The Science

Linear Slot Scanning Radiography

The Science

The Lodox system utilises a unique geometry, detector configuration and Linear Slot Scanning Radiography (LSSR) technology to achieve exceptionally high quality images with very low radiation dose. This combination of mechanisms allows us to produce an entire full-body X-ray  (up to 1.8m/70″) with minimal X-ray dose in just 13 seconds, and still achieve diagnostic quality images that are equivalent to, or better than, conventional X-ray images.More Technical reference papers can be accessed on the tab below.

Linear Slot Scanning Radiography

Linear slot-scanning radiography (LSSR) is the method of taking X-ray images whereby the X-ray source and detector move across the patient, or region of interest, during image acquisition. This contrasts with conventional or digital radiography systems, where a static source and detector are used, with a limited maximum field of view.

Fan beam versus Cone beam Geometry

In a conventional X-ray system, the X-ray beam emitted from the source has a conical shape, i.e. it spreads out in both width and length. The beam can be collimated to cover only the region of interest (ROI). The entire ROI is imaged in one exposure; hence, these systems are also referred to as full-field radiography systems.

In LSSR the beam is shaped as it exits the source by passing it through a very narrow slot. The resulting beam has a fan shape which spreads out only across the width of the detector, but is narrow in the scan direction. A further, tungsten collimator is used to trim the beam further in the scan direction. Typically, the thickness of the fan beam in the scan direction is about 6 mm when it reaches the detector. This has the effect of limiting the number of secondary, poorer quality, photons that form the X-ray beam. This means that only the higher-quality, primary photons are used to form the X-ray image, and that there are far fewer scattered photons throughout the surrounding area.

Linear Slit Scanning

Figure 1. A Diagram depicting a) full-field (conventional, cone beam) radiography versus b) LSS (fan beam) radiography.

 

 

Image Acquisition and Detector Configuraton

Once the X-rays have passed through the object being imaged, they are converted to light using Gadox (Rarex Green Fast) scintillators, and detected by an array of Charge-Coupled Device (CCD) cameras.

The image acquisition procedure makes use of a process called line scanning. In this process, the image is acquired by building up the complete image from successive rows of data that are acquired as the C-arm (X-ray source and detector) scans along the object being imaged. The data are processed using a technique called time-delay integration (TDI). This is the same process used in a fax machine or a flat-bed scanner, in which repeated ‘binning’ of image data during the scan increases the signal to noise ratio, and therefore the quality of the detected signal.

Furthermore, the detector is housed in a unique, scatter-rejecting housing, so that the few scattered X-rays that do traverse through the object of interest are not able to reach the detector, and therefore do not reduce image quality. This further improves the signal to noise ratio.

These varied scatter-reduction techniques mean that a post-patient anti-scatter grid is never required, even for larger patients, and the associated increased radiation exposure required to penetrate the grid is also not needed. This lower initial exposure contributes to the significantly decreased dose of the system.

The Inverse Square Law

A further advantage of using a fan beam over a cone beam is that the fan beam breaks the inverse square law. The inverse square law states that as an output from a source is measured, its intensity decreases by the square of the distance from the source. Mathematically,

I=\frac{1}{r^{2}}\cdot I_{0}

Where I is the intensity at a given distance r from the source, and I_{0} is the intensity at the source.

In the case of a fan beam, such as the Lodox system, the intensity decreases in direct proportion to the distance from the source, i.e.

I=\frac{1}{r}\cdot I_{0}

This means that the intensity of the X-ray fan beam decreases much less between the patient and the source than a conventional cone beam’s intensity decreases. This again allows a smaller dose to be generated at the source to start with, resulting in a lower dose to the patient.

8 Reasons that make Lodox X-ray Scanning Technology Effective

  1. A narrow fan beam consisting of mostly primary X-rays is emitted
  2. The scattered radiation is very low
  3. There is no need for an anti-scatter grid so higher power/dose at the source unnecessary
  4. LSSR breaks the inverse square law, i.e., 1/r vs 1/r2 geometry
  5. Beam hardening with aluminium and copper filters reduces dose to the patient
  6. The narrow beam scans over an area for a very short time (between 22 ms and 88 ms, depending on scan speed), resulting in a very low instantaneous X-ray exposure to any one part
  7. A high signal-to-noise ratio (SNR) is achieved with multiple resampling using TDI scanning
  8. Sensitive electronic detectors (CCD cameras) can detect lower power X-rays

 

 

Trauma Papers

Forensic Pathology Papers

 

Technical Papers

Technical papers on Statscan and linear slit scanning radiography (LSSR)

The following paper was the Winner of the prestigious ”Walter Berdon Award for the outstanding Basic Science Paper appearing in Pediatric Radiology in 2007″

Case Studies

haemo-, pneumothorax and air embolism in heart A Stab to the Neck – a Haemothorax, a Pneumothorax and an Air Embolism in the Heart (12/11/2015) - An air embolism is gas or air entrainment in the circulatory system, either in an artery(arterial embolism) or in a vein (venous embolism). This can occur when there is a breach in the cardiovascular system.... Continue Reading
Bronchiolitis with arrows Full-body Imaging to Obviate Autopsy in a case of Death from Bronchiolitis (6/1/2015) -

A case study from the Salt River Forensic Pathology Services Laboratory, Cape Town, South Africa.

Introduction Bronchiolitis is a respiratory tract infection of the bronchioles, the tiny terminal branches of the airways in the lungs. It is usually caused by a viral infection and mostly affects infants and young children because of their small airways. Although it is generally a mild disease, it can develop into [...]... Continue Reading

Multiple Gunshot case from Groote Schuur Hospital, Cape Town Lodox for the Multiple Gunshot Wound Patient (12/20/2013) -

A case study from Groote Schuur Hospital, Cape Town, South Africa.

Introduction

A patient with multiple gunshot wounds presents many challenges for the attending physician. Though resuscitation and definitive management must happen rapidly, the traditional imaging methods required to inform treatment are often slow, cumbersome and located outside of resuscitation areas. The advantage of the Lodox machine is that it facilitates a fast, low-dose, [...]... Continue Reading

Angio Case Study Image Use of Lodox for Emergency Room Angiography (10/7/2013) -

A case study from the Accident & Emergency Unit of the Charlotte Maxeke Johannesburg Academic Hospital, South Africa.

Introduction Suspected injury to peripheral vasculature is not an uncommon occurrence in the Emergency Room (ER), and could result from fracture, dislocation or other trauma to the limbs. Either soft signs (history of bleeding, injury in proximity to major vascular structure, small non-expanding haematoma or diminished pulse) or hard [...]... Continue Reading

TB case study image Full-body Imaging to Obviate Autopsy in a case of Death by Tuberculosis (8/21/2013) -

A case study from the Salt River Mortuary, Cape Town, South Africa; one of the world’s busiest mortuaries.

Introduction 

Tuberculosis (TB) is a common infectious disease, usually caused by Mycobacterium tuberculosis. The disease usually attacks the lungs, but may also affect other organs or areas of the body. It is spread through the air by sputum particles, particularly when the patient coughs or sneezes. Left untreated, the [...]... Continue Reading

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