Radiation Dose Reduction at Pediatric CT: Use of Low Tube Voltage and Iterative Reconstruction.

Given the growing awareness of and concern for potential carcinogenic effects of exposure of children to ionizing radiation at CT, optimizing acquisition parameters is crucial to achieve diagnostically acceptable image quality at the lowest possible radiation dose. Among currently available dose reduction techniques, recent technical innovations have allowed the implementation of low tube voltage scans and iterative reconstruction (IR) techniques into daily clinical practice for pediatric CT. The benefits of lowering tube voltage include a considerable reduction in radiation dose and improved contrast on images, especially when an iodinated contrast medium is used. The increase in noise, which is attributed to decreased photon penetration, is a major drawback but is not as severe as that at adult CT because of the small body size of children. In addition, use of IR algorithms can suppress increased noise, yielding wider applicability for low tube voltage scans. However, a careful implementation strategy and methodologic approach are necessary to maximize the potential for dose reduction while preserving diagnostic image quality under each clinical condition. The potential pitfalls of and topics related to these techniques include (a) the effect of tube voltage on the surface radiation dose, (b) the effect of window settings, (c) accentuation of metallic artifacts, (d) deterioration of low contrast detectability at low-dose settings, (e) interscanner variation of x-ray spectra, and (f) a comparison with the use of a spectral shaping technique. Appropriate use of low tube voltage and IR techniques is helpful for radiation dose reduction in most applications of pediatric CT. Online DICOM image stacks are available for this article . ©RSNA, 2018.

Radiation dose reduction using 100-kVp and a sinogram-affirmed iterative reconstruction algorithm in adolescent head CT: Impact on grey-white matter contrast and image noise.

OBJECTIVES: To retrospectively evaluate the image quality and radiation dose of 100-kVp scans with sinogram-affirmed iterative reconstruction (IR) for unenhanced head CT in adolescents. METHODS: Sixty-nine patients aged 12-17 years underwent head CT under 120- (n = 34) or 100-kVp (n = 35) protocols. The 120-kVp images were reconstructed with filtered back-projection (FBP), 100-kVp images with FBP (100-kVp-F) and sinogram-affirmed IR (100-kVp-S). We compared the effective dose (ED), grey-white matter (GM-WM) contrast, image noise, and contrast-to-noise ratio (CNR) between protocols in supratentorial (ST) and posterior fossa (PS). We also assessed GM-WM contrast, image noise, sharpness, artifacts, and overall image quality on a four-point scale. RESULTS: ED was 46% lower with 100- than 120-kVp (p < 0.001). GM-WM contrast was higher, and image noise was lower, on 100-kVp-S than 120-kVp at ST (p < 0.001). CNR of 100-kVp-S was higher than of 120-kVp (p < 0.001). GM-WM contrast of 100-kVp-S was subjectively rated as better than of 120-kVp (p < 0.001). There were no significant differences in the other criteria between 100-kVp-S and 120-kVp (p = 0.072-0.966). CONCLUSIONS: The 100-kVp with sinogram-affirmed IR facilitated dramatic radiation reduction and better GM-WM contrast without increasing image noise in adolescent head CT. KEY POINTS: • 100-kVp head CT provides 46% radiation dose reduction compared with 120-kVp. • 100-kVp scanning improves subjective and objective GM-WM contrast. • Sinogram-affirmed IR decreases head CT image noise, especially in supratentorial region. • 100-kVp protocol with sinogram-affirmed IR is suited for adolescent head CT.

Cerebral bone subtraction CT angiography using 80 kVp and sinogram-affirmed iterative reconstruction: contrast medium and radiation dose reduction with improvement of image quality.

INTRODUCTION: The purpose of this study was to evaluate the feasibility of a contrast medium (CM), radiation dose reduction protocol for cerebral bone-subtraction CT angiography (BSCTA) using 80-kVp and sinogram-affirmed iterative reconstruction (SAFIRE). METHODS: Seventy-five patients who had undergone BSCTA under the 120- (n = 37) or the 80-kVp protocol (n = 38) were included. CM was 370 mgI/kg for the 120-kVp and 296 mgI/kg for the 80-kVp protocol; the 120- and the 80-kVp images were reconstructed with filtered back-projection (FBP) and SAFIRE, respectively. We compared effective dose (ED), CT attenuation, image noise, and contrast-to-noise ratio (CNR) of two protocols. We also scored arterial contrast, sharpness, depiction of small arteries, visibility near skull base/clip, and overall image quality on a four-point scale. RESULTS: ED was 62% lower at 80- than 120-kVp (0.59 ± 0.06 vs 1.56 ± 0.13 mSv, p < 0.01). CT attenuation of the internal carotid artery (ICA) and middle cerebral artery (MCA) was significantly higher on 80- than 120-kVp (ICA: 557.4 ± 105.7 vs 370.0 ± 59.3 Hounsfield units (HU), p < 0.01; MCA: 551.9 ± 107.9 vs 364.6 ± 62.2 HU, p < 0.01). The CNR was also significantly higher on 80- than 120-kVp (ICA: 46.2 ± 10.2 vs 36.9 ± 7.6, p < 0.01; MCA: 45.7 ± 10.0 vs 35.7 ± 9.0, p < 0.01). Visibility near skull base and clip was not significantly different (p = 0.45). The other subjective scores were higher with the 80- than the 120-kVp protocol (p < 0.05). CONCLUSION: The 80-kVp acquisition with SAFIRE yields better image quality for BSCTA and substantial reduction in the radiation and CM dose compared to the 120-kVp with FBP protocol.

A case of sclerosing angiomatoid nodular transformation:the correlation between imaging and pathological findings.

A 53-year-old woman was referred to our hospital with a 40-mm splenic tumor, which was detected incidentally on abdominal computed tomography during hospitalization for pyelonephritis. The tumor was hypointense on T2-weighted imaging and gradually enhanced on dynamic study. The tumor increased in size over a six-month period. Since we could not exclude splenic malignancy, we performed laparoscopic partial splenectomy. Histological examination revealed multiple angiomatoid nodules with three distinct vessel types. Pathologically, the tumor was diagnosed as a sclerosing angiomatoid nodular transformation (SANT). We then examined the correlation between the imaging and pathological findings, and performed a review of previous reports, concluding that contrast-enhanced MRI was the most useful modality for diagnosing SANT.

Sublingual immunotherapy for cedar pollinosis possibly triggers eosinophilic esophagitis.

Sublingual immunotherapy (SLIT) is an effective and popular treatment for cedar pollinosis. Although SLIT can cause allergic side effects, eosinophilic esophagitis (EoE) is a lesser-known side effect of SLIT. A 26-year-old male with cedar pollinosis, wheat-dependent exercise-induced anaphylaxis, and food allergies to bananas and avocados presented with persistent throat itching, difficulty swallowing, heartburn, and anterior chest pain 8 days after starting SLIT for cedar pollinosis. Laboratory examination showed remarkably elevated eosinophils, and esophagogastroduodenoscopy revealed linear furrows in the entire esophagus. Histological examination of an esophageal biopsy specimen revealed high eosinophil levels. The patient was strongly suspected with EoE triggered by SLIT. The patient was advised to switch from the swallow to the spit method for SLIT, and the symptoms associated with SLIT-triggered EoE were reduced after switching to the spit method. This case highlights the importance of recognizing SLIT-triggered EoE as a potential side effect of SLIT for cedar pollinosis, especially with the increasing use of SLIT in clinical practice. EoE can occur within a month after initiating SLIT in patients with multiple allergic conditions, as observed in our case. Furthermore, the spit method should be recommended for patients who experience SLIT-triggered EoE before discontinuing SLIT.

Detection of flat colorectal polyps at screening CT colonography in comparison with conventional polypoid lesions.

BACKGROUND: Although the screening of small, flat polyps is clinically important, the role of CT colonography (CTC) screening in their detection has not been thoroughly investigated. PURPOSE: To evaluate the detection capability and usefulness of CTC in the screening of flat and polypoid lesions by comparing CTC with optic colonoscopy findings as the gold standard. MATERIAL AND METHODS: We evaluated the CTC detection capability for flat colorectal polyps with a flat surface and a height not exceeding 3 mm (n = 42) by comparing to conventional polypoid lesions (n = 418) according to the polyp diameter. Four types of reconstruction images including multiplanar reconstruction, volume rendering, virtual gross pathology, and virtual endoscopic images were used for visual analysis. We compared the abilities of the four reconstructions for polyp visualization. RESULTS: Detection sensitivity for flat polyps was 31.3%, 44.4%, and 87.5% for lesions measuring 2-3 mm, 4-5 mm, and ≥6 mm, respectively; the corresponding sensitivity for polypoid lesions was 47.6%, 79.0%, and 91.7%. The overall sensitivity for flat lesions (47.6%) was significantly lower than polypoid lesions (64.1%). Virtual endoscopic imaging showed best visualization among the four reconstructions. Colon cancers were detected in eight patients by optic colonoscopy, and CTC detected colon cancers in all eight patients. CONCLUSION: CTC using 64-row multidetector CT is useful for colon cancer screening to detect colorectal polyps while the detection of small, flat lesions is still challenging.

A case of malignant hypertension with multi-organ injury.

A 33-year-old woman visited our hospital due to visual loss. Her BP was 280/150 mm Hg and pulse rate was 111 beats per minute. A urinalysis showed protein in urine, suggesting kidney injury. A transthoracic echocardiography showed left ventricular hypertrophy. A Cardiac magnetic resonance imaging suggested left ventricular endocardial edema or inflammation. Ophthalmoscopy showed optic disc edema and hard exudates in both eyes. A brain MRI showed multiple high-intensity areas at the pons and white matter of the cerebrum and cerebellum. Although the patient had malignant hypertension, she was successfully treated by medication.

Multidetector computed tomography evaluation of coronary plaque morphology in patients with stable angina.

The purpose of this study was to evaluate the morphology and composition of atherosclerotic coronary plaques in patients with stable coronary artery disease by 64-row multidetector computed tomography (CT) angiography. A total of 56 patients were divided into an ischemia-related (n = 31) and a nonischemia-related lesion group (n = 25) based on myocardial perfusion scintigraphy, invasive angiography, and 1-year clinical follow-up. The 56 lesions detected by CT imaging were analyzed; the severity of stenosis, the lesion length, CT attenuation value, and calcium deposition of the plaques were evaluated. Clinical characteristics and CT findings were compared using univariate and multivariate logistic regression analyses. Ischemia-related lesions exhibited a greater severity of coronary stenosis, were longer (17.8 ± 8.5 vs 9.1 ± 3.9 mm), and had a higher CT attenuation value (101.7 ± 36.7 vs 81.6 ± 32.6 HU) and larger calcium deposition. By univariate logistic analysis, severity of stenosis, lesion length, CT attenuation value, and calcium deposition were significantly associated with ischemia-related plaques. The odds ratio (OR) of these parameters was 6.874 (P = 0.007), 1.371 (P = 0.001), 1.018 (P = 0.044), and 5.400 (P = 0.004), respectively. By multivariate logistic analysis, the severity of stenosis and lesion length were significantly associated with ischemia-related plaques (OR 7.588, P = 0.036 and OR 1.365, P = 0.003, respectively). In conclusion, coronary CT angiography is useful for the identification of morphological differences between ischemia-related and nonischemia-related plaques in patients with stable coronary artery disease.

Left Ventricular Apical Thrombus Mimicking Hypertrabeculation.

A 73-year-old man visited our hospital due to dyspnea and epigastralgia. His plasma brain natriuretic peptide level was 1,205 pg/mL. A 12-lead electrocardiogram showed ST segment depression in leads I, V5, and V6. Transthoracic echocardiography showed dilatation and severe hypokinesis of the left ventricle. Hypertrabeculation was observed at the septum, apex, and lateral wall. Delayed enhancement of cardiac magnetic resonance imaging revealed a relatively low uptake of contrast agent at a large apical trabecula. After treatment with diuretics, follow-up echocardiography showed the disappearance of the controversial apical trabecula, which was later confirmed to have been a thrombus.

Reduction of contrast material volume in 3D angiography of the brain using MDCT.

OBJECTIVE: Our aim was to investigate the image quality of MDCT angiography of the brain at a low-volume of contrast material. SUBJECTS AND METHODS: One hundred patients were randomly assigned to one of two groups, which differed with regard to contrast material volume and subsequent saline bolus: group A was administered 300 mg I/mL, 50 mL at an injection rate of 3.0 mL/s followed by a 20-mL saline bolus at 3.0 mL/s; group B was administered 300 mg I/mL, 100 mL at 3.0 mL/s. Of 100 total patients, 82 were analyzed: 45 in group A and 37 in group B. The attenuation and visualization of intracranial arteries were compared between the two groups. The regions of interest (ROIs) were drawn throughout the data set: internal carotid artery (ROI 1), anterior cerebral artery (ROI 2), middle cerebral artery (ROI 3), vertebral artery (ROI 4), basilar artery (ROI 5), and posterior cerebral artery (ROI 6). The differences were assessed with a Student's t test. Two readers evaluated images and graded vascular delineation of intracranial arteries by consensus. RESULTS: Eighty-two patients were investigated strictly according to the study protocol and were included in the per-protocol population. There were no statistically significant differences between the two groups in average attenuation (p = 0.21) and visual analysis (p = 0.84). CONCLUSION: When performing 3D angiography of the brain using 16-MDCT, the use of a 20-mL saline flush allows reduction of contrast material from 100 mL to 50 mL if all other factors are unchanged.

Late-gadolinium enhancement in a subject with normal left ventricular function.

A 27-year-old man visited our hospital after experiencing palpitations. His 12-lead electrocardiogram and chest radiograph were unremarkable. Blood test results showed normal plasma brain natriuretic peptide level (<5.8 pg/mL). Transthoracic echocardiography revealed normal left ventricular structure and function by demonstrating left ventricular wall thickness of 10 mm, end-diastolic dimension of 46 mm, end-systolic dimension of 31 mm, and ejection fraction of 64%. Pulsed-wave Doppler echocardiography demonstrated normal E/e' ratio of 7.5. Cardiac magnetic resonance imaging showed normal coronary artery. However, there was massive late-gadolinium enhancement at the mid-layer wall, suggesting massive left ventricular fibrosis. This case reveals that left ventricular function may be normal even in massive late-gadolinium enhancement. Pathophysiology other than fibrosis might have contributed to this specific finding in late-gadolinium enhancement.

Demonstration of the Adamkiewicz artery in patients with descending or thoracoabdominal aortic aneurysm: optimization of contrast-medium application for 64-detector-row CT angiography.

Our aim was to prospectively investigate the contrast agent concentration and the infusion rate to obtain optimal images of the Adamkiewicz artery by 64-row MDCT. Eighty patients were divided into four groups based on the following protocol: A, 100 mL of 300 mg I/mL at 5.0 mL/s; B, 100 mL of 350 mg I/mL at 5.0 mL/s; C, 100 mL of 300 mg I/mL at 3.5 mL/s; D, 100 mL of 350 mg I/mL at 3.5 mL/s. Quantitative evaluation was performed by calculating mean aortic attenuation value from T5 to L3 level. Visual evaluation of the Adamkiewicz artery was also performed. In a quantitative evaluation, the rapid injection (A, 473.4 +/- 82.6 HU; B, 506.7 +/- 71.9 HU) was significantly superior to the slow injection (C, 371.3 +/- 65.1 HU; D, 391.5 +/- 60.8 HU). In a visual evaluation, the Adamkiewicz artery was assessable in 15 of 20 (75%), 16 of 20 (80%), 9 of 20 (45%), and 10 of 20 (50%) patients in groups A, B, C, and D, respectively. The injection protocol of 1.75 g iodine/s provides both the adequate aortic attenuation of more than 450 HU to assess the Adamkiewicz artery and the best visualization of the Adamkiewicz artery in 64-row MDCT.

[A patient with an angiomyolipoma of the liver in whom the course of enlargement could be confirmed].

The patients was a 54-year-old woman. In the liver, a high-echo phyma was detected. The lesion increased from 5 to 23mm over 2 years and 4 months. On CT and MRI, it was difficult to differentiate the phyma from hepatocellular carcinoma. However, angiography revealed early outflow to the hepatic vein. In the late CTHA phase of angio-CT, there was no ring-like dark staining reaction (corona), as observed in hepatocellular carcinoma patients, outside the tumor. Hepatectomy was performed, suggesting angiomyolipoma. The course of enlargement could be followed-up, and we present findings that may be useful for differentiating this tumor from hepatocellular carcinoma.

Application of 80-kVp scan and raw data-based iterative reconstruction for reduced iodine load abdominal-pelvic CT in patients at risk of contrast-induced nephropathy referred for oncological assessment: effects on radiation dose, image quality and renal function.

OBJECTIVE: To evaluate the image quality, radiation dose, and renal safety of contrast medium (CM)-reduced abdominal-pelvic CT combining 80-kVp and sinogram-affirmed iterative reconstruction (SAFIRE) in patients with renal dysfunction for oncological assessment. METHODS: We included 45 patients with renal dysfunction (estimated glomerular filtration rate  <45 ml per min per 1.73 m2) who underwent reduced-CM abdominal-pelvic CT (360 mgI kg-1, 80-kVp, SAFIRE) for oncological assessment. Another 45 patients without renal dysfunction (estimated glomerular filtration rate >60 ml per lmin per 1.73 m2) who underwent standard oncological abdominal-pelvic CT (600 mgI kg-1, 120-kVp, filtered-back projection) were included as controls. CT attenuation, image noise, and contrast-to-noise ratio (CNR) were compared. Two observers performed subjective image analysis on a 4-point scale. Size-specific dose estimate and renal function 1-3 months after CT were measured. RESULTS: The size-specific dose estimate and iodine load of 80-kVp protocol were 32 and 41%,, respectively, lower than of 120-kVp protocol (p < 0.01). CT attenuation and contrast-to-noise ratio of parenchymal organs and vessels in 80-kVp images were significantly better than those of 120-kVp images (p < 0.05). There were no significant differences in quantitative or qualitative image noise or subjective overall quality (p > 0.05). No significant kidney injury associated with CM administration was observed. CONCLUSION: 80-kVp abdominal-pelvic CT with SAFIRE yields diagnostic image quality in oncology patients with renal dysfunction under substantially reduced iodine and radiation dose without renal safety concerns. Advances in knowledge: Using 80-kVp and SAFIRE allows for 40% iodine load and 32% radiation dose reduction for abdominal-pelvic CT without compromising image quality and renal function in oncology patients at risk of contrast-induced nephropathy.

In vitro evaluation of metallic coronary artery stents with sub-millimeter multi-slice computed tomography using an ECG-gated cardiac phantom: relationship between in-stent visualization and stent type.

The aim of this experimental study was to investigate visualization of various coronary artery stents with sub-millimeter multi-slice spiral computed tomography (MSCT) using a cardiac physical phantom. Four 3-mm stents of various designs were implanted in tubes with an inner diameter of 3 mm to simulate coronary artery. Stents were placed on a cardiac phantom and scanned at different heart rates. Retrospective ECG-gated adaptive segmental reconstruction technique was employed. Profile curves across longitudinal curved planar reconstruction images of the stents were generated. From the profile curve, the full width at half maximum was defined as the stent lumen index. The effect of heart rate and stent type on the stent lumen index was evaluated. Visual evaluation for each stent at various heart rates was also performed. The heart rate had no significant effect on in-stent visualization. However, in-stent visualization differed significantly for the various stent types for both profile curve analysis and visual evaluation (the Tukey-Kramer multiple comparisons test). Multiple regression analysis indicated that strut thickness, especially minimal strut thickness, was the significant influencing factor for the in-stent visualization. On the basis of four stent models examined it would appear that visualization of the coronary stent lumen varies depending on the stent type, but not on the heart rate. Stents with slim struts are preferable for in-stent evaluation with multi-slice spiral computed tomography.

Cardiac 16-MDCT for anatomic and functional analysis: assessment of a biphasic contrast injection protocol.

OBJECTIVE: The purpose of this study was to determine the optimal contrast injection protocol for clear delineation of the endocardial and epicardial contours and coronary vessels in anatomic and functional imaging with cardiac 16-MDCT. SUBJECTS AND METHODS: Thirty-eight patients were allocated to three groups according to contrast injection protocol: a long-duration biphasic protocol in which diluted contrast material was used in the latter phase (protocol A, 13 patients); a uniphasic protocol with saline flush (protocol B, 12 patients); a uniphasic protocol without a flush (protocol C, 13 patients). Six regions of interest were drawn within the left ventricle (LV), right ventricle (RV), and interventricular septum along the z-axis. Mean ventricular attenuation, mean difference between maximum and minimum ventricular attenuation, and ventricular-myocardial contrast-to-noise ratio (CNR) were calculated. Attenuation and visualization of the coronary vessels also were compared. RESULTS: The difference between maximum and minimum RV attenuation was significantly smaller in group A (58.1 H) than in groups B (179.5 H) and C (157.0 H). RV-myocardial CNR was significantly higher in group A (9.0) than in group B (5.5). The mean LV attenuation, difference between maximum and minimum LV attenuation, and LV-myocardial CNR were not significantly different among three groups. In protocol A, both endocardial and epicardial contours were clearly delineated, and cardiac functional analysis was feasible in all cases. Average attenuation and visualization of the coronary vessels were not significantly different among groups. The diagnostic accuracies in detection of coronary stenosis were 92%, 93%, and 91%, respectively, for protocols A, B, and C. CONCLUSION: The long-duration contrast injection protocol with diluted contrast material is optimal for assessing the coronary vessels and cardiac function.