MRI screening for silicone breast implant rupture: accuracy,inter- and intraobserver variability using explantation results as reference standard

Objectives

The recall of Poly Implant Prothèse (PIP) silicone breast implants in 2010 resulted in large numbers of asymptomatic women with implants who underwent magnetic resonance imaging (MRI) screening. This study’s aim was to assess the accuracy and interobserver variability of MRI screening in the detection of rupture and extracapsular silicone leakage.

Methods

A prospective study included 107 women with 214 PIP implants who underwent explantation preceded by MRI. In 2013, two radiologists blinded for previous MRI findings or outcome at surgery, independently re-evaluated all MRI examinations. A structured protocol described the MRI findings. The ex vivo findings served as reference standard.

Results

In 208 of the 214 explanted prostheses, radiologists agreed independently about the condition of the implants. In five of the six cases they disagreed (2.6 %), but subsequently reached consensus. A sensitivity of 93 %, specificity of 93 %, positive predictive value of 77 % and negative predictive value of 98 % was found. The interobserver agreement was excellent (kappa value of 0.92).

Conclusions

MRI has a high accuracy in diagnosing rupture in silicone breast implants. Considering the high kappa value of interobserver agreement, MRI appears to be a consistent diagnostic test. A simple, uniform classification, may improve communication between radiologist and plastic surgeon.

Key points

? MRI has a high accuracy in diagnosing rupture in silicone breast implants. ? MRI appears to be a consistent diagnostic test with excellent interobserver agreement. ? A simple, uniform classification system, improves communication between radiologist and plastic surgeon. ? The interobserver agreement on implant rupture is higher than on extracapsular leakage.     

Dual-energy computed tomography for the assessment of early treatment effects of regorafenib in a preclinical tumor model: comparison with dynamic contrast-enhanced CT and conventional contrast-enhanced single-energy CT

Objectives

The potential diagnostic value of dual-energy computed tomography (DE-CT) compared to dynamic contrast-enhanced CT (DCE-CT) and conventional contrast-enhanced CT (CE-CT) in the assessment of early regorafenib treatment effects was evaluated in a preclinical setting.

Methods

A rat GS9L glioma model was examined with contrast-enhanced dynamic DE-CT measurements (80 kV/140 kV) for 4 min before and on days 1 and 4 after the start of daily regorafenib or placebo treatment. Tumour time-density curves (0-240 s, 80 kV), DE-CT (60 s) derived iodine maps and the DCE-CT (0-30 s, 80 kV) based parameters blood flow (BF), blood volume (BV) and permeability (PMB) were calculated and compared to conventional CE-CT (60 s, 80 kV).

Results

The regorafenib group showed a marked decrease in the tumour time-density curve, a significantly lower iodine concentration and a significantly lower PMB on day 1 and 4 compared to baseline, which was not observed for the placebo group. CE-CT showed a significant decrease in tumour density on day 4 but not on day 1. The DE-CT-derived iodine concentrations correlated with PMB and BV but not with BF.

Conclusions

DE-CT allows early treatment monitoring, which correlates with DCE-CT. Superior performance was observed compared to single-energy CE-CT.

Key Points

? Regorafenib treatment response was evaluated by CT in a rat tumour model. ? Dual-energy contrast-enhanced CT allows early treatment monitoring of targeted anti-tumour therapies. ? Dual-energy CT showed higher diagnostic potential than conventional contrast enhanced single-energy CT. ? Dual-energy CT showed diagnostic potential comparable to dynamic contrast-enhanced CT. ? Dual-energy CT is a promising method for efficient clinical treatment response evaluation.     

Urinary stone differentiation in patients with large body size using dual-energy dual-source computed tomography

Objective

To evaluate the ability of 100/Sn140 kV (Sn, tin filter) dual-energy computed tomography (CT) to differentiate urinary stone types in a patient cohort with a wide range of body sizes.

Methods

Eighty human urinary stones were categorised into four groups (uric acid; cystine; struvite, oxalate and brushite together; and apatite) and imaged in 30–50-cm-wide water tanks using clinical 100/Sn140 kV protocols. The CT number ratio (CTR) between the low- and high-energy images was calculated. Thresholds for differentiating between stone groups were determined using receiver operating characteristics (ROC) analysis. Additionally, 86 stones from 66 patients were characterised using the size-adaptive CTR thresholds determined in the phantom study.

Results

In phantoms, the area under the ROC curve for differentiating between stone groups ranged from 0.71 to 1.00, depending on phantom size. In patients, body width ranged from 28.5 to 50.0 cm, and 79.1 % of stones were correctly characterised. Sensitivity and specificity for correctly identifying the stone category were 100 % and 100 % (group 1), 100 % and 95.3 % (group 2), 85.7 % and 60.9 % (group 3), and 52.6 % and 92.5 % (group 4).

Conclusion

Dual-energy CT can provide in vivo urinary stone characterisation for patients over a wide range of body sizes.

Key Points

? Dual-energy CT helps assessment of urinary stone composition in vivo. ? 100/Sn140 kV DECT differentiates among four stone types with 79.1 % accuracy. ? In vivo diagnostic test achievable in patients with many body sizes.     

Combination of chemical suppression techniques for dual suppression of fat and silicone at diffusion-weighted MR imaging in women with breast implants

Objectives

Silicone breast prostheses prove technically challenging when performing diffusion-weighted MR imaging in the breasts. We describe a combined fat and chemical suppression scheme to achieve dual suppression of fat and silicone, thereby improving the quality of diffusion-weighted images in women with breast implants.

Methods

MR imaging was performed at 3.0 and 1.5?T in women with silicone breast implants using short-tau inversion recovery (STIR) fat-suppressed echo-planar (EPI) diffusion-weighted MR imaging (DWI) on its own and combined with the slice-select gradient-reversal (SSGR) technique. Imaging was performed using dedicated breast imaging coils.

Results

Complete suppression of the fat and silicone signal was possible at 3.0?T using EPI DWI with STIR and SSGR, evaluated with dedicated breast coils. However, a residual silicone signal was still perceptible at 1.5?T using this combined approach. Nevertheless, a further reduction in silicone signal at 1.5?T could be achieved by employing thinner slice partitions and the addition of the chemical-selective fat-suppression (CHESS) technique.

Conclusions

DWI using combined STIR and SSGR chemical suppression techniques is feasible to eliminate or reduce silicone signal from prosthetic breast implants.

Key Points

? Breast magnetic resonance imaging (MRI) is frequently needed following breast implants ? Unsuppressed signal from silicone creates artefacts on diffusion-weighted MR sequences ? Dual fat/chemical suppression can eliminate signal from fat and silicone ? STIR with slice selective gradient reversal can suppress fat and silicone signal     

Changes in measured size of atherosclerotic plaque calcifications in dual-energy CT of ex vivo carotid endarterectomy specimens: effect of monochromatic keV image reconstructions

Objective

The aim of this study was to compare the size of the calcifications measured on the different keV images to a histological standard.

Methods

Five ex vivo carotid endarterectomy (CEA) specimens were imaged with a dual-energy CT. CT images were reconstructed at different monochromatic spectral energies (40, 60, 77, 80, 100, 120, 140 keV). Cross-sectional area of the plaque calcifications present on each CT image was measured. The histological calcium areas on each corresponding CEA specimen were traced manually on digitised images of Toluidine Blue/Basic Fuchsin stained plastic sections. The CT images and corresponding histology sections were matched. The CT-derived calcium areas on each keV image were compared to the calcified area measurements by histology.

Results

A total of 107 histology sections were matched to corresponding CT images. The average calcified area per section by histology was 7.6?±?7 mm² (range 0–26.4 mm²). There was no significant difference between the calcified areas measured by histology and those measured on CT–virtual monochromatic spectral (VMS) reconstructed images at 77 keV (P?=?0.08), 80 keV (P?=?0.20) and 100 keV (P?=?0.14).

Conclusions

Calcium area measured on the 80 keV image set was most comparable to the amount of calcium measured by histology.

Key Points

? Dual-energy computed tomography allows reconstruction of virtual monochromatic images. ? Virtual monochromatic images reconstructed at different keVs reveal different atherosclerotic calcification quantification. ? Virtual monochromatic images allows better evaluation of calcified atherosclerotic plaques.     

Characterisation of urinary stones in the presence of iodinated contrast medium using dual-energy CT: a phantom study

Objective

To develop a dual-energy CT (DECT) method for differentiating uric acid (UA) from non-UA stones in the presence of iodinated contrast medium.

Methods

Thirty UA and 45 non-UA stones were selected after infra-red spectroscopic analysis and independently placed in a 1.5-ml vial, which was filled first with saline and then with increasing concentrations of iodine. For each condition, tubes were put in a 35-cm water phantom and examined using a dual-source CT system at 100 and 140?kV. Virtual unenhanced images created from CT data sets of the stones in iodine-containing solutions provided position and volume information. This map was used to calculate a CT number ratio to differentiate stone type. A region-growing method was developed to improve the ability to differentiate between UA and non-UA stones with iodinated contrast medium.

Results

The sensitivity for detecting UA stones was 100?% for unenhanced images but fell to 18?% with 20?mgI/ml iodine solution and 0?% for higher concentrations. With region growing, the sensitivity for detecting UA stones was increased to 100?%, 82?%, 57?%, 50?% and 21?% for iodine solutions of 20, 40, 60, 80 and 100?mgI/ml.

Conclusion

The region-growing method improves differentiation of UA from non-UA stones on contrast-enhanced DECT urograms.

Key Points

? Computed tomography is widely used to assess renal tract calculi ? Dual-energy CT can assess stone composition and provide virtual unenhanced images ? However, iodinated contrast medium affects the volume estimation for urinary stones. ? CTR of stones is altered by the surrounding iodine in CT urograms. ? The region-growing method improves the identification of uric acid stones.     

Nitroglycerine use in transcatheter arterial (chemo)embolization in patients with hepatocellular carcinoma and dual-energy CT assessment of Lipiodol retention

Objectives

To investigate whether the addition of nitroglycerine to transcatheter arterial (chemo)embolization (TAE/TACE) can increase the delivery and effectiveness of TAE/TACE in patients with hepatocellular carcinoma (HCC) by dual-energy CT.

Methods

HCC patients (BCLC stage A or B) were randomized to (n?=?51) or not to (n?=?50) receive nitroglycerine and an emulsion of Lipiodol with or without doxorubicin, followed by embolization with Gelfoam pledgets. Dual-energy CT was performed pre- and 1 to 3?months post-embolization to assess changes in tumour diameter and Lipiodol levels in tumours.

Results

Median tumour diameter decreased from baseline in both groups with and without nitroglycerine (7.11?% vs. 12.5?%, respectively), and was statistically significant in the group receiving nitroglycerine (P?=?0.023). There was no difference between the two groups in disease response (P?=?0.237). The concentration and percentage of Lipiodol retained in tumours were significantly greater in patients treated with nitroglycerine compared to those without (median concentration 15.05?mg/mL vs. 4.40?mg/mL, respectively, P?P?Conclusions Nitroglycerine increased delivery of the Lipiodol emulsion via TAE/TACE to HCC tumours with significant tumour reduction. Dual-energy CT can accurately quantify the amount of Lipiodol deposited in tumours.

Key Points

? Nitroglycerine improves delivery of tumour-targeted therapy via enhanced permeability and retention. ? In hepatocellular carcinoma, nitroglycerine added to TAE/TACE showed greater tumour reduction. ? Dual-energy CT can reliably quantify the amount of Lipiodol in TAE/TACE.     

Ventilation imaging of the paranasal sinuses using xenon-enhanced dynamic single-energy CT and dual-energy CT: a feasibility study in a nasal cast

Objective

To show the feasibility of dual-energy CT (DECT) and dynamic CT for ventilation imaging of the paranasal sinuses in a nasal cast.

Methods

In a first trial, xenon gas was administered to a nasal cast with a laminar flow of 7?L/min. Dynamic CT acquisitions of the nasal cavity and the sinuses were performed. This procedure was repeated with pulsating xenon flow. Local xenon concentrations in the different compartments of the model were determined on the basis of the enhancement levels. In a second trial, DECT measurements were performed both during laminar and pulsating xenon administration and the xenon concentrations were quantified directly.

Results

Neither with dynamic CT nor DECT could xenon-related enhancement be detected in the sinuses during laminar airflow. Using pulsating flow, dynamic imaging showed a xenon wash-in and wash-out in the sinuses that followed a mono-exponential function with time constants of a few seconds. Accordingly, DECT revealed xenon enhancement in the sinuses only after pulsating xenon administration.

Conclusion

The feasibility of xenon-enhanced DECT for ventilation imaging was proven in a nasal cast. The superiority of pulsating gas flow for the administration of gas or aerosolised drugs to the paranasal sinuses was demonstrated.

Key Points

? Ventilation of the paranasal sinuses is poorly understood. ? Dual-energy CT ventilation imaging has been explored using phantom simulation. ? Xenon can be seen in the paranasal sinuses using pulsating xenon flow. ? Dual-energy CT uses a lower radiation dose compared with dynamic ventilation CT.     

Accuracy of dual-energy computed tomography for the measurement of iodine concentration using cardiac CT protocols: validation in a phantom model

Purpose

To assess the accuracy of dual-energy CT (DECT) for the quantification of iodine concentrations in a thoracic phantom across various cardiac DECT protocols and simulated patient sizes.

Materials and methods

Experiments were performed on first- and second-generation dual-source CT (DSCT) systems in DECT mode using various cardiac DECT protocols. An anthropomorphic thoracic phantom was equipped with tubular inserts containing known iodine concentrations (0–20 mg/mL) in the cardiac chamber and up to two fat-equivalent rings to simulate different patient sizes. DECT-derived iodine concentrations were measured using dedicated software and compared to true concentrations. General linear regression models were used to identify predictors of measurement accuracy

Results

Correlation between measured and true iodine concentrations (n?=?72) across CT systems and protocols was excellent (R?=?0.994–0.997, P?<?0.0001). Mean measurement errors were 3.0?±?7.0 % and ?2.9?±?3.8 % for first- and second-generation DSCT, respectively. This error increased with simulated patient size. The second-generation DSCT showed the most stable measurements across a wide range of iodine concentrations and simulated patient sizes.

Conclusion

Overall, DECT provides accurate measurements of iodine concentrations across cardiac CT protocols, strengthening the case for DECT-derived blood volume estimates as a surrogate of myocardial blood supply.

Key Points

? Dual-energy CT provides new opportunities for quantitative assessment in cardiac imaging. ? DECT can quantify myocardial iodine as a surrogate for myocardial perfusion. ? DECT measurements of iodine concentrations are overall very accurate. ? The accuracy of such measurements decreases as patient size increases.     

Cochlear implant with a non-removable magnet: preliminary research at 3-T MRI

Objective

To perform preliminary tests in vitro and with healthy volunteers to determine the 3-T MRI compatibility of a cochlear implant with a non-removable magnet.

Methods

In the in vitro phase, we tested six implants for temperature changes and internal malfunctioning. We measured the demagnetisation of 65 internal magnets with different tilt angles between the implant’s magnetic field (bi) and the main magnetic field (b0). In the in vivo phase, we tested 28 operational implants attached to the scalps of volunteers with the head in three different positions.

Results

The study did not find significant temperature changes or electronic malfunction in the implants tested in vitro. We found considerable demagnetisation of the cochlear implant magnets in the in vitro and in vivo testing influenced by the position of the magnet in the main magnetic field. We found that if the bi/b0 angle is <90°, there is no demagnetisation; if the bi/b0 angle is >90°, there is demagnetisation in almost 60 % of the cases. When the angle is around 90°, the risk of demagnetisation is low (6.6 %).

Conclusion

The preliminary results on cochlear implants with non-removable magnets indicate the need to maintain the contraindication of passage through 3-T MRI.

Key Points

? Magnetic resonance imaging can affect cochlear implants and vice versa. ? Demagnetisation of cochlear implant correlates with the angle between bi and b0. ? The position of the head in the MRI influences the demagnetisation. ? Three-Tesla MRI for cochlear implants is still contraindicated. ? However some future solutions are discussed.     

Can single-phase dual-energy CT reliably identify adrenal adenomas?

Purpose

To evaluate whether single-phase dual-energy-CT-based attenuation measurements can reliably differentiate lipid-rich adrenal adenomas from malignant adrenal lesions.

Materials and methods

We retrospectively identified 51 patients with adrenal masses who had undergone contrast-enhanced dual-energy-CT (140/100 or 140/80 kVp). Virtual non-contrast and colour-coded iodine images were generated, allowing for measurement of pre- and post-contrast density on a single-phase acquisition. Adrenal adenoma was diagnosed if density on virtual non-contrast images was ≤10 HU. Clinical follow-up, true non-contrast CT, PET/CT, in- and opposed-phase MRI, and histopathology served as the standard of reference.

Results

Based on the standard of reference, 46/57 (80.7 %) adrenal masses were characterised as adenomas or other benign lesions; 9 malignant lesions were detected. Based on a cutoff value of 10 HU, virtual non-contrast images allowed for correct identification of adrenal adenomas in 33 of 46 (71 %), whereas 13/46 (28 %) adrenal adenomas were lipid poor with a density ≥10 HU. Based on the threshold of 10 HU on the virtual non-contrast images, the sensitivity, specificity, and accuracy for detection of benign adrenal lesions was 73 %, 100 %, and 81 % respectively.

Conclusion

Virtual non-contrast images derived from dual-energy-CT allow for accurate characterisation of lipid-rich adrenal adenomas and can help to avoid additional follow-up imaging.

Key Points

? Adrenal adenomas are a common lesion of the adrenal glands. ? Differentiation of benign adrenal adenomas from malignant adrenal lesions is important. ? Dual-energy based virtual non-contrast images help to evaluate patients with adrenal adenomas.     

Single-source dual-energy CT angiography with reduced iodine load in patients referred for aortoiliofemoral evaluation before transcatheter aortic valve implantation: impact on image quality and radiation dose

Objectives

To compare image quality and radiation dose of pre-transcatheter aortic valve implantation (TAVI) aortoiliofemoral CT angiography (AICTA) provided by standard vs. dual-energy mode with reduced iodine load protocols.

Methods

One hundred and sixty-one patients underwent a two-step CTA protocol before TAVI including cardiac CTA with injection of 65 mL of iodinated contrast agent (ICA), immediately followed by AICTA. From this second acquisition, the following three different patient groups were identified: Group 1: 52 patients with standard AICTA (60 mL ICA, 100 kVp, mA automodulation); Group 2: 48 patients with dual-energy AICTA with 50 % iodine load reduction (30 mL ICA, fast kVp switching, 600 mA); Group 3: 61 patients with an identical protocol to Group 2, but exposed to 375 mA. The qualitative/subjective image quality (13-point score) and quantitative/objective image quality (contrast attenuation and image noise) were evaluated. The radiation dose was recorded.

Results

There was no significant difference in non-diagnostic images between the three protocols. Contrast attenuation, signal-to-noise ratio and contrast-to-noise ratio were significantly higher, whereas noise was significantly lower in the standard protocol (all P?P?Conclusions Dual-energy AICTA before TAVI results in a reduction of iodine load while maintaining sufficient diagnostic information despite increased noise.

Key Points

? Dual-energy AICTA before TAVI results in a 50 % reduction of iodine load. ?The reduction of iodine load maintains sufficient image quality despite increased noise. ? Using 375 mA in dual-energy mode results in a reduction of radiation dose. ? A high tube current setting (600 mA) should be used in overweight patients.     

Dual-energy CT with tin filter technology for the discrimination of renal lesion proxies containing blood, protein, and contrast-agent. An experimental phantom study

Purpose

To differentiate proxy renal cystic lesions containing protein, blood, iodine contrast or saline solutions using dual-energy CT (DECT) equipped with a new tin filter technology (TFT).

Materials and methods

70 proxies (saline, protein, blood and contrast agent) were placed in unenhanced and contrast-enhanced kidney phantoms. DECT was performed at 80/140 kV with and without tin filtering. Two readers measured the CT attenuation values in all proxies twice. An 80/140 kV ratio was calculated.

Results

All intra- and interobserver agreements were excellent (r?=?0.93–0.97; p?<?0.001). All CT attenuation values were significantly higher in the enhanced than in the unenhanced setting (p?<?0.05; average increase, 12.5?±?3.6HU), while the ratios remained similar (each, p?>?0.05). The CT attenuation of protein, blood and contrast agent solution differed significantly with tin filtering (p?<?0.01–0.05). Significant differences were found between the ratios of protein and blood compared to contrast medium solution (each, p?<?0.05) and between the ratios of protein and blood in both phantoms with tin filtering (each, p?<?0.05).

Conclusion

DECT allows discrimination between a proxy renal lesion containing contrast agent and lesions containing protein and blood through their different attenuation at 80 kV and 140 kV. Further discrimination between protein and blood containing proxies is possible when using a tin filter.     

Can virtual non-enhanced CT be used to replace true non-enhanced CT for the detection of palpable cervical lymph nodes? A preliminary study

Purpose

To investigate the potential of virtual non-contrast CT (VNCT) from dual-energy CT to replace true nonenhanced CT (TNCT) for the detection of enlarged cervical lymph nodes.

Materials and methods

Thirty-nine patients with 94 histopathologically proven cervical lymph nodes were imaged with the dual-energy CT technique. VNCT images from the arterial [VNCT-A] and venous phases [VNCT-V] were obtained with the liver VNC application. The mean CT number and signal-to-noise ratio (SNR) were compared. Image quality was evaluated with a score scale of 1–5. Effective dose (ED) was calculated and compared.

Results

Mean CT numbers of cervical lymph nodes were higher on VNCT than on TNCT (P = 0.034). There was no difference in the SNR among three sets of non-enhanced CT images, but the CNR of VNCT images was higher than that of TNCT images (P < 0.001). Image quality of VNCT from two phases was comparable to that of TNCT (P = 0.070). There was no difference in image quality of three sets of non-enhanced CT images (P > 0.05). ED from dual-phase dual-energy CT was lower than that from tri-phase CT scans (P < 0.001).

Conclusion

VNCT images from dual-energy CT of the neck had diagnostic image quality; they have the potential to replace TNCT, thus reducing the radiation dose.     

Visualization of joint and bone using dual-energy CT arthrography with contrast subtraction: in vitro feasibility study using porcine joints

Objective

To assess the feasibility of subtracting various concentrations of iodinated contrast material on dual-energy computed tomographic (DECT) arthrography to provide both CT arthrography and virtual unenhanced CT (VUCT) in a single CT acquisition.

Materials and Methods

This was an in vitro study for which institutional review board approval was not required. CT arthrographies of 12 joints of pig cadavers were obtained using dual-energy CT. Various concentrations of iodinated contrast material, 25% (75 mg/ml), 50% (150 mg/ml), 75% (225 mg/ml), and 100% (300 mg/ml) were used for the DECT arthrography. The paired regions of interest (ROI) were drawn over the same location on two paired CT scans at different tube voltages (80 kVp and 140 kVp). The average Hounsfield units (HU) ratio of the contrast media(HU on CT at 80 kVp/HU on CT at 140 kVp) was calculated for each joint. Subtraction of contrast material was carried out using VUCT application

Results

The 25% iodinated contrast mixture was successfully subtracted from DECT arthrography of four joints, in which the average HU ratio ranged from 1.95 to 2.0. The subtraction of the 50%,75%, and 100% iodine contrast mixtures was not successful, because of the upper demonstrable HU limit in dual-energy CT.

Conclusions

DECT arthrography with 25% iodinated contrast medium injection can provide both CT arthrography and virtual unenhanced images in a single CT acquisition     

Topogram-based automated selection of the tube potential and current in thoraco-abdominal trauma CT – a comparison to fixed kV with mAs modulation alone

Objective

To investigate the impact of automated attenuation-based tube potential selection on image quality and exposure parameters in polytrauma patients undergoing contrast-enhanced thoraco-abdominal CT.

Methods

One hundred patients were examined on a 16-slice device at 120 kV with 190 ref.mAs and automated mA modulation only. Another 100 patients underwent 128-slice CT with automated mA modulation and topogram-based automated tube potential selection (autokV) at 100, 120 or 140 kV. Volume CT dose index (CTDI_vol), dose–length product (DLP), body diameters, noise, signal-to-noise ratio (SNR) and subjective image quality were compared.

Results

In the autokV group, 100 kV was automatically selected in 82 patients, 120 kV in 12 patients and 140 kV in 6 patients. Patient diameters increased with higher kV settings. The median CTDI_vol (8.3 vs. 12.4 mGy; ?33 %) and DLP (594 vs. 909 mGy cm; ?35 %) in the entire autokV group were significantly lower than in the group with fixed 120 kV (p?<?0.05 for both). Image quality remained at a constantly high level at any selected kV level.

Conclusion

Topogram-based automated selection of the tube potential allows for significant dose savings in thoraco-abdominal trauma CT while image quality remains at a constantly high level.

Key Points

? Automated kV selection in thoraco-abdominal trauma CT results in significant dose savings ? Most patients benefit from a 100-kV protocol with relevant DLP reduction ? Constantly good image quality is ensured ? Image quality benefits from higher kV when arms are positioned downward     

Differentiation of heroin and cocaine using dual-energy CT—an experimental study

Objective

To evaluate if heroin and cocaine can be distinguished using dual-energy CT.

Materials and methods

Twenty samples of heroin and cocaine at different concentrations and standardized compression (SC) were scanned in dual-energy mode on a newest generation Dual Energy 64-row MDCT scanner. CT number, spectral graphs, and dual-energy index (DEI) were evaluated. Results were prospectively tested on six original samples from a body packer. Wilcoxon’s test was used for statistical evaluation.

Results

Values are given as median and range. Under SC, the CT number of cocaine samples (?29.87 Hounsfield unit (HU) [?125.85; 16.16 HU]) was higher than the CT number of heroin samples (?184.37 HU [?199.81; ?159.25 HU]; p?<?0.01). Slope of spectral curves for cocaine was ?2.36 HU/keV [?7.15; ?0.67 HU/keV], and for heroin, 1.75 HU/keV [1.28; 2.5 HU/keV] (p?<?0.01). DEI was 0.0352 [0.0081; 0.0528] for cocaine and significantly higher than for heroin samples (?0.0127 [?0.0097; ?0.0159]; p?<?0.001). While CT number was inconclusive, all six original packs were correctly classified after evaluation of the spectral curve and DEI. In contrast to the CT number, slope of the spectral curve and DEI were independent of concentration and compression.

Conclusion

The slope of the spectral curve and the DEI from dual-energy CT data can be used to distinguish heroin and cocaine in vitro; these results are independent of compression and concentration in the measured range.     

Dual-energy computed tomography after endovascular aortic aneurysm repair: The role of hard plaque imaging for endoleak detection

Objectives

To assess the diagnostic accuracy of dual-energy computed tomography (DECT) for detection of endoleaks and aneurysm sac calcifications after endovascular aneurysm repair (EVAR) using hard plaque imaging algorithms.

Materials and methods

One hundred five patients received 108 triple-phase contrast-enhanced CT (non-contrast, arterial and delayed phase) after EVAR. The delayed phase was acquired in dual-energy and post-processed using the standard (HPI-S) and a modified (HPI-M) hard plaque imaging algorithm. The reference standard was determined using the triple-phase CT and contrast-enhanced ultrasound. All images were analysed separately for the presence of endoleaks and calcifications by two independent readers; sensitivity, specificity and interobserver agreement were calculated.

Results

Endoleaks and calcifications were present in 25.9 % (28/108) and 20.4 % (22/108) of images. The HPI-S images had a sensitivity/specificity of 54 %/100 % (reader 1) and 57 %/99 % (reader 2), the HPI-M images of 93 %/92 % (reader 1) and 96 %/92 % (reader 2) for detection of endoleaks. For detection of calcifications HPI-S had a sensitivity/specificity of 91 %/99 % (reader 1) and 95 %/97 % (reader 2), the HPI-M images of 91 %/99 % (reader 1) and 91 %/99 % (reader 2), respectively.

Conclusion

Using HPI-M, DECT enables an accurate diagnosis of endoleaks after EVAR and allows distinguishing between endoleaks and calcifications with high diagnostic accuracy.

Key Points

? Dual-energy computed tomography allows the diagnosis of aortic pathologies after EVAR. ? Hard plaque imaging algorithms can distinguish between endoleaks and aneurysm sac calcifications. ? The modified hard plaque imaging algorithm detects endoleaks with high diagnostic accuracy.     

Detection of pulmonary fat embolism with dual-energy CT: an experimental study in rabbits

Objectives

To evaluate the use of dual-energy CT imaging of the lung perfused blood volume (PBV) for the detection of pulmonary fat embolism (PFE).

Methods

Dual-energy CT was performed in 24 rabbits before and 1 hour, 1 day, 4 days and 7 days after artificial induction of PFE via the right ear vein. CT pulmonary angiography (CTPA) and lung PBV images were evaluated by two radiologists, who recorded the presence, number, and location of PFE on a per-lobe basis. Sensitivity, specificity, and accuracy of CTPA and lung PBV for detecting PFE were calculated using histopathological evaluation as the reference standard.

Results

A total of 144 lung lobes in 24 rabbits were evaluated and 70 fat emboli were detected on histopathological analysis. The overall sensitivity, specificity and accuracy were 25.4 %, 98.6 %, and 62.5 % for CTPA, and 82.6 %, 76.0 %, and 79.2 % for lung PBV. Higher sensitivity (p?<?0.001) and accuracy (p?<?0.01), but lower specificity (p?<?0.001), were found for lung PBV compared with CTPA. Dual-energy CT can detect PFE earlier than CTPA (all p?<?0.01).

Conclusion

Dual-energy CT provided higher sensitivity and accuracy in the detection of PFE as well as earlier detection compared with conventional CTPA in this animal model study.

Key points

? Fat embolism occurs commonly in patients with traumatic bone injury.? Dual-energy CT improves diagnostic performance for pulmonary fat embolism detection.? Dual-energy CT can detect pulmonary fat embolism earlier than CTPA.

     

Urinary stone detection and characterisation with dual-energy CT urography after furosemide intravenous injection: preliminary results

Objectives

To investigate the added advantage of IV furosemide injection and the subsequent urine dilution in the detection of urinary calculi in the excretory phase of dual-source dual-energy (DE) computed tomography (CT) urography, and to investigate the feasibility of characterising the calculi through diluted urine.

Methods

Twenty-three urinary calculi were detected in 116 patients who underwent DECT urography for macroscopic haematuria with a split bolus two- or three-acquisition protocol, including a true unenhanced series and at least a mixed nephrographic excretory phase. Virtual unenhanced images were reconstructed from contrast-enhanced DE data. Calculi were recorded on all series and characterised based on their X-ray absorption characteristics at 100 kVp and 140 kVp in both true unenhanced and nephrographic excretory phase series.

Results

All calculi with a diameter more than 2 mm were detected in the virtual unenhanced phase and in the nephrographic excretory phase. Thirteen of these calculi could be characterised in the true unenhanced phase and in the mixed nephrographic excretory phase. The results were strictly identical for both phases, six of them being recognised as non-uric acid calculi and seven as uric acid calculi.

Conclusions

Mixed nephrographic excretory phase DECT after furosemide administration allows both detection and characterisation of clinically significant calculi, through the diluted urine.

Key points

? Urinary tract stones can be detected on excretory phase through diluted urine. ? Urinary tract stone characterisation with dual-energy CT (DECT) is possible through diluted urine. ? A dual energy split-bolus CT urography simultaneously enables urinary stone detection and characterisation.