Control system for gamma camera

In a system for imaging the distribution within a region of interest of a radiation-emitting isotope, said system including solid state detector means having charge characterized outputs representative of the energy and spatial disposition of corresponding interactions of said radiation with said detector means, the improvement comprising:

• amplifier means responsive to said detector means outputs and having output signals corresponding thereto;
• first summing means responsive to said amplifier means output signals for deriving spatial signals in correspondence with spatial orientations of said interactions;
• second summing means responsive to said amplifier means output signals for deriving energy signals of value corresponding with the energy values of said first summing means spatial signals, said second summing means including a stage deriving the time derivatives of said energy values of said amplifier output signals;
• evaluating means responsive to said second summing means energy signals for evaluating the peak value of substantially each said energy signal over a time, t.sub.e, and having a select output when said energy signal peak value lies within predetermined limits;
• means actuable to treat said spatial signals to improve the signal-to-noise aspects of said system;
• readout means responsive, when actuated, to receive said treated spatial signals and derive output information representative thereof;
• comparator means responsive to the value of each said second summing means derivative signal equaling or exceeding a predetermined reference value for deriving a start output;
• and
• control means responsive to said comparator means start output for actuating said means treating said spatial signal, so as to effect the commencement of an operational cycle of said system.

In gamma camera apparatus suited for imaging the distribution of a radiation emitting isotope, said system including a germanium solid state detector arrangement configured having orthogonally disposed arrays of axially aligned strip regions, each strip within each said array being associated with a discrete resistor of a charge splitting resistor network, said networks being arranged to receive radiation-induced charges in spatial disposition corresponding with the interaction location of said radiation with respect to said strips and having termini for providing outputs corresponding to said spatial disposition, said detector arrangement and said resistor networks exhibiting a collection time constant, .tau..sub.D, the improvement comprising:

• preamplification means coupled at the termini of each said resistor network and having output signals corresponding with said charge receipt;
• antisymmetric summing means coupled with said preamplification means for subtractively summing said output signals and deriving coordinate Gaussian filtered spatial signals corresponding to the spatial orientation of a said interaction location;
• summing means for additively summing said preamplification means output signals to derive energy signals corresponding with said spatial signals, said summing means including a Gaussian filter having a high pass stage deriving, as a signal, the time derivative of said summed output signals;
• gated integrator means coupled with said antisymmetric summing means and configured to receive and integrate said spatial signals over an interval, t.sub.s, as defined by an initial and subsequent gating thereof, to provide trapezoidal filtering of said spatial signals;
• evaluating means responsive to said summing means energy signals for evaluating the peak value thereof over a time interval, t.sub.e, and having a select output when said energy peak value lies within predetermined upper and lower limit value, said time, t.sub.e, being greater than said time, t.sub.s ;
• readout means responsive, when actuated, to receive said filtered spatial signals and derive output information representative thereof;
• comparator means responsive to the voltage value of each said summing means derivative signal equaling or exceeding a predetermined reference value for deriving a start output;
• and
• control means for regulating an operational cycle of said system, responsive to said comparator means start output for carrying out said initial gating of said gated integrator means to commence said integration over said interval, t.sub.s, and for actuating said readout means upon the occurrence of said evaluating means select output.