Sedat Alibek

High-pitch spiral computed tomography: effect on image quality and radiation dose in pediatric chest computed tomography.

Objectives:Computed tomography (CT) is considered the method of choice in thoracic imaging for a variety of indications. Sedation is usually necessary to enable CT and to avoid deterioration of image quality because of patient movement in small children. We evaluated a new, subsecond high-pitch scan mode (HPM), which obviates the need of sedation and to hold the breath. Material and Methods:A total of 60 patients were included in this study. 30 patients (mean age, 14 ± 17 month; range, 0–55 month) were examined with a dual source CT system in an HPM. Scan parameters were as follows: pitch = 3.0, 128 × 0.6 mm slice acquisition, 0.28 seconds gantry rotation time, ref. mAs adapted to the body weight (50–100 mAs) at 80 kV. Images were reconstructed with a slice thickness of 0.75 mm. None of the children was sedated for the CT examination and no breathing instructions were given. Image quality was assessed focusing on motion artifacts and delineation of the vascular structures and lung parenchyma. Thirty patients (mean age, 15 ± 17 month; range, 0–55 month) were examined under sedation on 2 different CT systems (10-slice CT, n = 18; 64-slice CT, n = 13 patients) in conventional pitch mode (CPM). Dose values were calculated from the dose length product provided in the patient protocol/dose reports, Monte Carlo simulations were performed to assess dose distribution for CPM and HPM. Results:All scans were performed without complications. Image quality was superior with HPM, because of a significant reduction in motion artifacts, as compared to CPM with 10- and 64-slice CT. In the control group, artifacts were encountered at the level of the diaphragm (n = 30; 100%), the borders of the heart (n = 30; 100%), and the ribs (n = 20; 67%) and spine (n = 6; 20%), whereas motion artifacts were detected in the HPM-group only in 6 patients in the lung parenchyma next to the diaphragm or the heart (P < 0,001). Dose values were within the same range in the patient examinations (CPM, 1.9 ± 0.6 mSv; HPM, 1.9 ± 0.5 mSv; P = 0.95), although z-overscanning increased with the increase of detector width and pitch-value. Conclusion:High-pitch chest CT is a robust method to provide highest image quality making sedation or controlled ventilation for the examination of infants, small or uncooperative children unnecessary, whereas maintaining low radiation dose values.

Contrast-enhanced T1-weighted fluid-attenuated inversion-recovery BLADE magnetic resonance imaging of the brain: an alternative to spin-echo technique for detection of brain lesions in the unsedated pediatric patient?

RATIONALE AND OBJECTIVES We compared contrast-enhanced T1-weighted magnetic resonance (MR) imaging of the brain using different types of data acquisition techniques: periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER, BLADE) imaging versus standard k-space sampling (conventional spin-echo pulse sequence) in the unsedated pediatric patient with focus on artifact reduction, overall image quality, and lesion detectability. MATERIALS AND METHODS Forty-eight pediatric patients (aged 3 months to 18 years) were scanned with a clinical 1.5-T whole body MR scanner. Cross-sectional contrast-enhanced T1-weighted spin-echo sequence was compared to a T1-weighted dark-fluid fluid-attenuated inversion-recovery (FLAIR) BLADE sequence for qualitative and quantitative criteria (image artifacts, image quality, lesion detectability) by two experienced radiologists. Imaging protocols were matched for imaging parameters. Reader agreement was assessed using the exact Bowker test. RESULTS BLADE images showed significantly less pulsation and motion artifacts than the standard T1-weighted spin-echo sequence scan. BLADE images showed statistically significant lower signal-to-noise ratio but higher contrast-to-noise ratios with superior gray-white matter contrast. All lesions were demonstrated on FLAIR BLADE imaging, and one false-positive lesion was visible in spin-echo sequence images. CONCLUSION BLADE MR imaging at 1.5 T is applicable for central nervous system imaging of the unsedated pediatric patient, reduces motion and pulsation artifacts, and minimizes the need for sedation or general anesthesia without loss of relevant diagnostic information.

Reduction of X-ray induced DNA double-strand breaks in blood lymphocytes during coronary CT angiography using high-pitch spiral data acquisition with prospective ECG-triggering.

Objectives:Purpose of this study was to compare the effect of high-pitch spiral data acquisition with prospective electrocardiography (ECG)-triggering on the x-ray induced DNA damages to blood lymphocytes with commonly used low-pitch spiral scans. Materials and Methods:Thirty four patients underwent coronary computed tomography angiography either using high-pitch spiral data acquisition (n = 15; dual-source computed tomography (CT) scanner, 38.4 mm collimation, 100–120 kV, 320–456 mAs/rotation, pitch value 3.2–3.4) or using a low-pitch protocol (n = 19; dual-source CT scanner, 19.2 mm collimation, 120 kV, 330–438 mAs/rotation, pitch 0.2–0.39, ECG-based tube current modulation). Blood samples were obtained before and 30 minutes after CT. Lymphocytes were isolated, stained against the phosphorylated histone variant &ggr;H2AX, and DNA double-strand breaks (DSBs) were visualized using fluorescence microscopy. Radiation dose to the blood was estimated by relating in vivo DSB levels to values of in vitro irradiated blood samples (50 mGy). Dose length product was registered as provided by the patient protocol. Results:Total dose length product ranged from 101 to 237 (median 112) mGy cm in high-pitch and from 524 to 1283 (median 1025) mGy cm in low-pitch scans (P < 0.0001). The median CT induced DSB level 30 minutes after exposure was significantly lower after high-pitch (0.04 DSBs/cell, range 0.02–0.10 DSBs/cell) compared with low-pitch scans (0.39 DSBs/cell, 0.22–0.71 DSBs/cell, P < 0.0001). Both DSB levels and radiation dose to the blood showed a significant correlation to the dose length product (r = 0.82, P < 0.0001). The radiation dose to the blood was significantly reduced in the high-pitch (median 3.1, range 2.0–8.1 mGy) compared with the low-pitch group (median 26.9; range 14.2–44.9 mGy, P < 0.0001). Conclusions:Prospectively ECG-triggered high-pitch spiral data acquisition can considerably reduce the radiation dose to the blood in coronary CT angiography as compared with low pitch protocols.

Value of Dual Energy Computed Tomography for detection of myocardial iron deposition in Thalassaemia patients: Initial experience

PURPOSE The aim of our study was to compare the value of cardiac DECT (cDECT) for detection of myocardial iron deposition to T2*w cardiac MRI (cMRI). MATERIAL AND METHODS Nineteen patients with clinical history of Thalassaemia underwent T2*-weighted cardiac MRI (cMRI) with a 1.5 T MR scanner (MAGNETOM Symphony, Siemens Medical Solutions, Erlangen, Germany) and cardiac dual energy CT (cDECT) with a DSCT scanner (SOMATOM Definition, Siemens Medical Solutions, Erlangen, Germany) on the same day. HU values obtained from cDECT scans and T2*-values from cMRI were statistically correlated to calculate significance levels. Table times were measured for both cDECT and cMRI and compared. Patients were asked to grade their subjective comfort during the examination. RESULTS In all patients cDECT scans were successfully acquired. HU values of septal muscle correlated strongly with T2*-values, whereas no correlation was found for paraspinal muscle. Table time was significantly shorter for cDECT compared to cMRI (mean: 3.7 min vs. 11.2 min) and subjective patient comfort was rated comfortable for cDECT and average to poor for cMRI. Mean radiation dose was 0.71 mSv. CONCLUSION cDECT scans seem to be possible for evaluation of myocardial iron load in pediatric Thalassaemia patients.

T2-weighted MRI of the upper abdomen: comparison of four fat-suppressed T2-weighted sequences including PROPELLER (BLADE) technique.

RATIONALE AND OBJECTIVES The aim of this study was to compare four different fat-suppressed T2-weighted sequences with different techniques with regard to image quality and lesion detection in upper abdominal magnetic resonance imaging (MRI) scans. MATERIALS AND METHODS Thirty-two consecutive patients referred for upper abdominal MRI for the evaluation of various suspected pathologies were included in this study. Different T2-weighted sequences (free-breathing navigator-triggered turbo spin-echo [TSE], free-breathing navigator-triggered TSE with restore pulse (RP), breath-hold TSE with RP, and free-breathing navigator-triggered TSE with RP using the periodically rotated overlapping parallel lines with enhanced reconstruction technique [using BLADE, a Siemens implementation of this technique]) were used on all patients. All images were assessed independently by two radiologists. Assessments of motion artifacts; the edge sharpness of the liver, pancreas, and intrahepatic vessels; depictions of the intrahepatic vessels; and overall image quality were performed qualitatively. Quantitative analysis was performed by calculation of the signal-to-noise ratios for liver tissue and gallbladder as well as contrast-to-noise ratios of liver to spleen. RESULTS Liver and gallbladder signal-to-noise ratios as well as liver to spleen contrast-to-noise ratios were significantly higher (P < .05) for the BLADE technique compared to all other sequences. In qualitative analysis, the severity of motion artifacts was significantly lower with T2-weighted free-breathing navigator-triggered BLADE sequences compared to other sequences (P < .01). The edge sharpness of the liver, pancreas, and intrahepatic vessels; depictions of the intrahepatic vessels; and overall image quality were significantly better with the BLADE sequence (P < .05). CONCLUSION The T2-weighted free-breathing navigator-triggered TSE sequence with the BLADE technique is a promising approach for reducing motion artifacts and improving image quality in upper abdominal MRI scans.

Diffusion Weighted Imaging of Pediatric and Adolescent Malignancies with Regard to Detection and Delineation: Initial Experience2

RATIONALE AND OBJECTIVE To assess the value of diffusion weighted imaging (DWI) magnetic resonance imaging (MRI) in pediatric and adolescent tumor patients with focus on detection and delineation of malignant tumors of the central nervous system, chest, abdomen, and musculoskeletal system. MATERIALS AND METHODS Twenty-nine pediatric and adolescent patients (17 males, 12 females, age, 2 months-20 years, mean age: 8.9 years) with clinically suspected malignant tumors were examined with use of a 1.5-T MR scanner with open bore design without sedation or general anesthesia. DWI images were acquired with a single-shot echo planar imaging (EPI) sequence in free breathing with b-values of 0, 500, and 1000 mm/s(2). Images were assessed by two readers in consensus. Artifacts in DWI were graded as not relevant, acceptable, or nondiagnostic. DWI/apparent diffusion coefficient maps were correlated with T1-weighted post-contrast images, and the detectability and correct delineation of the tumors were graded using a three grade scale. RESULTS Free-breathing DWI was successfully performed in all patients. In 27 patients, no relevant artifacts were observed; acceptable artifacts were seen in two patients. In all patients, malignancies were detected both on DWI and T1-weighted gadolinium images. Detection and delineation of tumors were possible in all cases with both sequences; T1-weighted gadolinium imaging was superior to DWI in only three patients. Additionally, small diffusion restricted lymph nodes were detected in three patients. CONCLUSION DWI is reliable for the accurate detection and delineation of malignant pediatric and adolescent tumors.

Dose Reduction in Pediatric Computed Tomography with Automated Exposure Control

RATIONALE AND OBJECTIVES Since the introduction of computed tomographic (CT) imaging in the 1970s, the number of examinations has increased steadily. CT imaging is an essential part of routine workup in diagnostic radiology. The great advantage of multidetector computed tomography is the acquisition of a large amount of data in a short time period, thus speeding up diagnostic procedures. To protect patients from unnecessary radiation exposure, different approaches have been developed. In this study, the efficacy of automated exposure control (AEC) software in multidetector CT imaging with a focus on dose reduction in pediatric examinations was assessed. MATERIALS AND METHODS Between August 2004 and September 2005, a total of 71 children (40 male, 31 female; age range, 2-13 years; mean age, 7.2 years) were examined using a multisource CT scanner. Three different regions (chest, upper abdomen, and pelvis) were examined. Overall image quality was assessed with a subjective scale (1 = excellent, 2 = diagnostic, 3 = nondiagnostic). For all examinations, AEC was used. From the scanners patient protocol, dose-length product, volume CT dose index, and tube current-time product were calculated for each examination. RESULTS With AEC, a mean dose reduction of 30.6% was calculated. Images were rated as excellent (n = 39) or diagnostic (n = 32). Nondiagnostic image quality was not seen. Dose-length product and volume CT dose index were reduced by 30.4% and 29.5%, respectively. Overall, a mean dose reduction of 30.1% of the effective dose (5.8 ± 3.1 vs 8.4 ± 4.6 mSv) was achieved (P < .001). CONCLUSIONS With AEC software, a mean dose reduction of 30% without any loss in diagnostic image quality is possible.

Calcifying tendonitis of the shoulder joint : predictive value of pretreatment sonography for the response to low-dose radiotherapy.

Background and Purpose:Calcifying tendonitis is a degenerative inflammatory joint disorder. Pain relief can be successfully achieved with low-dose radiotherapy. It is actually unknown which types of calcifying tendonitis respond to radiotherapy and which do not. The authors tried to get predictive objectives for the response to radiotherapy on the basis of different morphological patterns of calcifications evaluated by X-ray and ultrasound.Patients and Methods:Between August 1999 and September 2002, a total of 102 patients with 115 painful shoulder joints underwent low-dose radiotherapy. At the beginning of radiotherapy, every shoulder joint was examined with a radiograph in two planes. In addition, sonography was performed before and during therapy. This examination was repeated 6 and 18 months after irradiation. Radiotherapy consisted of two series with a total dose of 6.0 Gy. 29 joints with calcifying tendonitis could be further divided using the sonographic and radiographic classification according to Farin and Gärtner, respectively.Results:Pain relief was achieved in 94/115 joints (82%) at a follow-up of 18 months (median). A different response to radiotherapy was found using the sonographic classification of Farin: calcifying tendonitis type III (n = 18) responded well in contrast to a significantly worse result in type I (n = 11). The radiologic classification did not provide a predictive value.Conclusion:Sonographic classification of calcifying tendonitis is predictive for the outcome after radiotherapy. Especially patients with Farin type III calcification will benefit from low-dose radiotherapy.Hintergrund und Ziel:Die Tendinosis calcarea ist eine degenerativ-entzündliche Gelenkerkrankung, bei der zur Schmerzlinderung auch die niedrigdosierte Strahlentherapie erfolgreich eingesetzt wird. Bisher ist nicht bekannt, welche Formen der Tendinosis calcarea auf die Radiotherapie ansprechen. Deshalb versuchten die Autoren, aufgrund der unterschiedlichen morphologischen Verkalkungsmuster im Ultraschall und Röntgenbild eine prädiktive Aussage zum Therapieansprechen zu treffen.Patienten und Methodik:Von August 1999 bis September 2002 wurden insgesamt 102 Patienten mit 115 symptomatischen Schultergelenken behandelt (Tabelle 1). Neben einer konventionellen Röntgenaufnahme des Schultergelenks in zwei Ebenen wurden alle Schultergelenke vor und unter Radiotherapie sowie 6 und 18 Monate nach Therapieende sonographisch untersucht. Die Strahlentherapie umfasste zwei Behandlungsserien bis zu einer Gesamtdosis von 6,0 Gy. Bei 29 Schultergelenken mit Tendinosis calcarea erfolgte die Subtypisierung hinsichtlich des Verkalkungstyps sonographisch nach Farin sowie röntgenologisch nach Gärtner (Tabelle 4).Ergebnisse:Insgesamt trat bei 94/115 Schultergelenken (82%) nach 18-monatiger Verlaufskontrolle eine Beschwerdebesserung ein. Bei der sonographischen Klassifizierung fand sich ein unterschiedliches Therapieansprechen: Die Tendinosis calcarea Typ Farin III (n = 18) sprach sehr gut auf die Therapie an (Abbildung 1), Typ Farin I (n = 11) zeigte ein signifikant schlechteres Therapieansprechen (Abbildung 2). Mit der röntgenologischen Subklassifizierung konnte keine prädiktive Aussage getroffen werden (Tabelle 3).Schlussfolgerung:Die Subtypisierung der Tendinosis calcarea im Ultraschall nach Farin ermöglicht eine genauere prädiktive Aussage bezüglich des Ansprechens auf eine niedrigdosierte Strahlentherapie. Zukünftig sollten inbesondere Patienten mit einem Verkalkungstyp III einer Strahlentherapie zugeführt werden.

Dual-echo TFE MRI for the assessment of myocardial iron overload in beta-thalassemia major patients.

PURPOSE Cardiac failure due to myocardial iron overload is the most common cause of death in beta-thalassemia patients. Multi/ two echo times-turbo field echo (TE-TFE) magnetic resonance imaging (MRI) is considered the gold standard technique in the evaluation of myocardial iron accumulation. However, multi TE-TFE technique is not available in all scanners. The aim of our study was to show the role of black blood dualecho cardiac triggered TFE in the assessment of myocardial iron overload. MATERIALS AND METHODS Sixteen beta-thalassemia major patients (10 males) with a mean age of 19 years who were receiving parenteral deferoxamine and oral deferiprone treatment were included in this study. Baseline measurement of myocardial T2* values were < 20 ms in all patients. Cardiac MRI was performed after 6 months, 12 months, and 18 months with the same technique. RESULTS The average baseline value of T2* was 8.2 +/- 3.6 ms. After treatment of combined deferoxamine and deferiprone, the average measurements of myocardial T2* at 6, 12, and 18 months were 11.3 +/- 6.0, 13.6 +/- 7.5, and 15.7 +/- 7.4 ms, respectively (P < 0.05). The basal ejection fraction (EF) value was 49 +/- 8.7%. The EFs were 54.4 +/- 11% at 6 months, 54.8 +/- 6.9% at 12 months, and 58.6 +/- 3.6% at 18 months of followup (P > 0.05). CONCLUSION Cardiac MRI with dual TE-TFE technique can be used to determine myocardial iron accumulation and response to the chelation treatment.

Incidental findings of cardiac MSCT: Who might benefit from scanning the entire thorax on Ca score imaging?

PURPOSE We aimed to report incidental noncoronary findings of coronary MSCT angiography and to evaluate the feasibility of scanning the entire thorax on Ca score imaging. METHODS 514 patients underwent cardiac MSCT. Instead of scanning just the heart, 124 of them were scanned extensively from the lung apex to the base in order to evaluate the entire thorax for additional findings. Furthermore, we calculated dose length product (DLP) in order to determine mean increase of radiation exposure resulting from lengthened scan field. RESULTS Coronary artery disease were established in 122 patients (24%) and 273 noncoronary findings were identified in 189 patients (37%). 37 pulmonary nodules (PN) > or =5 mm, 6 of which were over the level of pulmonary trunk, were detected. The mean age (62+/-8 vs.49+/-10, respectively; p<0.0001) and the smoking rate (74% vs. 56%, respectively; p<0.05) of the patients with PN were significantly higher than subjects without PN. All patients with PN over the level of pulmonary artery were smokers >50 of age. On Ca score imaging, radiation exposure of widely scanned group was significantly higher than the others (221.3+/-35.2 mGy cm vs.145.3+/-11.7 mGy cm of DLP, respectively; p<0.0001). CONCLUSION Since MSCT data contain also information about the other structures in the thorax, the images should be evaluated by radiologist in addition to cardiologist. It seems reasonable to scan the entire thorax on Ca score imaging for smokers over 50 in order to detect pulmonary nodules having malignancy potential.