Anthropomorphic phantoms for computed tomography scanner performance evaluation

Phantom simulating materials and geometries encountered in computed tomography of the head and body have been constructed. They permit the quantitative study of artifactual behavior as well as low contrast detectability and spatial resolution of a computed tomography (CT) scanner. These phantoms may be useful in comparative evaluation of CT performance and in quality control programs.     

Anthropomorphic breast phantoms for qualification of Investigators for ACRIN Protocol 6666

The purpose of this study was to evaluate various ultrasonic properties of breast phantoms developed for use in qualifying investigators for participation in the American College of Radiology Imaging Network (ACRIN) protocol 6666, "Screening Breast Ultrasound in High-Risk Women." Specifically, a tool was sought to consistently measure the performance of radiology personnel in detecting and characterizing lesions similar to those expected with screening breast ultrasonography (US). The phantoms are equivalent to one another except for the randomization of positions of 14 of the 17 simulated lesions. The lesions differ in depth and ultrasonic properties. Representative values of propagation speed, attenuation, relative echogenicity, and mass density are reported for all tissue-mimicking components. Beam refraction occurs at the interface between the subcutaneous fat layer and the glandular parenchyma and can result in beam distortion artifacts similar to those encountered in clinical breast US.     

Anthropomorphic carotid bifurcation phantom for MRI applications.

Anthropomorphic carotid bifurcation flow phantoms that incorporate different stenotic geometries within the internal carotid artery have been developed. This technique produces high-fidelity, life-size vascular flow models that are compatible with magnetic resonance techniques. The models, in conjunction with a computer-controlled flow pump, address the need for a complex vascular geometry that can be used to verify magnetic resonance angiography (MRA) techniques that quantify stenosis severity and blood flow. Stenotic geometries, with up to 80% diameter reduction, have been fabricated in two different phantom materials. Plastic phantoms provide a durable, rigid geometry where the absolute dimensions of the model are well known. Agar gel phantoms provide tissue-like signal (T1, T2) up to the lumen boundary and are also compatible with ultrasound techniques. In this paper the technique to produce vascular flow phantoms is outlined and the compatibility of these phantoms with MRA techniques is demonstrated. J. Magn. Reson. Imaging 1999;10:533-544.     

Anthropomorphic test objects for CT scanners.

Numerous types of artifacts can result in clinical misinterpretations in computed tomography. The authors have evaluated phantom materials and techniques of construction which would produce objects similar enough to the human body to test the accuracy of CT in vivo. The object used for this purpose is a thoracic section with five soft-tissue materials, representing adipose tissue, muscle, heart, esophagus, and lung, and three bone materials representing cortical bone, average rib, and "inner" (trabecular) bone. The accuracy of CT numbers for studies of different organs was assessed and sources of error in five commercial scanners were identified.     

Percutaneous radiologic gastrostomy

Gastrostomy is a preferred method of nutrition in patients with impaired ability to eat. Although surgical gastrostomy is a well-established method and has been widely performed in the last century, beginning with early 1980s, percutaneous gastrostomy techniques, either endoscopic or radiologic, has widely gained acceptance. As percutaneous methods have been shown to be an effective, safe, easy to perform and low-cost techniques with low morbidity and mortality rates, nowadays percutaneous gastrostomy is the first method of choice in need of nutrition in patients with functioning gut. In this article authors review the technique of percutaneous radiologic gastrostomy, as well as indications, contraindications, variations of technique, ethical considerations, controversies and comparison with surgical and endoscopic methods.     

In-vitro phantoms for estimating diffusion tensor tractography

No literature has reported on in-vitro diffusion tensor tractography, although it is a useful method to visualize neuronal fiber projections in the living human brain. We applied this technique to phantoms of asparagus stems and bundled polyester yarn, and obtained tractography with high-quality images. On the asparagus stem phantom, straight tracts along the axis were displayed. On the polyester phantom, these tracts followed the course of the bundle whether it was straight or curved. These phantoms are useful for in-vitro evaluation of diffusion tensor tractography.     

Digital subtraction angiography system evaluation with phantoms

Advances in digital subtraction angiography imaging demonstrate the need for critical evaluation of the performance of digital subtraction equipment. The design of a phantom set for noninvasive assessment of the imaging quality of digital subtraction equipment is described; components include a remotely controlled transport system and individual patterns to evaluate the contrast and detail properties of the image intensifier, low-contrast sensitivity and resolution of the system, geometric distortion of image, linearity, mechanical and electronic stability of equipment, and effects of bone and bowel gas on iodine perception. The performance of an add-on digital radiographic system is presented, along with radiation exposure levels at the image intensifier for a range of radiographic techniques.     

Nickel-doped agarose gel phantoms in MR imaging

A method for the production of a tissue-mimicking phantom material for MR imaging is described. The material consists of a nickel-doped agarose gel. The T1 and T2 values of the gel can be varied independently by changing the relative amounts of nickel and agarose. Practically any T1 and T2 combination of clinical interest can be obtained. The long-term stability was studied and found to be good. The relaxation times were estimated using an MR analyzer. The accuracy and the reproducibility of these measurements were evaluated and found to be reassuring. Gel phantoms were also scanned in an MR unit. The signal strength of an inversion recovery sequence was evaluated using the gel phantoms in order to verify their usefulness. These measurements were compared to theory with good agreement. Furthermore, tissue-equivalent phantoms were made. Gels resembling gray matter, white matter, and CSF were scanned. Comparisons with clinical in vivo scans, as well as calculated levels were made. It is anticipated that the gel phantoms described here will be useful in quality assurance as well as in pulse sequence optimization.     

Use of Novel Anthropomorphic Breast Ultrasound Phantoms for Radiology Resident Education

Purpose

This study evaluated the training and assessment role of anthropomorphic breast ultrasound phantoms that simulated both the morphological and sonographic characteristics of breast tissue, including lesions, in a group of radiology residents at a large academic medical center.