Quantitative beta imaging with a digital single lens reflex camera

Objectives To image the spatial distribution of beta (+/-) emitters in vitro using various contact scintillators viewed with a digital SLR.

Methods A modern digital SLR camera (Pentax K-x; Sigma EX macro lens) was through-mounted into a small dark box, focused onto a thin (2 mm) scintillator in contact with the beta-emitting source, e.g. a thin layer chromatograph (TLC) plate, mounted on a rotating stage. A 1P28 photomultiplier (PM) tube in the current mode acts as a light meter, and a switched lamp provides light field registration. Five scintillator materials were evaluated, as well as Cerenkov emission from various stopping media. Submillimeter spatial resolution was achieved, with exposure factors (ISO and time) scaled by the PM current. The relative light output [PM nanoAmps] varies ten-fold; CsI(Tl) > EJ212 > EJ260 (green) > Meltelex, and hundred-fold over Cerenkov for both F-18 and Cu-64. Recognizing that the PM and SLR have differing spectral sensitivity, at f=2.8, ISO 12,800, a 1 mCi, 7 mm diam spot of F-18 is well-imaged in ≈ 1 sec. The digital images are transferred to ImageJ running on an iMac, for quantitation as TLC profiles or regions of interest.

Results This SLR-based device must stand an honest comparison against other bench-top beta scanners and phosphor-plate systems in terms of dynamic range, signal/noise, versatility, simplicity, cost and regulatory compliance. The phosphor plate image storage device is the clear winner in sub-nCi applications, while a good beta scanner is favored by regulatory authorities. This SLR device gains its strength from its simplicity and immediate readout by image free ware. The rotating source capability allows 3-dimensional imaging, such as the location of residual activity on the inner surfaces of reaction glassware, immersed in liquid scintillation fluid.

Conclusions The SLR beta imaging device fills a niche in the nuclear research laboratory, where the spatial distribution of a planar beta source must be quickly determined, to guide the subsequent synthesis.

Research Support NIH/NCI T32 CA0920