fig. 2 New, thick CsI:T1l, 1.5 mm columnar structure
Enlargement

3 mm thick columnar CsI:T1

3 mm thick columnar CsI:T1

An image of a hand phantom obtained using **175 micron thick microcolumnar CsI:Tl coupled to a 5 x 9 cm² area CCD developed at RMD. The X-ray settings were 40 kVp, 8 mAs

Cesium Iodide Scintillator Films

-----RMD's development of microstructured scintillators has benefited from many SBIR programs, including NIH, NSF and DOD, and has contributed to the understanding of microstructured CsI(Tl), now widely used in advanced digital X-ray imaging systems.

-----RMD's ongoing research is improving this technology beyond its current capabilities, and newer sensors demonstrate superior spatial resolution, light output and X-ray sensitivity, and substantially improved detective quantum efficiency in digital X-ray imaging systems compared to any other X-ray imaging screens on the market.

-----Research at RMD focuses on CsI(Tl) material modifications to minimize the associated hysteresis and afterglow, and developes microstructured films of this new material. We have succeeded in reducing the afterglow by a factor >50, making these films suitable for high speed X-ray imaging for such applications as fluoroscopy and time resolved X-ray diffraction studies. Also, the technology of microstructured film growth is being extended to form films of materials other than CsI(Tl), which are of critical importance to X-ray and radionuclide imaging in medical radiography and nuclear medicine applications. RMD is also investigating semiconductor films of PbI2 and HgI2 for direct imaging.

-----RMD has invested internal and external commercial funds in developing a sophisticated research and production facility for prototyping and manufacturing up to 47x47 cm² high-resolution microstructured CsI(Tl) screens. RMD has commercialized its CsI(Tl) sensor technology through RMD Instruments, LLC, resulting in regular sales for a wide variety of imaging applications in many fields, including mammography, dentistry, structural biology, time resolved X-ray crystallography, and nondestructive testing.

-----RMD regularly presents its CsI(Tl) technology at trade shows, including the RSNA (2001-2005) and SPIE Medical Imaging (2002-2005) meetings, helping to form a substantial client base for these products.

-----RMD is also investigating semiconductor imaging films of PbI2 and HgI2. RMD has sold many prototype films and devices, and has received Phase III development funds and prototype sales.

Structured CsI

• High resolution, high MTF
• High light output
• Increased X-ray stopping power
• Uniform response across sensor

Intra-Oral Radiology

RMD screens have good contrast in the diagnostic region of 2.5 to 6 line pairs/mm and spatial resolution of 10% MTF @ 10 lp/mm. Screen models include a substrate that is either a fiberoptic plate or graphite.

Mammography

RMD CsI(Tl) screens produced with low energies of 26 kVp, used typically in mammography, offer very high sensitivity, low noise, and a high detective quantum efficiency (DQE(f)) when coupled to an imaging detector. While these screens can be deposited on a variety of substrates, the preferred substrate is graphite. Screens offer a minimum guaranteed performance of 10% MTF at 8 lp/mm as measured on RMD's reference system.

Micro-CT

RMD Cesium Iodide (Tl) screens for microtomography have a fiberoptic substrate that may be coupled to the customer's fiberoptic taper.

General Radiology

This screen has an active area of 47 x 47 cm and a graphite substrate. Screen performance target is a high spatial resolution. Light output is at least 1.5 x Lanex Regular, measured at 70 kVp x-ray and 2.7 mm Al filter on RMD's reference system of fiberoptic block to CCD camera.

Nondestructive Testing

RMD CsI(Tl) screens for nondestructive testing are designed for use with a wide energy range of 50 kVp to 420 kVp. These sensors are available in various sizes, ranging from 2.5 x 2.5 cm² to 10 x 10 cm² with a thickness ranging from 50 µm to 1 mm. Screens offer either high signal yield and/or a high spatial resolution. Spatial resolution offered by the thinner screens can exceed 14 lp/mm, while resolution of the thicker variety is over 4 lp/mm. An image of a turbine blade acquired using the RMD scintillator shows excellent resolution and dynamic range achievable when 420 kVp X-rays are used (see fig. 3).

Crystallography, including Structural Biology

Crystallography screens are generally thin, measuring only about 20 to 50 mm, and can offer spatial resolution ranging from 10 lp/mm to over 30 lp/mm. In addition to the conventional graphite or fiberoptic substrates, these screens can be made on a flexible substrate with a reflective surface.

Sizes and Substrate Types Customized for Each Application

• High Modulation Transfer Function, MTF(f)
• Improved Detective Quantum Efficiency, DQE(f)
• Low Noise Power Spectrum
• Sensor Area 20 mm x 30 mm 50 mm x 50 mm typical. larger if desired   (see fig.1)
• CsI(T1) thickness tailored for each application, optimal system performance is achieved with a CsI(T1) thickness in the range of 30-200 microns (100 µm is ~ 42 mg/cm²) (see fig. 2)

X-rays Convert to Optical Image
-----This sensor includes a thin layer of cesium iodide material on a substrate. The cesium iodide layer consists of many thin, rod-shaped, cesium iodide crystals (approximately 6 - 10 microns in diameter) aligned parallel to one another, and extending from the top surface of the cesium layer to the substrate on which they were produced. The crystals are thallium-doped, cesium iodide, which is represented chemically as CsI(T1) and usually referred to as cesium iodide. When an X-ray or gamma photon is absorbed in a cesium iodide fiber, the cesium iodide "scintillates" and produces light. The light reflects within the fiber and is transmitted from one end of the fiber. The sensors are most frequently delivered on a substrate which is a fiberoptic glass plate, and transmits the scintillation light out through the substrate and, typically, to a CCD array. An exceptionally fine spatial resolution present in the X-ray pattern is preserved in the light from the cesium iodide sensor. The same technology also produces cesium iodide arrays on other substrates, such as an opaque, low-atomic-number sheet, in which case the sensor is manufactured to transmit light from the top surface of the fiber layer.

RMD Cesium Iodide Imaging Sensors

Improved system performance - Better images

• Sensors are manufactured to each customer's area and performance specifications.
• Performance specifications typically include the value and relative importance of spatial resolution, light output, and signal-to-noise ratio.
• CsI(T1) sensor production and ISO 9001 manufacturing performed on site.
• RMD provides high-quality products and excellent service.

Sructured CsI Brochure CsI Screens Brochure