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CBCT

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drmithila's picture
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Two-dimensional imaging modalities have been used in dentistry since the first intra-oral radiograph was taken in 1896. Significant progress in dental imaging techniques has since been made, including panoramic imaging and tomography, which enable reduced radiation and faster processing times. However, the imaging geometry has not changed with these commonly used intra-oral and panoramic technologies.

Cone-beam computed tomography (CBCT) is a new medical imaging technique that generates 3-D images at a lower cost and absorbed dose compared with conventional computed tomography (CT). This imaging technique is based on a cone-shaped X-ray beam centred on a 2-D detector that performs one rotation around the object, producing a series of 2-D images. These images are re-constructed in 3-D using a modification of the original cone-beam algorithm developed by Feldkamp et al. in 1984.[1] Images of the craniofacial region are often collected with a higher resolution than those collected with a conventional CT. In addition, the new systems are more practical, as they come in smaller sizes
Today, much attention is focused on the clinical applications—diagnosis, treatment and follow-up—of CBCT in the various dental disciplines. The goal of the following systemic review is to review the available clinical and scientific literature pertaining to different clinical application of CBCT in the dental practice.

Materials and methods

Clinical and scientific literature discussing CBCT imaging in dental clinical applications was reviewed. A MEDLINE (PubMed) search from 1 January 1998 to 15 July 2010 was conducted. Cone-beam computed tomography in dentistry was used as key phrase to extend the search to all the various dental disciplines. The search revealed 540 papers that were screened in detail. Owing to a lack of relevance to the subject, 406 papers were excluded. Thus, the systemic review consisted of 134 clinically relevant papers, which were analysed and categorised (Table I).

Analysis

Oral and maxillofacial surgery

CBCT enables the analysis of jaw pathology,[3–11] the assessment of impacted teeth (Fig. 1), supernumerary teeth and their relation to vital structures,[6,12–21] changes in the cortical and trabecular bone related to bisphosphonate-associated osteonecrosis of the jaw[5,22–23] and the assessment of bone grafts.[24] It is also helpful in analysing and assessing paranasal sinuses[6,25] and obstructive sleep apnea.[27–28]

As the images are collected from many different 2-D slices, the system has proven its superiority in overcoming superimpositions and calculating surface distances.[28–29] This advantage made it the technique of choice in mid-face fracture cases,[30–31] orbital fracture assessment and management[32] and for inter-operative visualisation of the facial bones after fracture.[33–34] Since it is not a magnetic resonance technique, it is the best option for intra-operative navigation during procedures, including gun-shot wounds.[35–36]

CBCT is largely used in orthognathic surgery planning when facial orthomorphic surgery is indicated that requires detailed visualisation of the inter-occlusal relationship in order to augment the 3-D virtual skull model with a detailed dental surface. With the aid of advanced software, CBCT facilitates the visualisation of soft tissue to allow for control of post-treatment aesthetics, for example in cleft palate cases to evaluate lip and palate bony depressions.[37–42]

Endodontics

CBCT is a very useful tool in diagnosing apical lesions (Figs. 2a & b).[21,45–56] A number of studies have demonstrated its ability to enable a differential diagnosis of apical lesions by measuring the density from the contrasted images of these lesions, in whether the lesion is an apical granuloma or an apical cyst (Figs. 3a & b).[49,55–57] Cotton et al.46 used CBCT as a tool to assess whether the lesion was of endodontic or non-endodontic origin.

CBCT also demonstrated superiority to 2-D radiographs in detecting fractured roots. Vertical and horizontal root fracture detection is described in several clinical cases.[21,46,55–59] It is also agreed that CBCT is superior to peri-apical radiographs in detecting these fractures, whether they are bucco-lingual or mesiodistaln cases with inflammatory root resorption, lesions are detected much easier in early stages with CBCT compared to conventional 2-D X-rayIn other cases, such as external root resorption, external cervical and internal resorption, not only the presence of resorption was detected, but also the extent of it]

CBCT can also be used to determine root morphology, the number of roots, canals and accessory canals, as well as to establishing the working length and angulations of roots and canals.[It also is accurate in assessing root-canal fillings.[] Owing to its accuracy, it is very helpful in detecting the pulpal extensions in talon cusps[68] and the position of fractured instruments]

It is also a reliable tool for pre-surgical assessment of the proximity of the tooth to adjacent vital structures, size and extent of lesions, as well as the anatomy and morphology of roots with very accurate measurements
Additionally, in cases in which teeth are assessed after trauma and in emergency cases, its application can be a useful aid in reaching a proper diagnosis and treatment approach.[

Recently, owing to its reliability and accuracy, CBCT has also been used to evaluate the canal preparation in different instrumentation techniques.

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Recently, owing to its reliability and accuracy, CBCT has also been used to evaluate the canal preparation in different instrumentation techniques.[75–76]

Implantology

With increased demand for replacing missing teeth with dental implants, accurate measurements are needed to avoid damage to vital structures. This was achievable with conventional CT. However, with CBCT giving more accurate measurements at lower dosages, it is the preferred option in implant dentistry today (Figs. 4a & b).[2,6,11,18,70,77–89]

With new software that constructs surgical guides, damage is also reduced further.[77,84,90–93] Heiland et al.94 describe a technique in which CBCT was used inter-operatively in two cases to navigate the implant insertion following microsurgical bone transfer.

CBCT enables the assessment of bone quality and bone quantity.[18,26,70,80–81,85,88,95–97] This leads to reduced implant failure, as case selection can be based on much more reliable information. This advantage is also used for post-treatment evaluation and to assess the success of bone grafts (Figs. 5a–d).[18,88]

Orthodontics

Orthodontists can use CBCT images in orthodontic assessment and cephalometric analysis.[6,70,84,98–99] Today, CBCT is already the tool of choice in the assessment of facial growth, age, airway function and disturbances in tooth eruption.[100–103] CBCT is a reliable tool in the assessment of the proximity to vital structures that may interfere with orthodontic treatment.[104–105] In cases in which mini-screw implants are placed to serve as a temporary anchorage, CBCT is useful for ensuring a safe insertion[106–108] and to assess the bone density before, during and after treatment (Fig. 6).[109–110]

Having different views in one scan, such as frontal, right and left lateral, 45-degree views and sub-mental, also adds to the advantages of CBCT.[111,124] As the images are self-corrected from the magnification to produce orthogonal images with 1:1 ratio, higher accuracy is ensured. CBCT is thus considered a better option for the clinician.[113]

Temporomandibular joint disorder

One of the major advantages of CBCT is its ability to define the true position of the condyle in the fossa, which often reveals possible dislocation of the disk in the joint, and the extent of translation of the condyle in the fossa.[18,56,114] With its accuracy, measurements of the roof of the glenoid fossa can be done easily.[115–116] Another advantage of some of the available devices is their ability to visualise soft tissue around the TMJ, which may reduce the need for magnetic resonance imaging in these cases.[117]

Owing to these advantages, CBCT is the imaging device of choice in cases of trauma, pain, dysfunction, fibro-osseous ankylosis and in detecting condylar cortical erosion and cysts.[70,87,118–120] With the use of the 3-D features, the image-guided puncture technique, which is a treatment modality for TMJ disk adhesion, can safely be performed.[121]

Periodontics

CBCT can be used in assessing a detailed morphologic description of the bone because it has proved to be accurate with only minimal error margins.] The measurements proved to be as accurate as direct measurements with a periodontal probe.[56,123] Furthermore, it also aids in assessing furcation involvements]

CBCT can be used to detect buccal and lingual defects, which was previously not possible with conventional 2-D radiographs.[] Additionally, owing to the high accuracy of CBCT measurements, intra-bony defects can accurately be measured and dehiscence, fenestration defects and periodontal cysts assessed.[ CBCT has also proved its superiority in evaluating the outcome of regenerative periodontal therapy.[]

General dentistry

Based on the available literature, CBCT is not justified for use in detecting occlusal caries, since the dose is much higher than conventional radiographs with no additional information gained. However, it proved to be useful in assessing proximal caries and its depth.[20] Table II shows examples of typical doses of various dental radiological procedures in dental practice.

Forensic dentistry

Many dental age estimation methods, which are a key element in forensic science, are described in the literature. CBCT was established as a non-invasive method to estimate the age of a person based on the pulp–tooth ratio.[]

Discussion

CBCT scanners represent a great advance in dento-maxillofacial (DMF) imaging. This technology, introduced into dental use in the late 1990s,[] has advanced dentistry significantly. The number of CBCT-related papers published each year has increased tremendously in the last years. The above systematic review of the lite­rature related to CBCT-imaging applications in dental practice was undertaken in order to summarise concisely the indications of this new image technique in different dental specialties.

Cone-beam computed tomography in dentistry was used as key phrase in this systemic review. Other terminology encountered in the literature, such as cone-beam volumetric scanning, volumetric computed tomography, dental CT, dental 3-D CT and cone-beam volumetric imaging, did not result in additional relevant papers.[]

The clinical applications for CBCT imaging in dentistry are increasing. The results of this review demonstrate that 134 papers were clinically relevant and that the most common clinical applications are in the field of oral and maxillofacial surgery, implant dentistry, and endodontics. CBCT has limited use in operative dentistry owing to the high radiation dose required in relation to its diagnostic value.

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What is CBCT?

To better explain what Cone Beam CT ( CBCT ) is, we should first explain what regular CT is:

Computed tomography (CT) imaging, also referred to as a computed axial tomography (CAT) scan, involves the use of rotating x-ray equipment, combined with a digital computer, to obtain images of the body. Using CT imaging, cross sectional images of body organs and tissues can be produced. Though there are many other imaging techniques, CT imaging has the unique ability to offer clear images of different types of tissue. CT imaging can provide views of soft tissue, bone, muscle, and blood vessels, without sacrificing clarity. Other imaging techniques are much more limited in the types of images they can provide.
To understand the difference between CT imaging and other techniques, consider an x-ray of the head. Using basic x-ray techniques, the bone structures of the skull can be viewed. With magnetic resonance imaging (MRI), blood vessels and soft tissue can be viewed, but clear, detailed images of bony structures cannot be obtained. On the other hand, x-ray angiography can provide a look at the blood vessels of the head, but not soft tissue. CT imaging of the head can provide clear images not only of soft tissue, but also of bones and blood vessels.

CT imaging is commonly used for diagnostic purposes. In fact, it is a chief imaging method used in diagnosing a variety of cancers, including those affecting the lungs, pancreas, and liver. Using CT imaging, not only can physicians confirm that tumors exist, but they can also pinpoint their locations, accurately measure the size of tumors, and determine whether or not they’ve spread to neighboring tissues.
In addition to the diagnosis of certain cancers, CT imaging is used for planning and administering radiation cancer treatments, as well as for planning certain types of surgeries. It is useful for guiding biopsies and a range of other procedures categorized as minimally invasive. Thanks to its ability to provide clear images of bone, muscle, and blood vessels, CT imaging is a valuable tool for the diagnosis and treatment of musculoskeletal disorders and injuries. It is often used to measure bone mineral density and to detect injuries to internal organs. CT imaging is even used for the diagnosis and treatment of certain vascular diseases that, undetected and untreated, have the potential to cause renal failure, stroke, or death.

So, what exactly is Cone Beam CT?

In layman's terms, CBCT is a compact, faster and safer version of the regular CT. Through the use of a cone shaped X-Ray beam, the size of the scanner, radiation dosage and time needed for scanning are all dramatically reduced.
A typical CBCT scanner can fit easily into any dental ( or otherwise ) practice and is easily accessible by patients. The time needed for a full scan is typically under one minute and the radiation dosage is up to a hundred times less than that of a regular CT scanner.

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Patient Benefits

Regular MDCT scanners are large-sized machines mostly available at hospital and major diagnostic scanning centers,while Cone Beam scanners are much smaller in size and mostly available at the clinicians’ office or at dedicated maxillofacial scanning centers.

What is a CAT scan?

What does the CBCT equipment look like?

Most of the CBCT scanners are square like machines with a chair. You will sit upright while a C-arm rotates around your head.Within the arm there is an X-ray source and detector (X-ray receiver),which will make one complete 360° rotation for each scan. While the arm is rotating, it is capturing multiple images of your head from different angles. These images are then reconstructed to create a 3D image of your internal anatomy. Some of the CBCT scanners have you lay down on a table that can move up or down, and slide into and out of the center of a hole, while a gantry makes the 360° rotation.

How does the CT scan help my Physician or Dentist?

It allows him/her to:

• Visualize internal anatomy that can not be diagnosed externally

• Plan treatment and surgery

• Prepare necessary aids

• Assess risk

• Analyze the position and orientation of critical structures, like nerves, teeth roots, previous implants, the sinus and nose

Is it painful?

No, the CBCT scan process is completely painless.

Is it handicap-accessible?

The iCAT scanner from Imaging Sciences International is handicap Accessible

What are the Cone Beam scanners used for?

• Oral surgery

• Implant planning (learn more about implants)

• Orthodontic planning & implant anchorage

• Cephalometric analysis

• TMJ analysis

• Airway study (sleep apnea)

• Jaw tumors

• Impacted teeth

• Periodontal diseases

• Endodontic anomalies

How much does a scan Cost?

Cone Beam scans cost between Rs.1500 to 3000 depending on locality.

Why a CBCT scanner rather than a regular Medical CT scanner?

• X-Ray Radiation exposure to the patient is up 10 times
less than a regular CT scanner.

• Much faster scan time. Scan on a CBCT takes between 10-40 sec, while on a regular CT scanner it takes a few minutes.

• Cheaper, average price of a CBCT scan could be up to 50% less than a regular MDCT scan.

What are the benefits versus risks?

Benefits
• Unlike regular x-rays CT scans can discriminate between many types of tissue including bone, teeth, nerves and soft tissue.

• CT scans are noninvasive, and can eliminate the need for exploratory surgery in some cases.

• CT can identify the effects of conditions such as infection and tumors.

• A cost effective tool for imaging a wide range of clinical problems.

Risks
As with all imaging modalities that use ionizing radiation, the use of CBCT does involve a consideration of risk to the patient. However, it has the benefit of providing useful information needed to assist in making a diagnosis and/or in facilitating treatment. When your doctor refers you for an x-ray examination, he has made the determination that the benefit outweighs the risk. Of course, it is ultimately up to you to decide whether to undergo the examination.Bear in mind that the risk of most x-ray examinations are much less than other risks we commonly accept in daily life.

How should I prepare for the scan?

No special preparation is needed for a CBCT scan of the head. You should wear comfortable, loose-fitting clothing for your CBCT exam. Anything that might interfere with imaging such as earrings, necklaces,piercing, hairpins or eyeglasses should be removed. The x-ray technician may ask you to also remove dentures or other appliances, but it is advisable to bring these along to the appointment as the technician may on occasion want to use them.

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The popularity of advanced imaging devices such as cone-beam computed tomography (CBCT) and digital x-rays will make dental imaging a $1.4 billion market by 2012, projects Millennium Research Group's "U.S. Markets for Dental Imaging 2008" report.
"Robust sales" will be the main driving force behind this growth, according to the company.

"With these advances in dental imaging, practitioners can enhance patient understanding of dental conditions," said David Plow, manager at Millennium Research Group, in a press release. "Because images can be viewed instantly using these x-rays, practitioners can propose treatment options faster. Allowing patients to visualize [dental] problems encourages greater treatment acceptance."

The report includes information on dental cameras, CBCT, and dental x-ray systems.

Some of the key industry players mentioned are AFP Imaging, Air Techniques, Ashtel Dental, Carestream Health, Dexis, Digital Doc, Gendex Dental Systems, Imaging Sciences International, Instrumentarium Dental, Lester A. Dine, Planmeca, Progeny Dental, Planmeca, SciCan, Sirona Dental Systems, and Suni Medical Imaging.

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For the past several decades, CT has enabled researchers to examine mummies without damaging the remains and study ancient mummification processes, as well as the humans' health status -- including dental condition -- at the time of death.

Now researchers have used multidetector-row CT to image the mummies from the Redpath Museum at McGill University in Montreal. The dental findings of one male mummy in particular piqued the researchers' interest for further study as the CT images show a unique example of early dental intervention in ancient Egypt (International Journal of Paleopathology, October 3, 2012).

The mummy had "dental packing of a large interproximal carious lesion with a protective linen barrier," the researchers reported. "The dental packing ... is unique among ancient Egyptian mummies studied to date, and represents one of only a few recorded dental interventions in ancient Egypt," lead author Andrew D. Wade, PhD, and colleagues wrote. "Such a finding lends further support for the existence of a group of dental specialists practicing interventional medicine in ancient Egypt."
Ancient dentistry 101

Ancient and classical texts indicate the existence of a dental profession that attempted to ease the pain and discomfort of dental disease, according to the study authors. Ancient toothache remedies included bitumen, cedar oil, wild olive gum, and fig juice on wool inserted into the cavity -- and, of course, extraction. Egyptian medical texts mention other dental remedies, including preventing tooth loss and how to "fasten a tooth" with ochre, honey, frankincense, and malachite.

Later the Greeks and Romans described filling materials and methods that included shredded alum wrapped in wool and inserted into the cavity, or filling with lint or lead and extracting the tooth.

There are examples of prostheses, but the authors stated that there is "serious doubt over their use in the lifetime of the individual, and these may represent embalming prostheses intended to restore the natural form of the mummy for its use in the afterlife," just as other body parts were repaired or replaced by embalmers.

While dental remedies are described in ancient texts, little physical evidence exists of interventional dental practices, making the Redpath Museum mummy with dental packing an interesting case study, the authors noted.

Imaging and radiocarbon dating

The mummy, known as the Theban Male (RM2718), is a young adult male that was acquired by Montreal politician James Ferrier during a trip to Egypt in 1859, according to co-author Barbara Lawson, curator of world cultures at the Redpath Museum.

In 1995, the mummy was imaged using plain film radiographs and CT with 3-mm slice thickness. His teeth were later examined by Odin Langsjoen, DDS, of the University of Minnesota-Duluth. "A dense rounded mass was noted in the largest of the carious lesions, which indicated that the individual may have received medical treatment during life," the authors reported.

In April 2011, the museum's mummy collection, which included two other female human mummies, was reimaged with higher-resolution CT as part of the IMPACT project. Wade and colleagues reported their findings of all three mummies earlier this year (RadioGraphics, July-August 2012, Vol. 32:4, pp. 1235-1250). They estimated the male mummy's age at death to be 20 to 30 years based on dental eruption and skeletal features.
The whole-body CT scans were performed at the Montreal Neurological Institute and Hospital using an Aquilion One 320-slice scanner (Toshiba America Medical Systems) with 0.5-mm-thick slices, offering much greater detail than the CT imaging performed in 1995 and also the ability to create 3D reconstructions, using Vital Images' Vitrea software and OsiriX software.

"We wanted to look closer at the dental packing because it is unique, so far, in published accounts of mummified human remains from Egypt," Wade wrote in an email to DrBicuspid.com. "We wanted to showcase the power of the recent scanning technology, too, in the hopes that more rescanning is done on mummies. CT scans from the '90s were great at the time, but we've come a long way in terms of spatial resolution."

In addition, in the fall of 2011, the mummy's outer linen wrapping underwent radiocarbon analysis, which dated the mummy as being from the Ptolemaic Period at approximately 350-360 before the common era (BCE) -- much younger than the New Kingdom Period (1550-1069 BCE) previously thought based on the museum's records.

Overall, the dental condition of the mummy is poor, the researchers reported. The maxillary and mandibular teeth show occlusal attrition and abrasion, while the maxillary teeth also have numerous periapical abscesses and large interproximal carious lesions.

"Abscesses were found at the apices of the maxillary right first molar and second incisor and of the left first incisor and molars," they wrote. "The abscesses of the left maxillary molars communicate with the maxillary sinus and inferior meatus. Interproximal caries are noted in the maxillary right second premolar."

In fact, the dental condition of the young man may have caused his death. "An infection, such as that seen here extending into the sinuses, was likely accompanied by substantial pain and swelling during the life of this individual, and may have ultimately led to his death," Wade and colleagues wrote.

The researchers also identified the mass previously found by Dr. Langsjoen in the carious lesions of the left first and second molars, and described it as a low-density, homogeneous ball of material, such as linen. It measures 7.7 x 7.1 x 3.7 mm, larger than the lesion's opening of 5.5 x 6.8 mm, but it remains loose within the cavity, they noted.

The mass is evidence of "therapeutic dental packing" that was used before death, according to the authors. No antemortem dental packing has been identified before, and this wasn't done postmortem, as the mass was not formed to the tooth's shape for a lifelike appearance and function in the afterlife, and not all of the cavities are filled, they explained. Also, the material wouldn't have been able to restore strength or stability to the tooth. But it may have delivered a medicine such as cedar oil or fig juice to treat the pain, prevented food particles from entering the cavity, and protected the nerve from contact with the tongue or foreign bodies, they noted.

The researchers also pointed out the unusual appearance of the maxillary left first and right second incisors, which are smooth and flat with the same chiseled shape. The pulp chambers of both are exposed anteriorly, but the incisor in between doesn't have the same damage.

Sweet tooth?

Heavy attrition and abrasion are the most common dental conditions of the ancient Egyptians, often resulting in periapical abscesses from the exposure of the pulp to bacteria, according to the researchers. The cause is due to the Egyptian diet, which consisted in large part of coarse-milled flour that was often mixed with millstone debris and sand from the desert, they noted.

"The heavy occlusal wear resulting from chewing these components is evident in both noble and commoner mummies throughout Egyptian history and even in modern Egyptian farmers," Wade and colleagues wrote. "While the high level of attrition serves to wear smooth the pits and grooves where cariogenic bacteria adhere, the high-carbohydrate component of the ancient Egyptian diet, including bread and a weak porridge-like beer, was still a cariogenic risk for nonocclusal surfaces."
"Only the upper teeth have cavities or abscesses, and lots of them; the lower teeth are in fine shape for an ancient Egyptian," Wade wrote on his blog. "Given what we know about the effect of soft, sticky food on the teeth, our thought was that this man was eating something that he could keep isolated on the roof of his mouth. This would keep it off the lower teeth until it was swallowed and leave them in good shape." His theory was perhaps honey or some other soft, sticky, sugary food may have been eaten.

And what about the unusual wear pattern of the incisors? From the 1995 CT scans, it was believed that these teeth had been broken, but the condition of the incisors is consistent with antemortem slow wear of the surface, according to the authors. Since the ancient Egyptians weren't known for modifying the shape of their teeth and the attrition and abrasion wear pattern of ancient Egypt is occlusal in nature, the wear pattern of these incisors is not from mastication, but may be from using the teeth as tools of some sort, they noted.

What's next for the Redpath mummies?

With the cranial and mandibular skeletal data from the recent CT scans, 3D printing was used to make solid, three-dimensional models, and forensic artist Victoria Lywood is creating facial reconstructions of the Redpath mummies to be displayed at the museum.

More research on the mummies will be published soon, according to Wade. "RM2718 and all of the Redpath mummies are a fascinating bunch," he told DrBicuspid.com. "And all of them are part of the IMPACT Radiological Mummy Database at Western, designed to make primary imaging datasets available online to researchers around the world."

 

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Suni Medical Imaging has entered into an agreement with DentalSharing.com that will enable Suni to offer cloud-based sharing of digital x-rays to its digital customers in the U.S.

The new DentalSharing feature set allows users to share images and patient documents easily and instantly, and allows dental professionals to manage the patient information in a safe and secure HIPAA environment, according to Suni.

No additional hardware or software is required to enable the new feature set, and it will be directly integrated within Prof Suni Imaging Software, the software that powers the SuniRay and Dr SuniPlus lines of digital x-ray sensors.

For launch, Suni will offer this new service as a trial offer for 30 days at no charge. Customers can then upgrade their accounts for a nominal yearly fee

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Multiple CT scans in childhood can triple the risk of developing brain cancer or leukaemia, a study suggests.

The Newcastle University-led team examined the NHS medical records of almost 180,000 young patients.

But writing in The Lancet the authors emphasised that the benefits of the scans usually outweighed the risks.

They said the study underlined the fact the scans should only be used when necessary and that ways of cutting their radiation should be pursued.

During a CT (computerised tomography) scan, an X-ray tube rotates around the patient's body to produce detailed images of internal organs and other parts of the body.

In the first long-term study of its kind, the researchers looked at the records of patients aged under 21 who had CT scans at a range of British hospitals between 1985 and 2002.

Because radiation-related cancer takes time to develop, they examined data on cancer cases and mortality up until 2009.

Brain cancer and leukaemia are rare diseases.

'Significant increases'
The study estimated that the increased risk translated into one extra case of leukaemia and one extra brain tumour among 10,000 CT head scans of children aged under ten.

Dr Mark Pearce, an epidemiologist from Newcastle University who led the study, said: "We found significant increases in the risk of leukaemia and brain tumours, following CT in childhood and young adulthood.

"The immediate benefits of CT outweigh the risks in many settings.

"Doses have come down dramatically over time - but we need to do more to reduce them. This should be a priority for the clinical community and manufacturers."

CT scans are useful for children because anaesthesia and sedation are not required.

This type of check is often ordered after serious accidents, to look for internal injuries, and for finding out more about possible lung disease.

Regulations on their use in the UK mean CT scans should only be done when clinically justified - and the researchers said their study underlined that point.

Professor Sir Alan Craft, a co-author and leading expert in child health, said: "The important thing is that parents can be reassured that if a doctor in the UK suggests a child should have a CT scan, the radiation and cancer risks will have been taken into account.

"There's a much greater risk of not doing a CT scan when it's suggested.

"This study will push us to be even more circumspect about using it. We have much stricter rules here about using CT than in the United States, for example."

Dr Hilary Cass, the president of the Royal College of Paediatrics and Child Health, said: "We have to take very seriously the link between repeated CT scans and increased risk of these cancers amongst children and young people.

"But with both tumours rare, the absolute risk remains low."

A Department of Health spokesman said: "The UK uses lower levels of radiation in CT scans than other countries.

"We also have clear regulations to ensure a CT scan is only carried out when clinically justified."

 

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Researchers from the University of Düsseldorf found that PET/MRI achieved accuracy of 93%, compared with 88% for DWI-MRI. PET/MRI also reached sensitivity of 72%, compared with 36% for DWI-MRI.

Lymph node status has prognostic value in head and neck cancer because patients with metastases need neck dissection and adjuvant treatment. Therefore, precise lymph node staging is a necessity, noted lead author Christian Buchbender, MD.

"Currently available imaging modalities are restricted in their diagnostic performance for lymph node metastases detection," he added. "For example, CT and MRI fall short in sensitivity when compared to FDG-PET or FDG-PET/CT. On the other hand, FDG-PET/CT suffers from a large amount of false-positive results."

Thus, new modalities or a combination of modalities are needed to improve lymph node metastases detection in these cancer patients, he said.

The prospective study included 14 head and neck cancer patients with a mean age of 67 years. Prior to surgery, the patients received both FDG-PET/CT and 3-tesla MRI, including diffusion-weighted imaging. The patients then underwent bilateral neck dissection.

Using image fusion software, the researchers created two sets of images. One set consisted of PET/MR images, which were created by fusing FDG-PET results with contrast-enhanced, T1-weighted, fat-saturated MR images. The second set consisted of DWI-MR images, created by fusing DWI results with T1-weighted, fat-saturated MR images.

Buchbender and colleagues then analyzed both sets of images for the presence of lymph node metastases and found that PET/MRI detected 26 (93%) of 28 lymph node metastases, compared with 20 (71%) detected by DWI-MRI.

"When we compared these results to available data on PET/CT, we found that PET/MRI pretty much equals the performance of PET/CT," Buchbender added.

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CBCT

Dental practitioners need to make sure they use age-appropriate settings when performing cone-beam CT scans on adult and pediatric patients, according to a new study in the American Journal of Orthodontics and Dentofacial Orthopedics (June 2013, Vol. 143:6, pp. 784-792).

Given that children represent a significant proportion of orthodontic patients and that similar cone-beam CT exposure settings likely result in higher equivalent doses to the head and neck organs in children than in adults, researchers from the State University of New York at Stony Brook wanted to measure the difference in equivalent organ doses from different scanners under similar settings in children compared with adults.

Two phantom heads were used, representing a 33-year-old woman and a 5-year-old boy. Optically stimulated dosimeters were placed at eight key head and neck organs, and equivalent doses to these organs were calculated after scanning. The manufacturers' predefined exposure settings were used. One scanner had a pediatric preset option; the other did not.

Scanning the child's phantom head with the adult settings resulted in significantly higher equivalent radiation doses to children compared with adults, ranging from a 117% average ratio of equivalent dose to 341%, the researchers reported. When the pediatric preset was used for the scans, there was a decrease in the ratio of equivalent dose to the child mandible and thyroid.

Collimation should be used when possible to reduce the radiation dose to the patient, and use of cone-beam CT scans should be justified on a specific case-by-case basis, the study authors concluded.

 

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CBCT

Dental practitioners should take a "restrained approach" to cone-beam CT (CBCT), using it only when conventional radiography will not yield enough information to adequately treat a patient, according to an evidence-based review in Oral Surgery (June 18, 2013).

"Dental CBCT has been available for only about 15 years, but has already found many uses in the practice of oral surgery despite a limited evidence base for its diagnostic efficacy," wrote Keith Horner, BChD, MSc, PhD, Odont Dr, a professor at the University of Manchester School of Dentistry.

Because CBCT is often associated with higher radiation doses than conventional radiographic techniques, "careful attention must be given to justification and optimization," he added.

Much of the published literature involving CBCT is dominated by opinion and case reports, Dr. Horner noted, with few studies focused on patient outcome efficacy.

 

 

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