Imaging modalities in x-ray computerized tomography and in selected volume tomography

Abstract

This review of different principles used in x-ray computerized tomography (CT) starts with attenuation (transmission) CT. The pros and cons of different geometrical solutions, single-ray, fan-beam and cone-beam, are discussed. Attenuation CT measures the spatial distribution of the linear attenuation coefficient, mu. The contributions of different interaction processes to mu have also been used for CT. Fluorescence CT is based on measurements of the contribution, cZtauZ/rho, from an element Z with concentration cZ, to the linear attenuation coefficient. Diffraction CT measures the differential coherent cross section d sigma (theta)(coh)/d omega, Compton CT the incoherent scatter cross section sigma. The usefulness of these modalities is illustrated. CT methods based on secondary photons have a competitor in selected volume tomography. These two tomography methods are compared. A proposal to perform Compton profile tomography is also discussed, as is the promising method of phase-contrast x-ray CT.

Asymmetry assessment using cone beam CT

“…These images use a built-in reconstruction algorithm to correct known distortions due to projection geometry, 6 and allow clinicians to assess skull anatomy either through three-dimensional surface renderings or through accurate two-dimensional slices through the skull. Previous methods of asymmetry assessment relied on two-dimensional radiographs with inherent problems not present in CBCT images.…”

Coded apertures for x-ray scatter imaging

“…In this section we compare Radon imaging and SVT with CAXSI for 2D tomography under the constraint SVT is a scatter imaging technique that uses collimation at the source and detector so that each measurement is sensitive to a single object voxel [7]. Using an array of detectors collimated appropriately, snapshot measurement is possible using SVT.…”

“…Scatter tomography has used Radon methods [5] and energy resolved detection [6]. The most common strategy, however, relies on SVT using collimation filters at the source and at the detector [7]. CAXSI is a novel approach to scatter imaging that uses coded masks between the scattering object and the detector array.…”

Ortodontide Kullanılan Kayıtların Standardizasyonu Bölüm 2: Baş ve Yüz Görüntüleme Teknikleri

“…İleri (3 Boyutlu) Görüntüleme Teknikleri Bilgisayar Tomografisi (BT) Tomografi bir dokunun görüntüsünü kesit şeklinde sağlar ve görüntüleme tekniğinde kullanılan genel bir terimdir (19). TME, maksilla ve mandibulanın kesitleri gibi maksillo fasiyal yapıların doğru görüntüsü tomografi ile elde edilebilir.…”

“…Advanced (Three Dimensional) Imaging Techniques Computed tomography (CT) Tomography provides an image of a tissue by getting layers and common term of an imaging technique (19). Accurate imaging of maxillofacial structures, including TMJs and cross-sectional imaging of the maxilla and mandible can be achieved by tomography CT imagines are obtained from thin X ray beam and opposite sensor that is synchronic return to the patient and data are processed in computer (20).…”