TU-F-213AB-01: Diagnostic Workforce and Manpower Survey.

Since AAPM Report No. 33 on Diagnostic Radiology Physics staffing is more than 20 years old, the Diagnostic Work and Workforce Study Subcommittee (DWWSS) of the Professional Council was formed to conduct a new study and update the data. The intent of the DWWSS study has two goals. First, it wanted to assess the number of FTE diagnostic physicists needed to support the QC, acceptance tests, radiation safety and other clinical functions for various imaging modalities, such as: CT scanners, MRI units, angiography rooms, ultrasound units, nuclear medicine imagers and other equipment. For example, the preliminary results indicate that the median annual physics support for one CT scanner is 0.007 FTE or 12.6 hours per unit. Second, the study wanted to provide an estimate of the cost of these physics services in terms of a fraction of a dollar per patient examination performed. For example, the cost for physics support of CT would be $0.27 for each CT procedure. This information would be similar to the Abt study conducted in Radiation Oncology. Radiation therapy physicists have utilized the Abt studies to generate re-imbursement for physics services and to justify financially the cost of their work efforts. Appropriate recognition for physics efforts in Diagnostic Radiology has never been properly quantified nor appreciated. With all the current and future changes occurring in healthcare, the information from the DWWSS survey could be important to the future of diagnostic physicists. Although diagnostic physicists are involved with many other activities such as teaching of residents and research, information about the clinical equipment support effort could be used to assess diagnostic physics staffing needs. The goals of the DWWSS study and the preliminary findings will be presented. OBJECTIVE: 1. Present the goals of the DWWSS Diagnostic Physicist Survey.2. Present potential benefits to the AAPM members from this survey.3. Present findings from the preliminary analysis of the survey.

SU-E-I-110: Minimized Pediatric Dose in Direct Radiography (DR).

PURPOSE: Pediatric x-rays techniques are not standardized. They depend upon: patient size, anatomical localized and equipment manufacturers. Most pediatric techniques use the default factory settings. This project's goal is to find the best compromise between dose to pediatric patients and optimal image quality. METHODS: Low contrast discrimination is the key to image quality. The manufacturers (Philips and GE) specific techniques were used to establish baseline values. The following factors were evaluated: kVp, mA, time, use of grid, collimation, focal spot size, AEC/manual, and added filters. The entrance skin exposure, entrance exposure to detector, equipment exposure index (EI) and contrast to noise ratio (CNR) for different thickness from neonatal to average child were assessed. RESULTS: Overall, some manufacturer's specific pediatric exposures techniques have higher entrance skin exposure than typical specified techniques. Equipment reported exposure index are not accurate enough to be used as 'dosimeter'. Lower kVp, mA with longer exposure time will increase the low contrast detectability with better CNR but these also change the entrance skin exposure. Removal of grid, filters do reduce the entrance skin exposure, but these also reduce low contrast detectability. Focal spot size does not make a big impact in image quality due to the average detector pixel size. Collimation does make a difference in AEC sensitivity and exposure index (EI). CONCLUSIONS: There is no single technique that is the best technique. It is all depend upon many factors like exam type and the size of the patients. Moreover, it is difficult to program the generator to use low kVp techniques, add or remove of filters, collimation, and use of AEC or manual mode, grid on or off in order to optimize the image quality while minimizing the dose to the patients. Some pediatric techniques with their associate CNR and radiation dose will be presented.

SU-E-I-71: Susceptibility Weighted Imaging (SWI) Software for Post-Processing of SWI Data.

PURPOSE: To develop open source software for post processing of susceptibility weighted (SWI) MR images using magnitude and phase data. METHODS: SWI data was acquired using Philips MRI 3T scanner with the following parameter: 3D T1 FFE axial with TR=40ms, TE=25ms, FOV=22 cm, acquisition matrix of 440×440 and 40 slices. Both magnitude and phase data was stored for SWI post processing. The SWI homodyne filtering is performed by converting the magnitude and phase image to complex real and imaginary images. The SWI software was implemented in C++ using ITK (Image registration and segmentation toolkit) toolkit. To generate SWI maps the user needs to provide the DICOM data directory, the series number of DICOM SWI series, low pass filter size and the weighting factor of phase mask. This outputted SWI series is saved as DICOM and appended to the patient series and can be viewed in any DICOM compatible viewer. The software also outputs SWI filtered phase maps which can be further used for iron quantification in organs like brain, liver etc. RESULTS: An open source implementation of SWI post-processing tool using ITK was provided. The SWI processed phase weighted data can be used for qualitative assessment of iron deposits. The filtered phase map outputted can be used for quantitative iron measurements. CONCLUSIONS: SWI post processing software is implemented here to provide qualitative SWI maps of iron deposits in brain and other organs. The post processed images can also be useful for MR Venography with minimum intensity projection. This tool would be useful to study disease processes involved with accumulation of iron in different organs.

Patient radiation exposure during diagnostic and therapeutic interventional neuroradiology procedures.

PURPOSE: Increasing in number and complexity, interventional neuroradiology (INR) procedures are becoming an important source of radiation exposure for patients. In accordance with the ALARA principle, radiation exposure during INR procedures should be curtailed as much as possible while reaching successful treatment outcomes. Moreover, the extent of radiation exposure should be one outcome measure used to assess new technologies and procedural efficacy, and training programs should include techniques for exposure limitation. This study provides a methodology and preliminary data to assess radiation exposure during different INR procedure types. MATERIALS AND METHODS: All patients undergoing endovascular procedures in two biplanar dedicated neuroangiography suites at a major academic medical center were monitored according to procedure type, pathological indication, fluoroscopy time and machine-generated patient dose estimates between April 2006 and July 2008. RESULTS: 1678 patients underwent cerebral arteriography during the study period. Women (62.1%) accounted for the majority of patients, but men (38.9%) were more likely to undergo an interventional procedure than women (32.8%). Diagnostic studies accounted for 64.9% of procedures. Variable exposures were found between diagnostic and interventional procedures. Exposure differed depending on indications for the procedure and procedure type. CONCLUSION: Radiation exposure is an increasingly important consideration in the development of minimally invasive neurological procedures including cerebral angiography and INR. The type of procedure and lesion type allow the practitioner to estimate radiation exposure. Such information informs the clinical decision making process. Normative data should be collected and used for comparison purposes as one measure of technical and procedural success.

A comparative study of thoracic radiation doses from 64-slice cardiac CT.

The goal of this study was to measure radiation doses for 64-slice cardiac CT angiography studies and to study the dose-savings features of these CT scanners. This was done using various phantoms. These radiation doses were compared with those from typical helical body CT scans, fluoroscopy cardiac catheterization studies and mammography examinations. Radiation measurements were made with a CT ionization detector and a solid state dosimeter. A GE 64-slice Lightspeed VCT and a Siemens Somatom Sensation 64 CT were used to scan a standard 32 cm acrylic phantom and an anthropomorphic phantom. Data were collected in axial and various gated cardiac helical modes. Organ doses and the effective doses were calculated from the measurements. In gated CT cardiac mode with the 32 cm acrylic phantom, the measured radiation doses per study were generally three to seven times greater than those from typical body helical CT examinations; the range depended upon selectable scan parameters. With the anatomical phantom, the surface doses in the anteroposterior (AP) plane were typically 20-60% higher than those measured using the 32 cm phantom. The lateral surface doses were -4% to +15%. These results can be attributed to the shorter AP dimension and the air in the lungs. The CT skin entrance radiation doses were 80-90% less than diagnostic cardiac catheterization studies, and organ doses were similar. Because 64-slice cardiac gated CT uses pitches equal to 0.20-0.27 and high mAs values, the patient radiation doses are appreciably higher than in routine body CT examinations. The female breast, which could receive a radiation dose 10-30 times that received from mammography screening, is an organ of particular concern.

Comparison of computed radiography and film/screen combination using a contrast-detail phantom.

The purpose of this work is to compare computed radiography (Kodak CR 400) and film/screen combination (Speed 400) systems in regards of patient dose, technique settings, and contrast-detail detectability. A special contrast-detail phantom with drilled holes of varying diameter (detail) and varying depth (contrast) was utilized. Various thicknesses of the Lucite sheets were utilized to simulate scattering tissues. Images of the phantom were acquired using a range of 60-120 kVp for film/screen and CR with a conventional x-ray tube and then for CR with additional 2 mm aluminum added filtration to the x-ray beam. The patient entrance skin dose was measured while maintaining 1.6 o.d. for film/screen images and 1900 Exposure Index for CR images. CR phantom images were displayed on the diagnostic workstation for soft copy reading as well as printed on films for hard copy reading on viewbox. Four physicists evaluated the images by scoring the threshold target depth along the row of the same target diameter. Detection ratio was calculated by counting the number of detectable targets divided by the total number of targets in the phantom. The overall score was related to the patient entrance skin dose, kVp, and the thickness of the scattering material. The patient entrance skin dose was reduced as the additional aluminum filter was added to the x-ray beam. Our findings suggested using a higher kVp setting and additional added filtration would reduce the patient entrance skin dose without compromising the contrast-detail detectability, which was compensated by the contrast manipulation on soft-copy display workstations.

Radiation doses during CT fluoroscopy.

CT fluoroscopy (CTF) is a relatively new imaging modality that is particularly useful for performing complex biopsy procedures. Despite the obvious benefits, the potential exists to deliver considerable radiation doses to both the patients and medical staff. The purpose of our study was to quantify the radiation levels based upon typical clinical procedures. To assess the potential radiation risks, the patient radiation doses via the CT dose index (CTDI) method were measured during CTF for a GE Pro-Speed CT scanner using standardized head and body phantoms and a CT ionization chamber. The measurements were performed for a variety of kVp, mA, and slice thickness settings. To determine patient radiation doses, the CT kVp, mA, and total CTF scan times were recorded for various biopsy procedures. To determine the radiation doses to the hands of the radiologists, a radiation survey meter was used to measure the scattered radiation from standard phantoms. The effectiveness of various types of leaded gloves and shields were also determined. The measured CTDI values ranged from 20.4 cGy min(-1) to 63.1 cGy min(-1) of CTF. For a group of 78 patients, the clinically utilized imaging times varied from 13.0 to 407 s with an mean time of 96.6 s +/- 78.9 s (1 standard deviation). The scattered x-ray radiation at the position of the radiologists hands performing the biopsy procedures was measured to be 0.6 to 1.5 mGy min(-1). The thin leaded gloves provided a relatively minimal reduction in the scattered radiation to the hands between 11% and 44% dependent upon the kVp and the type of glove. However, floor mounted radiation shields reduced the scattered radiation levels to the body by 94% to 99%. In comparison to standard x-ray fluoroscopy, CTF employs much higher radiation dose rates due to the higher kVp, mA, and rotating geometry. It is important to minimize the radiation dose to patients and staff by limiting the imaging times, employing lower mA settings, and using appropriate radiation protection measures.

Monthly monitoring program on DryView laser imager: one year experience on five Imation units.

Dry-processing film systems have become popular particularly in a network environment. This is mainly due to its ability to produce high quality images without wet chemistry processing. In this paper we describe a monthly monitoring program on five Model 8700 DryView Laser Imagers in our institution. A SMPTE pattern is generated via DryView Laser Imager software. The 100% patch is used for checking the base-plus-fog of the Imager. The 40% patch is used as the speed index. The optical density difference between patches 10% and 70% is used as the contrast index. These numbers are plotted for testing system consistency. In addition, the SMPTE pattern is examined to verify the sharpness of the bar patterns and the visibility of subtle contrasts-95% inset in the 100% patch and a 5% inset in the 0% patch. The clinical films are checked for processor artifacts, such as residuals from the drum. Stability of the dry processors has also been studied using three strips per day obtained at three different times of the day over a period of ten consecutive working days. The coefficient of variation is 0.05 for the speed index and 0.04 for the contrast index. The monthly monitoring program has been carried out in our institution since January 1997. The problems found by this monthly monitoring program assess the necessity of routine QC for DryView Laser Imagers. The instability of the post-processing dry silver films, and, consequently, the film handling requirements, are also discussed.

Proposition: a pregnant resident physician should be excused from training rotations such as angiography and nuclear medicine because of the potential exposure of the fetus.

It has been reasonably well documented that a pregnant resident physician can assume radiology rotations, including higher-exposure rotations such as angiography and nuclear medicine, without exposing the fetus to radiation levels that exceed national and international guidelines. Hence, many medical physicists support the contention that rotations should not be altered because a resident is pregnant. On the other hand, many if not most physicists subscribe to the ALARA (as low as reasonably achievable) principle, especially in cases of fetal exposure where increased radiation susceptibility is combined with an inability to decide for one-self. In addition, altered rotations usually can be accommodated by swapping rotations with other residents, with the pregnant resident taking high exposure rotations after delivery of the child. Policies on this issue vary among institutions, possibly because medical physicists have not come to closure on the issue. This issue of Point/Counterpoint is directed toward that objective.

CT scans through metal scanning technique versus hardware composition.

OBJECTIVE: Streak artifact on CT scans of metal containing areas has been a long standing problem. Although several artifact reducing methods have been used to improve image quality, most have been limited by requiring specialized equipment or lengthy complex calculations that are not automated. Others have shown that increasing the beam energy results in increased thickness of metal that may be imaged by CT without severe image degradation. We have studied the image quality of bone surrounding metal both with titanium and cobalt-chrome prostheses using various scanning techniques. METHODS: In a double blind fashion, 28 radiology residents and attendings were surveyed as to the best technique for imaging bone detail surrounding metal. A series of images was arranged of an implanted titanium prosthesis, a cobalt-chrome prosthesis and a pelvis repaired with stainless steel pelvic reconstruction plates. Scans were performed using three techniques: 120 kVp, 170 mA, 2 s, 360 degrees rotation, 140 kVp, 140 mA, 3 s, 360 degrees rotation, 140 kVp, 140 mA, 4 s, 420 degrees rotation. RESULTS: Titanium was superior to cobalt-chrome (p < .0001 Wilcoxon Signed Rank Test). No advantage was noted for higher kVp or increased scan arc of 420 degrees compared to the standard 360 degrees. CONCLUSION: Titanium allows improved bone detail surround the metal than CT cobalt-chrome. We have found no advantage to using either high kVp or a 420 degrees scan arc to improve the image quality of bone surrounded by metal.

Value of the coronal plane in MRI of internal derangement of the knee.

Sagittal images usually receive the most scrutiny in the magnetic resonance evaluation of meniscal and anterior cruciate ligament tears. We assessed the relative contribution of the coronal view. All knee magnetic resonance examinations performed over a 2-year period that had surgical confirmation were reviewed with respect to the presence of meniscal and anterior cruciate ligament tears. The appearance of an attenuated but uninterrupted anterior cruciate ligament was also evaluated. The coronal and sagittal plane images were evaluated separately. The study included 68 medial menisci, 67 lateral menisci, and 71 anterior cruciate ligaments. The coronal view is especially useful in the evaluation of the lateral meniscus. An anterior cruciate ligament that appears attennated but uninterrupted should be considered intact. The anterior cruciate ligament may be evaluated on the coronal view. The coronal view should be regarded as similar to the lateral chest radiograph, which supplements, but does not replace, the frontal chest radiograph.

Factors affecting x-ray spectra.

The x-ray spectrum is defined as the energy distribution of the radiation produced in an x-ray exposure. The x-ray spectrum has a major impact on image quality and radiation dose delivered to patients. The authors explored the effects of three key factors on x-ray spectra: generator type, peak tube potential, and filtration. Different generator types are characterized by the amount of ripple in the kilovoltage waveform. Those with high (100%) ripple such as single-phase units produce less penetrating radiation than units with low (4%) ripple such as three-phase, 12-pulse generators. As peak tube potential increases, the half-value layer increases nearly linearly; radiation output increases by approximately the square of the tube potential. Filtration materials with atomic numbers less than 42, such as aluminum, titanium, copper, and niobium, produce similar spectra, with only slight variations in efficiency. Although aluminum has the lowest efficiency, this may be compensated for by increasing milliampere seconds. Filtration in addition to the inherent filtration provided by the tube reduces both skin surface dose and average depth-dose, with the optimal amount being approximately 2-3 mm or less of aluminum-equivalent material.

Correlating magnetic resonance imaging with the biochemical content of the normal human intervertebral disc.

Magnetic resonance imaging was used to determine the T2 relaxation times of prepared proteoglycan solutions and of normal human intervertebral disc tissue from the annulus fibrosus (AF) and nucleus pulposus (NP). The collagen, proteoglycan, and water contents of the disc tissue samples were determined by biochemical assays after they were scanned. Correlations among 1/T2, collagen, proteoglycan, and water contents of the tissue samples and among 1/T2, water, and proteoglycan contents of the proteoglycan solutions were calculated. A moderate negative correlation between 1/T2 and water content was noted for the tissue samples, and a very high negative correlation was found between 1/T2 and water content for the proteoglycan solutions. The very high positive correlation between 1/T2 and proteoglycan content of the proteoglycan solutions is probably due to this negative correlation between 1/T2 and water content. There was no significant correlation between 1/T2 and proteoglycan content of the tissues. The moderate positive correlation between 1/T2 and collagen content is probably due to the high negative correlation between collagen content and water content. No significant correlation was found between the collagen and proteoglycan contents of the tissues. Thus it appears that the data confirm previous reports in the literature that the collagen of the disc tissue functions to control its water content.

Radiographic detail and variation of the nominal focal spot size: the "focal effect".

It is not generally appreciated that there is a gradation of the focal spot size from the anode to cathode end of an x-ray field that can dramatically affect radiographic detail from one end of a radiograph to the other. The authors name this gradation the "focal effect." Gradations in radiation intensity and focal spot size were measured from anode end to cathode end of a 14 x 17-inch field and were visually demonstrated with lymphangiograms and line-pair patterns. The degradation in spatial resolution along the anode-cathode axis was found to be as much as 75%, depending on the orientation of the patient with respect to the x-ray tube. Radiographic detail is, therefore, significantly improved (even when the large focal spot is used) by exploiting the focal effect and placing the body part requiring the best radiographic detail at the anode end of the table.

Technologic advances in diagnostic radiology.

Technologic advances in radiographic equipment and procedures for four different areas of diagnostic radiology are reviewed: bone mineral assessments, musculoskeletal imaging, mammography, and chest imaging. For bone mineral assessments the accuracy and precision obtained using single- and dual-energy photon absorptiometry, dual-energy x-ray absorptiometry, and quantitative CT are summarized. Various digital systems employed in musculoskeletal imaging are reviewed. In mammography, papers related to accreditation and research interests are highlighted. The use of photo-simulated phosphor plates and scanned equalization radiographic systems for chest imaging are discussed. Finally advances in radiographic film processing are noted.

Mammographic resolution: influence of focal spot intensity distribution and geometry.

The influence of focal spot intensity distribution and geometry upon mammographic image quality were evaluated. The modulation transfer functions (MTF's) for eight different intensity distributions were determined and plotted in a manner to eliminate the effects of magnification and focal spot dimension. The results indicated that the total cross-sectional area is important for focal spots with uniform intensity distributions and equivalent diameters. For equivalent focal spot dimensions, intensity distributions with edge bands were shown to have less spatial resolution than uniform intensity distributions. Focal spots with greater intensities towards their centers provided better resolution than either uniform intensity distributions or distributions with edge bands for equivalent sizes. The type of intensity distribution was also shown to affect the accuracy of star pattern measurements of focal spot size; this method of measurement is only precise for a uniform square intensity distribution. Errors obtained with several other intensity distributions were tabulated. The variations of the effective focal spot size with position along the anode-cathode axis were shown to be of a factor of approximately two to three. The combined effects of geometric blur and film/screen blur were present for various heights above the cassette tray on several different mammographic systems.

A quality-control phantom for digitization of radiographs.

Quality control is fundamental to the clinical application of digital radiography. A 14 x 17-in phantom radiograph was designed to test digital image quality by measurement of five parameters: high-contrast spatial resolution, low-contrast discrimination, linearity of gray-scale response, high-frequency noise, and geometric distortion. The phantom was used to evaluate the AT&T-Philips CommView picture archival and communications system (AT&T Bell Laboratories, West Long Branch, NJ; Philips Medical Systems, Shelton, CT). High-contrast resolution was found to be greater along the diagonal axis of the system than along either the horizontal or vertical axis. Problems with low-contrast discrimination and linearity of gray-scale response were identified. This phantom provides a simple tool for daily quality assurance testing and an objective standard for comparison of image quality between different digital radiography systems.