by supplying the video signals to said imaging means.

Claim 8

A method of photographing a scintillation image of a subject on a film at a density best suited for diagnosis and for use in a diagnostic nuclear medical apparatus, said developed film image having a maximum photographic density, comprising a digital scintillation camera unit including a two-dimensional radiation detector for detecting radiation dosed for each of pixels arranged in a two-dimensional array to provide detection data, representing counts of detection of radiation, in the form of a digital signal; data processing means coupled to said digital scintillation camera unit for converting the radiation detection digital data into an analog video information signal; and video imaging means coupled to data processing means for visually displaying a scintigram image representing the radioisotope distribution of said subject, the scintigram image displayed by said video imaging means being photographed on a photographic film; said method comprising the steps of: measuring a characteristic of conversion of a video signal to photographic density on a developed film by supplying a test pattern video signal to said video imaging means; preparing a first conversion table showing the measured characteristic of conversion of video signal to photographic density in said data processing means; displaying a scintigram image of the subject by counting radiation emitted from the subject in said video imaging means; setting a region-of -interest in the scintigram image of the subject; computing an average value AV and standard deviation value SD of the radiation detection count per pixel in the region-of-interest in said data processing means; computing in said data processing means an upper count level WU from the average value AV and standard deviation value SD as follows: WU=AV+a×SD where a is a constant; preparing a second conversion table representing a linear characteristic of conversion of count to photographic density such that the upper count level WU is displayed at said maximum photographic density on the film in said data processing means; preparing, in said data processing means, by referring to said first and second conversion tables a third conversion table showing a characteristic of conversion of count to gray scale such that the upper count level WU is displayed the said maximum photographic density of the film; converting detection data representing a scintigram of the subject into data signals having gray levels according to said third conversion table in said data processing means; converting the data signals having gray levels into video signals according to a linear characteristic of conversion of gray scale to amplitude level in said data processing means; and photographing the scintigram image of the subject on the film by supplying the video signals to said imaging means.