OBJECTIVE Phantoms with simulating mandibular trabecular bone structure fabricated using micro-stereolithography were applied for a quantitative evaluation of cone-beam computed tomography (CT) images. MATERIALS AND METHODS Phantoms with a three-dimensional lattice, in which a square pillar was set at 0.10, 0.20, 0.30 and 0.40 mm at the edge, spaced at 0.60 mm, were made of an acrylic resin u...

C-arms are well suited for obtaining cone-beam projections intra-operatively. Due to the compact size of the detector used, the data are usually truncated within the field of view. As a result, direct application of a standard cone-beam reconstruction algorithm gives rise to undesirable artifacts and incorrect values in the reconstructed image volume. When prior information such as a pre-operat...

internal inflammatory root resorption (iirr) is a rare condition of the root canal and if it is left untreated it may lead to destruction of the surrounding dental hard tissues. odontoclasts are responsible for this situation which can potentially perforate the root. many initiating factors have been mentioned for iirr, almost all causing chronic inflammation in the vital pulp. iirr is usually ...

conclusions ultrasound is recommended as the first choice when fb is located within the superficial soft tissues with no bone around it. in case of penetration of fb into deeper tissues or beneath bone, ct or cbct are recommended. otherwise, considering lower dose, cbct is preferred over ct. we can use mri if the fb is not ferromagnetic. however, ct is the first choice in emergency situations b...

use of rotary nickel-titanium (niti) instruments for endodontic preparation has introduced a new era in endodontic practice, but this issue has undergone dramatic modifications in order to achieve improved shaping abilities. cone-beam computed tomography (cbct) has made it possible to accurately evaluate geometrical changes following canal preparation. this study was carried out to compare cana...

Respiratory motion introduces uncertainties when planning and delivering radiotherapy for lung cancer patients. Cone-beam projections acquired in the treatment room could provide valuable information for building motion models, useful for gated treatment delivery or motion compensated reconstruction. We propose a method for estimating 3D+T respiratory motion from the 2D+T cone-beam projection s...

Single photon emission computed tomography (SPECT) imaging with cone-beam collimators provides improved sensitivity and spatial resolution for imaging small objects with large field-of-view detectors. It is known that Tuy’s cone-beam data sufficiency condition must be met to obtain artifact-free reconstructions. Even though Tuy’s condition was derived for an attenuation-free situation, we hypot...

Received November 11, 1983; accepted February 28, 1984 A convolution-backprojection formula is deduced for direct reconstruction of a three-dimensional density function from a set of two-dimensional projections. The formula is approximate but has useful properties, including errors that are relatively small in many practical instances and a form that leads to convenient computation. It reduces ...

A conventional 3rd generation Computed Tomography (CT) system with a single circular source trajectory is limited in terms of longitudinal scan coverage since extending the scan coverage beyond 40 mm results in significant cone-beam artifacts. A multiaxial CT acquisition is achieved by combining multiple sequential 3rd generation axial scans or by performing a single axial multisource CT scan w...

For spiral cone-beam CT, parallel computing is an effective approach to resolving the problem of heavy computation burden. It is well known that the major computation time is spent in the backprojection step for either filtered-backprojection (FBP) or backprojected-filtration (BPF) algorithms. By the cone-beam cover method [1], the backprojection procedure is driven by cone-beam projections, an...