Reduced radiation dose and improved image quality at cardiovascular CT angiography by automated attenuation-based tube voltage selection: intra-individual comparison

Objectives

To evaluate the effect of automated tube voltage selection on radiation dose and image quality at cardiovascular CT angiography (CTA).

Methods

We retrospectively analysed paired studies in 72 patients (41 male, 60.5?±?16.5 years), who had undergone CTA acquisitions of the heart or aorta both before and after the implementation of an automated x-ray tube voltage selection algorithm (ATVS). All other parameters were kept identical between the two acquisitions. Subjective image quality (IQ) was rated and objective IQ was measured by image noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and figure of merit (FOM). Image quality parameters and effective dose were compared between acquisitions.

Results

Overall subjective image quality improved with the percentage of cases scored as adequate or higher increasing from 79 % to 92 % after implementation of ATVS (P?=?0.03). SNR (14.1?±?5.9, 15.7?±?6.1, P?=?0.009), CNR (11.6?±?5.3, 13.2?±?5.6, P?=?0.011), and FOM (19.9?±?23.3, 43.8?±?51.1, P?P?=?0.048) and mean effective dose (10.6?±?5.9 mSv, 8.8?±?5.0 mSv, P?=?0.003) were significantly lower after implementation of ATVS.

Conclusions

Automated tube voltage selection can operator-independently optimize cardiovascular CTA image acquisition parameters with improved image quality at reduced dose.

Key Points

? Automatic tube voltage selection optimizes tube voltage for each individual patient. ? In this population, overall radiation dose decreased while image quality improved. ? This tool may become valuable for improving dose/quality ratio.     

Image noise-based dose adaptation in dynamic volume CT of the heart: dose and image quality optimisation in comparison with BMI-based dose adaptation

Objectives

To compare the image quality and radiation dose using image-noise (IN)-based determination of X-ray tube settings compared with a body mass index (BMI)-based protocol during CT coronary angiography (CTCA).

Methods

Two hundred consecutive patients referred for CTCA to our institution were divided into two groups: BMI-based, 100 patients had CTCA with the X-ray tube current adjusted to the patient’s BMI while maintaining a fixed tube potential of 120 kV; IN-based, 100 patients underwent imaging with the X-ray tube current and voltage adjusted to the IN measured within the mid-left ventricle on a pre-acquisition trans-axial image. Two independent cardiac radiologists performed blinded image quality assessment with quantification of the IN and signal-to-noise ratio (SNR) from the mid-LV and qualitative assessment using a three-point score. Radiation dose (CTDI and DLP) was recorded from the console.

Results

Results showed: IN (HU): BMI-based, 30.1?±?9.9; IN-based, 33.1?±?6.7; 32 % variation reduction (P?=?0.001); SNR: BMI-based, 18.6?±?7.1; IN-based, 15.4?±?3.7; 48 % variation reduction (P?<?0.0001). Visual scores: BMI-based, 2.3?±?0.6; IN-based, 2.2?±?0.5 (P?=?0.54). Radiation dose: CTDI (mGy), BMI-based, 22.68?±?8.9; IN-based, 17.16?±?7.6; 24.3 % reduction (P?<?0.001); DLP (mGy.cm), BMI-based, 309.3?±?127.5; IN-based, 230.6?±?105.5; 25.4 % reduction (P?<?0.001).

Conclusions

Image-noise-based stratification of X-ray tube parameters for CTCA results in 32 % improvement in image quality and 25 % reduction in radiation dose compared with a BMI-based protocol.

Key Points

? Image quality and radiation dose are closely related in CT coronary angiography. ? So too are the image quality, radiation dose and body mass index (BMI). ? An image-noise-based CTCA protocol reduces the radiation dose by 25 %. ? It improves inter-patient image homogeneity by 32 %.     

Contrast agent bolus tracking with a fixed threshold or a manual fast start for coronary CT angiography

Objectives

Comparison of bolus tracking with a fixed threshold versus a manual fast start for coronary CT angiography.

Methods

We retrospectively analysed 320-row coronary CT angiography of 50 patients with suspected or known coronary artery disease. Twenty-five examinations were initiated by a bolus tracking method (group 1), 25 examinations with a manual fast surestart (group 2).

Results

Mean attenuation values in the ascending aorta were 519?±?111 Hounsfield units (HU) in group 1 and 476?±?65 HU in group 2 (p?=?0.10). Assessable vessel lengths were 171?±?44 mm vs 172?±?29 mm for the right coronary artery (p?=?0.91), 11?±?4 mm vs 12?±?4 mm for the left main (p?=?0.9), 163?±?28 mm vs 151?±?26 mm for the left anterior descending coronary artery (p?=?0.11) and 125?±?41 mm vs 110?±?37 mm for the left circumflex coronary artery (p?=?0.18). Image quality for all coronary arteries was not significantly different between the groups (p?>?0.41). The attenuation ratio between the left and right ventricle was 2.8?±?0.7 vs 3.6?±?1.0 (p?=?0.003). Significantly less contrast agent was used in group 2 (64?±?6 ml vs 80?±?0 ml; p?<?0.001).

Conclusions

Bolus tracking with a fixed threshold and with a manual fast start are both suitable methods; the fast start allowed a reduction of contrast agent volumes.

Key Points

? Fixed threshold bolus tracking is suitable for coronary 320-row CT angiography ? Manual fast start bolus tracking can reduce contrast agent volumes ? Manual fast start and fixed threshold initiation achieve good image quality ? Fixed threshold bolus tracking achieves a more reliable contrast bolus position     

Dose reduction in dynamic CT stress myocardial perfusion imaging: comparison of 80-kV/370-mAs and 100-kV/300-mAs protocols

Objectives

To determine the effect of reduced 80-kV tube voltage with increased 370-mAs tube current on radiation dose, image quality and estimated myocardial blood flow (MBF) of dynamic CT stress myocardial perfusion imaging (CTP) in patients with a normal body mass index (BMI) compared with a 100-kV and 300-mAs protocol.

Methods

Thirty patients with a normal BMI (<25 kg/m²) with known or suspected coronary artery disease underwent adenosine-stress dual-source dynamic CTP. Patients were randomised to 80-kV/370-mAs (n?=?15) or 100-kV/300-mAs (n?=?15) imaging. Maximal enhancement and noise of the left ventricular (LV) cavity, contrast-to-noise ratio (CNR) and MBF of the two groups were compared.

Results

Imaging with 80-kV/370-mAs instead of 100-kV/300-mAs was associated with 40 % lower radiation dose (mean dose–length product, 359?±?66 vs 628?±?112 mGy?cm; P?<?0.001 ) with no significant difference in CNR (34.5?±?13.4 vs 33.5?±?10.4; P?=?0.81) or MBF in non-ischaemic myocardium (0.95?±?0.20 vs 0.99?±?0.25 ml/min/g; P?=?0.66). Studies obtained using 80-kV/370-mAs were associated with 30.9 % higher maximal enhancement (804?±?204 vs 614?±?115 HU; P?<?0.005), and 31.2 % greater noise (22.7?±?3.5 vs 17.4?±?2.6; P?<?0.001).

Conclusions

Dynamic CTP using 80-kV/370-mA instead of 100-kV/300-mAs allowed 40 % dose reduction without compromising image quality or MBF. Tube voltage of 80-kV should be considered for individuals with a normal BMI.

Key Points

? CT stress perfusion imaging (CTP) is increasingly used to assess myocardial function. ? Dynamic CTP is feasible at 80-kV in patients with normal BMI. ? An 80-kV/370-mAs protocol allows 40 % dose reduction compared with 100-kV/300-mAs. ? Contrast-to-noise ratio and myocardial blood flow of the two protocols were comparable.     

High-pitch dual-source CT angiography of supra-aortic arteries: assessment of image quality and radiation dose

Introduction

High-pitch CT angiography (CTA) is a recent innovation that allows significant shortening of scan time with volume coverage of 43 mm per second. The aim of our study was to assess this technique in CTA of the head and neck.

Methods

CTA of supra-aortic arteries was performed in 50 patients using two acquisition protocols: conventional single-source 64-slice (pitch 1.2) and high-pitch dual-source 128-slice CT (pitch 3.2). Subjective and objective image quality of supra-aortic vessel ostia as well as intra- and extra-cranial segments was retrospectively assessed by blinded readers and radiation dose compared between the two protocols.

Results

Conventional and high-pitch CTA achieved comparable signal-to-noise ratios in arterial (54.3?±?16.5 versus 57.3?±?14.8; p?=?0.50) and venous segments (15.8?±?6.7 versus 18.9?±?8.9; p?=?0.21). High-pitch scanning was, however, associated with sharper delineation of vessel contours and image quality significantly improved at the level of supra-aortic vessel ostia (p?<?0.0001) as well as along the brachiocephalic trunk (p?<?0.0001), the subclavian arteries (p?<?0.0001), proximal common carotid arteries (p?=?0.01), and vertebral V1 segments (p?<?0.0001). Using the high-pitch mode, the dose-length product was reduced by about 35 % (218.2?±?30 versus 141.8?±?20 mGy?×?cm).

Conclusions

Due to elimination of transmitted cardiac motion, high-pitch CTA of the neck improves image quality in the proximity of the aortic arch while significantly lowering radiation dose. The technique thus qualifies as a promising alternative to conventional spiral CTA and may be particularly useful for identification of ostial stenosis.     

Novel connecting tube for saline chaser in contrast-enhanced CT: the effect of spiral flow of saline on contrast enhancement

Objective

To evaluate the effect of a newly developed connecting tube, which generates a spiral flow of saline, on aortic and hepatic contrast enhancement during hepatic-arterial phase (HAP) and portal venous phase (PVP) computed tomography (CT).

Methods

Eighty patients were randomly assigned to one of two protocols: with a new or a conventional tube. The contrast material (600 mgI/kg) was delivered over 30 s; this was followed by the administration of 25 ml saline solution delivered at the same injection rate as the contrast material. Unenhanced and contrast-enhanced CT images of the upper abdomen were obtained. We calculated the changes in the CT number (?HU) for the aorta during HAP and PVP, and for the liver during PVP. We compared ?HU between protocols.

Results

The mean ?HU for the abdominal aorta during HAP was significantly higher with the new tube protocol than with the conventional tube protocol (322?±?53 vs. 290?±?53, P?<?0.01). There were no significant differences in the mean ?HU for the abdominal aorta and liver during PVP between the two protocols (P?>?0.05).

Conclusion

The new connecting tube increased the effect of a saline chaser and significantly improved aortic enhancement during HAP.

Key Points

? Optimal administration of intravenous contrast material is essential for optimal CT quality. ? A new connecting tube can generate spiral flow, which improves intravenous administration. ? The new connecting tube improved aortic contrast enhancement during the hepatic-arterial phase. ? The new connecting tube increased the effect of a saline chaser.     

Image quality of ultra-low radiation exposure coronary CT angiography with an effective dose <0.1 mSv using high-pitch spiral acquisition and raw data-based iterative reconstruction

Objectives

We evaluated the potential of prospectively ECG-triggered high-pitch spiral acquisition with low tube voltage and current in combination with iterative reconstruction to achieve coronary CT angiography with sufficient image quality at an effective dose below 0.1 mSv.

Methods

Contrast-enhanced coronary dual source CT angiography (2?×?128?×?0.6 mm, 80 kV, 50 mAs) in prospectively ECG-triggered high-pitch spiral acquisition mode was performed in 21 consecutive individuals (body weight <100 kg, heart rate ≤60/min). Images were reconstructed with raw data-based filtered back projection (FBP) and iterative reconstruction (IR). Image quality was assessed on a 4-point scale (1 = no artefacts, 4 = unevaluable).

Results

Mean effective dose was 0.06?±?0.01 mSv. Image noise was significantly reduced in IR (128.9?±?46.6 vs. 158.2?±?44.7 HU). The mean image quality score was lower for IR (1.9?±?1.1 vs. 2.2?±?1.0, P?<?0.0001). Of 292 coronary segments, 55 in FBP and 40 in IR (P?=?0.12) were graded “unevaluable”. In patients with a body weight ≤75 kg, both in FBP and in IR, the rates of fully evaluable segments were significantly higher in comparison to patients >75 kg.

Conclusions

Coronary CT angiography with an estimated effective dose <0.1 mSv may provide sufficient image quality in selected patients through the combination of high-pitch spiral acquisition and raw data-based iterative reconstruction.

Key Points

? Coronary CT angiography with an estimated effective dose <0.1 mSv is possible. ? Combination of high-pitch spiral acquisition with iterative reconstruction achieves sufficient image quality. ? Diagnostic accuracy remains to be assessed in future trials.     

Quantification and characterisation of coronary artery plaque volume and adverse plaque features by coronary computed tomographic angiography: a direct comparison to intravascular ultrasound

Objective

We evaluated the performance of manual measures of coronary plaque volumes and atherosclerotic plaque features from coronary CT angiography (CTA), using intravascular ultrasound (IVUS) as the reference.

Methods

Thirty individual coronary plaques with suitable fiduciary markers were identified. Plaque volumes on coronary CTA were manually quantified by two observers and compared to IVUS plaque volumes as interpreted by an independent laboratory. The presence of adverse plaque characteristics—low attenuation plaque (LAP), positive remodelling (PR) and spotty calcification (SC)—on coronary CTA was evaluated and compared to IVUS.

Results

High correlation in plaque volumes was detected between observers (r?=?0.94, P?<?0.0001; 95 % limits of agreement <48.7 mm³, bias 6.6 mm³). Excellent correlation (r?=?0.95, P?<?0.0001) was noted in plaque volume between independent observers and IVUS (95 % limits of agreement <40.6 mm³, bias ?4.4 mm³) and did not differ from IVUS (105.0?±?56.7 vs. 109.4?±?60.7 mm³, P?=?0.2). The frequency of LAP (10 % vs. 17 %), PR (7 % vs. 10 %) and SC (27 % vs. 33 %) was similar between coronary CTA and IVUS (all P?=?NS).

Conclusions

Plaque volume on coronary CTA determined by manual methods demonstrates high correlation and modest agreement to IVUS. Further, coronary CTA demonstrates high accuracy for the identification of adverse plaque characteristics, including LAP, PR and SC.

Key Points

? Coronary CT angiography is a non-invasive test that enables coronary plaque assessment ? Plaque quantification by coronary CT angiography correlates well with intravascular ultrasound findings ? Coronary CT angiography can identify adverse plaque characteristics     

Value of CT angiography for the detection of intracranial vascular lesions in patients with acute severe headache

Objectives

To retrospectively investigate the prevalence and characteristics of intracranial vascular lesions in patients with acute severe headache with the use of CT angiography (CTA).

Methods

We systematically searched for neurologically intact patients with acute severe headache and normal unenhanced head CT. The study group consisted of 512 patients; 251 male; mean age 46.2?±?12.4 years. All patients underwent CTA between 1 day and 2 months after the headache attack. CTA images were interpreted by two experienced neuroradiologists for the presence of vascular lesions.

Results

Thirty-four (6.6 %) of the 512 patients had intracranial vascular lesions on CTA, including 33 aneurysms (2 patients had 2 aneurysms each), 2 moyamoya disease and 1 arterial dissection. No gender- or age-related differences were found. Aneurysms arose most commonly on the internal carotid artery (n?=?12), followed by the anterior communicating artery (n?=?7), and the middle cerebral artery (n?=?7). Maximal diameters ranged from 2.0 to 13.1 mm (mean, 3.9?±?2.6 mm).

Conclusions

CTA is a feasible tool for diagnosing intracranial vascular lesions in patients with acute severe headache. The prevalence of vascular lesions in our series was 6.6 %, which is higher than that predicted in the general population.

Key Points

? Unruptured cerebral aneurysms may be a cause of acute severe headache ? CTA assesses intracranial vascular lesions in patients with acute severe headache ? The prevalence of vascular lesions in our series of patients was 6.6 %     

Determination of optimal intravenous contrast agent iodine dose for the detection of liver metastasis at 80-kVp CT

Objectives

To determine the optimal iodine mass (IM) to achieve a 50-HU increase in hepatic attenuation for the detection of liver metastasis based on total body weight (TBW) or body surface area (BSA) at 80-kVp computed tomography (CT) imaging of the liver.

Methods

One-hundred and fifty patients who underwent contrast-enhanced CT at 80-kVp were randomised into three groups: 0.5 gI/kg, 0.4 gI/kg and 0.3 gI/kg. Portal venous phase images were evaluated for hepatic parenchymal enhancement (?HU) and visualisation of liver metastasis. Iodine mass per BSA (gI/m²) calculated in individual patients were evaluated.

Results

Mean ?HU for the 0.5 gI/kg group (84.2 HU) was higher than in the 0.4 gI/kg (66.1 HU) and 0.3 gI/kg (53.7 HU) groups (P?<?0.001). Linear correlation equations between ?HU and IM per TBW or BSA are ?HU?=?7.0?+?153.0?×?IM/TBW (r?=?0.73, P?<?0.001) and ?HU?=?11.4?+?4.0?×?IM/BSA (r?=?0.75, P?<?0.001), respectively. The three groups were comparable for the visualisation of hepatic metastases.

Conclusions

The iodine mass to achieve a 50-HU increase in hepatic attenuation at 80-kVp CT was estimated to be 0.28 gI/kg of body weight or 9.6 gI/m² of body surface area.

Key Points

? Hepatic enhancement is expressed as ?HU?=?7.0?+?153.0?×?IM [g]/TBW [kg]. ? Hepatic enhancement is expressed as ?HU?=?11.4?+?4.0?×?IM [g]/BSA [m ² ]. ? Essential iodine dose at 80-kVp CT was 0.28 gI/kg or 9.6 gI/m ² .     

Impact of organ-specific dose reduction on the image quality of head and neck CT angiography

Objectives

Organ-specific dose reduction (OSDR) algorithms can reduce radiation on radiosensitive organs up to 59 %. This study evaluates the influence of a new OSDR algorithm on image quality of head and neck computed tomographic angiography (CTA) in clinical routine.

Methods

Sixty-two consecutive patients (68?±?13 years) were randomised into two groups and imaged using 128-row multidetector CT. Group A (n?=?31) underwent conventional CTA and group B (n?=?31) CTA with a novel OSDR algorithm. Subjective and objective image quality were statistically compared. Subjective image quality was rated on a five-point scale. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated with region-of-interest measurements.

Results

The SNR of the common carotid artery and middle cerebral artery was 53.6?±?22.7 and 43.3?±?15.3 (group A) versus 54.1?±?20.5 and 46.2?±?14.6 (group B). The CNR was 40.0?±?19.3 and 29.7?±?12.0 (group A) compared with 40.7?±?16.8 and 32.9?±?10.9 (group B), respectively. Subjective image quality was excellent in both groups (mean score 4.4?±?0.7 versus 4.4?±?0.6). Differences between the two groups were not significant.

Conclusions

The novel OSDR algorithm does not compromise image quality of head and neck CTA. Its application can be recommended for CTA in clinical routine to protect the thyroid gland and ocular lenses from unnecessary high radiation.

Key Points

? Organ-specific dose reduction (OSDR) can significantly reduce radiation exposure during CT ? OSDR does not compromise image quality of head and neck CTA ? OSDR can significantly lower the risk of radiation damage to sensitive organs ? OSDR can easily be applied in routine clinical practice     

Thrombus imaging in acute ischaemic stroke using thin-slice unenhanced CT: comparison of conventional sequential CT and helical CT

Objectives

Thin-slice helical unenhanced CT can be used for thrombus imaging but increases radiation exposure. Conventional sequential images obtained by multidetector CT can be reconstructed into thin-slice images. The purpose of this study was to evaluate if conventional sequential unenhanced CT images can replace helical unenhanced CT for thrombus imaging.

Methods

Fifty consecutive patients with acute ischaemic stroke underwent both 5-mm conventional sequential unenhanced CT and helical unenhanced CT. Each of the sequential and helical unenhanced CT images was subsequently reconstructed into four 1.25-mm images. Thrombus volumes and HU were measured semi-automatically using both types of unenhanced CT. Thrombus HU ratio (rHU) was calculated using the HU of the contralateral segment. The intraclass correlation coefficient (ICC) and Bland–Altman plots were used to assess measurement agreement.

Results

The mean rHUs were 1.47?±?0.17 for sequential unenhanced CT and 1.47?±?0.18 helical unenhanced CT (P?=?0.542). The mean thrombus volumes were 124.25?±?125.65?mm³ and 117.84?±?124.32?mm³ on sequential and helical unenhanced CT images, respectively (P?=?0.063). Measurement agreement between thrombus volumes from the two unenhanced CT images was high (ICC?=?0.981).

Conclusions

Thin-slice unenhanced CT images reconstructed from 5-mm sequential images can replace helical unenhanced CT for thrombus imaging in acute ischaemic stroke.

Key Points

? Unenhanced CT is used to evaluate intra-arterial thrombus. ? Thrombus HU and volume measurements using sequential or helical CT are comparable. ? Conventional sequential images can replace helical CT for thrombus imaging. ? Radiation dose for thrombus imaging can be reduced using sequential CT.     

Upright Cone CT of the hindfoot: Comparison of the non-weight-bearing with the upright weight-bearing position

Objectives

To prospectively compare computed tomography (CT) of the hindfoot in the supine non-weight-bearing position (NWBCT) with upright weight-bearing position (WBCT).

Methods

Institutional review board approval and informed consent of all patients were obtained. NWBCT and WBCT scans of the ankle were obtained in 22 patients (mean age, 46.0?±?17.1 years; range 19–75 years) using a conventional 64-row CT for NWBCT and a novel cone-beam CT for WBCT. Two musculoskeletal radiologists independently performed the following measurements: the hindfoot alignment angle, fibulocalcaneal and tibiocalcaneal distances, lateral talocalcaneal joint space width, talocalcaneal overlap and naviculocalcaneal distance. Significant changes between NWBCT and WBCT were sought using Wilcoxon signed-rank test. P values <0.05 were considered statistically significant.

Results

Significant differences were found for all measurements except the hindfoot alignment angle and tibiocalcaneal distance. Significant measurement results were as follows (NWBCT/WBCT reader 1; NWBCT/WBCT reader 2, mean ± standard deviation): fibulocalcaneal distance 3.6 mm?±?5.2/0.3 mm?±?6.0 (P?=?0.006); 1.4 mm?±?6.3/-1.1 mm?±?6.3 (P?=?0.002), lateral talocalcaneal joint space width 2.9 mm?±?1.7/2.2 mm?±?1.1 (P?=?0.005); 3.4 mm?±?1.9/2.4 mm?±?1.3 (P?=?0.001), talocalcaneal overlap 4.1 mm?±?3.9/1.4 mm?±?3.9 (P?=?0.001); 4.5 mm?±?4.3/1.4 mm?±?3.7 (P?<?0.001) and naviculocalcaneal distance 13.5 mm?±?4.0/15.3 mm?±?4.7 (P?=?0.037); 14.0 mm?±?4.4/15.7 mm?±?6.2 (P?=?0.100). Interreader agreement was good to excellent (ICC 0.48–0.94).

Conclusion

Alignment of the hindfoot significantly changes in the upright weight-bearing CT position. Differences can be visualised and measured using WBCT.

Key Points

? Cone-beam computed tomography (CBCT) offers new opportunities for musculoskeletal problems ? Visualization and quantification of hindfoot alignment are possible in upright weight-bearing CBCT ? Hindfoot alignment changes significantly from non-weight-bearing to weight-bearing CT ? The weight-bearing position leads to a decrease in the fibulocalcaneal distance and talocalcaneal overlap ? The naviculocalcaneal distance is increased in the weight-bearing position     

Subtracted 3D CT angiography for the evaluation of intracranial aneurysms in 256-slice multidetector CT: usefulness of the 80-kVp plus compact contrast medium bolus protocol

Objectives

To evaluate the usefulness of an 80-kVp and compact contrast material protocol for arterial phase subtracted cerebral 3D-CTA using 256-slice multidetector CT.

Methods

Thirty-two patients underwent CT with 100 kVp and received a contrast dose of 370 mgI/kg body weight over 15 s (protocol A). Thirty-three patients underwent CT with 100 kVp and received a contrast dose of 296 mgI/kg body weight over 10 s (protocol B). Thirty-three other patients underwent CT with 80 kVp and received a contrast medium dose of 296 mgI/kg body weight over 10 s (protocol C). We compared the arterial attenuation and contrast noise ratio (CNR) of each protocol. Two independent readers assessed overall image quality.

Results

Arterial attenuation was significantly higher under protocols A (418.6?±?71.1 HU) and C (442.7?±?79.3 HU) than under protocol B (355.8?±?107.2 HU; P?<?0.05). The CNR of protocol C (26.1?±?6.1) was higher than that of protocol A (20.7?±?8.4; P?<?0.05). The overall image quality of protocol A was higher than that of protocol C (P?<?0.01).

Conclusion

The 80-kVp plus compact contrast protocol is well suited to arterial phase subtracted cerebral 3D-CTA without confounding venous enhancement.

Key Points

? Subtracted 3D CT angiography is useful in the evaluation of intracranial aneurysms. ? A compact contrast material protocol increased arterial attenuation without venous contamination. ? Low-kVp CT compensated for the decreased amount of contrast medium. ? An 80-kVp CT with a compact enhancement bolus provides good intracranial 3D-CT angiography.     

Clinical impact of hyperattenuation of adrenal glands on contrast-enhanced computed tomography of polytraumatised patients

Objective

To evaluate the prognostic value of hyperattenuating adrenal glands on contrast-enhanced CT of polytraumatised patients.

Methods

Two hundred ninety-two patients (195 men and 97 women, mean age 45.3?±?23.3 years) were included in this retrospective study. CT examinations were performed 60 s after intravenous injection of contrast material. Image analysis was performed by two radiologists. Patients were assigned to one of two groups according to the attenuation of the adrenal gland [group 1: adrenal glands ≥ inferior vena cava (IVC); group 2: adrenal glands < IVC].

Results

Eighteen patients (42.2 years?±?24.2) were assigned to group 1 and 274 patients (48.4 years?±?22.4) to group 2. The average adrenal density was 150.8?±?36.1 HU in group 1 and 83.7?±?23.6 HU in group 2 (P?<?0.0001). Eight of the 18 patients in group 1 (44.4 %) and 33 of the 274 patients in group 2 (12.4 %) died during hospitalisation (P?<?0.05). Mean adrenal enhancement was significantly higher in patients who died (101.9?±?40.6 HU) compared with survivors (86.1?±?27.0 HU; P?<?0.001).

Conclusion

Hyperattenuation of adrenal glands is associated with a higher mortality rate in polytraumatised patients and may serve as a predictor of poor clinical outcome.

Key points

? Hyperattenuating adrenal glands can be observed in 6.2 % of polytraumatised patients. ? Hyperattenuating adrenal glands indicate poor clinical outcome in polytraumatised patients. ? In polytraumatised patients, hyperattenuating adrenal glands are associated with a high mortality rate. ? Adrenal enhancement is higher amongst patients who died than amongst survivors.     

Optimal table feed in run-off CT angiography in patients with abdominal aortic aneurysms

Objectives

To assess the influence of different table feeds (TFs) on vascular enhancement and image quality in patients with an abdominal aortic aneurysm (AAA) undergoing computed tomography (CT) angiography of the lower extremities (run-off CTA).

Methods

Seventy-nine patients (71?±?8 years) with an AAA (>30 mm) who underwent run-off CTA between January 2004 and August 2011 were included in this retrospective institutional review board-approved study. Run-off CTA was conducted using 16- and 64-row CT. The range of TFs was 30–86 mm/s and was categorised in quartiles TF1 (32.6?±?1.9 mm/s), TF2 (38.9?±?0.9 mm/s), TF3 (43.9?±?3.1 mm/s) and TF4 (57.4?±?10.5 mm/s). Image quality was rated independently by two radiologists and vessel enhancement was assessed.

Results

Image quality was diagnostic at all aortic, pelvic and almost all thigh levels. Below the knee, the number of diagnostic levels was highest for TF1 and decreased to TF4. Arterial enhancement between the aorta and fibular trunk was not different in all TF groups, P?>?0.05. At the calf and foot strongest arterial enhancement was noted for TF1 and TF2 and decreased to TF4, P?<?0.01.

Conclusion

Results indicate that the highest image quality of run-off CTA in patients with an AAA may be obtained using table feeds measuring 30–35 mm/s.

Key Points

? CTA has become a key investigation for peripheral vascular disease. ? Run-off CTA is more complex in patients with an abdominal aortic aneurysm. ? Run-off CTA is feasible with a short bolus of intravenous contrast medium. ? A constant 30–35 mm/s table feed provides the highest likelihood of diagnostic images.     

Dual source multidetector CT-angiography before Transcatheter Aortic Valve Implantation (TAVI) using a high-pitch spiral acquisition mode

Objectives

Transcatheter Aortic Valve Implantation (TAVI) is an alternative to surgical valve replacement in high risk patients. Angiography of the aortic root, aorta and iliac arteries is required to select suitable candidates, but contrast agents can be harmful due to impaired renal function. We evaluated ECG-triggered high-pitch spiral dual source Computed Tomography (CT) with minimized volume of contrast agent to assess aortic root anatomy and vascular access.

Methods

42 patients (82?±?6?years) scheduled for TAVI underwent dual source (DS) CT angiography (CTA) of the aorta using a prospectively ECG-triggered high-pitch spiral mode (pitch?=?3.4) with 40?mL iodinated contrast agent. We analyzed aortic root/iliac dimensions, attenuation, contrast to noise ratio (CNR), image noise and radiation exposure.

Results

Aortic root/iliac dimensions and distance of coronary ostia from the annulus could be determined in all cases. Mean aortic and iliac artery attenuation was 320?±?70 HU and 340?±?77 HU. Aortic/iliac CNR was 21.7?±?6.8 HU and 14.5?±?5.4 HU using 100?kV (18.8?±?4.1 HU and 8.7?±?2.6 HU using 120?kV). Mean effective dose was 4.5?±?1.2?mSv.

Conclusions

High-pitch spiral DSCTA can be used to assess the entire aorta and iliac arteries in TAVI candidates with a low volume of contrast agent while preserving diagnostic image quality. Key Points ? Transcatheter Aortic Valve Implantation (TAVI) offers an alternative to surgical valve replacement in high risk patients. ? Such procedures require essential information about aortic root anatomy and vascular access. ? High pitch ECG-triggered dual source Computed Tomography (CT) can provide this information ? Sufficient image quality can be maintained even with low volumes of contrast agent and reduced x-ray exposure.     

C-arm CT during hepatic arteriography tumour-to-liver contrast: intraindividual comparison of three different contrast media application protocols

Objective

To compare tumour-to-liver contrast (TLC) of C-arm CT during hepatic arteriography (CACTHA) acquired using three protocols in patients with HCC.

Methods

This prospective study was IRB approved and informed consent was obtained from each patient. Twenty-nine patients (mean age, 68?±?7 years; 27 men) with 55 HCCs (mean diameter, 2.6?±?1.5 cm) underwent three different CACTHA protocols in random order before chemoembolisation. Contrast medium (100 mg iodine/ml) was injected into the common hepatic artery (flow rate 4 ml/s). The imaging delay for the start of the CACTHA examination was 4 s (protocol A), 8 s (protocol B) and 12 s (protocol C) (total amount of injected contrast medium: 48 ml, 64 ml, 80 ml). TLC was measured by placing regions of interest (ROIs) in the HCC and liver parenchyma. Mixed model ANOVAs and Bonferroni corrected post hoc tests were used for statistical analysis.

Results

Mean values for TLC were 132?±?3.3 HU, 186?±?5.8 HU and 168?±?2.8 HU for protocols A, B and C. Protocol B provided significantly higher TLC than protocols A and C (p?<?0.001).

Conclusion

TLC was significantly higher using an imaging delay of 8 s compared with a delay of 4 or 12 s.

Key Points

? C-arm cone-beam CT (CACT) angiography offers additional information during hepatic intervention. ? CACT hepatic arteriography tumour-to-liver contrast is highest with an 8-s delay. ? An 8-s delay is recommended for early arterial phase CACTHA for hepatocelullar carcinoma.     

Computed tomography angiography of carotid and coronary artery via a single-bolus injection protocol: a feasibility study using 320-row multidetector CT

Objectives

To investigate the feasibility of using a single-dose injection protocol in CT angiography (CTA) of the carotid and coronary artery with 320-row multidetector CT.

Methods

A total of 82 consecutive patients with suspected carotid artery disease underwent an original CTA protocol aiming at capturing the extra-cranial carotid arteries and coronary arteries simultaneously using 320-row MDCT. The image quality, attenuation, and CNRs of the carotid and coronary arteries were assessed. The lag time (between two separated volumetric acquisitions) was compared between patients with and without cardiac venous opacification (CVO). The contrast medium volume and radiation dose were recorded.

Results

The image quality was 99.4 % diagnostic in carotid and 86.9 % in coronary artery segments. The mean attenuation of carotid and coronary arteries ranged from 462.2 Hu to 533.7 Hu, 415.9 Hu to 454.7 Hu respectively. The mean CNR of the carotid and coronary artery ranged from 15.8 to 18.9 and 17.7 to 20.4 respectively. The lag time in patients with and without CVO was 5.75?±?1.64 s vs. 4.21?±?1.14 s (p?<?0.05). The mean radiation dose was 6.6?±?4.1 mSv.The mean contrast media volume was 71.9?±?9.1 ml.

Conclusions

The carotid and coronary artery can be imaged simultaneously via our original single-dose injection CTA protocol using 320-row CT with adequate image quality.

Key Points

? Carotid and coronary 320-row CTA can be achieved in a single-dose injection. ? Longer coverage was achieved with two or more volumes using 320-row CT. ? The single-dose protocol allows a reduced contrast agent dose of about 72 ml.     

A cadaver study comparing intraoperative methods to analyze lower limb alignment

Background

Conventional intraoperative determination of lower limb alignment is essential for orthopedic surgical treatment. Current methods include the cable, alignment rod, and axis board methods.

Question/purposes

Are there differences in accuracy and reliability? What are the individual differences in applicability and radiation exposure?

Methods

Twenty legs from 12 fresh-frozen cadavers were randomly selected. After fixation of the legs, measurements were performed using the cable, alignment rod, and axis board methods. Afterwards, all cadavers were subjected to CT scanning. Intersection of the mechanical leg axis with the tibia plateau was calculated as the percentage of the tibia plateau, beginning at the medial border (0 %) and ending at the lateral border (100 %). Results are presented as mean ± standard deviation (SD).

Results

Compared with CT measurements, differences of the intersection at the tibia plateau were 3.9?±?8.5 % with the cable method, 3.6?±?7.6 % using the alignment rod, and 3.6?±?9.6 % using the axis board. The difference among all measurements was not statistically significant (p?=?0.450). The average intersection of the mechanical axis was 43.95?±?5.15 % using the cable method, 43.93?±?5.49 % using the alignment rod, and 43.77?±?5.92 % using the axis board. CT measurements revealed an average intersection of 42.46?±?5.22 %. There was no statistically significant difference among conventional results (p?=?0.976). We demonstrated good intraobserver reliability for all three methods (cable method, ICC?=?0.97; alignment rod, ICC?=?0.95; and axis board, ICC?=?0.96). There were no statistically significant differences regarding radiation time (p?=?0.349) or dose area product (p?=?0.823).

Conclusions

All described measurements demonstrated valid measurement of lower limb alignment. With minimal effort, all three methods present a practical and uncomplicated way to control the mechanical axis.