Strategies of computed tomography radiation dose reduction: justification and optimization

Medical imaging is an indispensible diagnostic tool in modern medicine enabling fast and accurate diagnosis. Recent technological advances in medical equipment and increased utilization of the imaging modality have resulted in a significant increase in the exposure to ionizing radiation. After the rapid adoption of multi-detector computed tomography, computed tomography (CT) is now the single largest source of diagnostic radiation exposure to patients. The risks and benefits from radiation must be carefully considered in all examinations using ionizing radiation, and the principles of justification and optimization should be considered in the proper use of CT examination. Justification means that the examination must be medically indicated and useful. Optimization means that the imaging should be performed using doses that are ALARA (as low as reasonably achievable), consistent with the diagnostic task. This includes understanding and changing CT protocols to perform the same diagnostic task with the minimal amount of radiation exposure while maintaining diagnostic accuracy. Protocols and guidelines are important tools for radiation dose reduction. Understanding the parameters and dose information for CT examination is essential for optimization. If the exam is justified, then the parameters must be optimized to the imaging indication, scan area, body size, age, and weight of the patients. The physician should always assess the radiation risk-benefit ratio for each patient before ordering an examination that uses radiation. Continuing education is essential for the implementation of the principles of patient radiation dose reduction. Physicians and radiologists must be aware of the radiation risks associated with CT exams.

Reduced Radiation Dose in Diagnostic Radiology

No abstract available.

Radiation exposure in diagnostic areas: issues and countermeasures

No abstract available.

A case of recurrent respiratory infection resulting from a congenital anomaly of the bronchial tree tracheal bronchus / 소아과

The term tracheal bronchus refers to an abnormal bronchus that comes directly off of the lateral wall of the trachea (above the carina) and supplies ventilation to the upper lobe. Tracheal bronchi occur almost exclusively on the right trachea and are associated with other congenital anomalies. In addition, tracheai bronchus may be related to other inflammatory conditions with persistent wheezing, such as recurrent pneumonia, chronic bronchitis and bronchiectasis, which is a result of the relatively poor local drainage of the involved bronchi. An infant with recurrent wheezing is likely to be a challenge for a clinician in the evaluation of the etiology of airway obstruction and in the differential diagnosis of wheezy breathing. The authors report a case of an 8-month-old female infant with a ventricular septal defect, who presented with stridor and recurrent respiratory infection and finally was finally diagnosed with a tracheal bronchus using computed tomography and a bronchoscopy. Therefore, tracheal bronchus should be included in the differential diagnosis of any child who presents with chronic or recurrent respiratory tract symptoms such as coughing, wheezing, stridor and recurrent respiratory infection, particularly in children with other congenital deformities.

Reviews of Radiation Protection and Shielding for Computed Tomography in Foreign Countries / 의학물리

A computed tomography (CT) is a powerful system for the effectively fast and accurate diagnosis. The CT system, therefore, has used substantially and developed for improving the performance over the past decade, resulting in growing concerns over the radiation dose from the CT. Advanced CT techniques, such as a multidetector row CT scanner and dual energy or dual source CT, have led to new clinical applications that could result in further increases of radiation does for both patients and workers. The objective of this study was to review the international guidelines of the shielding requirements for a CT facility required for a new installation or when modifying an existing one. We used Google Search Engine to search the following keywords: computed tomography, CT regulation or shield or protection, dual energy or dual source CT, multidetector CT, CT radiation protection, and regulatory or legislation or regulation CT. In addition, we searched some special websites, that were provided for sources of radiation protection, shielding, and regulation, RSNA, AAPM, FDA, NIH, RCR, ICRP, IRPA, ICRP, IAEA, WHO (See in Table 1 for full explanations of the abbreviations). We finally summarized results of the investigated materials for each country. The shielding requirement of the CT room design was very well documented in the countries of Canada, United States of America, and United Kingdom. The wall thickness of the CT room could be obtained by the iso-exposure contour or the point source method. Most of documents provided by international organizations were explained in importance of radiation reduction in patients and workers. However, there were no directly-related documents of shielding and patient exposure dose for the dual energy CT system. Based international guidelines, the guideline of the CT room shielding and radiation reduction in patients and workers should be specified for all kinds of CT systems, included in the dual energy CT. We proposed some possible strategies in this paper.

A Study on the Usefulness of the AAPM TG18 Evaluation Tool for Diagnostic Monitor QC

PURPOSE: We created an 'AAPM TG18 Evaluation Tool' and we determined its usefulness for the quality control of a diagnostic monitor. MATERIALS AND METHODS: We created an evaluation tool (the AAPM TG18) for conducting quality control of a diagnostic monitor, and we evaluated the measurement items of the AAPM TG18 evaluation tool. The measurement items were geometric distortion, fixed quantity assessment and visual assessment of the veiling glare, and we carried out adjustment for the luminance meter 0% calibration, which was used to revise the diagnostic monitor DICOM LUT. RESULTS: With the AAPM TG18 Evaluation Tool, we measured the 2-dimensional length when evaluating the quantitative geometric distortions in the TG18-QC test pattern, and we measured the veiling-glare ring response function, which provided information regarding the spatial extent of the luminance spread, and this measurement of the can be performed using the TG18-GV pattern. Additionally, the AAPM TG18 Evaluation Tool can be used for sensor calibration to standardize the basic rate of 0% luminance when performing periodic calibration. CONCLUSION: The evaluation tool is a very useful for easily evaluating many of the examination items of the AAPM TG18 for performing quality control of a diagnostic monitor.

Serial Correlation between the Ultrasonographic and Pathologic Findings of Intramuscular Hemorrhaging in an Experimental Rabbit

PURPOSE: to evaluate the serial ultrasonographic findings of experimental intramuscular hemorrhaging to determine if there is a correlation with the pathologic findings. MATERIALS AND METHODS: An uiltrasonography (US) was performed before and immediately after an intramuscular blood injection in nine rabbits. In addition, follow-up US images were obtained at 1, 4, 7, 10, 14, 21, and 28 days after the intramuscular blood injections in seven of the rabbits. The pathologic specimens, compared to the US findings on each date, and consisted of samples of left thigh muscle. RESULTS: A US, performed immediately after a blood injection, showed two patterns; 6 cases of hyperechoic muscle thickening and 3 cases of hyperechoic muscle thickening with extravasation between the epimysium and muscle bundle or within muscle bundle. A follow-up US showed a marked decrease in intramuscular hemorrhaging and microcalcifications, which appeared on the 4th, 7th and 10th day after the blood injection. The pathologic findings revealed several short echogenic lines in the muscular bundles which were hemosiderin. Moreover, a 28 day follow-up US revealed that the normal findings are correlated with the normal gross pathologic findings. CONCLUSION: The US findings of the intramuscular hemorrhaging, for each of the follow-up dates, in comparison to the pathologic findings, revealed a high correlation with the pathologic specimens. Consequently, a US transducer with high resolution can be considered as a helpful technique in the diagnosing and evaluating the follow-up treatment of intramuscular hemorrhaging.

Acute Aortic Thromboses Occurring in Cancer Patients Treated with Chemotherapy

An acute aortic thrombosis in the absence of atherosclerosis, aortic dissection, or aneurysm is an infrequent clinical entity and has been rarely reported in the literature. However, because of serious complications such as an embolism that can be fatal, one should always pay attention to the possibility of its occurrence. We report two cases of an acute aortic thrombosis of lung cancer patients treated with chemotherapy and a review of the literature.

Comparison of the CT and Pathologic Findings of Pulmonary Fat Embolism Induced by Triolein and Oleic Acid in Rabbits

PURPOSE: The aim of this study was to evaluate the CT findings of pulmonary fat embolism syndrome that was induced by triolein and oleic acid, along with its pathologic correlation. MATERIALS AND METHODS: 16 rabbits were included in this study. The rabbits in group I (n=8) were embolized with 0.2 mL triolein and the rabbits of group II (n=8) were embolized with 0.2 mL oleic acid through ear veins. HRCT scans were done prior to embolization and at 0.5, 4, 24, 48 and 72 hours post-embolization. The pathologic correlations were determined at 0.5, 24, 48 and 72 hours. RESULTS: At 24 hours, one group I rabbit showed abnormal CT findings that were composed of several 2-3 mm nodules and multiple ill-defined peripheral ground glass opacities. The pathologic finding of this rabbit at 48 hours was mainly intraarveolar edema. All the group II rabbits (n=8/8) showed ill-defined bilateral and peripheral ground glass opacities with (n=6/8) or without consolidations (n=2/8) on the 0.5 hour CT. All the rabbits (n=7/7) showed that the new ground glass opacities and ground glass opacities noted on the 0.5 hour CT were changed into consolidation. The margins of the ground glass opacities and consolidations were more sharpened on the 24 hours CT. All 6 rabbits (n=6/6) showed consolidations without ground glass opacities and the margins of the consolidations were more sharpened on the 48 hours CT. There was no significant interval change on the 72 hours CT. The pathologic findings of ground glass opacities were interstitial edema or mild intraalveolar edema. The pathologic findings of consolidation were intraalveolar edema, hemorrhage and coagulation necrosis. CONCLUSION: The CT findings after fat embolization using triolein and oleic acid were ill-defined peripheral ground glass opacities with/without consolidations. These findings occurred in only one triolein group with the time lag, but these findings were immediately and extensively seen in all group II rabbits. These CT findings may be important for making a diagnosis of pulmonary fat embolism syndrome.

Radiological Findings of Lung Cancer: Focus on Atypical Pattern / 결핵및호흡기질환

The clinical and radiographic findings of lung cancer have been well established many journals. Even if the radiographic findings of lung cancer show a typical pattern, the specific cell type of lung cancer sometimes needs to be determined prior to a pathological diagnosis. For example, the usual finding of a squamous cell carcinoma is similar to other cancer types such as an adenocarcinoma or a small cell carcinoma but with a lower incidence. Therefore, it should not be used to make a diagnosis of the cell type prior to a pathological diagnosis. Many unusual findings of lung cancer, so called atypical pattern have been reported, but atypical findings are widely accepted. The more important thing is not to diagnose a specific cell type of cancer but to differentiate it from other benign conditions such as tuberculosis, fungal infections or organizing pneumonia. This paper presents typical information of the cell type of lung cancer along with the atypical radiographic findings.

Correlation between Chest Radiographic Findings and Respiratory Indices in Neonates with Respiratory Distress Syndrome

PURPOSE: The relationship between chest X-ray findings and respiratory indices, including the arterial-alveolar oxygen partial pressure ratio(a/APO2) and the ventilatory index(VI), indicators of the clinical respiratory status in neonates with respiratory distress syndrome(RDS), was examined in the present study. METHODS: The records of 50 neonates, randomly chosen from 174 neonates treated with pulmonary surfactant(PS) in the Neonatal Intensive Care Unit of Kyunghee University Hospital from 1996 to 2000 were analyzed retrospectively. Chest radiographs taken at the time after birth were classified into four groups according to Bomsel's classification. The a/APO2 and VI values were calculated and compared with the corresponding chest radiographs. RESULTS: Among the 50 cases of RDS examined, three cases were classified into grade I(6%), eight cases into grade II(16%), 20 cases into grade III(40%), and 19 cases into grade IV(38%). The mean a/APO2 of the cases classified into grades I or II was 0.32 and the mean a/APO2 of those classified into grades III and IV was 0.18 and 0.09, respectively. The mean VI was 0.049 for the cases classified into grades I or II and 0.076 and 0.161 for those classified into grades III and IV, respectively. CONCLUSION: The severity of RDS according to chest X-ray findings correlate to the values of respiratory indices, a/APO2 and VI.

A Giant Cystic Mediastinal Tuberculosis Communicating with Pericardium / 결핵

We report a very rare case of mediastinal tuberculosis in a 57-year old woman who presented with a large mediastinal cyst on chest radiography. She had a 10-year history of exertional dyspnea, but felt comfortable at a rest. A subsequent chest CT suggested a mediastinal cyst with mediastinal lymphadenopathy and communicating pericardial sac. She underwent a thoracotomy and excision of the mass, which was histologically revealed to be of tuberculous origin. Although rare, the apparent increase in the incidence of tuberculosis may result mediastinal cysts being diagnosed mediastinal tuberculosis. We also briefly review mediastinal lymphadenopathy due to tuberculosis.

A case of Goodpasture syndrome with diffuse pulmonary hemorrhage / 대한내과학회지

Goodpasture syndrome is an autoimmune disease with a triad of acute renal failure due to rapidly progressive glomerulonephritis (RPGN), pulmonay hemorrhage and circulating anti-glomerular basement membrane antibody (anti-GBM Ab). It was commonly reported from Europe in male with a peak incidence in their 20's. If patients are affected with the disease, relief of symptoms can be expected by eliminating the anti-GBM Ab from the circulatory system through hemodialysis, plasmapheresis and immunoadsorption. However, if the diagnosis or treatment is delayed, the patients usually die from massive pulmonary hemorrhage. It has been revealed that the main target of anti-GBM Ab's is NC1 domain on the alpha3 chain of type IV collagen. Currently there are many studies underway using this information as a basis to identify the pathogenesis of Goodpasture syndrome and to develop new therapeutic approach. The patient was a 20-year-old male with a chief complaint of edema. Unlike patients in the two previous cases, reported in Korea who had massive hemorrhage, he showed diffuse pulmonary hemorrhage which improved in only one week by hemodialysis. Renal biopsy demonstrated crescents in over 90% of glomeruli and showed signs of acute renal failure due to RPGN, with 618 U/mL (normal range <19.9 U/mL) of anti-GBM Ab titer.

A Case of Cavitary Pulmonary Metastases of Primary Cavitary Lung Cancer / 결핵

Many disorders and abnormalities are accompanied by cavitary lesoin of the lung and one of the most common causes of cavitary lung disease are primary and metastatic lung neoplasms. but cavitary formation of primary lung cancer is not frequent and cavitary or cystic pulmonary metastases of this is also rare. We report a case of cavitary pulmonry metastases of primary lung cancer proven by bronchoscopic biopsy and chest CT. The patients was 60 year-old heavy smoker who had never been underlying lung diseases 7 years ago and complained chronic cough. The chest CT showed primary lung cancer in right low lobe with multiple cavitary or cystic metastases in both lungs and multiple lymphatic metastases.

Extraskeletal Mesenchymal Chondrosarcoma of the Mediastinum: A Case Report / 대한흉부외과학회지

Mesenchymal chondrosarcoma arising in soft tissue of mediastinum is a very rare tumor. This paper reports an extraskeletal mesenchymal chondrosarcoma occuring in the posterior mediastinum.

One Case of Tracheopathia Osteoplastica / 결핵

Tracheopathia osteoplastica is a rare, benign pathologic condition chahacterized the occurrence of numerous cartilage and bony nodules within the tissue of mucosa. We report a case of tracheopathia osteoplastica that involved both larynx and trachea. The patient was 73 years old male and had hoarseness. The neck CT showed thickened and irregular wall of the trachea extending to the level of the carina with multiple calcified nodules and plaques of bony density projecting into the lumen.

Biphasic pattern of flow-volume curve (Unilateral main bronchus stenosis) / 대한내과학회지

No abstract available.

Diffuse Esophageal Leiomyomatosis: A Case Report

Leiomyomas are the most common benign tumors found in the esophagus. They are mostly solitary and multiple diffuse lesions are rare, occurring in only 2.4% of cases (1). We describe the case of a 13-year-old boy with a history of Alport syndrome who complained of progressive dysphagia and postprandial vomiting, and in whom diffuse leiomyomatosis of the esophagus was diagnosed. Chest PA showed mediastinal widening, and a barium study revealed diffuse esophageal wall thickening with dilatation, and obstruction at the level of the distal esophagus. Manometry showed increased pressure in the lower esophagus, and CT demonstrated diffuse thickening of the entire esophageal wall and an intraluminal mass in the distal esophagus. Follow-up CT three years later showed further esophageal wall thickening, as well as luminal narrowing. By means of distal esophagectomy, diffuse leiomyomatosis involving the entire esophageal wall and intraluminal mass was diagnosed.

Low Attenuation on High Resolution Computed Tomography in Pulmonary Embolism: An Experimental Study in Pigs

PURPOSE: To evaluate the incidence and type of low attenuation seen on high resolution computed tomography (HRCT) performed after artificially induced pulmonary embolism. MATERIALS AND METHODS: Using permanent embolic materials, pulmonary embolism was induced in ten Yorkshire pigs. Pre- and postembolic pulmonary angiography was performed, and HRCT was performed immediately and 1, 3, and 6 weeks after embolization. The incidence and type of low attenuation of all segments, as seen on HRCT, was evaluated. Low attenuation was classified as mottled, lobular, segmental, or peripheral. The pigs were sacrified after 6 weeks and contact radiographs were obtained. RESULTS: Low attenuation developed in eight of ten pigs. Pulmonary angiography revealed arterial occlusion in 15 large and 19 small segmental arteries (34 of 45 segments). In the remaining 11 segments, follow-up HRCT demonstrated areas of low attenuation. This was present in 25 of 35 segments (71%) as seen on HRCT images obtained immediately; in 16 of 41 segments (39 %) on images obtained 1 week after embolization; in 17 of 41 segments (41 %) on those acquired at 3 weeks; and in 25 of 45 segments (56 %) on those acquired at 6 weeks. The overall incidence of low attenuation was 83/166 (50 %). The types of low attenuation were mottled in 32/83 cases, lobular in 13/83, segmental in 13/83, and peripheral in 25/83. In large segmental arterial occlusion, the incidence of low attenuation on HRCT was 100% immediately, 57% at 1 week, 60% at 3 weeks, and 80 % at 6 weeks. In small segmental arterial occlusion, the incidence was 47%, 25 %, 11 %, and 21 % respectively. The overall incidence of low attenuation was 40/55 (73 %) in large segmental arterial occlusion and 18/71 ( 25%) in small segmental arterial occlusion. CONCLUSION: Low attenuation on HRCT is a finding of pulmonary embolism and is more common on HRCT performed immediately after embolization (71%) and in large segmental arterial occlusion (73%). Low attenuation on HRCT is an ancillary finding and may be useful in the diagnosis of pulmonary embolism.

Pulmonary Fat Embolism Induced Intravenous Injection of Autologous Bone Marrow in Rabbit: CT and Pathologic Correlation

PURPOSE: To evaluate the correlation between CT and pathologic findings of pulmonary fat embolism in rabbits. MATERIALS AND METHODS: In 16 rabbits, pulmonary fat embolism was induced by intravenous injection of autologous bone marrow(mean 3.3 mL). Chest CT scans were obtained immediately(within 1 hour), and 1, 3, and 7 days after embolization. The rabbits were divided into four groups. Group 1 underwent CT scanning immediately after embolization, group 2 immediately and 1 day after embolization, group 3 immediately, 1 day and 3 days after embolization, group 4 immediately, 1 day, 3 days and 7 days after embolization. Pathologic specimens were obtained immediately after the last CT scan. RESULTS: The earliest CT findings of pulmonary fat embolism in rabbits were peripheral lung lucency(16/16, 1 00 %), perivascular ground-glass (12/16, 75.0 %) and enlargement of the central pulmonary artery(11/16, 6 8 .8 %). Pathologically, perivascular ground-glass opacity correlated with extensive perivascular alveolar congestion and enlargement of the central pulmonary artery correlated with perivascular connective tissue edema and reactive pulmonary arterial engorgement. Peripheral lung lucency was probably caused by embolic occlusion of the pulmonary artery and decreased perfusion and air trapping induced by arterial and bronchial s-pasm associated with hypoxia. CT scans obtained 1 and 3 days after embolization showed nodules and patchy ground-glass opacity and consolidation. Aggregation of nodules resulted in patch opacities. Pathologically, pulmonary nodules correlated with focal inflammation surrounding an artery and parenchymal opacity correlated with parenchymal consolidation and hemorrhagic edema. CT scans and pathologic specimens obtained 7 days after embolization showed improvement of parenchymal lung abnormalities. CONCLUSION: Pulmonary fat embolism in rabbits show CT and pathologic findings which vary with dynamic change. Typical earliest findings of pulmonary fat embolism were peripheral lung lucency, perivascular ground-glass opacity and enlargement of the central pulmonary artery.