A dynamic renal phantom for nuclear medicine studies

Dynamic radionuclide renal study (renography) provides functional and structural information of the kidney and urinary tract noninvasively. Our purpose in this study is to describe the construction and test results of a dynamic renal phantom with different clinical features of radionuclide renography. The phantom consisted of five pieces of different shaped Plexiglas boxes: Two kidneys, one liver, two square shaped boxes (one heart and one bladder). The bladder was internally divided into two compartments in order to collect each kidney output separately. The dynamic circulation of the phantom was maintained under a hydrostatic pressure approximately equal to 13.3 kPa (average human blood pressure). The standard dose distribution among different organs and different renographic parameters were calculated from series of normal patients study (91 with 99mTc-DTPA, 68 with 99mTc-EC). All the studies were performed with same camera (Siemens Orbiter Digitrac 7500) equipped with LEAP (low energy all purpose) collimator using ADAC Pegasys II analytic package program under the same clinical procedure. Different regions of interest (ROIs) were drawn for concerning organs and counts per second (CPS) were collected for each ROI. The series of renogram curves were generated by phantom-studies with different flow rates for left kidney (LK) and right kidney (RK). The renal index (RI) for an individual study was calculated as the product of two indexes: "Relative Renal Function" (RRF) (water-volume of LK/RK) and "Relative Renal Time" (RRT) (Tmax of LK/RK). The most significant correlation was found in total CPS for LK and RK between the EC group and phantom studies (p < 0.001). The calculated RI values were used to simulate the patients' study with different clinical features. The dynamics were found reproducible. The phantom is suitable for using in calibration and quality control protocols of the renogram procedure used in Nuclear Medicine.     

An electrically-activated dynamic tissue-equivalent phantom for assessment of diffuse optical imaging systems

A novel design of solid dynamic phantom with tissue-like optical properties is presented, which contains variable regions of contrast which are activated electrically. Reversible changes in absorption are produced by localized heating of targets impregnated with thermochromic pigment. A portable, battery-operated prototype has been constructed, and its optical and temporal characteristics have been investigated. The phantom has been developed as a means of assessing the performance of diffuse optical imaging systems, such as those used to monitor haemodynamic changes in the brain and other tissues. Images of the phantom have been reconstructed using data acquired with a continuous wave optical topography system.     

Sex chromosome aneuploidy and anthropometry: A new proportionality assessment using the phantom stratagem

Reported anthropometric data on 121 subjects with 47, XYY, 47,XXY, 47,XXX, and 45,X aneuploidies were compared to those from 578 male and female control subjects by use of a single, unisex reference person (“phantom”). Subjects and controls were geometrically scaled to a standard stature of 170.18 cm, thus eliminating variance due to height. Deviations of anthropometric variables from specified phantom values were expressed as standard z-scores. By comparing z-scores of individual aneuploidy classes with those of their controls, further differences in proportionality came to light. The stratagem disclosed a systematic proportionality pattern between subjects and controls which appeared to be related to each specific sex chromosome aneuploidy. The phantom stratagem for proportional growth assessment appears to merit further use in genetic investigations where individual differences in size and shape confound the analysis of anthropometric data.     

Cryoultrasonic and cryogenic equipment for medicine.

The problem of cryodestruction control in a biological object may be characterized by various decisions. This paper deals with technical solutions based on the use of cryogenic and cryoultrasonic equipment with different technological functions to provide, with an appropriate probability, the required and controlled tissue destruction.     

A new calibration phantom for quantitative computed tomography

We report on a new calibration phantom for quantitative computed tomography which has been improved with respect to reference materials and geometrical setup. Instead of liquid calibration solutions, we use polyethylene-based water- and bone-equivalent plastics. The size of the phantom is considerably reduced by using only two samples. This design guarantees long-term stability and it offers advantages with respect to radiation geometry.     

Comparison of techniques for stationary coded aperture imaging in nuclear medicine

The relative merits of different available coded aperture techniques are considered with reference to their applicability to nuclear medicine radionuclide imaging. The theory and practical implementation using gamma camera and computer system of two such methods deconvolution and arithmetic reconstruction technique are described. Some initial results are presented and the implications discussed.     

A complex flow phantom for medical imaging: ring vortex phantom design and technical specification

Abstract

Cardiovascular fluid dynamics exhibit complex flow patterns, such as recirculation and vortices. Quantitative analysis of these complexities supports diagnosis, leading to early prediction of pathologies. Quality assurance of technologies that image such flows is challenging but essential, and to this end, a novel, cost-effective, portable, complex flow phantom is proposed and the design specifications are provided. The vortex ring is the flow of choice because it offers patterns comparable to physiological flows and is stable, predictable, reproducible and controllable. This design employs a piston/cylinder system for vortex ring generation, coupled to an imaging tank full of fluid, for vortex propagation. The phantom is motor-driven and by varying piston speed, piston displacement and orifice size, vortex rings with different characteristics can be produced. Two measurement methods, namely Laser-PIV and an optical/video technique, were used to test the phantom under a combination of configurations. Vortex rings with a range of travelling velocities (approximately 1–80?cm/s) and different output-orifice diameters (10–25?mm) were produced with reproducibility typically better than ±10%. Although ultrasound compatibility has been demonstrated, longer-term ambitions include adapting the design to support comparative studies with different modalities, such as MRA and X-ray-CTA.     

A custom-built PET phantom design for quantitative imaging of printed distributions

This note presents a practical approach to a custom-made design of PET phantoms enabling the use of digital radioactive distributions with high quantitative accuracy and spatial resolution. The phantom design allows planar sources of any radioactivity distribution to be imaged in transaxial and axial (sagittal or coronal) planes. Although the design presented here is specially adapted to the high-resolution research tomograph (HRRT), the presented methods can be adapted to almost any PET scanner. Although the presented phantom design has many advantages, a number of practical issues had to be overcome such as positioning of the printed source, calibration, uniformity and reproducibility of printing. A well counter (WC) was used in the calibration procedure to find the nonlinear relationship between digital voxel intensities and the actual measured radioactive concentrations. Repeated printing together with WC measurements and computed radiography (CR) using phosphor imaging plates (IP) were used to evaluate the reproducibility and uniformity of such printing. Results show satisfactory printing uniformity and reproducibility; however, calibration is dependent on the printing mode and the physical state of the cartridge. As a demonstration of the utility of using printed phantoms, the image resolution and quantitative accuracy of reconstructed HRRT images are assessed. There is very good quantitative agreement in the calibration procedure between HRRT, CR and WC measurements. However, the high resolution of CR and its quantitative accuracy supported by WC measurements made it possible to show the degraded resolution of HRRT brain images caused by the partial-volume effect and the limits of iterative image reconstruction.     

A Wiener filter for nuclear medicine images

To improve the quality of digital nuclear medicine images, we have developed a new implementation of the Wiener restoration filter. The Wiener filter uses as its optimality criterion the minimization of the mean-square error between the undistorted image of the object and the filtered image. In order to form this filter, the object and noise power spectrums are needed. The noise power spectrum for the count-dependent Poisson noise of nuclear medicine images is shown to have a constant average magnitude equal to the total count in the image. The object power spectrum is taken to be the image power spectrum minus the total count, except in the noise dominated region of the image power spectrum where a least-squares-fitted exponential is used. Processing time is kept to a clinically acceptable time frame through use of an array processor. Pronounced noise suppression and detail enhancement are noted with use of this filter with clinical images.     

Molecular imaging of atheroslerotic plaque with nuclear medicine techniques

Atherosclerosis is a systemic disease of the vessel wall that mainly affects medium- and large-sized arteries, and accounts for 50% of all deaths in western countries. Imaging of atheromatous plaques has traditionally centered on assessing the degree of luminal narrowing. More recently it has become clear that it is of the utmost importance to identify the vulnerable atherosclerotic plaques responsible for the majority of life-threatening syndromes. Molecular imaging using nuclear medicine techniques such as single-photon emission computed tomography (SPECT) and positron emission tomography (PET), has the potential to characterize the activity of atheromas. In the present review we summarize the results of radionuclide imaging in the detection of vulnerable atherosclerotic lesions.     

A cadaveric breast cancer tissue phantom for phase-contrast X-ray imaging applications

Background : As mammography X-ray imaging technologies advance and provide elevated contrast in soft tissues, a need has developed for reliable imaging phantoms for use in system design and component calibration. In advanced imaging modalities such as refraction-based methods, it is critical that developed phantoms capture the biological details seen in clinical precancerous and cancerous cases while minimizing artifacts that may be caused due to phantom production. This work presents the fabric...     

A new test phantom with different breast tissue compositions for image quality assessment in conventional and digital mammography

Our objective is to describe a new test phantom that permits the objective assessment of image quality in conventional and digital mammography for different types of breast tissue. A test phantom, designed to represent a compressed breast, was made from tissue equivalent materials. Three separate regions, with different breast tissue compositions, are used to evaluate low and high contrast resolution, spatial resolution and image noise. The phantom was imaged over a range of kV using a Contour 2000 (Bennett) mammography unit with a Kodak MinR 2190-MinR L screen-film combination and a Senograph 2000D (General Electric) digital mammography unit. Objective image quality assessments for different breast tissue compositions were performed using the phantom for conventional and digital mammography. For a similar mean glandular dose (MGD), the digital system gives a significantly higher contrast-to-noise ratio (CNR) than the screen-film system for 100% glandular tissue. In conclusion, in mammography, a range of exposure conditions is used for imaging because of the different breast tissue compositions encountered clinically. Ideally, the patient dose-image quality relationship should be optimized over the range of exposure conditions. The test phantom presented in this work permits image quality parameters to be evaluated objectively for three different types of breast tissue. Thus, it is a useful tool for optimizing the patient dose-image quality relationship.     

Noninvasive nuclear factor-kappaB bioluminescence imaging for the assessment of host-biomaterial interaction in transgenic mice

The inflammatory response is a key component in the biocompatibility of biomaterials. Among the factors that control the development of inflammation is a critical molecule nuclear factor-kappaB (NF-kappaB). Therefore, the aim of this study was to assess the feasibility of noninvasive whole-body real-time imaging for the evaluation of host-biomaterial interaction in the NF-kappaB transgenic mice. Transgenic mice, carrying the luciferase gene under the control of NF-kappaB, were constructed. In vivo bioluminescence imaging showed that the constitutive and induced NF-kappaB activities of transgenic mice were detected in most of the lymphoid tissues, demonstrating that NF-kappaB-driven luminescence reflected the inflammatory response in vivo. By the implantation of genipin-cross-linked gelatin conduit (GGC) and bacterial endotoxin-immersed GGC in the dorsal region, we detected a strong and specific luminescent signal from the tissue around the bacterial endotoxin-immersed GGC implant. Histological and immunohistochemical analysis also demonstrated that inflammation, characterized by the infiltration of immune cells, the accumulation of fluid, and the activation of NF-kappaB, was evoked around the same region. The correlation between the bioluminescence imaging and histological changes indicated that noninvasive imaging technique could be used to monitor the real-time inflammation in the implanted mice.     

Optimizing bioimpedance measurement configuration for dual-gated nuclear medicine imaging: a sensitivity study

Motion artefacts due to respiration and cardiac contractions may deteriorate the quality of nuclear medicine imaging leading to incorrect diagnosis and inadequate treatment. Motion artefacts can be minimized by simultaneous respiratory and cardiac gating, dual-gating. Currently, only cardiac gating is often performed. In this study, an optimized bioimpedance measurement configuration was determined for simultaneous respiratory and cardiac gating signal acquisition. The optimized configuration was located on anterolateral upper thorax based on sensitivity simulations utilizing a simplified thorax model. The validity of the optimized configuration was studied with six healthy volunteers. In the peak-to-peak and frequency content analyses the optimized configuration showed consistently higher peak-to-peak values and frequency content than other studied measurement configurations. This study indicates that the bioimpedance method has potential for the dual-gating in nuclear medicine imaging. The method would minimize the need of additional equipment, is easy for the technologists to use and comfortable for the patients.