The Scanco Xtreme 3D quantiatitave computerised tomography (QCT) system is designed to measure the bone density and to quantify the three dimensional microarchitecture of the bone at the human tibia and fibula. It is presently housed in the MRC Elsie Widdowson volunteer suite in Cambridge.

The device is a key component of our systems biology approach to improving the understanding of bone microstructure and underlying control of bone remodelling. The machine helps us understand bone fragility, porosity and arthritis in common and rare bone diseases. Several therapeutic studies (including anti-sclerostin antibody therapy in osteogenesis imperfecta) use Xtreme QCT measures as primary efficacy endpoints. Local PI’s Ken Poole and Kate Ward, are experts in in-vivo computed tomography. Cambridge is one of only a handful of sites worldwide to have such access to such a system.

Since the Scanco Xtreme is an extremely high resolution scanner (82mm compared with 589mm in ordinary clinical CT), there is a need for patients to remain absolutely still, hence there are specific moulds for forearm and lower leg which are needed in order that the 3-5 minute duration scan will be of high quality. There is growing recognition of the need to study changes in bone geometry and density to gain a more complete understanding of bone health throughout the life course.  Current single slice pQCT techniques can be used to study geometry at the metaphysis and diaphysis but have limited spatial resolution and are only able to measure a single section of bone in each scan.  The Xtreme CT allows more detailed analysis of the changes in internal architecture and overall morphometry.

Bones break because the load and its direction exceed the strength of the bone.  This may be due to a reduction in the overall amount of bone or a combination of localised decreases in mass, the presence of critical defects or changes in material properties.  While the assessment of bone mass by DXA provides one estimate of bone strength it has become increasingly apparent that measures of localised bone mass (eg cortical thickness and porosis are important indicators of fragility which can only be reliably measured by high resolution QCT.

Specifications Field of view:  130 mm Max. Scan length: 150 mm Default Resolution: 4.8lp/mm (104μm) (can be set to 82 μm) Default Voxel size: 130μm Image matrix: 1024*1024(default), up to 3072*3072 Stack height: 8 mm Measurement time per stack (100 slices): 2 min Detector size: 3072*255 [pixels], 170 mm*14.5 mm X-Ray:    60 kVp, 60W Focal Spot Size: 70 μm Target: W Effective dose: <5μSv per measurement (ICPR91) Weight: 450 kg Size (W*D*H): 1.35m*0.9m*1.35m (without computer) Beam geometry: Cone Beam Specifications are subject to change without notice.

The two Emergency Stops, one near the ganyry and the other near the computer are mandatory and must be provided by the customer. The Emergency Stop switches must interrupt both, the phase and neutral and must withstand an impulse voltage of 4 kV (Overvoltage category III according IEC 61058-1 e.g. Siemens, type SIGNUM 22 mm Order No. 3SB38 01-0DG3-Z, Z=INC). For the protective earth conductor a wire gage of 2.5 mm² is recommended. The System is permanently installed.

The customer is responsible for the compliance of required electrical installations with local regulations.

For the radiation safety, the installation must follow national regulations. Therefore the customer is responsible for proper room shielding or additional protection for the operator if this is a requirement from the national regulations.

Due to the weight of this instrument, the floor must withstand a load capaciry of at least 300 kg/m².