Anna Winklehner

Automated attenuation-based tube potential selection for thoracoabdominal computed tomography angiography: improved dose effectiveness.

Purpose:To introduce a novel algorithm of automated attenuation-based tube potential selection and to assess its impact on image quality and radiation dose of body computed tomography angiography (CTA). Materials and Methods:In all, 40 patients (mean age 71 ± 11.8 years, body mass index (BMI) 25.7 ± 3.8 kg/m2, range 18.8–33.8 kg/m2) underwent 64-slice thoracoabdominal CTA (contrast material: 80 mL, 5 mL/s) using an automated tube potential selection algorithm (CAREkV), which optimizes tube-potential (70–140 kV) and tube-current (138.8 ± 18.6 effective mAs, range 106–177 mAs) based on the attenuation profile of the topogram and on the diagnostic task. Image quality was semiquantitatively assessed by 2 blinded and independent readers (scores 1: excellent to 5: nondiagnostic). Attenuation and noise were measured by another 2 blinded and independent readers. Contrast-to-noise ratio was calculated. The CT dose index (CTDIvol) was recorded and compared with the estimated CTDIvol of a standard 120 kV protocol without using the algorithm in each patient. Selected tube potentials were correlated with BMI and attenuation of the topogram. Results:Diagnostic image quality was obtained in all patients (excellent: 14; good: 21; moderate: 5; interreader agreement: &kgr; = 0.78). Mean attenuation, noise, and contrast-to-noise ratio were 260.8 ± 63.5 Hounsfield units, 15.5 ± 3.3 Hounsfield units, and 14 ± 4.2, respectively, with good to excellent agreement between readers (r = 0.50–0.99, P < 0.01 each). Automated attenuation-based tube potential selection resulted in a kV-reduction from 120 to 100 kV in 23 patients and to 80 kV in 1 patient, whereas tube potential increased to 140 kV in 1 patient. Automatically selected tube potential showed a significant correlation with both BMI (r = 0.427, P < 0.05) and attenuation of the topogram (r = 0.831, P < 0.001). CTDIvol (7.95 ± 2.6 mGy) was significantly lower when using the algorithm compared with the standard 120 kV protocol (10.59 ± 1.8 mGy, P < 0.001), corresponding to an overall dose reduction of 25.1%. Conclusion:Automated attenuation-based tube potential selection based on the attenuation profile of the topogram is feasible, provides a diagnostic image quality of body CTA, and reduces overall radiation dose by 25% as compared with a standard protocol with 120 kV.

Automated Attenuation-Based Kilovoltage Selection: Preliminary Observations in Patients After Endovascular Aneurysm Repair of the Abdominal Aorta

OBJECTIVE The objective of our study was to assess prospectively the impact of automated attenuation-based kilovoltage selection on image quality and radiation dose in patients undergoing body CT angiography (CTA) after endovascular aneurysm repair (EVAR) of the abdominal aorta. SUBJECTS AND METHODS Thirty-five patients (five women, 30 men; mean age ± SD, 69 ± 13 years; mean body mass index ± SD, 27.3 ± 4.5 kg/m(2)) underwent 64-MDCT angiography of the thoracoabdominal aorta using a fixed 120-kVp protocol (scan A: 120 mAs [reference]; rotation time, 0.33 second; pitch, 1.2) and, within a median time interval of 224 days, using a protocol with automated kilovoltage selection (scan B: tube voltage, 80-140 kVp). Subjective image quality (5-point scale: 1 [excellent] to 5 [nondiagnostic]) and objective image quality (aortic attenuation at four locations of the aortoiliac system, noise, contrast-to-noise ratio [CNR]) were assessed independently by two blinded radiologists. The volume CT dose index (CTDI(vol)) was compared between scans A and B. RESULTS The subjective image quality of scans A and B was similar (median score for both, 1; range, 1-4; p = 0.74), with all datasets being of diagnostic quality. Automated attenuation-based kilovoltage selection led to a reduction to 80 kVp in one patient (2.9%) and 100 kVp in 18 patients (51.4%). Fifteen of 35 patients (42.9%) were scanned at 120 kVp, whereas in one patient (2.9%) the kilovoltage setting increased to 140 kVp. Image noise (scan A vs scan B: mean ± SD, 12.8 ± 2.3 vs 13.7 ± 2.9 HU, respectively) was significantly (p < 0.05) higher in scan B than in scan A, whereas CNR was similar among scans (A vs B: mean ± SD, 15.7 ± 7.0 vs 16.9 ± 9.7; p = 0.43). The CTDI(vol) was significantly lower in scan B (mean ± SD, 8.9 ± 2.9 mGy; scan A, 10.6 ± 1.5 mGy; average reduction, 16%; p = 0.002) despite a higher tube current-exposure time product (B vs A: mean ± SD, 152 ± 27 vs 141 ± 29 mAs; p = 0.01). CONCLUSION In patients undergoing follow-up after EVAR of the abdominal aorta, body CTA using automated attenuation-based kilovoltage selection yields similar subjective image quality and CNR at a significantly reduced dose compared with a protocol that uses 120 kVp.

Low Kilovoltage CT of the Neck with 70 kVp: Comparison with a Standard Protocol

These authors imaged 27 patients with neck CT using 70 kVp and compared the scans with previous studies obtained using the typical 120-kVp technique on the same scanner. Two observers studied image quality and artifacts in 3 neck regions (upper, middle, and lower). They concluded that CT of the cervical soft tissues at 70 kVp is feasible, provides diagnostic image quality with improved contrast to noise, and reduces radiation dose by approximately 34% compared with a standard protocol at 120 kVp. In contrast, low kVp CT of the lower cervical spine suffers from compromised image quality. BACKGROUND AND PURPOSE: CT protocols should aim for radiation doses being as low as reasonably achievable. The purpose of our study was to assess the image quality and radiation dose of neck CT at a tube potential of 70 kVp. MATERIALS AND METHODS: Twenty patients (7 female, mean age 51.4 years, age range 19–81 years) underwent contrast-enhanced 64-section CT of the neck at 70 kVp (ATCM, effective tube current-time product 614 eff.mAs, range 467–713 eff.mAs). All 20 patients had a previous neck CT at 120 kVp on the same scanner. Two radiologists assessed image quality and artifacts in the upper, middle, and lower neck. Image noise and attenuation were measured, and the CNR was calculated. Effective radiation dose was calculated. RESULTS: Interobserver agreement regarding image quality of soft tissue for 70-kVp and 120-kVp scans was good to excellent. At 70 kVp, soft tissues were of diagnostic image quality in all scans, whereas the lower cervical spine was not of diagnostic quality in 3 and 4 scans per both readers. No difference was found among 70-kVp and 120-kVp scans for soft tissue image quality in the upper neck, while image quality was significantly better in the middle at 70 kVp (P < .05) and better in the lower third at 120 kVp (P < .05). CNR was significantly higher at 70 kVp in all levels for both readers (P < .001). Effective radiation dose at 70 kVp was significantly lower (0.88 ± 0.2mSv) than at 120 kVp (1.33 ± 0.2mSv, P < .001). CONCLUSIONS: CT of the cervical soft tissues at 70 kVp is feasible, provides diagnostic image quality with improved CNR, and reduces radiation dose by approximately 34% compared with a standard protocol at 120 kVp. In contrast, low kVp CT of the lower cervical spine suffers from compromised image quality.

Effect of automatic tube voltage selection on image quality and radiation dose in abdominal CT angiography of various body sizes: A phantom study

AIM To assess the effect of an automatic tube voltage selection technique on image quality and radiation dose in abdominal computed tomography (CT) angiography of various body sizes. MATERIALS AND METHODS An abdominal aortic phantom was filled with iodinated contrast medium and placed into three different cylindrical water containers, which simulated a small, intermediate-sized, and large patient. The phantom was scanned with a standard 120 kVp abdominal CT angiography protocol and with an optimized tube voltage protocol that was modulated by an automatic tube voltage technique. The attenuation of the aorta, background, and image noise was measured, and the contrast-to-noise ratio (CNR) was calculated. Three independent readers assessed the overall image quality. RESULTS The automatic tube voltage technique selected 70 kVp as the optimal tube voltage for the small phantom, 80 kVp for the intermediate phantom, and 100 kVp for the large phantom. Compared to the standard 120 kVp protocol, the automatic tube voltage selection yielded significantly increased CNR values in the small phantom (15.8 versus 19.4, p < 0.001), intermediate phantom (8.4 versus 8.7, p < 0.05), and large phantom (4.3 versus 4.6, p < 0.01). The automatic tube voltage selection resulted in a 55%, 49%, and 39% reduction in the volume CT dose index (CTDI(vol)) in the small, intermediate, and large phantoms, respectively. The subjective overall image quality of the three phantom sizes at different tube voltages ranged between poor and good. CONCLUSION Compared to a standard 120 kVp abdominal CT angiography protocol, the automatic tube voltage selection substantially reduced the radiation dose without compromising image quality in various simulated patient sizes.

Screening for interstitial lung disease in systemic sclerosis: performance of high-resolution CT with limited number of slices: a prospective study

Objectives Early diagnosis of interstitial lung disease (ILD), currently the main cause of death in systemic sclerosis (SSc), is needed. The gold standard is high-resolution CT (HRCT) of the chest, but regular screening faces the risk of increased radiation exposure. We performed a prospective validation of a dedicated, 9-slice HRCT protocol with reduced radiation dose for the detection of ILD in patients with SSc. Methods We analysed 170/205 consecutive patients with SSc. Whole-chest HRCT, serving as standard of reference, and the reduced HRCT with nine slices allocated according to a basal–apical gradient were obtained. ILD presence, extent (> or <20%) and diagnostic confidence were assessed. The reduced HRCT was independently analysed by two blinded radiologists, who also evaluated image quality. Radiation dose parameters were calculated. Results Standard chest HRCT showed ILD in 77/170 patients. With the reduced HRCT, 68/77 cases with ILD were identified (sensitivity 88.3%, both readers). The accuracy (91.8%, reader 1; 94.7%, reader 2), diagnostic confidence (98.8%, reader 1; 95.3%, reader 2) and image quality rates were high. Minimal ILD was correctly quantified in 73.1% (reader 1)/71.2% (reader 2) and extensive ILD in 88% (reader 1)/100% (reader 2). Importantly, the reduced HRCT had a significantly lower radiation dose. The mean dose length product (effective dose) was only 5.66±4.46 mGycm (0.08±0.06 mSv) compared with the standard protocol dose of 149.00±95.90 mGycm (2.09±1.34 mSv). Conclusions The above-described reduced chest HRCT protocol reliably detects even mild SSc-ILD in clinical practice, with the advantage of a much lower radiation dose compared with standard whole-chest HRCT.

Screening for interstitial lung disease in systemic sclerosis: the diagnostic accuracy of HRCT image series with high increment and reduced number of slices

Objectives The objective of this study is to assess diagnostic accuracy for the detection of interstitial lung disease (ILD) in image series with high increment and reduced number of slices in patients with systemic sclerosis (SSc). Methods 45 patients with SSc underwent high-resolution CT (HRCT). Three series of secondary captures were reconstructed as follows: series 1, series with 10 mm increment and 1 mm slices; series 2, seven axial images with baso-apical gradient; series 3, three axial images were obtained at the apical, at the level of the carina and basal. The presence and extent of ILD, and the degree of diagnostic confidence were recorded. The effective dose for each image series was estimated. Standard HRCT was the standard of reference. Results The prevalence of ILD was 55% (25/45). Diagnostic sensitivity and accuracy of series 1, series 2 and series 3 were 100% and 94.4%, 94% and 97.8%, 92% and 97.8%, respectively. The extent of ILD was underestimated in series 3 (p<0.05) and was comparable to the standard HRCT in series 1 and 2 (p>0.05). Estimated dose reduction was more than 90% in all image series. Conclusions HRCT image series with low sampling rate allow an accurate detection of ILD with very-low-radiation dose, making this approach potentially valuable for screening in patients with SSc.

MR imaging of degenerative disc disease

Magnet resonance imaging (MRI) is the most commonly used imaging modality for diagnosis of degenerative disc disease (DDD). Lack of precise observations and documentation of aspects within the complex entity of DDD might partially be the cause of poor correlation of radiographic findings to clinical symptoms. This literature review summarizes the current knowledge on MRI in DDD and outlines the diagnostic limitations. The review further sensitizes the reader toward awareness of potentially untended aspects of DDD and the interaction of DDD and endplate changes. A summary of the available classifications for DDD is provided.

Thoraco-abdominal high-pitch dual-source CT angiography: Experimental evaluation of injection protocols with an anatomical human vascular phantom

OBJECTIVE To experimentally evaluate three different contrast injection protocols at thoraco-abdominal high-pitch dual-source computed tomography angiography (CTA), with regard to level and homogeneity of vascular enhancement at different cardiac outputs. MATERIALS AND METHODS A uniphasic, a biphasic as well as an individually tailored contrast protocol were tested using a human vascular phantom. Each protocol was scanned at 5 different cardiac outputs (3-5L/min, steps of 0.5L/min) using an extracorporeal cardiac pump. Vascular enhancement of the thoraco-abdominal aorta was measured every 5 cm. Overall mean enhancement of each protocol and mean enhancement for each cardiac output within each protocol were calculated. Enhancement homogeneity along the z-axis was evaluated for each cardiac output and protocol. RESULTS Overall mean enhancement was significantly higher in the uniphasic than in the other two protocols (all p<.05), whereas the difference between the biphasic and tailored protocol was not significant (p=.76). Mean enhancement among each of the 5 cardiac outputs within each protocol was significantly different (all p<.05). Only within the tailored protocol mean enhancement differed not significantly at cardiac outputs of 3.5L/min vs. 5L/min (484 ± 25 HU vs. 476 ± 19 HU, p=.14) and 4 vs. 5L/min (443 ± 49 HU vs. 476 ± 19 HU, p=.05). Both, uniphasic and tailored protocol yielded homogenous enhancement at all cardiac outputs, whereas the biphasic protocol failed to achieve homogenous enhancement. CONCLUSION This phantom study suggests that diagnostic and homogenous enhancement at thoraco-abdominal high-pitch dual-source CTA is feasible with either a uniphasic or an individually tailored contrast protocol.

Interpretation of bedside chest X-rays in the ICU: is the radiologist still needed?

PURPOSE To compare diagnostic accuracy of intensivists to radiologists in reading bedside chest X-rays. METHODS In a retrospective trial, 33 bedside chest X-rays were evaluated by five radiologists and five intensivists with different experience. Images were evaluated for devices and lung pathologies. Interobserver agreement and diagnostic accuracy were calculated. Computed tomography served as reference standard. RESULTS Seniors had higher diagnostic accuracy than residents (mean-ExpB(Senior)=1.456; mean-ExpB(Resident)=1.635). Interobserver agreement for installations was more homogenously distributed between radiologists compared to intensivists (ExpB(Rad)=1.204-1.672; ExpB(Int)=1.005-2.368). Seniors had comparable diagnostic accuracy. CONCLUSION No significant difference in diagnostic performance was seen between seniors of both disciplines, whereas the resident intensivists might still benefit from an interdisciplinary dialogue.

Evaluation of calcium loss after transcatheter aortic valve implantation.

OBJECTIVES Aortic valve calcification and changes after transcatheter aortic valve implantation (TAVI) were specifically assessed by computed tomography (CT). The main difference between TAVI and the conventional technique is the compression of the cusps of the calcified native valve against the aortic wall before implantation. The objective of this study was to quantify the segmented calcification in the area of the basal annular plane before and after TAVI. METHODS The CT scans of 20 patients (13 male and 7 female; mean age: 82.9 ± 8.1 years) were assessed. The aortic valve calcification was segmented; derived from this segmentation volume, mass and Hounsfield units (HU)/density of the calcifications on the annulus and cusps before and after TAVI were evaluated. Pre- and postoperative data were compared regarding potential calcification loss and calcification distances to the left and right coronary ostia. RESULTS Significantly lower postprocedural mean volumes and masses for all cusps (P < 0.001) were found. The mean differences in the volume for the non-coronary, right-coronary and left-coronary cusp were -156.8 ± 53.73, -155.5 ± 62.54 and -115 ± 57.53 mm(3), respectively, and differences in mass were -88.78 ± 29.48, -95.2 ± 39.27 and -71.56 ± 35.62 mg, respectively. Over all cusps, mean HU increased after intervention [784.41 ± 92.5 HU (pre) and 818.63 ± 78.71 HU (post); P < 0.004]. In 80.03% of all cusps, calcification loss was found; all patients were affected. Significantly lower (P < 0.047) postprocedural mean distances were found from the left and right coronary ostia to the next calcification point. CONCLUSIONS Our results show a significant loss of calcification in all patients after TAVI, with a reduction in the calcification distances to the coronary ostia and the compression of calcification in the area of the device landing zone. The clinical implications of this finding need to be investigated further.