Type:
Educational Exhibit
Keywords:
Patterns of Care, Diagnostic procedure, Digital radiography, Conventional radiography, Radiation physics
Authors:
S. PHILLIPS1, K. Schmiedehausen2, S. Wells2; 1Cardiff/UK, 2Oxford/UK
DOI:
10.26044/ecr2019/C-2547
Findings and procedure details
The Technology
"Cold cathode" emitters rely on a process called field emission unlike conventional cathodes that use heat to excite electrons so that they can be fired into the vacuum.
Field emission relies on sharp tips on the cathode where the field gradients at the tip are strong enough to pull electrons into the vacuum without the addition of heat. Each emitter can either be a cluster of many tiny carbon nanotubes or a larger single tip made of a semiconductor or metal (Fig 6).
Compact field emitters can be arranged in one - and two - dimensional geometrical forms.
Prototype devices using a linear array of Carbon Nanotube (CNT) emitters have been used in initial clinical studies [10,11],
which were able to confirm the better image accuracy of DT compared to planar X-ray.
The benefits of this are:
- A faster image acquisition as there is no need to wait for the source to move.
- Avoidance of motion blur from either a continuously moving source,
or wobble after a 'step and shoot' movement.
An alternative is to use two-dimensional 'distributed arrays' in the form of a flat panel X-ray source [12] with the following additional advantages compared to conventional sources.
- A square array for tomosynthesis reconstruction allows the source to be used much closer to the patient than standard 2D X-ray or linear array systems (Fig 2),
transforming power requirements and reducing footprint. For example,
halving the standoff distance results in a fourfold decrease in required input power.
A further reduction is achieved by using a series of low-power acquisitions over time rather than a single high-power acquisition as in a 2D X-ray.
- The reduced input power and the fact that each emitter only illuminates part of the field of view and the nature of the substrates holding the X-ray targets all ameliorate the heat generation that is normally associated with X-ray tubes.
No rotating anodes or active cooling are required.
- Side-scattered radiation problems are also mitigated due to the reduced standoff distance.
- The lower input power per emitter also helps reduce the size of the focal spot that is possible to achieve.
- The reduction in size and weight could enable the introduction of a mobile DT system that could be brought to a patient's bedside.
- This new concept is complemented by the application of an advanced image reconstruction solution,
which utilises “sparse data” techniques along with other concepts to optimise image reconstruction [13].
Potential clinical applications
-
Point-of-Care imaging. Bringing mobile 3D imaging to more patients including those in Intensive Care Units,
Emergency Rooms,
remote areas and in developing countries.
Patients in a critical condition,
as well as paediatric patients,
should benefit from point-of-care,
low-dose 3D exams with a short acquisition time reducing motion artefacts.
This potentially improves the diagnostic accuracy of digital imaging [14] (Fig 7).
- Office and remote DT imaging. Small,
portable desktop devices for extremity imaging in orthopaedics would improve and accelerate the diagnosis of occult fractures for example in the scaphoid,
which often is a diagnostic challenge,
in particular,
if the bone fragments are non-displaced [15].
Introducing a portable DT device to fracture clinics and orthopaedic offices is likely able to address the important challenge of inconclusive 2D X-rays,
and help the diagnosis and follow up of erosive joint disease and degenerative changes (Figs 8 & 9).
- Point-of-Care Technology for Cancer diagnostics in low and middle-income (LMIC) countries. It is anticipated that by 2030,
two-thirds of cancer diagnoses will be made in LMIC.
The burden of detection,
diagnosis and therapeutic follow up will be high [16].
This technology will potentially be more affordable and adaptable allowing greater population access at a lower cost with improved patient clinical outcomes (Fig 10).
- Wider clinical application. Other areas that could benefit from static tomosynthesis include chairside 3D dental imaging and breast imaging where a static tomosynthesis source could afford more accessible and comfortable imaging for patients [11].