Euromedim 2006 :1st European Conference on Molecular Imaging Technology

Clinical evaluation of pixelated NaI:Tl and continuous LaBr3:Ce compact scintillation cameras for breast tumors imaging

11 May 2006, 14:00

1h

Palais du Pharo, Marseille

poster • Status of animal and clinical PET, SPECT and CT (biomedical and technical) Poster session : Imaging systems, Molecular Imaging

Speaker

Prof. Roberto Pani (INFN Dept Experimental Medicine and Pathology - University of Rome "La Sapienza"-Italy)

Description

Although scintimammography was introduced more than 10 years ago, it has never become routine in the majority of Nuclear Medicine Centers. The principal limiting factor in the clinical acceptance is certainly its low sensitivity for cancers sized < 1cm, mainly due to the lack of equipment specifically designed for breast imaging. The very low sensitivity of scintimammography for tumors under 1 cm diameter is not trivial, because the ability in visualizing small breast cancers is really crucial for the future development and clinical acceptance of scintimammography. To this aim a number of dedicated gamma cameras with superior imaging performances were specifically designed for the breast. Hundreds of clinical trials have been currently performed by dedicated gamma cameras based on Position Sensitive Photo-Multiplier Tubes (PSPMT) coupled to scintillation arrays and cadmium-zinc-telluride (CZT) semiconductor cameras. In particular the latter shows higher performances due to 6.5% of energy resolution, that causes a better scattered radiation rejection. Finally INFN has been developing a new scintillation camera based on the latest scintillator generation, LaBr3:Ce, that is demonstrating superior imaging performances than CZT detector with comparable energy resolution. In order to foresee future advances in functional breast imaging, in this paper we propose a clinical comparison and evaluation between this gamma camera with the one previously developed under “IMI” Italian project for technological transfer of INFN. The gamma camera, made by CAEN and Pol.Hi.Tech, has an overall dimension of 112x120x75.3mm3 and consists of an array of 42 one in. PSPMTs Hamamatsu H8520-C12 closely packed, a NaI(Tl) scintillation array (1.8 x1.8x 6mm3 pixel) and a general purpose collimator. A clinical experience is performing by this gamma camera on a number of patients with breast cancer suspicion.. Latest generation detector consists of continuous LaBr3:Ce scintillator coupled to a Hamamatsu H8500 Flat Panel PMT. The planar LaBr3:Ce integral assembly, realized by Saint Gobain, is 50.8×50.8 mm2 size and 4 mm thick with a 3 mm thick glass window. Basic detector principle is the same of Anger camera with scaled dimensions. The detector showed 1 mm intrinsic spatial resolution and 70% detection efficiency. In this paper we show how high spatial resolution, high energy resolution and continuous position response improve detector imaging performances to better categorize the lesions by the morphology of the radiotracer distribution in the breast tissue. The clinical experiment consisted of the co-registration of the breast examination from the two dedicated cameras. The comparison between standard and high resolution images of two cases of breast cancer suspicion, highlights how Anger camera poorly imaged malignant lesions. Otherwise, the high resolution scans produced by LaBr3:Ce camera showed higher tumor contrast with a detailed imaging of uptake area than pixelated NaI(Tl) dedicated camera. Furthermore a dramatic increase of Signal to Noise Ratio (SNR) of lesion with a consequent strong improvement of tumor detectability. represents the most impressive result, bearing in mind that the definition of a breast lesion malignancy is determined by a focal concentration of radioactivity (hot spot) in the breast tissue. These results were confirmed by byoptical findings.