Hungarian Radiology

[Digital volume tomography - The use of cone beam CT in dentistry, oral and maxillofacial surgery]

PLACHTOVICS Márk

DECEMBER 21, 2009

Hungarian Radiology - 2009;83(04)

[Oral and maxillofacial radiology is a subspecialty with its own field of indication. The goal is to achieve proper diagnostic image quality with the minimal amount of harmful radiation. The most common acquisition techniques are the intraoral radiograph and the panoramic radiograph which result in an overview picture of the whole dental status of the patient or the full mouth survey with the higher doses of radiation indicated for periodontological treatment. The next level is the supplementary radiograph such as occlusal radiograph, transversal tomography (some panoramic radiographs have this option), lateral cephalometric projection, submentovertex view or Waters projection, etc. More over cone beam CT acquisition or digital volume tomography as is called. In case of some described special indications CT, MRI or sometimes US acquisition can be made. In the field of three dimensional radio-diagnostics, the CT has a superior place with well-known advantages for everybody, and the usage has been limited only by the high radiation dose. The main point of the acquisition is the image quality. The load of radiation only makes the field of indication narrow. In every day practice - because of the higher radiation load of each high quality CT - the pictures passing to the doctor are preferred to take with lower resolution and wider slices although the diagnostic value of this never reaches the wanted level. This is why this new acquisition system also mentioned in the title would be better known. This system works with reasonable low radiation coupling with the possibilities of the high fidelity 3D imaging focusing on the bony structures of the head and neck region. The purpose of this article is to give a comprehensive introduction to this method in use for more than a decade. From 2006 in Hungary we also have the option to use the technology.]

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[Cervical space occupying lesions: diagnosis at sonoelastography]

UJLAKI Mátyás, MAGYAR Péter, KARLINGER Kinga

[Among cervical (neck) region tumours, the thyroid lesions and the metastatic lymph nodes are the most detectable with conventional B-mode ultrasonography (US). The use of MRI and CT scans are limited because of the cost, and in case of CT, the radiation. With the introduction and constant development of sonoelastography, we have in our hands a new imaging procedure which is cheap, fast and harmless, yet giving more information to the examiner than conventional US. The elastographic examination of thyroid lesions is a more explored area than the elastographic visualisation of cervical lymph nodes. The ‘off-line’ elastography showed the highest accuracy allowing to calculate and analyse the strain index of cervical lymph nodes - strain index > 1.5 (85% sensitivity, 98% specificity) - but the ‘off-line’ processing of US elastograms is still too time consuming to be used in busy clinical settings. During the examinations of the thyroid gland both real-time and off-line processed strain imaging were used. An Italian team made a great leap forward as they standardized the degree of distorsion under the application of the external force. Then using the Ueno and Itoh elasticity score they achieved remarkable accuracy with real-time sonoelastography (P <0.0001). On the other hand only those organs are suitable for the US elastography characterization which can be slightly compressed, consequently the examination of a lesion with calcified shell cannot give useful information. Near to the pulsating arteries substantial amounts of decorrelation noise may appear and the examiner has to pay attention what structures are in the ROI box since the sonoelastography method assumes computations relative to the average strain inside the box. To detect a follicular carcinoma in the thyroid gland remains a big challenge. Despite of the limitations most researchers agree on the fact that sonoelastography is a perfect tool to use in addition to the conventional US examination. B-mode US combined with sonoelastography raised the accuracy in differentiation in all cases. With this modality it is also possible to deduce the number of cases when healthy lymph nodes or tissue peaces are taken for biopsy during FNAB.]

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