Design study of a Laue lens for nuclear medicine

A Laue lens is an ensemble of crystals capable of focusing, through diffraction in transmission geometry, a fraction of the photons emitted by an X- or gamma-ray source onto a small area of a detector. The present study allows obtaining a thorough understanding about the effect of each system parameter on the efficiency, the resolution, and the field of view of the lens. In this way, the structure and the size of the crystals can be set to achieve a compact lens capable of providing a high-resolution image of the radioactivity distribution lying inside a restricted region of the patient's body. As an application, a Laue lens optimized at 140.5 keV, the gamma-line emitted by 99mTc, has been designed. The lens is composed by 10 rings of Ge crystals with curved diffracting planes and focuses the photons onto a detector 50 cm apart from the source with 1.16x10^-5 efficiency and 0.2 mm resolution. The combination of these two important figures of merit makes the proposed device to be better performing than a pinhole SPECT (Single Photon Emission Computed Tomography), which is the technique employed for top-resolution images in nuclear medicine. Finally, the imaging capability of the designed lens has been tested through simulations performed with a custom-made Monte Carlo code.