X-ray backscatter detection system

Radiant energy imaging apparatus for detecting objects carried on a person's body comprising:

• radiant energy imaging means providing an image signal representative of said person's body and objects carried on said person's body by detecting radiant energy modulated by the body;
• memory means for storing a library of reference image features derived from previously imaged human bodies;
• computational means for comparing features of said image signal to anatomical features of said reference image features to identify anatomical features of said image signal;
• and
• display means for presenting a display signal representative of said image signal wherein its anatomical features have been suppressed.

Apparatus for searching a subject comprising primarily a first low Z material for concealed objects of a second low Z material, comprising:

• a source of X-rays;
• collimation means for forming a beam of X-rays from said X-ray source, wherein said beam intersects said subject at a region of intersection corresponding to a pixel having a pixel value;
• scanning means for moving said region of intersection over the surface of said subject in a scanning cycle so that a plurality of pixels is defined, said scanning cycle being sufficiently short that said subject is exposed to a radiation dose of less than 10 microRem;
• a detector adjacent said scanning means for detecting a substantial portion of X-rays backscattered from said subject and providing an image signal comprising a plurality of pixel values representative of X-rays backscattered from said subject as a result of being scanned by said beam wherein said plurality of pixel values has a coefficient of variation resulting from X-ray statistical noise of less than 10 percent;
• and
• display means for visually presenting said image signal.

In an X-ray backscatter imaging system for searching for a first low Z material on a background having second low Z, said first low Z being lower than said second low Z, a method comprising the steps of:

• positioning said background body in an imaging area;
• operating an X-ray tube to produce X-rays having a low dose directed toward said imaging area;
• collimating said X-rays into a pencil beam of a cross-section measured where said pencil beam intersects said imaging area, said cross-section corresponding to one of a plurality of pixels each pixel having a pixel value;
• scanning said pencil beam of X-rays over said image area at a sufficiently high rate to impart less than 10 microRem of radiation dose to said background body;
• detecting X-rays that are backscattered from said pencil beam as a result of interacting with matter positioned in said image area;
• and
• displaying a digitally represented image comprising said plurality of pixels wherein each pixel of said plurality is representative of the detected backscattered X-rays produced by matter located at its corresponding cross-section and a coefficient of variation of all pixel values of said plurality of pixels resulting from X-ray statistical noise of less than 10 percent.

In an X-ray backscatter imaging system for searching a person for concealed plastic explosive, a method comprising the steps of:

• positioning said person in an imaging area;
• operating an X-ray tube to produce X-rays directed toward said imaging area;
• collimating said X-rays into a pencil beam of cross-section measured where said pencil beam intersects said imaging area;
• scanning said pencil beam over said image area at a sufficiently high rate to impart less than 10 microRem of radiation dose to said person;
• detecting a sufficient quantity of X-rays that are backscattered from said pencil beam as a result of interacting with matter positioned in said image area so that modulation of the backscattered X-rays resulting from the presence of said plastic explosive is distinguishable from statistical noise of the detected X-rays;
• and
• displaying an image representative of the modulation resulting from the presence of said plastic explosive in said imaging area.