Multi modality X-ray and nuclear medicine mammography imaging system and method

#The present invention relates generally to an imaging system, and more particularly to an multi modality X-ray and nuclear medicine mammography imaging system.

#Various multi modality imaging sensors are currently being developed. For example, an article by Mark B. Williams, et al. “Multimodality Imaging of Small Animals,” published on the internet at http://ej.rsna.org/ej3/0107-99.fin/dual99.htm describes an experimental, multi modality system for imaging small animals, such as mice and rats. This system combines a conventional, two dimensional X-ray imaging system with a conventional two dimensional nuclear medicine imaging system. Another article by Mark B. Williams, et. al., “Integrated CT-SPECT System For Small Animal Imaging” published on the internet at http://imaging.med.virginia.edu/mbwlab/ct_spect_ms.pdf describes an experimental multi modality X-ray computed tomography (CT) and nuclear medicine single photon emission computed tomography (SPECT) system for imaging small animals. However, these systems are not adapted to image human patients. The two dimensional images do not yield the optimum amount of information, while the tomography systems which can generate three dimensional (“3D”) images are complex because they require 360 degree angular scanning of the animal. Furthermore, the CT subsystem exposes the animal to an undesirably high dose of X-rays to generate a three dimensional image.

#For human patients, X-ray mammography is the modality of choice for breast cancer screening. However, the sensitivity of mammography is relatively low (between 70 and 80%), and the false positive rate is very high (between 70 and 90% of biopsies are normal). Conventional breast imaging is based on standard two dimensional (“2D”) X-ray mammography for screening and other modalities (ultrasound, MRI, or nuclear medicine) for diagnostic follow up. X-ray mammography may also be used for diagnostic follow up. Each modality has its unique strengths and weaknesses. For example, X-ray is typically used for detection characterization of microcalcifications and masses, while nuclear medicine can potentially provide differentiation between benign and malignant masses. However, combining (i.e., registering) the images obtained from X-ray and nuclear medicine mammography systems is very difficult since the x-ray exam is done with the breast compressed and the nuclear medicine exam is typically done by scanning an uncompressed breast.

#FIG. 1 is a block diagram of a system according to preferred embodiments of the invention.

#FIG. 2 is a block diagram of a subsystem according to the first preferred embodiment of the invention.

#FIG. 3 is a three dimensional view of the subsystem according to the first preferred embodiment of the invention.

#The present inventors have realized that a multi modality system and method for mammography (i.e., human breast imaging) combining X-ray and nuclear medicine combines the strengths of two previously distinct modalities to address the limitations of today's breast imaging technologies. Specifically, in the multi modality mammography imaging system, a breast compression paddle is used to compress the breast during the X-ray and the nuclear medicine examinations. Thus, both the X-ray mammography imaging subsystem and the nuclear medicine mammography imaging subsystem of the system are adapted to image a breast compressed by the paddle. Breast compression for both modalities is preferably the same. However, compression may be reduced for the nuclear medicine imaging because it takes longer than X-ray imaging. Therefore, the ease of registration of the images obtained from X-ray and nuclear medicine mammography subsystems is improved since both the x-ray and the nuclear medicine exams are done with the breast compressed in the same position. The registered images may be fused to display a combined two or three dimensional image of the breast.

#Imaging of a compressed breast provides significant advantages in mammography, both for x-ray and nuclear medicine imaging. Compression of the breast spreads and separates complex structures in the breast and reduces overall x-ray absorption, thus reducing the X-ray dose needed for imaging. The scintimammography images are also taken with the patient's breast compressed, to improve signal to noise ratio in the activity reconstructions (due to less gamma attenuation in the intervening breast tissue) and to improve the spatial resolution, since the collimator is closer to the breast in a compressed configuration. The use of breast compression for both modalities is also beneficial because the patient is immobilized and positioned in the same manner as with conventional X-ray mammography.

#FIG. 1 illustrates a schematic of the multi modality imaging system 1. The system 1 includes an X-ray mammography imaging subsystem 3 and a nuclear medicine mammography imaging subsystem 5. These systems may optionally be directly electrically connected to share information, as indicated by the dashed line. The system 1 also contains an image fusion and visualization work station 7. This work station 7 may comprise a general or special purpose computer or any other type of image processor. The work station 7 receives data acquired by the subsystems 3 and 5 to form the image. Preferably, the work station 7 contains a processor which registers an X-ray image with a nuclear medicine image and a display with displays a fused X-ray and nuclear medicine image.