Wolfgang Wuest

Skeletal SPECT/CT of the peripheral extremities.

OBJECTIVE Hybrid cameras that combine SPECT and helical CT can be used to correlate scintigraphic information with morphologic information in one imaging session. The purpose of this study was to investigate, in comparison with the value of scintigraphy and SPECT alone, the incremental diagnostic value of skeletal SPECT/CT in the care of patients with pain of the extremities. MATERIALS AND METHODS Seventy-one patients without cancer who had pain in the extremities underwent three-phase bone scintigraphy and SPECT/CT of either the upper (n = 20) or the lower (n = 51) extremities. Planar scintigraphic and SPECT images and planar scintigraphic and SPECT/CT images were interpreted independently from each other. The findings were classified into the following diagnostic categories: normal, trauma, tumor, osteomyelitis, and osteoarthritis. RESULTS Four patients had no abnormal bone metabolism or CT abnormality in the extremities. Among 34 lesions classified as osteoarthritis on planar and SPECT images, seven were reclassified as fracture and one as benign tumor at SPECT/CT. Of 15 lesions initially classified as osteomyelitis, four were diagnosed as osteoarthritis, four as fracture, and one as inflammation of the soft tissue only. Of eight diagnoses of fracture with the conventional approach, two were reclassified as osteomyelitis and two as osteoarthritis. In one of 10 patients with the initial diagnosis of a tumorlike lesion, the diagnosis was changed to trauma on the basis of SPECT/CT findings, and in another patient, the diagnosis was changed to osteoarthritis. Overall, SPECT/CT findings led to revision of the diagnostic category in the cases of 23 of 71 patients (p < 0.01). CONCLUSION Compared with bone scintigraphy and SPECT, the use of SPECT/CT increases diagnostic accuracy in the evaluation of orthopedic disorders affecting the extremities.

Accuracy of prospectively ECG-triggered very low-dose coronary dual-source CT angiography using iterative reconstruction for the detection of coronary artery stenosis: comparison with invasive catheterization

OBJECTIVE To evaluate the image quality and diagnostic accuracy of very low-dose computed tomography (CT) angiography (CTA) for the evaluation of coronary artery stenosis. BACKGROUND Iterative reconstruction (IR) has shown to substantially reduce image noise and hence permit the use of very low-dose data acquisition protocols in coronary CTA. METHODS Fifty symptomatic patients with an intermediate likelihood for coronary artery disease underwent coronary CTA (heart rate: 59 ± 5 bpm, prospectively ECG-triggered axial acquisition, 100 kV, 160 mAs, 2 × 128 × 0.6 mm collimation, 60 mL contrast, 6 mL/s) prior to invasive coronary angiography. CTA images were reconstructed using both standard filtered back projection (FBP) and a raw data-based IR algorithm [Sinogram Affirmed Iterative Reconstruction (SAFIRE), Siemens Healthcare]. Subjective image quality (four-point Likert scale from 0 = non-diagnostic to 3 = excellent image quality), image noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), as well as the presence of coronary stenosis >50% were independently determined by two observers. RESULTS The mean dose-length product was 46.8 ± 3.5 mGy cm (estimated effective dose 0.66 ± 0.05 mSv). IR led to significantly improved objective image quality compared with FBP (image noise: 41 ± 12 vs. 49 ± 11 HU, P < 0.0001; CNR: 16 ± 8 vs. 12 ± 4, P < 0.0001; SNR: 13 ± 7 vs. 10 ± 3, P < 0.0001). Four coronary segments were not evaluable on FBP data, whereas all segments showed diagnostic image quality with IR. To detect significant coronary stenosis, sensitivity, specificity, positive predictive value, and negative predictive value were 69% (11/16), 97% (175/180), 69% (11/16), and 97% (175/180) per vessel with FBP data sets, respectively. With IR data sets, the corresponding values were 81% (13/16), 97% (178/184), 68% (13/19), and 98% (178/181). These differences were not statistically significant (P = 0.617). CONCLUSIONS Raw data-based IR significantly improves image quality in very low-dose prospectively ECG-triggered coronary dual-source CTA when compared with standard reconstruction using FBP.

Low-Dose Dual-Source CT Angiography With Iterative Reconstruction for Coronary Artery Stent Evaluation

OBJECTIVES The purpose of this study was to evaluate the image quality and diagnostic accuracy of very low-dose, dual-source computed tomography (DSCT) angiography for the evaluation of coronary stents. BACKGROUND Iterative reconstruction (IR) leads to substantial reduction of image noise and hence permits the use of very low-dose data acquisition protocols in coronary computed tomography angiography. METHODS Fifty symptomatic patients with 87 coronary stents (diameter 3.0 ± 0.4 mm) underwent coronary DSCT angiography (heart rate, 60 ± 6 beats/min; prospectively electrocardiography-triggered axial acquisition; 80 kV, 165 mA, 2 × 128 × 0.6-mm collimation; 60 ml of contrast at 6 ml/s) before invasive coronary angiography. DSCT images were reconstructed using both standard filtered back projection and a raw data-based IR algorithm (SAFIRE, Siemens Healthcare, Forchheim, Germany). Subjective image quality (4-point scale from 0 [nondiagnostic] to 3 [excellent image quality]), image noise, contrast-to-noise ratio as well as the presence of in-stent stenosis >50% were independently determined by 2 observers. RESULTS The median dose-length product was 23.0 (22.0; 23.0) mGy · cm (median estimated effective dose of 0.32 [0.31; 0.32] mSv). IR led to significantly improved image quality compared with filtered back projection (image quality score, 1.8 ± 0.6 vs. 1.5 ± 0.5, p < 0.05; image noise, 70 Hounsfield units [62; 80 Hounsfield units] vs. 96 Hounsfield units [82; 113 Hounsfield units], p < 0.001; contrast-to-noise ratio, 11.0 [9.6; 12.4] vs. 8.0 [6.2; 9.3], p < 0.001). To detect significant coronary stenosis in filtered back projection reconstructions, the sensitivity, specificity, positive predictive value, and negative predictive value were 97% (32 of 33), 53% (9 of 17), 80% (32 of 40), and 90% (9 of 10) per patient, respectively; 89% (43 of 48), 79% (120 of 152), 57% (42 of 74), and 96% (121 of 126) per vessel, respectively; and 85% (12 of 14), 69% (51 of 73), 32% (11 of 34), and 96% (51 of 53) per stent, respectively. In reconstructions obtained by IR, the corresponding values were 100% (33 of 33), 65% (11 of 17), 85% (33 of 39), and 100% (11 of 11) per patient, respectively; 96% (46 of 48), 84% (129 of 152), 66% (47 of 71), and 98% (127 of 129) per vessel, respectively; and 100% (14 of 14), 75% (55 of 73), 44% (14 of 32), and 100% (55 of 55) per stent, respectively. These differences were not significant. CONCLUSIONS In selected patients, prospectively electrocardiography-triggered image acquisition with 80-kV tube voltage and low current in combination with IR permits the evaluation of patients with implanted coronary artery stents with reasonable diagnostic accuracy at very low radiation exposure.

Automated tube voltage selection in thoracoabdominal computed tomography at high pitch using a third-generation dual-source scanner: image quality and radiation dose performance.

ObjectivesThe objective of this study was to evaluate the radiation dose and image quality performance of thoracoabdominal examinations with an automated tube voltage selection (tube voltage adaptation), tube current modulation, and high pitch using a third-generation dual-source computed tomography (CT) compared intraindividually with 120-kV examinations with tube current modulation with special attention on clinically relevant lesions in the liver, the lungs, and extrahepatic soft tissues. Materials and MethodsThis study was approved by the institutional review board. Computed tomography of the body was performed using a third-generation dual-source system in 95 patients (mean body mass index, 25 kg/m2; range, 18–35 kg/m2). For 49 of these patients, all calculated tube settings and resulting dose values were recorded for each of the 12 gradual contrast weightings of the tube voltage adaptation algorithm. Spiral CT was performed for all patients with an intermediate weighting (grade 7) in a portal venous phase at 120 reference kV, 180 reference mAs, and pitch of 1.55. Objective image quality was assessed on the basis of contrast-to-noise ratio. Subjective image quality was assessed on the basis of clarity and sharpness of anatomical and pathological structures as well as interfering beam hardening and spiral and motion artifacts (heart, lungs, diaphragm). Previous examinations on a 64-slice scanner served as reference. ResultsAll examinations were rated good or excellent for clinical diagnosis. Automated tube voltage selection resulted in significantly lower effective radiation dose (9.5 mSv) compared with the reference (12.0 mSv; P < 0.01). Contrast-to-noise ratio and image quality of soft tissue lesions were significantly increased (P < 0.01). Motion artifacts were significantly reduced (P < 0.01). ConclusionsAutomated tube voltage adaptation combined with high-pitch protocols allows for a substantial radiation dose reduction while substantially increasing the image quality, even at large-volume exposure.

Influence of Cardiac MR Imaging on DNA Double-Strand Breaks in Human Blood Lymphocytes

PURPOSE To evaluate the ability of magnetic resonance (MR) imaging to induce deoxyribonucleic acid (DNA) damage in patients who underwent cardiac MR imaging in daily routine by using γ-H2AX immunofluorescence microscopy. MATERIALS AND METHODS This study complies with the Declaration of Helsinki and was performed according to local ethics committee approval. Informed patient consent was obtained. Blood samples from 45 patients (13 women, 32 men; mean age, 50.3 years [age range, 20-89 years]) were obtained before and after contrast agent-enhanced cardiac MR imaging. MR imaging-induced double-strand breaks (DSBs) were quantified in isolated blood lymphocytes by using immunofluorescence microscopy after staining the phosphorylated histone variant γ-H2AX. Twenty-nine patients were examined with a myocarditis protocol (group A), 10 patients with a stress-testing protocol (group B), and six patients with flow measurements and angiography (group C). Paired t test was performed to compare excess foci before and after MR imaging. RESULTS The mean baseline DSB level before MR imaging and 5 minutes after MR imaging was, respectively, 0.116 DSB per cell ± 0.019 (standard deviation) and 0.117 DSB per cell ± 0.019 (P = .71). There was also no significant difference in DSBs in these subgroups (group A: DSB per cell before and after MR imaging, respectively, 0.114 and 0.114, P = .91; group B: DSB per cell before and after MR imaging, respectively, 0.123 and 0.124, P = .78; group C: DSB per cell before and after MR imaging, respectively, 0.114 and 0.115, P = .36). CONCLUSION By using γ-H2AX immunofluorescence microscopy, no DNA DSBs were detected after cardiac MR imaging.

Attenuation-based automatic kilovolt (kV)-selection in computed tomography of the chest: Effects on radiation exposure and image quality

OBJECTIVES To evaluate an automated attenuation-based kV-selection in computed tomography of the chest in respect to radiation dose and image quality, compared to a standard 120 kV protocol. MATERIALS AND METHODS 104 patients were examined using a 128-slice scanner. Fifty examinations (58 ± 15 years, study group) were performed using the automated adaption of tube potential (100-140 kV), based on the attenuation profile of the scout scan, 54 examinations (62 ± 14 years, control group) with fixed 120 kV. Estimated CT dose index (CTDI) of the software-proposed setting was compared with a 120 kV protocol. After the scan CTDI volume (CTDIvol) and dose length product (DLP) were recorded. Image quality was assessed by region of interest (ROI) measurements, subjective image quality by two observers with a 4-point scale (3--excellent, 0--not diagnostic). RESULTS The algorithm selected 100 kV in 78% and 120 kV in 22%. Overall CTDIvol reduction was 26.6% (34% in 100 kV) overall DLP reduction was 22.8% (32.1% in 100 kV) (all p<0.001). Subjective image quality was excellent in both groups. CONCLUSION The attenuation based kV-selection algorithm enables relevant dose reduction (~27%) in chest-CT while keeping image quality parameters at high levels.

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.

Dual-Energy Computed Tomography Angiography of the Head and Neck With Single-Source Computed Tomography: A New Technical (Split Filter) Approach for Bone Removal.

ObjectivesDual-energy computed tomographic angiography (DE-CTA) has been demonstrated to improve the visualization of the head and neck vessels. The aim of this study was to test the potential of split-filter single-source dual-energy CT to automatically remove bone from the final CTA data set. Materials and MethodsDual-energy CTA was performed in 50 consecutive patients to evaluate the supra-aortic arteries, either to grade carotid artery stenosis or to rule out traumatic dissections. Dual-energy CTA was performed on a 128-slice single-source CT system equipped with a special filter array to separate the 120-kV spectrum into a high- and a low-energy spectrum for DE-based automated bone removal. Image quality of fully automated bone suppression and subsequent manual optimization was evaluated by 2 radiologists on maximum intensity projections using a 4-grade scoring system. The effect of image reconstruction with an iterative metal artifact reduction algorithm on DE postprocessing was tested using a 3-grade scoring system, and the time demand for each postprocessing step was measured. ResultsTwo patients were excluded due to insufficient arterial contrast enhancement; in the remaining 48 patients, automated bone removal could be performed successfully. The addition of iterative metal artifact reduction algorithm improved image quality in 58.3% of the cases. After manual optimization, DE-CTA image quality was rated excellent in 7, good in 29, and moderate in 10 patients. Interobserver agreement was high (&kgr; = 0.85). Stenosis grading was not influenced using DE-CTA with bone removal as compared with the original CTA. The time demand for DE image reconstruction was significantly higher than for single-energy reconstruction (42.1 vs 20.9 seconds). ConclusionsOur results suggest that bone removal in DE-CTA of the head and neck vessels with a single-source CT is feasible and can be performed within acceptable time and moderate user interaction.

Functional cardiac CT imaging: a new contrast application strategy for a better visualization of the cardiac chambers.

PURPOSE Evaluation of a new protocol for Dual-source CT contrast-enhanced cardiac imaging for better visualization of right ventricle structures. METHODS A total of 106 patients were included in this prospective, controlled study. The control group (n=53) underwent our clinics standard procedure for contrast-enhanced imaging of coronary arteries. The study group (n=53) was imaged using a protocol with the dual flow injection protocol in which the saline chaser bolus contained 20% contrast media. The images were analyzed for mean density values using defined ROIs in the septum and both ventricles. In addition the data sets were semi-quantitatively evaluated for visual delineation between right ventricle and septum. To investigate whether this new protocol influenced the visualization of coronary arteries, mean density was also measured in the right and left coronary artery. RESULTS The dual flow concept allows for a statistically significant better delineation of the septum in Dual-source cardiac computed tomography for both the quantitative and semi-quantitative analyses. Also, the dual flow concept allows for statistically relevant higher coronary attenuation. CONCLUSION Using a saline chaser containing 20% contrast medium improves septal delineation for functional ventricular analysis as well as unimpaired coronary visualization.

Skeletal SPECT/CT of the peripheral extremities -interdisciplinary approach in orthopaedic disorders-first clinical results

Bone scintigraphy, although quite sensitive to detect skeletal lesions, has a comparatively low specificity. Hybrid-cameras combining single-photon emission computed tomography (SPECT) and spiral-CT offer the opportunity to correlate scintigraphic information with high-quality visualization of morphology in one session. This may lead to an improvement in diagnostic accuracy and anatomic lesion localization. We present 11 patients, who underwent SPECT/CT of the feet (n=10) and hands (n = 1). The examinations were performed due to pain in foot or hand with the following suspected clinical diagnoses: arthrosis (n=1); fracture (n=3); osteomyelitis (n=4); reflex dystrophia (n=1); and, pain of unclear origin (n=2). All patients underwent SPECT/CT hybrid imaging using a dual-headed SPECT camera integrated with a 2-slice spiral CT scanner in one gantry. SPECT, CT, and SPECT/CT were evaluated independently from each other with respect to main diagnosis, anatomic lesion localization, and detection of a possible additional diagnosis. SPECT/CT improved lesion localization in 8 of 11 patients (73%) in comparison to SPECT alone, and in 4 of 11 patients (36%) in comparison to CT alone. Diagnostic accuracy was improved in 4 of 11 patients (36%) in comparison to either SPECT or CT alone. In conclusion, skeletal SPECT/CT improves diagnostic accuracy and lesion localization of orthopedic disorders in the feet and hands. The obtained results encouraged extensive studies to further investigate the potential gain in diagnostic accuracy brought about by SPECT/spiral-CT hybrid imaging in orthopedic disorders of the peripheral extremities.