Impact of cone-beam computed tomography artifacts on dose calculation accuracy for lung cancer.

Background: To implement image-guided adaptive radiotherapy (IGART), many studies investigated dose calculations on cone-beam computed tomography (CBCT). A high HU accuracy is crucial for a high dose calculation accuracy and many imaging sites showed satisfactory results. It has been shown that the dose calculation accuracy for lung cancer lags behind.

Improving linac integrated cone beam computed tomography image quality using tube current modulation.

Purpose: Linac integrated cone beam CT (CBCT) scanners have become widespread tool for image guidance in radiotherapy. The current implementation uses constant imaging fluence across all the projection angles, which leads to anisotropic noise properties and suboptimal image quality for noncircular symmetric objects. Tube current modulation (TCM) is widely used in conventional CT.

Optimal combination of anti-scatter grids and software correction for CBCT imaging.

Purpose: Cone beam computed tomography (CBCT) has been widely adopted in clinical practice for image-guided radiotherapy. Soft tissue contrast and Hounsfield units are impaired to the presence of scattered radiation. In our previous work, we proposed a high selectivity anti-scatter grid (ASG) as a possible solution to the problem.

Clinical introduction of image lag correction for a cone beam CT system.

Purpose: Image lag in the flat-panel detector used for Linac integrated cone beam computed tomography (CBCT) has a degrading effect on CBCT image quality. The most prominent visible artifact is the presence of bright semicircular structure in the transverse view of the scans, known also as radar artifact. Several correction strategies have been proposed, but until now the clinical introduction of such corrections remains unreported.

Improved image quality of cone beam CT scans for radiotherapy image guidance using fiber-interspaced antiscatter grid.

Purpose: Medical linear accelerator mounted cone beam CT (CBCT) scanner provides useful soft tissue contrast for purposes of image guidance in radiotherapy. The presence of extensive scattered radiation has a negative effect on soft tissue visibility and uniformity of CBCT scans. Antiscatter grids (ASG) are used in the field of diagnostic radiography to mitigate the scatter.

Discrimination between benign and malignant prostate biopsies using three-dimensional chromatin texture analysis by confocal laser scanning microscopy.

Objective: To evaluate the clinical usefulness of computing three-dimensional (3-D) nuclear texture features on prostate biopsy specimens to discriminate among benign, prostatic intraepithelial neoplasia (PIN), and malignant specimens.

Study Design: Twelve prostate cancer biopsy specimens were selected, diagnosed as either benign (N = 4), PIN (N = 4), or malignant (N = 4). Sections 14 microm thick were stained.

A novel method for megavoltage scatter correction in cone-beam CT acquired concurrent with rotational irradiation.

Background And Purpose: Acquisition of cone-beam CT (CBCT) concurrent with VMAT results in scatter of the megavoltage (MV) beam onto the kilovoltage (kV) detector deteriorating CBCT image quality. The aim of this paper is to develop a method to estimate and correct for MV scatter reaching the kV panel.

Material And Methods: The correction method is based on an alternating pulse sequence such that the kV source is enabled in only every other frame.

A restaining method to restore faded fluorescence in tissue specimens for quantitative confocal microscopy.

The aim of this study was to develop a procedure to remove the TO-PRO-3 fluorescent dye from tissue sections and restain with TO-PRO-3, still allowing calculation of DNA content and distribution by confocal laser scanning microscopy (CLSM). This would allow repeated measurements on the same tissue sections and prevents loss of tissue material from valuable clinical samples. Thick sections (14 microm) were cut from a paraffin block of adrenal tissue and stained using TO-PRO-3.

Discrimination between benign and malignant prostate tissue using chromatin texture analysis in 3-D by confocal laser scanning microscopy.

Background: Analysis of chromatin texture may improve both the diagnosis and the assessment of the prognosis of prostate cancer. Confocal laser scanning microscopy (CLSM) allows performing measurements in nuclei reconstructed in 3-D. The aim of this study was to evaluate the clinical usefulness of 3-D texture analysis of prostate tissue.

Development of 3D chromatin texture analysis using confocal laser scanning microscopy.

Introduction: Analysis of nuclear texture features as a measure of nuclear chromatin changes has been proven to be useful when measured on thin (5-6 microm) tissue sections using conventional 2D bright field microscopy. The drawback of this approach is that most nuclei are not intact because of those thin sections. Confocal laser scanning microscopy (CLSM) allows measurements of texture in 3D reconstructed nuclei.

Implementation of accurate and fast DNA cytometry by confocal microscopy in 3D.

Background: DNA cytometry is a powerful method for measuring genomic instability. Standard approaches that measure DNA content of isolated cells may induce selection bias and do not allow interpretation of genomic instability in the context of the tissue. Confocal Laser Scanning Microscopy (CLSM) provides the opportunity to perform 3D DNA content measurements on intact cells in thick histological sections.

Confocal 3D DNA cytometry: assessment of required coefficient of variation by computer simulation.

Background: Confocal Laser Scanning Microscopy (CLSM) provides the opportunity to perform 3D DNA content measurements on intact cells in thick histological sections. So far, sample size has been limited by the time consuming nature of the technology. Since the power of DNA histograms to resolve different stemlines depends on both the sample size and the coefficient of variation (CV) of histogram peaks, interpretation of 3D CLSM DNA histograms might be hampered by both a small sample size and a large CV.

Leaf trajectory verification during dynamic intensity modulated radiotherapy using an amorphous silicon flat panel imager.

An independent verification of the leaf trajectories during each treatment fraction improves the safety of IMRT delivery. In order to verify dynamic IMRT with an electronic portal imaging device (EPID), the EPID response should be accurate and fast such that the effect of motion blurring on the detected moving field edge position is limited. In the past, it was shown that the errors in the detected position of a moving field edge determined by a scanning liquid-filled ionization chamber (SLIC) EPID are negligible in clinical practice.

Application of video imaging for improvement of patient set-up.

Background And Purpose: For radiotherapy of prostate cancer, the patient is usually positioned in the left-right (LR) direction by aligning a single marker on the skin with the projection of a room laser. The aim of this study is to investigate the feasibility of a room-mounted video camera in combination with previously acquired CT data to improve patient set-up along the LR axis.

Material And Methods: The camera was mounted in the treatment room at the caudal side of the patient.

Evaluation of cost functions for gray value matching of two-dimensional images in radiotherapy.

In external beam radiotherapy, portal imaging is applied for verification of the patient setup. Current automatic methods for portal image registration, which are often based on segmentation of anatomical structures, are especially successful for images of the pelvic region. For portal images of more complicated anatomical structures, e.

Feasibility of geometrical verification of patient set-up using body contours and computed tomography data.

Background And Purpose: Body contours can potentially be used for patient set-up verification in external-beam radiotherapy and might enable more accurate set-up of patients prior to irradiation. The aim of this study is to test the feasibility of patient set-up verification using a body contour scanner.

Material And Methods: Body contour scans of 33 lung cancer and 21 head-and-neck cancer patients were acquired on a simulator.

Confocal DNA cytometry: a contour-based segmentation algorithm for automated three-dimensional image segmentation.

Background: Confocal laser scanning microscopy (CLSM) presents the opportunity to perform three-dimensional (3D) DNA content measurements on intact cells in thick histological sections. So far, these measurements have been performed manually, which is quite time-consuming.

Methods: In this study, an intuitive contour-based segmentation algorithm for automatic 3D CLSM image cytometry of nuclei in thick histological sections is presented.

A method for geometrical verification of dynamic intensity modulated radiotherapy using a scanning electronic portal imaging device.

In order to guarantee the safe delivery of dynamic intensity modulated radiotherapy (IMRT), verification of the leaf trajectories during the treatment is necessary. Our aim in this study is to develop a method for on-line verification of leaf trajectories using an electronic portal imaging device with scanning read-out, independent of the multileaf collimator. Examples of such scanning imagers are electronic portal imaging devices (EPIDs) based on liquid-filled ionization chambers and those based on amorphous silicon.