Comprobación del control automático de exposición en el tomógrafo Canon Aquilion ONE / Verification of the automatic exposure control on the Canon Aquilion ONE tomograph

Resumen Dado el uso incrementado de la tomografía computarizada en la Caja Costarricense del Seguro Social durante los últimos 10 años, se ha vuelto cada vez más importante obtener imágenes de la calidad diagnóstica requerida con la mínima dosis de radiación posible al paciente. Para lograr esto, en los sistemas de tomografía computarizada se utiliza, rutinariamente, el control automático de exposición, el cual modula la corriente del tubo según la atenuación del haz que produce el paciente y que se obtiene en el escanograma. Objetivo: Comprobar el funcionamiento del control automático de exposición de un tomógrafo Canon Aquilion ONE en la dosis suministrada al paciente y verificar la importancia de realizar un simple o doble escanograma para diferentes protocolos clínicos. Métodos: Se analizó el comportamiento de la dosis, el ruido y la intensidad de la corriente obtenida en un maniquí con diferentes secciones elípticas que varían sus dimensiones en los ejes X-Y. Se determinó el producto dosis longitud en diferentes protocolos clínicos con el control automático de exposición activado debido a un simple o doble escanograma. Resultados: Para intensidades de corrientes fijas, a medida que aumenta el tamaño de cada sección del maniquí, la dosis se reduce, aproximadamente hasta el 72% y, cuando disminuye el tamaño de cada sección, mejora hasta en un 21% la calidad de la imagen debido a la reducción del ruido. Conclusiones: Se pudo observar que, a pesar de que las dosis para localización son bajas, la utilización de un simple escanograma, en la mayoría de los protocolos, no solo permite reducir la dosis suministrada al paciente, sino también efectuar menor cantidad de disparos en el equipo e incrementar la vida útil del tubo de rayos X, pues el aporte de un segundo escanograma no representa un impacto significativo en la calidad de imagen.

Abstract Given the increased use of computed tomography in the Costa Rican Social Security Fund during the last 10 years, it has become increasingly important to obtain images of the required diagnostic quality with the minimum radiation dose to the patient. To achieve this, computed tomography systems routinely use automatic exposure control, modulating the tube current according to the attenuation of the beam produced by the patient and obtained on scanogram. Aim: Check the operation of the automatic exposure control of a Canon Aquilion ONE scanner at the dose delivered to the patient and to verify the importance of performing a single or double scanogram for different clinical protocols. Methods : The behavior of the dose, the noise and the intensity of the current was analyzed in a phantom with different elliptical sections that vary their dimensions in the X-Y axes. The dose-length product was determined in different clinical protocols with the automatic exposure control activated due to a single or a double scanogram. Results: For fixed current intensities, as the size of each section of the phantom increases, the dose is reduced, approximately, up to 72% and when the size of each section decreases, the quality of image improves, due to noise reduction, up to 21%. Conclusions: It was observed that, despite the fact that the doses for localization are low, the use of a simple scanogram in most protocols not only reduces the dose to the patient, but also makes fewer shots in the equipment and increases the useful life of the X-ray tube, since the contribution of a second scanogram does not represent a significant impact on image quality.

Computed Tomography Scanner Productivity and Entry-Level Models in the Global Market.

Objective: This study evaluated the productivity of computed tomography (CT) models and characterized their simplest (entry-level) models' supply in the world market. Methods: CT exam times were measured in eight health facilities in the state of Rio de Janeiro, Brazil. Exams were divided into six stages: (1) arrival of patient records to the examination room; (2) patient arrival; (3) patient positioning; (4) data input prior to exam; (5) image acquisition; and (6) patient departure. CT exam productivity was calculated by dividing the total weekly working time by the total exam time for each model. Additionally, an internet search identified full-body CT manufacturers and their offered entry-level models. Results: The time durations of 111 CT exams were obtained. Differences among average exam times were not large, and they were mainly due to stages not directly related to data acquisition or image reconstruction. The survey identified that most manufacturers offer 2- to 4-slice models for Asia, South America, and Africa, and one offers single-slice models (Asia). In the USA, two manufacturers offer models below 16-slice. Conclusion: Productivity gains are not linearly related to "slice" number. It is suggested that the use of "shareable platforms" could make CTs cheaper, increasing their availability.

Cone beam CT: a current overview of devices.

The purpose of this study was to review and compare the properties of all the available cone beam CT (CBCT) devices offered on the market, while focusing especially on Europe. In this study, we included all the different commonly used CBCT devices currently available on the European market. Information about the properties of each device was obtained from the manufacturers' official available data, which was later confirmed by their representatives in cases where it was necessary. The main features of a total of 47 CBCT devices that are currently marketed by 20 companies were presented, compared and discussed in this study. All these CBCT devices differ in specific properties according to the companies that produce them. The summarized technical data from a large number of CBCT devices currently on the market offer a wide range of imaging possibilities in the oral and maxillofacial region.

Relationship between the use of new or used computed tomography scanners and image retake rates in South Korea.

BACKGROUND: The use of high-cost imaging has increased worldwide, contributing to increased healthcare expenditures. Without proper quality verification, the installation of used imaging equipment may lead to wasteful increases in cost due to ineffective and poor-quality imaging that requires repeat scans. PURPOSE: To examine the relationship between the use of new or used computed tomography (CT) scanners and image retake rates to evaluate the comparative quality of used and new CT scanners. MATERIAL AND METHODS: This was a retrospective cohort study of patients who first underwent CT from January 1 to June 30, 2008 (n = 258,572). Data were obtained by linking the Health Care Institution Registration Data with the Korean National Health Insurance Claims Database. Image retake rates within 30, 60, 90, and 180 days after the first CT scan were calculated, and differences in the image retake rate by new versus used CT scanners were assessed. RESULTS: After adjusting for confounders, use of a used CT scanner for the first scan increased the odds of retake within 30 days (odds ratio [OR]: 1.34, 95% confidence interval [CI]: 1.22-1.48), 60 days (OR: 1.59, 95% CI: 1.47-1.72), 90 days (OR: 1.48, 95% CI: 1.38-1.59), and 180 days (OR: 1.38, 95% CI: 1.30-1.46) compared with use of a new CT scanner. Such results were evident in scans of the spine, abdomen, chest, and face or skull base. CONCLUSION: The quality control associated with import of used CT scanners should be improved. Moreover, regular and detailed quality inspections of used CT scanners currently operating in healthcare institutions are necessary.

The imaging question.

Imaging technologies such as CT scanners and MRI are major investments. Trustees should ask three questions to ensure these purchases support strategic priorities.

High-throughput measurement of rice tillers using a conveyor equipped with x-ray computed tomography.

Tillering is one of the most important agronomic traits because the number of shoots per plant determines panicle number, a key component of grain yield. The conventional method of counting tillers is still manual. Under the condition of mass measurement, the accuracy and efficiency could be gradually degraded along with fatigue of experienced staff. Thus, manual measurement, including counting and recording, is not only time consuming but also lack objectivity. To automate this process, we developed a high-throughput facility, dubbed high-throughput system for measuring automatically rice tillers (H-SMART), for measuring rice tillers based on a conventional x-ray computed tomography (CT) system and industrial conveyor. Each pot-grown rice plant was delivered into the CT system for scanning via the conveyor equipment. A filtered back-projection algorithm was used to reconstruct the transverse section image of the rice culms. The number of tillers was then automatically extracted by image segmentation. To evaluate the accuracy of this system, three batches of rice at different growth stages (tillering, heading, or filling) were tested, yielding absolute mean absolute errors of 0.22, 0.36, and 0.36, respectively. Subsequently, the complete machine was used under industry conditions to estimate its efficiency, which was 4320 pots per continuous 24 h workday. Thus, the H-SMART could determine the number of tillers of pot-grown rice plants, providing three advantages over the manual tillering method: absence of human disturbance, automation, and high throughput. This facility expands the application of agricultural photonics in plant phenomics.

[Total body CT scan as the primary diagnostic modality in multi-trauma patients]. / Primaire totale lichaams-CT bij multitraumapatiënten.

Radiological imaging is highly protocolized during initial assessment of severely injured trauma patients. After an initial examination, radiography and ultrasound are performed. Imaging is frequently supplemented by CT scan of selective body areas. Technical features of CT scanners have improved drastically and the number of CT scanners located near or in trauma resuscitation rooms is increasing. These developments enable early CT scanning in trauma patients. Currently there is an ongoing discussion as to whether 'total body' CT scan (TBCT) should be used as a primary and sole diagnostic imaging tool during workup of trauma patients. Recent research on TBCT in multi-trauma patients shows promising results and several large European trauma centers have already protocolized this strategy. These studies lack a good study design, so more prospective research on clinical outcomes, cost effectiveness and radiation exposure is necessary. As part of a pilot study in preparation for a randomized multicenter study, the University Medical Centre in Amsterdam in the Netherlands is performing TBCT in severely injured trauma patients.

CT in your ED? Make sure you've got enough space.

ED managers in small and medium-sized hospitals should think creatively when seeking approval for a department computed tomography scan. Safety considerations can make a compelling argument. Piggyback your request onto a larger performance improvement initiative. You may find a surprisingly supportive ally in the radiology department.

Screening for ventricular shunt function in children with hydrocephalus secondary to meningomyelocele.

OBJECTIVE: To evaluate the current method of using computerized tomographic (CT) scans to screen for ventricular shunt failure in children who have hydrocephalus. DESIGN: Retrospective review of 112 randomly selected charts. PATIENTS: Children diagnosed with infantile hydrocephalus secondary to meningomyelocele, who were treated at the Andrew J. Kirch Developmental Services Center since 1978. RESULTS: One hundred and twelve patients were monitored with CT scans for an average of 12.2 years. There was a total of 2,869 CT scans and an average of 2.1 CT scans per year. Shunt failure was diagnosed 76% of the time by symptoms, 15% by physical findings and 8% by routine CT scans. Sixteen patients had no shunt failure, whereas the remaining 96 had 255 shunt failures. Complications occurred during 30 of the 255 admissions. One child died due to complications directly related to shunt failure. No statistically significant correlations were found between the length of stay or complications and method of diagnosis. CONCLUSIONS: Although children in this study received frequent CT scans, 76% of the episodes of shunt failure were diagnosed because of symptoms. Children admitted to the hospital with symptomatic shunt failure did not have more complications or a longer stay than those diagnosed by routine CT scan. This study suggests that the use of routine CT scans to diagnose shunt failure while patients are asymptomatic does not lead to significantly better medical outcomes and is not cost-effective. However, before routine CT scans are eliminated, a prospective study needs to be conducted that examines outcomes such as cognitive and psychological functioning.

CT technology overview.

I hope that you will find the product matrix to be a useful tool for making comparisons between vendors and scanners. Please keep in mind that the vendors have directly provided the specific answers to the questions within the matrix. Neither the author nor Radiology Management shall be held responsible for any misrepresented or erroneous data.

Use of portable CT in the R Adams Cowley Shock Trauma Center. Experiences in the admitting area, ICU, and operating room.

The author's experience with portable CT has been positive. Nurses and clinical physicians have been pleased with this new imaging capability also, and have written testimonial letters endorsing its value. Recently, the STC extended availability of the mobile CT to the University of Maryland Hospital, an adjoining 600-bed center with numerous medical and surgical patients in ICU. They are particularly interested in assessing use of portable CT in the neonatal ICU, where patient transport outside the unit is particularly difficult and dangerous. Technical improvements for portable CT are in development. Soon, helical volume scanning will be available, allowing faster image acquisition and better two- and three-dimensional image reformations (Fig. 12). A new, more powerful x-ray tube is in development that will permit more slices to be acquired without tube cooling interruptions. Gantry translate capability coupled with a radiolucent backboard extender has the potential to permit scanning of the head, neck, spine, face, and upper torso without the patient being moved from the ICU bed. For applications in head, face, and neck surgery, a radiolucent cranial fixation device also has been developed. Other potential improvements include extended battery power for more scanning between charges, a larger tube heat unit storage for extended scanning situations, decreased system weight for easier transport, and more detector efficiency for improved image quality while maintaining significant dose reduction over conventional scanning. The capability of portable CT scanning for emergency, intensive care, and intraoperative studies exists now. The commercially marketed cost for this system is between $400,000 and $500,000. Further studies are anticipated to clarify the economic and clinical benefits of this technology.