J Gallet

Characterization of collagen by high-frequency ultrasound: evidence for different acoustic properties based on collagen fiber morphologic characteristics.

Fibrous tissue on conventional ultrasound images appears as an echo-bright area. We have observed that on high-frequency ultrasonography images of thin sections of myocardium, fibrous tissue may appear as either a dark or light area. This study was designed to test the hypothesis that echo characteristics of fibrous tissue on high-frequency ultrasonography are determined by collagen fiber morphologic characteristics. We examined 16 tissue specimens from human beings and rats containing different forms of fibrosis. The specimens were sectioned at 5 microns, placed on a glass slide, and imaged with a 600 MHz transducer. On ultrasound images, collagen appeared either as a dark amorphous area or a light area that had a fibrillar pattern. The same specimens were then stained with picrosirius red and examined with polarized light. When viewed with polarized light microscopy, thick collagen fibers appear red or orange and thin fibers appear green or yellow. Polarized light microscopy revealed that dark areas on ultrasound images corresponded to thick collagen fibers that were predominantly longitudinally sectioned. In contrast, light areas corresponded to regions of thin, loosely packed fibers, or to thick collagen fibers that were obliquely sectioned. Collagen has different appearances on high-frequency ultrasound images depending on collagen fiber morphologic characteristics. If such variation in echo intensity also occurs with lower frequency transducers used in clinical echocardiography, the differentiation between normal myocardium and immature scar may be difficult.

Maintaining Quality Control Using a Radiological Digital X-ray Dashboard

Repeats are indicators for the quality-imaging manager to schedule additional training and to be used as a basis for dialog with the reading radiologists to improve the service and quality to patients and referring physicians. Through the thoughtful application of software and networking, dose management, X-ray usage, and repeat analysis data can be made available centrally. This provides clinically useful technologist-centric results greatly benefiting an enterprise. This study tracked a radiology department’s use of a digital X-ray dashboard software application. It was discovered that 80% of the exams were performed by only 21% of the technologists and that the technologist with the highest throughput had a personal repeat rate of 6.5% compared to the department average of 7.6%. This study indicated that useful information could be derived and used as a basis for improving the radiology department’s operations and in maintaining high quality standards.

Visualization of myocardial cellular architecture using acoustic microscopy

The resolution of an ultrasound transducer depends on its frequency. The resolution improves when higher frequency transducers are used. A 1000 MHz transducer has a resolution of approximately 1 micron. Acoustic microscopy utilizes very high-frequency ultrasound (600 to 1000 MHz) to visualize structures on a microscopic level. Unstained, deparaffinized, 5 microns sections of myocardial biopsy specimens from 10 patients were placed on a slide and imaged using an Olympus UH3 scanning acoustic microscope. To compare with light microscopy, the section used for acoustic microscopy was subsequently stained with hematoxylin and eosin and a serial section from the paraffin block was stained with PTAH stain. Myocytes, myofibrils, and interstitial tissue were accurately imaged. Pathologic phenomena such as cell fallout, interstitial fibrosis, and lymphocytic infiltration were identified by acoustic microscopy. Intramural vessels, nuclei of endothelial cells, and the media were clearly identified by this technique. There was close correlation between findings by acoustic microscopy and light microscopy. Acoustic microscopy permitted the visualization of cardiac cellular detail with a resolution similar to that of light microscopy. Unlike light microscopy, acoustic microscopy requires no staining of the specimen.

An investigation of possible effects of high-frequency ultrasound on cellular integrity of cultured fibroblasts

Several investigators have demonstrated the feasibility of imaging at the cellular level using acoustical microscopy. It has also been proposed that acoustical microscopy technology might be adopted for in vivo applications. Before such applications are implemented, it is important to demonstrate that any major deleterious effects are highly unlikely. To this end, we have repeatedly scanned NIH/3T3 mouse fibroblasts in culture using an Olympus UH3 acoustical microscope operating at 600 MHz. No adverse effects were observed even after exposures for 1 h. Spatial peak temporal averaged intensities were estimated to be below 300 mW/cm2.

Imaging of Normal and Atherosclerotic Arteries by Acoustic Microscopy

Atherosclerotic vascular disease is a major cause of morbidity and mortality in this country. A technique that accurately diagnoses atherosclerotic lesions and is capable of detecting regression of such lesions, will be of considerable value to both the clinician and researcher. Intravascular ultrasound which uses high frequency transducers has been shown to be a useful technique in the diagnosis of atherosclerosis.

SU‐E‐I‐57: CT Dose Metrics: What Are We Tracking

PURPOSE Recent guidance by The Joint Commission and CRCPD recommendations require establishing CT reference dose levels (RDLs) for clinical protocols and recording CT dose metrics in the patients medical record. This presentation addresses which dose values in the CT report should be recorded for the purposes of monitoring patient dose and determining RDLs effectively. METHODS CT dose reports are commonly recorded in the PACS as screen captures, although structured reporting is becoming available on current CT scanners and PACS systems. The goal is to obtain data that correctly reflects the patients dose, but the dose information captured is not standardized across vendors and can be difficult to compare. Multi-phase studies, deviations from established protocols and dynamic scanning present problems when recording numbers to establish RDLs because of the lack of information on the anatomy scanned. The cumulative DLP and CTDIvol manually entered by radiologic technologists into the electronic medical record were compared with more detailed dose metrics compiled from PACS images. RESULTS Analysis of this data showed that simple cumulative metrics are a poor indicator of patient dose. Major problems are 1) the inclusion of dynamic scan doses associated with bolus tracking, which can skew protocol CTDIvol values by a factor of up to 20, and 2) add-on scans of non-overlapping anatomy which can inaccurately increase apparent patient dose. CONCLUSIONS Recording CTDIvol to monitor patient doses is not straightforward, since details of the actual anatomy scanned are lacking without image-based review. More granular dose reporting which identifies individual acquisitions is required; however, current RIS systems do not provide the flexibility necessary to capture all this information.

SU‐E‐I‐82: CT Protocol Translation in a Multi‐Vendor, Multi‐Hospital Environment

Purpose: To review issues involved with designing CT protocols for achieving consistent standards in a multi‐vendor and multi‐institutional enterprise.Methods: Achieving consistent CT protocols is complicated by a variety of factors. Even in a given institution, CTs from different vendors complicate standardizing protocols. An approach based on uniform CTDI values for exam types may meet with resistance due to individual radiologistimage preference. The situation is further complicated in multi‐institutional settings where patient demographics, radiologist, and clinician cultures can vary widely. At UT Southwestern, there are three major institutions using CT equipment from different vendors and servicing distinct patient population groups. A childrens hospital, a teaching county hospital, and a university hospital are serviced by a common radiology group. Recent media attention to CTdose, and recommendations by the Conference of Radiation Control Program Directors (CRCPD) have spurred State regulatory bodies to draft requirements for dosemanagement. Examples are given outlining methods to achieve consistent protocols across our facilities, based on experience at UT Southwestern.Results: The approach at UT Southwestern was based on CRCPD recommendations. Further guidance was found in ACR, the Image Gently, and Image Wisely campaigns. A specific result, is given of translating a set of pediatric protocols from the childrens hospital to adult facilities employing CTs from different vendors Conclusions: CT protocols can be standardized in multi‐vendor and multi‐ institutional environments. A critical aspect of the process is buy‐in from the radiology staff and further support from management.

SU‐E‐I‐83: Filling the Gap: Using Detailed Machine Parameters to Refine Skin Dose Calculations for Fluoroscopic Sentinel Events

Purpose: To examine the role that detailed machine logs, supplementary procedural documentation and vendor‐generated technique and dosimetry information can play in refining calculation of peak skin dose for sentinel event investigations.Methods: Vendor‐specific machine logs, skin‐dose estimations, and procedural observations can supplement the fluoroscopic times and air kerma values that all fluoroscopic machines are required to report since 2006. Information available from vendors varies considerably, and in some cases specific application products must be purchased to access this information. Information embodied may include table position, c‐arm geometry, collimation, individual run and fluoro acquisition dosimetry, technique factors (mA, kVp, pulse configuration), mode of operation and other data. Peak skin dose estimates based on HIS/RIS data and DICOM image headers were compared to calculations supplemented by the detailed machine logs and vendor dosimetry estimates. Skin dose maps were generated from air kerma readings and from the DICOM information associated with each run. Assumptions are necessary in this approach to apportion the fluoroscopic contribution, which can be 80% of the air kerma. Corresponding skin dose maps were generated with inclusion of more detailed machine log data and the resulting peak skin dose location and magnitudes were compared.Results: Significant deviations were observed between peak skin dose calculations based on DICOM information alone with attendant assumptions versus those obtained with more detailed machine log data. Detailed logs provide complementary information that replaces assumptions on fluoroscopic dose contributions with more reliable values. Conclusions: Additional information from vendors logs and dose‐ estimates and from other sources can increase the confidence in skin‐dose calculations, but the specific assumptions made by both the physicist and the vendor in making such estimates must be carefully examined. The comparison enables the stand‐alone assumptions to be validated and also allows evaluation of vendor dosimetry estimates.

SU‐E‐I‐08: Do CTDI Measurements Approximate Peak Skin Dose for Wide‐Beam Volumetric Scans?

PURPOSE To investigate the relationship between peak skin dose and CTDI measurements for wide-beam volumetric (stationary table) CT scanning. METHODS Air-kerma (AK) measurements were performed in head and body CTDI phantoms using conventional CTDI, extended CTDI (CTDIe), and AAPM TG-111 protocols. These measurements were compared to skin dose estimates obtained using a small volume (0.1 ml) ion chamber (IC) mounted on the anterior surface of the phantoms. Measurements were made on a volumetric CT scanner (Toshiba Aquilion ONE) for collimations of 40, 80, 120 and 160 mm and at kVp settings of 80, 100, and 120. Anterior and lateral surface dose measurements were also made on anthropomorphic phantoms at the same fixed techniques. RESULTS In the CTDI body phantom, peripheral CTDIe nearly equals surface dose while CTDIevol underestimates surface dose by 10-30% over the collimation range. In the CTDI head phantom, either the peripheral or the volume CTDIe values fall within approximately 5% of the surface dose for collimations greater than 80 mm. At smaller collimation, CTDIe values overestimate surface dose in the head phantom. TG-111 f(0) measurements in the anterior peripheral location slightly overestimate anterior surface dose measurement results for both head and body CTDI phantoms. Surface measurements on the anthropomorphic phantoms exhibit variations between anterior and lateral locations, with lateral doses being smaller. CONCLUSION Values derived from CTDIe measurements are useful indicators of peak skin dose for cylindrical phantoms at beam widths in excess of 80 mm. In patients, geometrical correction factors similar to the Size Specific Dose Estimate (SSDE) methodology might be used to account for actual body habitus. Toshiba America Medical Systems is supporting an associated research project on the scanner used for this work. Dr Di Zhang is an employee of Toshiba America Medical Systems.

SU‐E‐P‐23: Diversity in Medical Physics: Are We There Yet?

PURPOSE This presentation will reflect on the role of Diversity in Medical Physics and provide means to achieving a successful program based on the fundamental principles of Diversity. METHODS A data review was conducted from available public resources to determine demographics in physics and in particular, Medical Physics. This data was compared year-to-year to achieve a relatively confident view of changes that have occurred over the past decade. A comparison of current trending in Diversity was also researched in order to better define its philosophical basis and implementation within a scientific environment. In essence, a definition of Diversity was developed within the context of Medical Physics. Gaps that require more understanding were identified. RESULTS A working definition of Diversity was developed to better understand the demographics and trends as it applies in Medical Physics. Certain areas of Diversity within a Medical Physics context were identified as needing improvement such as a formal mentoring program. Even though the gender gap has narrowed over the years, other aspects within the working definition of Diversity are somewhat lagging behind. CONCLUSION Diversity within a scientific context such as is required for Medical Physicists is a complex undertaking. There is still much to be studied before implementing a successful Diversity program.