| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Thoracic Imaging |
1 From the Department of Radiology, Hospital Calmette, University Center of Lille, Boulevard Jules Leclerc, 59037 Lille, France (I.M., M.R.J., J.R.); Department of Medical Statistics, University of Lille, France (V.D., A.D.); and Siemens Medical Systems, Forchheim, Germany (C. Scherf, C. Suess). From the 2001 RSNA scientific assembly. Received October 28, 2002; revision requested January 10, 2003; revision received January 29; accepted May 19. Address correspondence to M.R.J. (e-mail: mremy-jardin@chru-lille.fr).
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
|---|
MATERIALS AND METHODS: A total of 100 patients were evaluated for thoracic outlet arterial syndrome with spiral CT angiography (collimation, 4 x 1 mm; pitch, 1.75) both with and without dose reduction by means of anatomically adapted online tube current modulation and preset minimum dose savings. Preset minimum savings of 20% and of 32% were applied in two groups of 50 patients (groups 1 and 2). In each group, low-dose scanning was performed in 25 patients in the neutral position and in 25 patients after postural maneuver. Tube current–time product, noise, presence and quality of graininess and of linear streak artifacts on transverse CT scans, and diagnostic value of sagittal reformations and volume-rendered images were evaluated and recorded for each data set. 
2 test was used to compare frequencies; paired Wilcoxon rank test, to compare subjective and objective image quality scores. P < .05 indicated a significant difference.
RESULTS: In group 1, mean tube current–time product was 3,225 mAs for reference scans and 2,101 mAs for low-dose scans (mean reduction, 35%; range, 27%–47%). In group 2, mean was 3,070 mAs for reference scans and 2,068 mAs for low-dose scans (mean reduction, 33%; range, 17%–38%). In group 1, no differences in frequencies of graininess and linear streaking or in noise level were found between images acquired with or without dose reduction. In group 2, no difference was found in noise level between low-dose and reference scans. On low-dose scans, moderate linear streaking was observed with lower frequency and moderate graininess was observed with higher frequency, but artifacts did not compromise image quality or prevent confident assessment of arterial diameter in the three compartments of the thoracic outlet.
CONCLUSION: Online tube current modulation with a preset minimum dose saving of 20% allowed 35% reduction in mean tube current–time product, with no loss in image quality.
© RSNA, 2003
Index terms: Arteries, subclavian • Computed tomography (CT), angiography, 91.12916, 942.12916 • Computed tomography, radiation exposure • Shoulder, CT, 41.12115
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
|---|
One technique for reducing radiation exposure involves the use of tube current modulation to adjust the dose according to actual local attenuation (11). This technique, when applied to the evaluation of the thoracic outlet region with single-section CT angiography, was shown to provide low-dose high-quality diagnostic images (12,13). A variant of the technique, which includes user predefinition of the minimum dose saving for a given examination, was developed for use at multi–detector row spiral CT. During scanning, the level of attenuation is measured and the milliamperage is adjusted accordingly. The system controls the average milliamperage applied online and ensures that the selected minimum dose saving is achieved either by modulating the tube current or by scaling down the calculated tube current curve for each rotation. The purpose of this study was to evaluate image quality at multi–detector row spiral CT angiography of the thoracic outlet with dose reduction achieved with online tube current modulation and preset minimum dose savings.
|
MATERIALS AND METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
|---|
Study Population
Groups 1 and 2 were composed of 50 patients each, all of whom had been referred for radiologic evaluation on clinical suspicion of thoracic outlet arterial syndrome. The investigation started with group 1 patients, for whom the minimum dose saving was preset at 20%. Twenty-five patients in group 1 (designated group 1a) were imaged first without and then with the low-dose technique while in the neutral position. Low-dose imaging was performed after postural maneuver in the other 25 patients (group 1b), in whom the thoracic outlet region had morphologic characteristics similar to those in group 1a patients. To avoid differences in image quality between the two subgroups as a result of different anatomy, patients in groups 1a and 1b were matched according to the transverse diameter of the thorax, which was measured at the level of the upper half of the humeral head. The second part of the study was similarly designed and implemented, with similar selection, matching, and imaging of group 2a and 2b patients. For group 2 patients, however, the minimum dose saving was preset at 32%.
Group 1 included 38 women and 12 men with a mean age (± SD) of 42 years ± 10. The mean weight of group 1 patients was 62 kg ± 11, and the mean height was 165 cm ± 7. Group 2 included 32 women and 18 men with a mean age of 44 years ± 9.6. The mean weight of group 2 patients was 69 kg ± 13, and the mean height was 167 cm ± 9.1. The mean transverse diameter of the thorax was 196.6 mm ± 12.2 in group 1 and 203.5 mm ± 14.7 in group 2. Unlike mean height, which did not differ between the two groups, mean weight and mean transverse diameter of the thorax were statistically significantly higher in group 2 than in group 1 (P = .01 and P = .05, respectively).
CT Examinations
Spiral CT examinations were performed with a Volume Zoom scanner (Siemens Medical Systems, Forchheim, Germany). In order to depict postural changes at the level of the axillary and subclavian arteries, two acquisitions were performed for each patient: one in the neutral position (ie, with both arms alongside the body and the head medially located) and the other after a postural maneuver to exacerbate vascular compression at the level of the thoracic outlet. This postural maneuver combined the positional characteristics of two maneuvers currently used in the clinical evaluation of thoracic outlet syndrome—namely, the Adson maneuver and the Wright maneuver—and included a 130° hyperabduction with external rotation of the affected arm, ipsilateral rotation of the head, and positioning of the contralateral arm alongside the body (13,14). The mean z-axis coverage for each acquisition was 92.6 mm ± 8.5 in group 1 and 85.4 mm ± 8.3 in group 2, extending from the upper margin of the transverse process of the seventh cervical vertebra to the lower margin of the anterior extremity of the first rib. The mean duration of each data acquisition was 11.2 seconds ± 0.9 in group 1 and 10 seconds ± 0.9 in group 2. Scanning began 15–20 seconds after initiation of a monophasic bolus injection of 90 mL of iohexol containing 300 mg of iodine per milliliter (Omnipaque 300; Amersham Health, Pantin, France) at a rate of 4 mL/sec. From each data set, an image series for diagnostic purposes was reconstructed that included (a) a contiguous transverse CT scan, (b) sagittal reformations from the medial junction of the upper thoracic vertebrae to the humeral head, spaced 7 mm apart, and (c) volume-rendered images of the arterial and bone structures.
Evaluation of Dose Reduction
CT protocols for reference and low-dose examinations.—The following scanning parameters were selected for reference examinations: kilovoltage of 140 kV, tube current–time product of 140 mAs per rotation, scanning time of 0.75 second, collimation of 4 x 1 mm, pitch of 1.75, craniocaudal scanning direction. Similar parameters were chosen for low-dose scanning, but the tube current–time product was set at 170 mAs per rotation. The increase in the tube current–time product per rotation for low-dose acquisitions was recommended by the manufacturer to avoid impaired image quality on lateral views of the thoracic outlet. For each patient, one of the two acquisitions was obtained with online tube current modulation (the so-called Care Dose system) and preset minimum dose saving, the latter of which limited the maximum value of the tube current. This system had been installed as an option on the CT scanner. In both group 1 and group 2, the low-dose technique was activated in the neutral position for the first 25 patients (groups 1a and 2a). To evaluate the influence of the arm position on dose reduction and image quality, we activated the dose-reduction system at scanning in the second 25 patients (groups 1b and 2b) after postural maneuver. To avoid differences in image quality as a result of differences in patient anatomy, we matched the patients in groups 1a and 1b, as well as those in groups 2a and 2b, according to the transverse diameter of the thorax at the level of the upper half of the humeral head, as measured on a scout digital radiograph.
Evaluation of image quality.—Subjective evaluation of image quality was performed by two authors (I.M., M.R.J.) on the two sets of contiguous transverse CT scans generated for each patient (ie, reference and low-dose scans). These images were similarly reconstructed with a soft kernel (B20) and a small field of view (160–200 mm), and hard copies were obtained at mediastinal window settings (window width, 350 HU; window center, 30 HU). Observations of image noise, as defined by a grainy appearance, and of linear streak artifacts were systematically recorded, and these visual phenomena were graded as very minimal, minimal, moderate, or severe. CT images were reviewed and analyzed in random order and by consensus of two radiologists (M.R.J., I.M.) with 8 and 4 years of experience, respectively, in interpreting CT angiograms of the thoracic outlet. The two readers were blinded to the scanning protocol used in each case. Although all images were systematically analyzed, particular attention was given to transverse CT scans with moderate to severe artifacts, to determine whether these artifacts altered the quality of the source images in such a way as to interfere with the diagnostic value of two- and three-dimensional reconstructions.
Objective evaluation of image noise was based on measurement of the SD in CT numbers for pixels in a circular region of interest (ROI) placed in the trachea. Window settings (window width, 500 HU; window center, -900 HU) were chosen to avoid superimposition of the ROI on the inner portion of the tracheal wall. For each examination, the ROI was placed by one of the two readers, in consensus with the other reader, on the CT scan depicting the costoclavicular space. ROI placement and noise measurement were performed on images retrospectively reconstructed from raw data stored on optical disks. The mean area of measurement was 1.3 cm2 ± 0.9.
Calculation of dose reduction.—For each patient, the total tube current–time product per scan was recorded separately for each of the two acquisitions. Dose reduction was expressed as the percentage obtained by dividing the difference between the tube current–time products of the reference examination and the examination with dose reduction by the tube current–time product of the reference examination. Patient dose was expressed as the weighted CT dose index (CTDIw) for the respective sets of scanning parameters.
In two representative patients, one from each group, we also calculated the tissue dose reduction that resulted from tube current modulation. These two cases illustrate the high quality of low-dose scans obtained in the two groups overall. To determine the dose reduction in these two patients, we used the Monte Carlo–based simulation software ImpactMC (15). With this software, the dose is calculated from the CT data acquired in the patient; therefore, the individual patient anatomy is a factor in the calculations, and the dose values are specific to that anatomy. The influence of CT scanner settings on dose distribution also is considered in the calculations. To simulate the tube current modulation, we entered the tube current curves from the respective acquisitions. For each of these two patients, we performed two calculations: one for scanning with tube current modulation, and one for scanning without it.
Evaluation of arterial stenosis.—Systematic analysis of the subclavian and axillary arteries was performed on sagittal reformations of low-dose image data obtained in the neutral position and after postural maneuver in each patient. The images were interpreted by consensus of the same two radiologists who performed the overall analysis of image quality. In the three compartments of potential compression—the interscalene triangle, the costoclavicular space, and the subcoracoid tunnel—the subclavian and axillary arteries were graded for the presence of stenosis on a four-point scale: 0 for no stenosis, 1 for stenosis of less than 50%, 2 for 50%–99% stenosis, and 3 for occlusion. Because a slight (<30%) reduction in the anteroposterior diameter of the part of the subclavian artery located behind the anterior scalene muscle was a frequent finding, a grade 1 stenosis of this arterial segment was defined by a reduction in the arterial diameter of more than 30% and less than 50%. Whereas sagittal reformations were assessed for the site and severity of arterial stenoses, volume-rendered images of the thoracic outlet were systematically analyzed for overall image quality because these images simultaneously depict both the arterial bundle and the surrounding bone structures and thereby help clinicians visualize the anatomic situation.
Statistical Analysis
Statistical analysis was performed with commercially available software (SAS version 8.2; SAS Institute, Cary, NC). Comparisons of means and frequencies were carried out with the 2 test. Subjective and objective image quality scores for the subpopulations of groups 1 and 2 were compared by using the paired Wilcoxon rank test to evaluate for differences between the two patient positions within a given group. A P value lower than .05 was considered to indicate a statistically significant difference.
|
RESULTS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
|---|
The quality of low-dose scans was compared with that of reference scans in groups 1a and 1b (Table 1) (Fig 1). No significant difference was found in the frequency of graininess (P = .705 in the neutral position, P = .166 after postural maneuver) or of linear streak artifacts (P = .733 in the neutral position, P = .433 after postural maneuver). The noise level also did not significantly differ between low-dose and reference scans in groups 1a (P = .94) and 1b (P = .38). The 95% CIs for difference in mean noise value for the two subgroups were narrow: -2.3, 3.0 in group 1a, and -3.2, 2.6 in group 1b.
|
|
|
|
|
When the image quality of low-dose scans was compared with that of reference scans in groups 2a and 2b (Table 2) (Fig 2), significant differences were found in the frequencies of graininess from very minimal to severe (P < .001 in the neutral position, P < .001 after postural maneuver) and linear streak artifacts (P = .017 in the neutral position, P < .001 after postural maneuver). Moderate graininess was observed more frequently on low-dose scans in groups 2a and 2b with no alteration of the diagnostic value of the CT scans, whereas moderate linear streaking was observed less frequently on low-dose scans in the same subgroups. Graininess and linear streak artifacts graded severe were observed in three patients with high weight (range, 60–85 kg) relative to their stature (range, 152–165 cm), but the presence of these artifacts did not compromise the diagnostic value of sagittal reformations and volume-rendered images of the examinations. The noise level did not significantly differ between low-dose and reference scans in groups 2a (P = .89) and 2b (P = .39), and no statistically significant difference was found between low-dose scans obtained after postural maneuver and low-dose scans obtained in the neutral position. The 95% CIs for differences in mean noise level for the two subgroups are narrow: -2.3, 3.0 in group 2a, and -3.9, 2.0 in group 2b. The images in Figures 1 and 3 and in Figures 2 and 4 are representative of patients in group 1 and group 2, respectively.
|
|
|
|
|
|
|
|
|
|
|
Depiction of Arterial Stenosis
Table 3 summarizes the frequency and severity of arterial stenoses observed in the study group. Among group 1 patients with CT findings of arterial stenosis (n = 27), stenosis was found exclusively after postural maneuver in 23 patients, 22 of whom had it in the costoclavicular space and one of whom had it in the subcoracoid tunnel. Among the four group 1 patients in whom arterial stenosis was depicted at both acquisitions, the site of stenosis was the interscalene triangle on all images obtained with the patient in the neutral position. On images obtained after postural maneuver, the site of stenosis was the interscalene triangle in one patient and the costoclavicular space in the other three patients. In group 1, a total of 31 stenoses were depicted. Of these, 27 were identified on images obtained after postural maneuver, including 11 stenoses on low-dose scans and 16 on reference scans. Four stenoses were depicted on images obtained with the patient in the neutral position, including two depicted on low-dose scans and two on reference scans.
|
|
DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
|---|
These results support the conclusions of Itoh et al (8) regarding low-dose spiral CT scanning of the thorax. After investigating the use of single-section spiral CT in lung cancer screening, the authors determined that the minimum tube current required for screening helical CT differs for different locations in the lung and that an ideal CT protocol for lung cancer screening should permit the tube current to be changed during helical CT scanning. This conclusion led to the development of new technology for reducing the patient radiation dose at CT by varying the tube current. An early manifestation of this technology was the SmartScan system (GE Medical Systems, Milwaukee, Wis) (16,17), in which dose modulation is based on attenuation measurements from two localizer radiographs. This system uses a predefined sinusoidal angular modulation over a complete anatomic range with a modulation amplitude of only 50%.
Another approach reported in the literature (11) involves the use of tube current modulation during the 360° tube rotation to enable dose reduction for acquisitions with relatively low attenuation—mostly those obtained in the anteroposterior direction. Applying this technique in an adult population, Greess et al (18) achieved a substantially greater dose reduction in the thorax, abdomen, and pelvis than reductions reported for the alternative approach (sinusoidal angular modulation). In the thorax, dose reductions achieved by Greess et al with this technique averaged 22%, compared with 3.3% (16), 7% (19), and 15% (17) reductions achieved with the latter system. More recently, the same authors investigated the effectiveness of this technique in CT examinations of children, a group of patients in whom it is of the utmost importance to reduce radiation exposure to the minimum necessary for diagnosis (20). Evaluating four different anatomic regions with single-section CT, these authors found that the tube current–time product was typically reduced by 10%–50% for the volume scanned, depending on the anatomic region and the patient geometry, without any deterioration in image quality. However, as emphasized by Greess et al (20), Monte Carlo dose simulations for scanning performed with attenuation-based online modulation of tube current showed that actual patient dose was reduced more markedly than indicated by the reduction in tube current–time product (15). In the present investigation, the mean reduction along the z axis was 40% and 46%, respectively, for representative patients from group 1 and group 2; the maximum reduction per rotation was 52% for the group 1 patient and 54% for the group 2 patient.
At CT of the shoulder region, structured noise may affect diagnostic capability, and depiction of normal structures is strongly influenced by lower tube currents. With regard to objective image quality, we found no significant difference in noise level when comparing low-dose scans with references scans in groups 1a and 1b and in groups 2a and 2b. Analysis of subjective image quality in group 1 also showed no significant difference between low-dose and reference scans, regardless of the patient’s position when dose-reduction techniques were applied. On scans obtained at a preset dose saving of 32% (ie, group 2 scans), significant differences were observed in the overall frequencies of graininess and linear streak artifacts. Significant differences were found also in the frequency distribution of the subcategories (from very minimal to severe) of graininess and linear streak artifacts on low-dose scans obtained in the neutral position and after postural maneuver. Because of the potential effect of noise on the diagnostic value of images, particular attention was paid to the frequency of moderate and severe artifacts. Moderate graininess was observed more frequently on low-dose scans in groups 2a and 2b with no alteration of the diagnostic value of these CT scans, whereas moderate linear streak artifacts were observed less frequently on low-dose scans in groups 2a and 2b. The latter finding confirms the preliminary results of an earlier study (11) in which this technique was applied to scanning of phantoms and cadavers; those results indicated that the image noise on low-dose scans was improved with respect to amplitude and structure. Severe artifacts were present in only three CT data sets in both subgroups. These quality deficiencies were observed only on transverse images obtained in female patients with high body weight relative to their height, and they provide further confirmation of the need, emphasized by Wilting et al (21), to adapt milliamperage to patient height and weight. Because sagittal reformations and volume-rendered images provide more diagnostic information than do source images, care was taken in assessing the diagnostic value of transverse CT scans obtained in all patients, particularly scans on which severe artifacts were observed. All sagittal reformations and volume-rendered images from group 2 patients were suitable for assessment of the subclavian and axillary arterial diameters, as well as for identification of muscular or osseous compression of the arterial bundle.
Our study had several limitations. First, the results obtained in group 1 and group 2 are not strictly comparable because the anatomy of patients in the two groups differed slightly. Second, the use of increased tube current–time product per section selected for low-dose acquisitions lessened the expected dose reduction. This recommendation from the manufacturer was dictated by the anatomic characteristics of the region scanned and was necessary for avoiding too low a tube current–time product in lateral projections where high-attenuating bone structures are located. However, whereas it seems logical to take this precaution in scanning patients with high weight relative to their height, we do not think it necessary to follow this recommendation in scanning patients of average size (unpublished data). Third, we based our evaluation of dose reduction on total tube current–time product instead of on estimated effective dose because the latter calculations could not be made under routine clinical conditions. This is not a trivial matter, given that the effective radiation dose depends not only on the scanning parameters but also on the volume and radiosensitivity of the tissues irradiated (4). To overcome this limitation, we calculated the reduction in tissue dose by using a Monte Carlo–based simulation software in two representative patients from group 1 and group 2.
In conclusion, in this study we evaluated image quality obtained with a dose-reduction system based on anatomically adapted online tube current modulation and preset dose saving at multi–detector row spiral CT angiography of the thoracic outlet. Given the overall high quality of the images reconstructed from the low-dose acquisitions, we believe that this dose-reduction system should be applied during CT data acquisition in the neutral position and that it is even more effective after postural maneuver. This system enabled a reduction in patient radiation dose, expressed as CTDIw, from a mean of 19.4 mGy for conventional scanning to 8–10 mGy for low-dose scanning, with no loss in image quality. In patients with average body type (weight, 
65 kg), online dose modulation and prospective dose saving predefined at 32% are recommended to maximize dose reduction without compromising image quality; in larger patients (weight, >65 kg), the preset minimum dose saving should be lowered to 20% in order to maintain image quality at the level obtained on reference scans. Although our study results and recommendations are necessarily a function of our study population and the scanning system used, the dose-reduction system described in this article should be generally applicable to the evaluation of patients with thoracic outlet syndrome and may be adapted for use in other clinical situations.
|
ACKNOWLEDGMENTS |
|---|
|
FOOTNOTES |
|---|
Author contributions: Guarantor of integrity of entire study, M.R.J., J.R.; study concepts, C. Scherf, M.R.J., J.R.; study design, M.R.J., J.R.; literature research, M.R.J., J.R.; clinical studies, I.M., M.R.J., J.R.; data acquisition, I.M., M.R.J., J.R.; data analysis/interpretation, I.M., M.R.J.; statistical analysis, A.D., V.D.; manuscript preparation and definition of intellectual content, M.R.J.; manuscript editing, M.R.J., J.R.; manuscript revision/review and final version approval, M.R.J., J.R., C. Suess
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
|---|
This article has been cited by other articles:
|
|
 |
|
  S. Matsuoka, A. R. Hunsaker, R. R. Gill, I. B. Oliva, B. Trotman-Dickenson, F. L. Jacobson, and H. Hatabu Vascular Enhancement and Image Quality of MDCT Pulmonary Angiography in 400 Cases: Comparison of Standard and Low Kilovoltage Settings Am. J. Roentgenol., June 1, 2009; 192(6): 1651 - 1656. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. B. Smith, W. P. Dillon, B. C. Lau, R. Gould, F. R. Verdun, E. B. Lopez, and M. Wintermark Radiation Dose Reduction Strategy for CT Protocols: Successful Implementation in Neuroradiology Section Radiology, May 1, 2008; 247(2): 499 - 506. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 U.K. Udayasankar, K. Braithwaite, M. Arvaniti, D. Tudorascu, W.C. Small, S. Little, and S. Palasis Low-Dose Nonenhanced Head CT Protocol for Follow-Up Evaluation of Children with Ventriculoperitoneal Shunt: Reduction of Radiation and Effect on Image Quality AJNR Am. J. Neuroradiol., April 1, 2008; 29(4): 802 - 806. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Kubo, P.-J. P. Lin, W. Stiller, M. Takahashi, H.-U. Kauczor, Y. Ohno, and H. Hatabu Radiation Dose Reduction in Chest CT: A Review Am. J. Roentgenol., February 1, 2008; 190(2): 335 - 343. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. M. Kramer, M. J. Budoff, Z. A. Fayad, V. A. Ferrari, C. Goldman, J. R. Lesser, E. T. Martin, S. Rajagopalan, J. P. Reilly, G. P. Rodgers, et al. ACCF/AHA 2007 Clinical Competence Statement on vascular imaging with computed tomography and magnetic resonance Vascular Medicine, November 1, 2007; 12(4): 359 - 378. [PDF]
|
|
|
|
|
|
A.B. Smith, W.P. Dillon, R. Gould, and M. Wintermark Radiation Dose-Reduction Strategies for Neuroradiology CT Protocols AJNR Am. J. Neuroradiol., October 1, 2007; 28(9): 1628 - 1632. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. M. Kramer, M. J. Budoff, Z. A. Fayad, V. A. Ferrari, C. Goldman, J. R. Lesser, E. T. Martin, S. Rajagopalan, J. P. Reilly, G. P. Rodgers, et al. ACCF/AHA 2007 Clinical Competence Statement on Vascular Imaging With Computed Tomography and Magnetic Resonance: A Report of the American College of Cardiology Foundation/American Heart Association/American College of Physicians Task Force on Clinical Competence and Training Developed in Collaboration With the Society of Atherosclerosis Imaging and Prevention, the Society for Cardiovascular Angiography and Interventions, the Society of Cardiovascular Computed Tomography, the Society for Cardiovascular Magnetic Resonance, and the Society for Vascular Medicine and Biology J. Am. Coll. Cardiol., September 11, 2007; 50(11): 1097 - 1114. [Full Text] [PDF]
|
|
|
|
|
|
K. M. Kanal, B. K. Stewart, O. Kolokythas, and W. P. Shuman Impact of Operator-Selected Image Noise Index and Reconstruction Slice Thickness on Patient Radiation Dose in 64-MDCT Am. J. Roentgenol., July 1, 2007; 189(1): 219 - 225. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. Ou, P. Schmit, W. Layouss, D. Sidi, D. Bonnet, and F. Brunelle CT Angiography of the Artery of Adamkiewicz with 64-Section Technology: First Experience in Children AJNR Am. J. Neuroradiol., February 1, 2007; 28(2): 216 - 219. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Namasivayam, M.K. Kalra, K.M. Pottala, S.M. Waldrop, and P.A. Hudgins Optimization of Z-Axis Automatic Exposure Control for Multidetector Row CT Evaluation of Neck and Comparison with Fixed Tube Current Technique for Image Quality and Radiation Dose AJNR Am. J. Neuroradiol., November 1, 2006; 27(10): 2221 - 2225. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. Coche, S. Vynckier, and M. Octave-Prignot Pulmonary Embolism: Radiation Dose with Multi-Detector Row CT and Digital Angiography for Diagnosis Radiology, September 1, 2006; 240(3): 690 - 697. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. H. Mulkens, P. Bellinck, M. Baeyaert, D. Ghysen, X. Van Dijck, E. Mussen, C. Venstermans, and J.-L. Termote Use of an Automatic Exposure Control Mechanism for Dose Optimization in Multi-Detector Row CT Examinations: Clinical Evaluation Radiology, October 1, 2005; 237(1): 213 - 223. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. M. R. Rizzo, M. K. Kalra, B. Schmidt, J.-F. Paul, A. Sigal-Cinqualbre, and H. Abada Automatic Exposure Control Techniques for Individual Dose Adaptation * Dr Paul and colleagues respond: Radiology, April 1, 2005; 235(1): 335 - 336. [Full Text] [PDF]
|
|
|
|
|
|
J.-F. Paul, H. T. Abada, and A. B. Sigal-Cinqualbre Automatic Dose Reduction Should Not Mask Needs for Individual Dose Reduction Radiology, October 1, 2004; 233(1): 297 - 297. [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| RADIOLOGY | RADIOGRAPHICS | RSNA JOURNALS ONLINE |
