Show others and affiliations English In: Simulated pathology is a valuable complement to clinical images in studies aiming at evaluating an imaging technique. In order for a study using simulated pathology to be valid, it is important that the simulated pathology in a realistic way reflect the characteristics of real pathology. To perform a thorough evaluation of a nodule simulation method for chest tomosynthesis, comparing the detection rate and appearance of the artificial nodules with those of real nodules in an observer performance experiment.
CT is an accurate technique for diagnosis of abdominal diseases. Its uses include diagnosis and staging of cancer, as well as follow up after cancer treatment to assess response. It is commonly used to investigate acute abdominal pain. Extremities[ edit ] CT is often used to image complex fracturesespecially ones around joints, because of its ability to reconstruct the area of interest in multiple planes.
Fractures, ligamentous injuries and dislocations can easily be recognised with a 0. First, CT completely eliminates the superimposition of images of structures outside the area of interest. Finally, data from a single CT imaging procedure consisting of either multiple contiguous or one helical scan can be viewed as images in the axialcoronalor sagittal planes, depending on the diagnostic task.
This is referred to as multiplanar reformatted imaging. CT is regarded as a moderate- to high- radiation diagnostic technique.
The improved resolution of CT has permitted the development of new investigations, which may have advantages; compared to conventional radiography, for example, CT angiography avoids the invasive insertion of a catheter. CT colonography also known as virtual colonoscopy or VC for short is far more accurate than a barium enema for detection of tumors, and uses a lower radiation dose.
CT VC is increasingly being used in the UK and US as a screening test for colon polyps and colon cancer and can negate the need for a colonoscopy in some cases. The radiation dose for a particular study depends on multiple factors: Computed tomography CT scan has been shown to be more accurate than radiographs in evaluating anterior interbody fusion but may still over-read the extent of fusion.
The radiation doses received from CT scans is variable. Compared to the lowest dose x-ray techniques, CT scans can have to 1, times higher dose than conventional X-rays. In general, the radiation dose associated with a routine abdominal CT has a radiation dose similar to 3 years average background radiation from cosmic radiation.
Some experts project that in the future, between three and five percent of all cancers would result from medical imaging.
In this group one in every CT scans was followed by an excess cancer. People with mild kidney impairment are usually advised to ensure full hydration for several hours before and after the injection. For moderate kidney failure, the use of iodinated contrast should be avoided; this may mean using an alternative technique instead of CT.
Those with severe renal failure requiring dialysis require less strict precautions, as their kidneys have so little function remaining that any further damage would not be noticeable and the dialysis will remove the contrast agent; it is normally recommended, however, to arrange dialysis as soon as possible following contrast administration to minimize any adverse effects of the contrast.
In addition to the use of intravenous contrast, orally administered contrast agents are frequently used when examining the abdomen. However, oral alternatives to iodinated contrast exist, such as very dilute 0. Dilute barium sulfate has the advantage that it does not cause allergic-type reactions or kidney failure, but cannot be used in patients with suspected bowel perforation or suspected bowel injury, as leakage of barium sulfate from damaged bowel can cause fatal peritonitis.
CT scanner with cover removed to show internal components. Gantry rotation Left image is a sinogram which is a graphic representation of the raw data obtained from a CT scan. At right is an image sample derived from the raw data. Operation of computed tomography Computed tomography operates by using an X-ray generator that rotates around the object; X-ray detectors are positioned on the opposite side of the circle from the X-ray source.
A visual representation of the raw data obtained is called a sinogram, yet it is not sufficient for interpretation. Once the scan data has been acquired, the data must be processed using a form of tomographic reconstructionwhich produces a series of cross-sectional images.
Pixels in an image obtained by CT scanning are displayed in terms of relative radiodensity. Pixel is a two dimensional unit based on the matrix size and the field of view. When the CT slice thickness is also factored in, the unit is known as a Voxelwhich is a three-dimensional unit. The phenomenon that one part of the detector cannot differentiate between different tissues is called the "Partial Volume Effect".
That means that a big amount of cartilage and a thin layer of compact bone can cause the same attenuation in a voxel as hyperdense cartilage alone. The attenuation of metallic implants depends on atomic number of the element used: Artifacts are caused by abrupt transitions between low- and high-density materials, which results in data values that exceed the dynamic range of the processing electronics.
Two-dimensional CT images are conventionally rendered so that the view is as though looking up at it from the patient's feet. This left-right interchange corresponds to the view that physicians generally have in reality when positioned in front of patients.
CT data sets have a very high dynamic range which must be reduced for display or printing.
Request PDF on ResearchGate | Pulmonary nodule size evaluation with chest tomosynthesis and CT: A phantom study | Objective: We compared digital tomosynthesis (TOMO) and chest CT in terms of. the superior detection sensitivity of digital tomosynthesis to that of chest radiography for CT-proven pulmonary nodules [15, 16, 20]. However, to the best of our knowledge, no clinical study until date has evaluated the diagnostic performance of tomosynthesis for the detection of pulmonary emphysema. Chest digital tomosynthesis (CDT) system has recently been introduced and studied. This system offers the potential to be a substantial improvement over conventional chest radiography for the lung nodule detection and reduces the radiation dose with limited angles.
This is typically done via a process of "windowing", which maps a range the "window" of pixel values to a grayscale ramp. Pixel values of 0 and lower, are displayed as black; values of 80 and higher are displayed as white; values within the window are displayed as a grey intensity proportional to position within the window.
The window used for display must be matched to the X-ray density of the object of interest, in order to optimize the visible detail.To assess the capability of digital tomosynthesis (DTS) of the chest compared to a postero-anterior (PA) and lateral chest radiograph (CXR) in the diagnosis of suspected but unconfirmed pulmonary nodules and hilar lesions detected on a CXR.
February 14, Low-dose digital tomosynthesis (DT) of the thorax administers a similar radiation dose to plain radiography but is far more accurate, can be applied to most lung nodule evaluations, and is useful for follow-up of the size change of nodules or .
For example, studies investigating the detection rate of pulmonary nodules with chest tomosynthesis using chest CT as reference have found that for nodules with sizes suggestive of follow-up or further diagnostic evaluation (nodule diameter of 5mm or larger), 85%–% were visible in chest tomosynthesis images (18, 19, 20).
Digital tomosynthesis showed significantly improved potentially other pathologies) with chest tomosynthesis than with detection sensitivity for lung nodules in all three size groups, when conventional chest radiography.
OVERVIEW: What every practitioner needs to know about pulmonary nodules. A pulmonary nodule is a round lesion less than 3 cm in diameter within the pulmonary parenchyma (completely surrounded by.
The sensitivity for lung nodule detection of peripheral lung cancers by conventional chest radiographs is still very low. There is a critical need for alternative imaging strategies and image processing techniques to improve the sensitivity of detection.