Raw data from emission scanners contained in ECT sinograms can provide an abundance of information about the position of an object in the camera's field-of-view. Since some cancers can be detected by PET and SPECT which are not seen clearly on mammograms, CT or other scans, sinogram data could potentially be used to guide tumor biopsy. For example, positron-emitting (18F-labeled Fluoro-deoxyglucose) and single-photon emitting (99mTc-labeled-sestamibi) radiopharmaceuticals have been used successfully to detect many types of breast cancer. By utilizing some relatively simple geometric relationships, a sinogram-based method for biopsy of radiopharmaceutical-avid breast masses guided by data from PET and SPECT scanners has been developed and validated in phantom studies.
Methods: A pair of projection views from a series of sinograms is used to calculate the position of photon-emitting objects. Calculated positions of spheres ranging in size from 1.6 to 3.4 cm diameters containing 18F and 99mTc were compared with measured positions. By adding a single radioactive fiducial marker, emission-guided biopsy of simulated breast lesions was performed with a specially designed phantom containing photon-emitting spheres 12.7 mm in diameter.
Results: Correlation between calculated and measured object coordinates were excellent (R = 1.0, R = 1.0 and R = 0.998; x, y and z coordinates, respectively). The maximum error in localization was +/- 3 mm. One hundred percent (10 of 10) of the attempted biopsies of simulated tumors were successful.
Conclusion: A method for rapidly determining the position of photon-emitting objects in an emission scanner has been developed and tested. This technique, which does not require standard emission or anatomic images, could be used with dedicated biopsy machines or incorporated into "add-on" biopsy devices for existing PET or SPECT cameras.