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Difference Between Ct And Cbct Pdf

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Sensible Solutions for Refurbished Radiology

A comparison of image quality and dose delivered between two differing computed tomography CT imaging modalities—fan beam and cone beam—was performed. A literature review of quantitative analyses for various image quality aspects such as uniformity, signal-to-noise ratio, artifact presence, spatial resolution, modulation transfer function MTF , and low contrast resolution was generated.

With these aspects quantified, cone beam computed tomography CBCT shows a superior spatial resolution to that of fan beam, while fan beam shows a greater ability to produce clear and anatomically correct images with better soft tissue differentiation. The results indicate that fan beam CT produces superior images to that of on-board imaging OBI cone beam CT systems, while providing a considerably less dose to the patient.

Better image quality will improve visualization of anatomical detail, increase ability to diagnose disease, and improve accuracy of the image guidance process during radiotherapy. Under clinical pelvis and head and neck protocols, numerous scan modes were implemented. The images were then assessed for various image quality parameters to determine which modalities produced the more desirable images. The following analysis of the literature leads to the conclusion that FBCT is more desirable for in vivo imaging.

This type of scan involved acquiring sequential, thin axial scans through the patient's volume. This method allowed the visualization of soft tissue, which led this technology to become very popular. We will refer to it as FBCT. Building on this, a great advancement was made in the field of radiation therapy with the integration of linear accelerator mounted CBCT for radiation therapy units.

This integration of CBCT imaging with radiotherapy units has allowed the patient to be imaged directly before therapy. This has the advantage of providing pretreatment verification of patient target and normal tissue anatomy. This simultaneously assures that the patient is correctly positioned for treatment.

As stated in a study by Verellen, et al. This reduction in dose may prove to be beneficial to the patient, but it may reduce the quality of the images and the accuracy of the assigned Hounsfield unit HU. Compounding this issue is the intrinsic problem that the large cone geometry produces more artifacts and scatter than the conventional fan beam CT [ 1 ].

This comparison can be accomplished by analyzing the quality of reconstructed images, defining specific image quality, and examining absorbed dose statistics that will take subjective bias out of the equation. This system used a kV X-ray source with orthogonal detectors mounted on the gantry. Utilizing a head and neck protocol, the following parameters were used: full-fan cone beam with bow tie filtration, source to detector distance of mm, 3-mm slice thickness, transversal FOV of mm, and longitudinal FOV of mm.

The protocol incorporated the parameters: mm FOV, x pixel matrix, sharp filter, 3-mm slice thickness, and 16x0. The fan beam CT used a helical technique with a pitch of 0. In order to evaluate image quality, there have to be some nominal values and features to compare the results to. For this reason the use of a phantom was employed in the studies mentioned earlier. Each of these modules have many purposes in evaluating image quality. Bottom left: CTP tungsten carbide bead used to analyze spatial resolution.

Bottom right: CTP utilizes inserts of various contrasts to evaluate low contrast detectability [ 2 ]. It would prove beneficial to discuss each of the phantom modules used in the studies. The CTP uses uniform material to mimic the density of water [ 1 - 2 ].

Being able to compare the nominal density of the slice to the scan measurement, gives the ability to assess Hounsfield unit uniformity and accuracy. This also gives information on the amount of noise. The CTP incorporates various groups of lines of varying frequencies. This ability of the detector to discriminate the various line frequencies allows for the assessment of spatial resolution. Last but not least, the CTP module uses a bead made of a tungsten-carbide that is embedded in uniform water equivalent material.

Similar to CTP , this module can also be used to assess spatial resolution [ 1 - 2 ]. This will allow a quantitative view of the differences between the two imaging modalities. In order to quantify these parameters, various image statistics were developed.

The modulation transfer function MTF represents a measure of spatial resolution in the imaging system. This measure is evaluated within the Catphan CTP module [ 1 ]. Essentially, using the CTP , the system will image the sets of lines of varying frequency.

The MTF is a quantitative way to decide how well a device can resolve small spatial changes. Both studies by Garayoa, et al. The study by Garayoa, et al. Using the CTP module, an image is acquired where the system response to a small tungsten bead is analyzed. Further details on the derivation of these quantities like MTF can be found in a study performed by Grimmer, et al [ 5 ]. The image uniformity and noise were evaluated in multiple ways using the water-equivalent module.

As mentioned in the previous section, the CTP mimics the density of water, so this gives it a nominal Hounsfield unit value of zero.

Therefore, a scan should return a value of zero for each voxel in the image and give a mean value of zero. When the standard deviation from the mean is considered, it will give a quantitative measure of the variation in the detector response as well as the deconvolution process.

A positive value represents capping, while a negative C-value represents cupping. Another aspect to consider is the signal-to-noise ratio. The signal from the noise would represent the amount of signal that is due to random scattering effects. When the signal-to-noise ratio is decreased, that will produce a grainier image.

It is generally assumed that the cone-beam imaging modality will intrinsically produce relatively more noise from scattering due to its large cone geometry [ 1 ]. One way to measure image quality was to define a value known as low contrast visibility LCV. In addition to the feature of image quality, it is worth discussing the dose delivered by the two differing imaging modalities. In a study by Kan, et al. To calculate the absorbed dose, the study based the calculation on an Institution of Physics and Engineering in Medicine and Biology IPEMB protocol for low-energy X-rays, which resulted in the following [ 6 - 7 ]:.

The doses to various organs were calculated under three protocols: head and neck, chest, and pelvis. These calculations of dose can help quantify the real possibility of increased risk of tissue damage and secondary cancers from the two differing CT systems. These results are consistent with a study performed by McCann, et al. However, it is important to note that the MTF values obtained by McCann vary greatly with applied protocol [ 8 ]. In addition, the study performed by Garayoa, et al.

This leads to the suggestion that fan beam CT produces images with less random noise. Scattering, beam hardening, and noise can bring about artifacts in the images. This was also the case in the Garayoa, et al. The greater UI and C-values result in images that have greater presence of artifacts in the CBCT images such as: capping, cupping, ring, and streaking artifacts. As mentioned earlier, this was referred to as the systems' low contrast visibility LCV. Another factor that is important to consider is the dose delivered to a patient from each respective imaging modality.

In the study by Kan, et al. In addition, the three scans, head and neck, chest, and pelvis, shows that CBCT produces a larger effective dose to the body and a larger absorbed dose to critical organs [ 6 ]. Each scan site can be analyzed as follows. During the head and neck scans performed by Kan, et al. Some critical organs to consider would be the skin, thyroid, esophagus, thymus, brain, lens of the eye, spinal cord, and others.

FBCT on the other hand irradiated the same organs but produced significantly lower doses. FBCT produces less damaging radiation dose to the critical organs and less effective dose to the body under the head and neck scan [ 6 ]. The chest scan has a longitudinal length of The pelvis scan had a longitudinal length of This third scan tells the same story as the previous two scan sites discussed [ 6 ].

The quantitative analysis of the image quality studies comparing cone beam CT and fan beam CT brought forth many results. The fan beam CT system appears to have lower artifact presence, less noise, greater signal-to-noise ratio, and a greater ability to discriminate low contrast objects compared to CBCT.

These greater MTF values imply that CBCT has a greater ability to distinguish small spatial variations, though its important to reiterate that these MTF values can vary greatly on protocol as mentioned earlier.

Although this is important, it may take this evaluation full-circle to apply qualitative analysis to actual images taken by the two competing systems.

The CBCT images b - f show a greater presence of crescent artifact in the neck, as well as streaking throughout the image compared to the minimal artifacts with FBCT. As seen, the FBCT image is more anatomically revealing and clear. Cone beam CT left vs. Aside from pure image quality, the patient receives significantly less radiation per scan under FBCT than CBCT, around two to three times less dose to be more exact [ 6 ].

This aspect is important to consider, given that some treatments can have numerous fractions that require daily scans. These daily scans can cause large amounts of dose to accumulate on critical organs. Furthermore, the effective dose is considerably greater for those patients undergoing CBCT scans for IGRT, which can increase the chance of secondary cancers.

Fan beam CT produces overall superior images due to the uniformity, accuracy, and clarity. These results not only indicate better image quality, it also allows the patient to receive considerably less dose with each successive scan, lowering the risk of secondary cancers and irreparable damage to critical organs.

With the help of various studies discussed in this work, it can be concluded that images taken directly before treatment with CBCT suffer from a drop in quality and visualization with an increased risk of adverse health effects compared to FBCT images.

Cureus is not responsible for the scientific accuracy or reliability of data or conclusions published herein. All content published within Cureus is intended only for educational, research and reference purposes. Additionally, articles published within Cureus should not be deemed a suitable substitute for the advice of a qualified health care professional. Do not disregard or avoid professional medical advice due to content published within Cureus.

The authors have declared that no competing interests exist.

Sensible Solutions for Refurbished Radiology

A comparison of image quality and dose delivered between two differing computed tomography CT imaging modalities—fan beam and cone beam—was performed. A literature review of quantitative analyses for various image quality aspects such as uniformity, signal-to-noise ratio, artifact presence, spatial resolution, modulation transfer function MTF , and low contrast resolution was generated. With these aspects quantified, cone beam computed tomography CBCT shows a superior spatial resolution to that of fan beam, while fan beam shows a greater ability to produce clear and anatomically correct images with better soft tissue differentiation. The results indicate that fan beam CT produces superior images to that of on-board imaging OBI cone beam CT systems, while providing a considerably less dose to the patient. Better image quality will improve visualization of anatomical detail, increase ability to diagnose disease, and improve accuracy of the image guidance process during radiotherapy.

The Traditional CT scanner and the Cone Beam CT scanner are two ways of doing the same thing-scanning-with each method claiming its fair share of advantages and disadvantages. When people think of a CT scan, they generally envision a huge machine that takes up a whole room scanning their entire body. Thanks to ever dynamic technology, there is much more than ordinary in the field of CT scans. Let us look at the Traditional vs. A CT scan is basically pictures of internal body structures generated by a computer from multiple X-ray images.

Sensible Solutions for Refurbished Radiology

Dental cone beam computed tomography CT is a special type of x-ray equipment used when regular dental or facial x-rays are not sufficient. Your doctor may use this technology to produce three dimensional 3-D images of your teeth, soft tissues, nerve pathways and bone in a single scan. This procedure requires little to no special preparation.

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Introduction and background

Стратмор подошел еще ближе. Он хотел прикоснуться к ней, но не посмел. Услышав имя Дэвида, произнесенное вслух, Сьюзан дала волю своему горю. Сначала она едва заметно вздрогнула, словно от озноба, и тут же ее захлестнула волна отчаяния. Приоткрыв дрожащие губы, она попыталась что-то сказать, но слов не последовало. Не спуская со Стратмора ледяного взгляда, Сьюзан сделала шаг вперед и протянула к нему руку с зажатым в ней предметом. Стратмор был почти уверен, что в руке Сьюзан сжимала беретту, нацеленную ему в живот, но пистолет лежал на полу, стиснутый в пальцах Хейла.

Dental Cone Beam CT

 Ну .

Чатрукьян замер от неожиданности. - Но, сэр, мутация… - Немедленно! - крикнул Стратмор. Чатрукьян некоторое время смотрел на него, лишившись дара речи, а потом бегом направился прочь из шифровалки. Стратмор повернулся и с удивлением увидел Хейла.

Панк изумленно взглянул на бутылку, потом отпил изрядный глоток и тупо уставился на Беккера. - Чего вы от меня хотите, мистер. Беккер улыбнулся: - Я ищу одну девушку.

5 Comments

Taylor F. 10.06.2021 at 17:31

CT CBCT 2. Traditional computerized tomography records data with a fan-​shaped X-ray beam onto image detectors arranged in an arc.

Denisse V. 10.06.2021 at 21:48

Cone beam computed tomography (CBCT) is an emerging imaging modality in the field of dentomaxillofacial radiology, and it has some.

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Cheryl B. 19.06.2021 at 02:09

One of the main differences between CBCT and CT is that CBCT has a higher spatial resolution [25] [26][27], which makes it a more effective tool.

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