Stranded seed displacement, migration, and loss after permanent prostate brachytherapy as estimated by Day 0 fluoroscopy and 4-month postimplant pelvic x-ray

PURPOSE

The aim of the study was to determine the incidence of local displacement, distant seed migration to the chest, and seed loss after permanent prostate brachytherapy (PPB) with stranded seeds (SSs) using sequential two-dimensional fluoroscopic pelvic and chest x-rays.

METHODS AND MATERIALS

Between October 2010 and April 2014, a total of 137 patients underwent PPB and 4-month followup pelvic and chest x-ray imaging. All patients had exclusively SSs placed and an immediate postimplant fluoroscopic image of the seed cluster. Followup x-ray images were evaluated for the number, location, and displacement of seeds in comparison to Day 0 fluoroscopic images. Significant seed displacement was defined as seed displacement >1 cm from the seed cluster. Followup chest x-rays were evaluated for seed migration to the chest.

RESULTS

Seed migration to the chest occurred in 3 of the 137 patients (2%). Seed loss occurred in 38 of the 137 patients (28%), with median loss of one seed (range, 1-16), and total seeds loss of 104 of 10,088 (1.0%) implanted. Local seed displacement was seen in 12 of the 137 patients (8.8%), and total seeds displaced were 0.15% (15/10,088).

CONCLUSIONS

SS placement in PPB is associated with low rates of substantial seed loss, local displacement, or migration to the chest. Comparing immediate postimplant fluoroscopic images to followup plain x-ray images is a straightforward method to supplement quality assurance in PPB and was found to be useful in identifying cases where seed loss was potentially of clinical significance.

3D C-arm conebeam CT angiography as an adjunct in the precise anatomic characterization of spinal dural arteriovenous fistulas

BACKGROUND AND PURPOSE

Precise anatomic understanding of the vascular anatomy of SDAVFs is required before treatment. This study demonstrates the utility of C-arm conebeam CT to locate precisely the fistulous point in SDAVFs and the courses of their feeding arteries and draining veins.

MATERIALS AND METHODS

This retrospective study reports 14 consecutive patients with SDAVFs who underwent DSA and C-arm conebeam CT angiography. SDAVF sites included 5 thoracic, 7 lumbar, and 2 sacral fistulas. Selective DSA initially identified the location and arterial supply of the SDAVF. C-arm conebeam CT angiography was then performed with selective injection into the feeding artery. Reconstructed images were reviewed at a workstation with the referring surgeon, in conjunction with the standard 2D DSA images. The value of C-arm conebeam CT in depicting the fistula and the relationship to adjacent structures was qualitatively assessed.

RESULTS

In all 14 patients, C-arm conebeam CT angiography was technically successful and precisely demonstrated the site of the fistula, feeding arteries, draining veins, and the relationship of the fistula to adjacent osseous structures. Information obtained from the C-arm conebeam CT angiogram was considered useful in all surgically (12 patients) and endovascularly (2 patients) treated SDAVFs.

CONCLUSIONS

3D C-arm conebeam CT angiography is a useful adjunct to 2D DSA in the anatomic characterization of SDAVFs. The technique allowed improved visualization of the vascular anatomy of the SDAVFs and clearer definition of their spatial relationships to adjacent structures.

Radiation exposure to the primary operator during endovascular surgical neuroradiology procedures

Endovascular surgical neuroradiologists can receive a substantial amount of occupational radiation exposure. We evaluated the amount of radiation exposure that results from the practice of performing hand injections during digital subtraction angiography (DSA). The primary operator can significantly decrease the radiation dose by leaving the room for DSA procedures. However, the total radiation dose for the primary operator is relatively low and is certainly within allowable regulatory limits when extrapolated to a yearly dose.

A survey of clinical factors and patient dose in mammography

A survey was conducted to estimate the mean glandular dose (MGD) for women undergoing mammography and to report the distribution of doses, compressed breast thickness, glandular tissue content, and mammographic technique factors used. From 24,471 mammograms, of 6,006 women, clinical data were collected. The survey data included mammograms from seven modern units using a molybdenum (Mo) anode and either Mo or rhodium (Rh) filter. Exposure factors for each mammogram were recorded automatically onto a floppy disk on each unit. All mammography units were calibrated individually using breast tissue equivalent attenuation slabs of varying glandular content, so the breast glandular content could be estimated on the basis of exposure factors and compressed breast thickness. The MGD was estimated for each mammogram based on the normalized glandular dose and calculated entrance exposure in air. The survey found a median MGD of 2.6 mGy. The median breast glandular tissue content was 28% and the median compressed breast thickness was 5.1 cm. Also, patient attenuation data were converted to equivalent BR-12 and acrylic thickness to help determine appropriate phantom thicknesses required for mammography unit automatic exposure control performance assessment.

Digital radiology equipment acquisition and installation procedures: a team approach at Mayo Clinic, Rochester, MN

Digital imaging system integration is a complex process. A project team and a defined process for system planning, evaluation, and implementation can improve the chance for success. In this presentation, our project team relates their experiences.

Quantification of fluoroscopic imaging system contrast by using video waveform monitoring

A noninvasive method was developed for quantifying the overall contrast of fluoroscopic imaging systems within the clinical setting by using a simple phantom and common video test equipment. In this method, an acrylic phantom with four holes filled with varying amounts of air and aluminum is placed on the entrance exposure side of a patient-equivalent acrylic phantom. The air- and aluminum-filled holes provide a stepped gray-scale pattern that is displayed on the examination room viewing monitor when the phantom is fluoroscopically imaged under automatic brightness control. A video waveform monitor or oscilloscope is then used to quantify those video signal voltage levels as a contrast index value, which is defined as the maximum range of the video signal voltage levels of the gray-scale steps. The method is repeatable and allows quantification of the contrast of the imaging system. It can also be used to optimize video parameters, provide comparative data for quality control monitoring, and characterize overall contrast differences between systems. Experience with this method suggests that there is excellent correlation between the clinical perception of image contrast and the contrast index, with contrast index changes of approximately 15% being seen clinically.

Artefacts found in computed radiography

Artefacts on radiographic images are distracting and may compromise accurate diagnosis. Although most artefacts that occur in conventional radiography have become familiar, computed radiography (CR) systems produce artefacts that differ from those found in conventional radiography. We have encountered a variety of artefacts in CR images that were produced from four different models plate reader. These artefacts have been identified and traced to the imaging plate, plate reader, image processing software or laser printer or to operator error. Understanding the potential sources of CR artefacts will aid in identifying and resolving problems quickly and help prevent future occurrences.

The AAPM/RSNA physics tutorial for residents: general overview of fluoroscopic imaging

Fluoroscopy is used to visualize the motion of internal fluids, structures, and devices. During a fluoroscopic examination, the operator controls activation of the x-ray tube for real-time imaging of the patient. The article provides a general overview of fluoroscopic imaging from its initial development to modern use. Early fluoroscopes produced a dim image on a fluorescent screen that required dark adaptation of the physician's eyes to optimize viewing conditions. Image intensifiers were later developed to replace the fluorescent screen and increase image brightness. Modern fluoroscopy systems include an image intensifier with television image display and a choice of several different types of image recording devices. Fluoroscopic equipment is available in many different configurations for use in a wide variety of clinical applications.

Calculation of effective dose

The concept of "effective dose" was introduced in 1975 to provide a mechanism for assessing the radiation detriment from partial body irradiations in terms of data derived from whole body irradiations. The effective dose is the mean absorbed dose from a uniform whole-body irradiation that results in the same total radiation detriment as from the nonuniform, partial-body irradiation in question. The effective dose is calculated as the weighted average of the mean absorbed dose to the various body organs and tissues, where the weighting factor is the radiation detriment for a given organ (from a whole-body irradiation) as a fraction of the total radiation detriment. In this review, effective dose equivalent and effective dose, as established by the International Commission on Radiological Protection in 1977 and 1990, respectively, are defined and various methods of calculating these quantities are presented for radionuclides, radiography, fluoroscopy, computed tomography and mammography. In order to calculate either quantity, it is first necessary to estimate the radiation dose to individual organs. One common method of determining organ doses is through Monte Carlo simulations of photon interactions within a simplified mathematical model of the human body. Several groups have performed these calculations and published their results in the form of data tables of organ dose per unit activity or exposure. These data tables are specified according to particular examination parameters, such as radiopharmaceutical, x-ray projection, x-ray beam energy spectra or patient size. Sources of these organ dose conversion coefficients are presented and differences between them are examined. The estimates of effective dose equivalent or effective dose calculated using these data, although not intended to describe the dose to an individual, can be used as a relative measure of stochastic radiation detriment. The calculated values, in units of sievert (or rem), indicate the amount of whole-body irradiation that would yield the equivalent radiation detriment as the exam in question. In this manner, the detriment associated with partial or organ-specific irradiations, as are common in diagnostic radiology, can be assessed.

MRI compatibility and visibility assessment of implantable medical devices

We have developed a protocol to evaluate the magnetic resonance (MR) compatibility of implantable medical devices. The testing protocol consists of the evaluation of magnetic field-induced movement, electric current, heating, image distortion, and device operation. In addition, current induction is evaluated with a finite element analysis simulation technique that models the effect of radiofrequency fields on each device. The protocol has been applied to several implantable infusion pumps and neurostimulators with associated attachments. Experiments were performed using a 1.5-T whole-body MR system with parameters selected to approximate the intended clinical and worst case configuration. The devices exhibited moderate magnetic field-induced deflection and torque but had significant image artifacts. No heating was detected for any of the devices. Pump operation was halted in the magnetic field, but resumed after removed. Exposure to the magnetic field activated some of the neurostimulators.

Clinical applications of basic x-ray physics principles

The application of basic x-ray physics principles to clinical radiography requires consideration of many factors that have complex interrelationships. For any given radiographic examination, proper understanding and application of each of these factors is essential. The exposure factors--tube voltage, tube current, and exposure time--determine the basic characteristics of radiation exposure to the patient and image receptor. In addition, equipment factors (focal spot size, grid use, x-ray generator design) and geometry (source-object distance and source-image receptor distance) also influence patient dose and the quality of the radiograph. The basis for evaluation of exposure parameter selection is the optimization of image quality, including contrast, density, motion unsharpness, and geometric unsharpness, while minimizing patient exposure. Selection of radiographic technique often involves consideration of trade-offs between various measures of image quality and exposure.

Suitability of laser stimulated TLD arrays as patient dose monitors in high dose x-ray imaging

Skin entrance doses of patients undergoing interventional x-ray procedures are capable of causing skin damage and should be monitored routinely. Single TLD chips are not suitable because the location of maximum skin exposure cannot be predicted. Most photographic films are too sensitive at diagnostic x-ray energies for dosimetry, exhibit temporal changes in response, and require special packaging by the user. We have investigated the suitability of laser heated MgB4O7 TLDs in a polyimide binder in the range of 0.2-20 Gy. These are available in radioluscent arrays up to 30 x 30 cm for direct measurement of patient skin dose. Dose response was compared with a calibrated ion chamber dosimeter. Exposures were made at 60, 90, and 120 kVp, at low (fluoroscopy) and high (DSA) dose rates, and at different beam incidence angles. Longitudinal reproducibility and response to temperature changes during exposure were also checked. The dose response is linear below approximately 6 Gy where the slope starts to increase 2% per Gy. Errors were less than +/- 2% over a 0-80 degrees range of beam incidence angles; less than +/- 3% for both dose rate variations and kVp differences between 70 and 120 kVp. The response was unaffected by temperature changes between 20 and 37 degrees C. Reproducibility is current +/- 7%. MgB4O7 TLD arrays are suitable for patient dosimetry in high dose fluoroscopy procedures if appropriate calibrations are used. Uncertainty in skin dose measurement is less than 10%, which is substantially better than film dosimetry.

Three-dimensional vascular reconstruction with a clinical x-ray angiography system

RATIONALE AND OBJECTIVES

The authors developed a technique to produce high-resolution, three-dimensional images of vasculature from a set of x-ray projections in an attempt to provide detailed anatomic representations of complex vasculature.

MATERIALS AND METHODS

Projection images were acquired with a clinical angiographic system by using biplanar rotational digital subtraction angiography. The images were reconstructed with an additive algebraic reconstruction technique.

RESULTS

The feasibility of the technique was tested by reconstructing three-dimensional images of several phantoms, including a wire phantom and an anatomic flow phantom. The anatomic phantom allowed replication of contrast material flow and image noise that are characteristic of patient examinations. The reconstruction procedure was then used to examine a carotid artery and a cerebral aneurysm in two patients.

CONCLUSION

A method of reconstructing vasculature from x-ray angiograms has been developed and validated with geometric and anatomic phantoms. Preliminary patient applications indicate that this technique enables enhanced visualization of complex vascular relationships and structures.

Radiation exposure and efficacy of exposure-reduction techniques during cardiac catheterization in children

OBJECTIVE

The purpose of this study was to measure radiation exposure levels in children undergoing cardiac catheterization. This information was used to assess methods of reducing exposure and to characterize total exposures.

SUBJECTS AND METHODS

The radiation exposure area product was determined for a total of 175 patients during three study intervals over 10 years. Examinations included biplane fluoroscopy and cineangiography for the diagnosis and treatment of congenital heart disease.

RESULTS

The use of pulsed progressive fluoroscopy was found to reduce patients' fluoroscopic exposure rates by approximately 40% as compared with interlaced mode fluoroscopy. Combining exposures from the frontal and lateral projections, the median fluoroscopic time for diagnostic procedures was 21 min and the median time for cineangiography was 42 sec. Median total exposure area product was 2063 R-cm2 with cineangiography accounting for 44% of the total exposure. For an estimated X-ray beam entrance area of 50-100 cm2, the median total entrance exposure was in the range of 20-40 R. Fluoroscopy times for interventional procedures were found to be 1.5 to 2.5 times longer than for diagnostic procedures, with total exposures approximately three times higher.

CONCLUSION

This study suggests that pulsed progressive fluoroscopy is an effective method of reducing radiation exposure in children undergoing cardiac catheterization.

Risk factors leading to cerebral arterial rupture by intravascular balloon

PURPOSE

To clarify what is safe use of balloons in interventional neuroradiologic procedures.

METHODS

Critical parameter values of balloon inflation and cerebral artery dilatation and rupture were determined. Dimensions and internal pressure were measured for a variety of latex and silicone balloons during inflation in both unconstrained and constrained environments including glass tubes, cadaveric human cerebral arteries, and canine basilar arteries.

RESULTS

For unconstrained inflation, pressures within balloons inflated to the recommended maximum volume ranged from 200 to 650 mm Hg. When constrained, pressures became much higher for the same injected fluid volume. Balloon dilatation until artery rupture occurred only for balloons with diameters greater than 2.5 times the unstretched vessel diameter. Balloon pressures at vessel rupture ranged from 1000 to 2000 mm Hg.

CONCLUSION

Pressures within inflated balloons vary with balloon type, material, degree of inflation, and constraint. Constrained balloons have markedly higher internal pressures, which may lead to vessel rupture if balloons are much larger than the vessel diameter.

A comparison of mammography screen-film combinations

A comparison study was performed to evaluate the image quality and radiation dose of six mammographic screen-film combinations: a Min-R screen with OM-1, SO-155, and SO-177 films (Eastman Kodak); a Min-R medium screen (Eastman Kodak) with OM-1 film; an HR Mammo medium screen (Fuji Medical Systems USA) with OM-1 film; and a Min-R fast screen with T-Mat M II film (Eastman Kodak). SO-177 films were processed with an extended cycle. Exposures of an acrylic test object with embedded masses, fibers, and specks and of a preserved breast specimen were made, for two paired image comparison tests in which the visibility of diagnostic features, contrast, and noise were judged. In most areas of image quality evaluated, a Min-R screen with OM-1, SO-155, and SO-177 films was superior. These three screen-film combinations had similar imaging characteristics, even though OM-1 film requires a higher radiation exposure. Images produced with a Min-R fast screen and T-Mat M II film were significantly lower in quality.

Solitary pulmonary nodule: CT evaluation of enhancement with iodinated contrast material--a preliminary report

The authors hypothesized that the degree of contrast material enhancement of a pulmonary nodule, measured with computed tomography (CT), may indicate the likelihood of malignancy. Fifty-two patients with uncalcified solitary pulmonary nodules (diameter, 6-30 mm) were studied. Five single serial thin-section CT scans were obtained at 1-minute intervals after injection of 100 mL of nonionic contrast material. Twenty-two patients were excluded because the diagnosis was not clearly established: The observation period was less than 2 years, or the examination was technically inadequate. Malignant nodules were identified in 23 of the 30 remaining patients, and benign nodules were identified in seven. Within the first 2 minutes after the injection, all the malignant nodules had enhanced by 20 HU or greater (only one benign nodule had that degree of enhancement). The authors conclude that the degree of contrast material enhancement of pulmonary nodules as measured with CT may indicate the likelihood of malignancy.