Radiation dose savings for adult pulmonary embolus 64-MDCT using bismuth breast shields, lower peak kilovoltage, and automatic tube current modulation.

OBJECTIVE: The purpose of this study was to assess whether radiation dose savings using a lower peak kilovoltage (kVp) setting, bismuth breast shields, and automatic tube current modulation could be achieved while preserving the image quality of MDCT scans obtained to assess for pulmonary embolus (PE). MATERIALS AND METHODS: CT angiography (CTA) examinations were performed to assess for the presence or absence of pulmonary artery emboli using a 64-MDCT scanner with automatic tube current modulation (noise level=10 HU), two kVp settings (120 and 140 kVp), and bismuth breast shields. Absorbed organ doses were measured using anthropomorphic phantoms and metal oxide semiconductor field effect transistor (MOSFET) detectors. Image quality was assessed quantitatively as well as qualitatively in various anatomic sites of the thorax. RESULTS: Using a lower kVp (120 vs 140 kVp) and automatic tube current modulation resulted in a dose savings of 27% to the breast and 47% to the lungs. The use of a lower kVp (120 kVp), automatic tube current modulation, and bismuth shields placed directly on the anterior chest wall reduced absorbed breast and lung doses by 55% and 45%, respectively. Qualitative assessment of the images showed no change in image quality of the lungs and mediastinum when using a lower kVp, bismuth shields, or both. CONCLUSION: The use of bismuth breast shields together with a lower kVp and automatic tube current modulation will reduce the absorbed radiation dose to the breast and lungs without degradation of image quality to the organs of the thorax for CTA detection of PE.

Radiation dose from contemporary cardiothoracic multidetector CT protocols with an anthropomorphic female phantom: implications for cancer induction.

PURPOSE: To measure prospectively and directly both organ dose and effective dose (ED) for adult cardiac and pulmonary computed tomographic (CT) angiography by using current clinical protocols for 64-detector CT in an anthropomorphic female phantom and to estimate lifetime attributable risk of breast and lung cancer incidence on the basis of measured ED and organ dose. MATERIALS AND METHODS: Cardiac and pulmonary 64-detector CT angiography was performed by using current clinical protocols to evaluate the pulmonary veins (electrocardiographically [ECG] gated, 64 sections at 0.625-mm collimation, 120 kVp, 300 mA, 0.35-second tube rotation), native coronary arteries (ECG gated; 64 sections at 0.625 mm; 120 kVp; maximum current, 500-750 mA; minimum, 100-350 mA; 0.35-second tube rotation) and pulmonary embolus (64 sections at 1.25 mm, 140 kVp, 645 mA, 0.5-second tube rotation). Absorbed organ doses were measured by using an anthropomorphic female phantom and metal oxide semiconductor field effect transistor detectors. ED was calculated from measured organ doses and the dose-length product. RESULTS: ED for current adult cardiac and pulmonary 64-detector CT angiography protocols were 12.4-31.8 mSv. Overall, skin, breast, and esophagus and heart had the highest recorded absorbed organ doses. Relative risk for breast cancer incidence for girls and women was 1.004-1.042 for a single examination. Relative risk for lung cancer incidence for men and women was 1.005-1.076 from a single examination. CONCLUSION: EDs and organ doses from 64-detector CT are higher than those previously reported for adult cardiac and pulmonary CT angiography protocols. Risk for breast and lung cancer induction from these studies is greatest for the younger patient population.

Validation of metal oxide semiconductor field effect transistor technology for organ dose assessment during CT: comparison with thermoluminescent dosimetry.

OBJECTIVE: The purposes of this study were to apply near-real-time dose-measurement technology with metal oxide semiconductor field effect transistors (MOSFETs) to the assessment of organ dose during CT and to validate the method in comparison with the thermoluminescent dosimeter (TLD) method. MATERIALS AND METHODS: Dosimetry measurements were performed in two ways, one with TLDs and the other with MOSFETs. Twenty organ locations were selected in an adult anthropomorphic female phantom. High-sensitivity MOSFET dosimeters were used. For the reference standard, TLDs were placed in the same organ locations as the MOSFETs. Both MOSFET and TLD detectors were calibrated with an X-ray beam equivalent in quality to that of a commercial CT scanner (half-value layer, approximately 7 mm Al at 120 kVp). Organ dose was determined with a scan protocol for pulmonary embolus studies on a 4-MDCT scanner. RESULTS: Measurements for selected organ doses and the percentage difference for TLDs and MOSFETs, respectively, were as follows: thyroid (0.34 cGy, 0.31 cGy, -8%), middle lobe of lung (2.4 cGy, 3.0 cGy, +26%), bone marrow of thoracic spine (2.2 cGy, 2.5 cGy, +11%), stomach (1.0 cGy, 0.93 cGy, -6%), liver (2.5 cGy, 2.6 cGy, +6%), and left breast (3.0 cGy, 2.9 cGy, -1%). Bland-Altman analysis showed that the MOSFET results agreed with the TLD results (bias, 0.042). CONCLUSION: We found good agreement between the results with the MOSFET and TLD methods. Near-real-time CT organ dose assessment not previously feasible with TLDs was achieved with MOSFETs. MOSFET technology can be used for protocol development in the rapidly changing MDCT scanner environment, in which organ dose data are extremely limited.

Radiation dose to the female breast from 16-MDCT body protocols.

OBJECTIVE: The objective of our study was to determine the radiation dose to the female breast from current 16-MDCT body examinations. MATERIALS AND METHODS: Metal oxide semiconductor field effect transistor (MOSFET) detectors were placed in four quadrants of the breast of a female-configured anthropomorphic phantom to determine radiation dose to the breast. Imaging was performed on a 16-MDCT scanner (LightSpeed, GE Healthcare) using current clinical protocols designed to assess pulmonary embolus (PE) (140 kVp, 380 mA, 0.8-sec rotation, 16 x 1.25 mm collimation), appendicitis (140 kVp, 340 mA, 0.5-sec rotation, 16 x 0.625 mm collimation), and renal calculus (140 kVp, 160 mA, 0.5-sec rotation, 16 x 0.625 mm collimation). RESULTS: Radiation dose to the breast ranged from 4 to 6 cGy for the PE protocol and up to 1-2 cGy in the inferior aspect of the right breast and lateral aspect of the left breast for the appendicitis protocol. The renal calculus protocol yielded less than 150 microGy absorbed breast dose. CONCLUSION: Current clinical chest and abdomen protocols result in vairable radiation doses to the breast. The magnitude of exposure may have implications for imaging strategies.

Relationship Between Time of First Publication and Subsequent Publication Success Among Non-PhD Physician-Scientists.

BACKGROUND: Studies have shown that publication of work during medical school and residency is associated with higher numbers of later publications and citations of published research. However, it is unknown whether this association exists for non-PhD physician-scientists and whether the association persists later into their careers. METHODS: We extracted publication records from the curricula vitae (CVs) of 102 corresponding authors of articles published in 2008 in the New England Journal of Medicine and JAMA, and obtained those authors' citation records from Web of Science. We used regression models to examine the association between time of first publication and later publication and citation rates for the entire postgraduate career and a recent 2-year period. RESULTS: After adjusting for time since medical school graduation, sex, location of medical school (United States or not United States), and additional non-PhD degrees, we found that authors who first published before graduating from medical school had a greater mean number of publications after medical school and during the period from 2006 to 2007 (164 and 28, respectively) than those who first published during the 5 years afterward (111 and 19, respectively) and those who first published more than 5 years after graduation (59 and 13, respectively). Similarly, authors who first published before graduating from medical school had a greater mean number of citations of their published work since graduation and of publications from 2006 to 2007 (4634 and 333, respectively) than those who first published during the 5 years afterward (2936 and 183, respectively) and those who first published more than 5 years after graduation (1512 and 143, respectively). CONCLUSIONS: Early publication is associated with higher numbers of publications and more citations of published research among non-PhD physician-scientists. This association persists well into a researcher's career.

Effect of improving the quality of radiographic interpretation on the ability to predict pulmonary tuberculosis relapse.

RATIONALE AND OBJECTIVES: Chest radiographic findings are important for diagnosis and management of tuberculosis. The reliability of these findings is therefore of interest. We sought to describe interobserver reliability of chest radiographic findings in pulmonary tuberculosis, and to understand how the reliability of these findings might affect the utility of radiographic findings in predicting tuberculosis relapse. MATERIALS AND METHODS: Three blinded readers independently reviewed chest radiographs from a randomly selected group of 10% of HIV-seronegative subjects participating in a tuberculosis treatment trial. The three readers then arrived at a fourth, consensus radiographic interpretation. RESULTS: A total of 241 films obtained from 99 patients were reviewed. Agreement among the independent readers was very good for the findings of bilateral disease (kappa = 0.71-0.86 among readers) and cavitation (kappa = 0.66-0.73). The original interpretation was reasonably sensitive and specific (compared to the consensus interpretation) for bilateral disease, but the sensitivity for cavity decreased from 81% for the 2-month film to 47% at end of treatment (P = 0.013). Substituting the consensus interpretation for the original interpretation increased the odds ratio for the association between cavitation on early chest radiograph and subsequent tuberculosis relapse from 4.97 to 8.97. CONCLUSION: Radiographic findings were reasonably reliable between independent reviewers and the original interpretations. The original investigators, who knew the patient's clinical course, were less likely to identify cavitation on the end of treatment chest radiograph. Improving the reliability of these findings could improve the utility of chest radiographs for predicting tuberculosis relapse.

Effective dose determination using an anthropomorphic phantom and metal oxide semiconductor field effect transistor technology for clinical adult body multidetector array computed tomography protocols.

PURPOSE: To determine the organ doses and total body effective dose (ED) delivered to an anthropomorphic phantom by multidetector array computed tomography (MDCT) when using standard clinical adult body imaging protocols. MATERIALS AND METHODS: Metal oxide semiconductor field effect transistor (MOSFET) technology was applied during the scanning of a female anthropomorphic phantom to determine 20 organ doses delivered during clinical body computed tomography (CT) imaging protocols. A 16-row MDCT scanner (LightSpeed, General Electric Healthcare, Milwaukee, Wis) was used. Effective dose was calculated as the sum of organ doses multiplied by a weighting factor determinant found in the International Commission on Radiological Protection Publication 60. Volume CT dose index and dose length product (DLP) values were recorded at the same time for the same scan. RESULTS: Effective dose (mSv) for body MDCT imaging protocols were as follows: standard chest CT, 6.80 +/- 0.6; pulmonary embolus CT, 13.7 +/- 0.4; gated coronary CT angiography, 20.6 +/- 0.4; standard abdomen and pelvic CT, 13.3 + 1.0; renal stone CT, 4.51 + 0.45. Effective dose calculated by direct organ measurements in the phantom was 14% to 37% greater than those determined by the DLP method. CONCLUSIONS: Effective dose calculated by the DLP method underestimates ED as compared with direct organ measurements for the same CT examination. Organ doses and total body ED are higher than previously reported for MDCT clinical body imaging protocols.

Radiation dose to the fetus from body MDCT during early gestation.

OBJECTIVE: The purpose of our study was to determine radiation dose to the fetus at early gestation when contemporary MDCT scanners are used for common clinical indications. MATERIALS AND METHODS: Anthropomorphic phantoms were constructed to reflect a pregnant woman. Thermoluminescence dosimeters (TLDs) and metal oxide semiconductor field effect transistor (MOSFET) detectors were placed in appropriate locations to determine real-time radiation exposure to the fetus at 0 and 3 months' gestation. Imaging was performed on a 16-MDCT scanner using current institutional CT protocols: renal stone (140 kVp, 160 mA, rotation time of 0.5 sec, 16 x 0.625 mm), appendix (140 kVp, 340 mA, rotation time of 0.5 sec, 16 x 0.625 mm), and pulmonary embolus (140 kVp, 380 mA, rotation time of 0.8 sec, 16 x 1.25 mm). RESULTS: The radiation dose to the fetus at 0 and 3 months, respectively, was as follows: renal stone protocol, 0.8-1.2 and 0.4-0.7 cGy; appendix protocol, 1.52-1.68 and 2-4 cGy; and pulmonary embolus protocol, 0.024-0.047 and 0.061-0.066 cGy. CONCLUSION: Radiation doses to the fetus from institutional MDCT protocols that may be used during pregnancy (for pulmonary embolus, appendicitis, and renal colic) are below the level thought to induce neurologic detriment to the fetus. Imaging the mother for appendicitis theoretically may double the fetal risk for developing a childhood cancer. Radiation doses to the fetus from pulmonary embolus chest CT angiography are of the same magnitude as ventilation-perfusion (V/Q) scanning.

Double-ring esophageal sign: pathognomonic for esophageal lipomatosis.

The peculiar appearance of the proximal esophagus on CT attributed to esophageal lipomatosis is not well recognized. We have recently encountered seven cases from over a period of 2 months and report them to reach a broader audience of radiologists who may be unaware of its existence. Its typical CT features should lead to the correct diagnosis and be differentiated from other fatty lesions known to involve the esophagus, namely, lipoma and liposarcoma.