70 kV computed tomography of the thorax: valence for computer-assisted nodule evaluation and radiation dose - first clinical results.

BACKGROUND: Computed tomography (CT) is the gold standard for evaluation of pulmonary nodules and is at the same time responsible for the majority of the collective effective dose. PURPOSE: To evaluate radiation dose and efficacy of computer-assisted detection (CAD) for solid pulmonary nodules in low dose chest CT performed at 70 kV. MATERIAL AND METHODS: CAD was performed upon chest CT with 70 kV and 100 kV (gold standard) at manufacture's recommended tube current of 87 mAs (collimation, 64 × 0.6 mm). Detection rate for pulmonary nodules and size measurements of both techniques were compared to each other. Radiation dosage in terms of effective dose (E) was measured using an Alderson-Rando Phantom. RESULTS: Seventy-four patients with 301 solid nodules were included in the study. CAD detection rate was similar for 70 kV (94.7%) and 100 kV (92.4%). Mean transversal nodule diameter was 5.5 mm for 70 kV and 5.7 mm for 100 kV with an average volume of 0.12 mL (both techniques). Derived from the phantom measurements patient examinations resulted in an E of 0.51 mSv (70 kV) versus 2.02 mSv (100 kV). CONCLUSION: 70 kV low-dose chest CT is suitable for CAD based lung nodule analysis at a fraction of the radiation burden of the standard technique. Since the measurements are highly accurate, 70 kV CT could be used for detection of pulmonal lesions as well as follow-up studies.

CT-based evaluation of tissue expansion in cryoablation of ex vivo kidney.

OBJECTIVES: To evaluate tissue expansion during cryoablation, the displacement of markers in ex vivo kidney tissue was determined using computed tomographic (CT) imaging. METHODS: CT-guided cryoablation was performed in nine porcine kidneys over a 10 min period. Markers and fiber optic temperature probes were positioned perpendicular to the cryoprobe shaft in an axial orientation. The temperature measurement was performed simultaneously with the acquisitions of the CT images in 5 s intervals. The distance change of the markers to the cryoprobe was determined in each CT image and equated to the measured temperature at the marker. RESULTS: The greatest increase in the distance between the markers and the cryoprobe was observed in the initial phase of cryoablation. The maximum displacement of the markers was determined to be 0.31±0.2 mm and 2.8±0.02 %, respectively. CONCLUSIONS: The mean expansion of ex vivo kidney tissue during cryoablation with a single cryoprobe is 0.31±0.2 mm. The results can be used for identification of basic parameters for optimization of therapy planning.

Accuracy and speed of robotic assisted needle interventions using a modern cone beam computed tomography intervention suite: a phantom study.

OBJECTIVE: To analyse the feasibility and accuracy of robotic aided interventions on a phantom when using a modern C-arm-mounted cone beam computed tomography (CBCT) device in combination with needle guidance software. METHODS: A small robotic device capable of holding and guiding needles was attached to the intervention table. After acquiring a 3D data set the access path was planned on the CBCT workstation and shown on the intervention monitor. Then the robot was aligned to the live fluorosopic image. A total of 40 punctures were randomly conducted on a phantom armed with several targets (diameter 2 mm) in single and double oblique trajectory (n = 20 each). Target distance, needle deviation and time for the procedures were analysed. RESULTS: All phantom interventions (n = 40) could be performed successfully. Mean target access path within the phantom was 8.5 cm (min 4.2 cm, max 13.5 cm). Average needle tip deviation was 1.1 mm (min 0 mm, max 4.5 mm), time duration was 3:59 min (min 2:07 min, max 10:37 min). CONCLUSION: When using the proposed robot device in a CBCT intervention suite, highly accurate needle-based interventional punctures are possible in a reasonable timely manner in single as well as in double oblique trajectories.

The influence of Nd:YAG laser irradiation on Fluoroptic® temperature measurement: an experimental evaluation.

The aim of this study was to experimentally evaluate temperature monitoring with a Fluoroptic® temperature probe in the presence of laser irradiation from a Nd:YAG laser, which is mainly used for clinical MR-guided laser-induced interstitial thermotherapy. Temperature measurements were performed using a Fluoroptic® probe in comparison to a thermocouple probe in a gel phantom and an ex vivo pig liver at distances of 6.5 to 14 mm to the laser applicator (laser energy of 30.8 W). To evaluate the artifacts in the temperature measurement, the laser was turned on and off three times during the entire experiment. A comparison of the fiber-optic measurements with MR thermometry was also performed in pig liver by means of the proton resonance frequency method at a distance of 6 mm. Depending on the distance, the temperature measured by the fiber-optic probe deviated from the thermocouple probe temperature. The phantom deviations of 0.4 to 34.3 % were observed. The differences in the liver were smaller and ranged from 1.6 to 5.2 %. The Bland-Altman mean of differences between MR and fiber-optic temperature measurements was 0.02 °C and the 95 % limits of agreement value was ± 2.25°C. During laser application, considerable artifacts occurred in the Fluoroptic® measurements in short distances which was induced by laser energy absorption by the probe coating. No artifacts were verifiable at a distance of 14 mm in both mediums. The good conformity with MR thermometry resulted from the shorter turn-on times of the laser since the laser irradiation had only a minor effect on the measurements.

Automatic bone removal technique in whole-body dual-energy CT angiography: performance and image quality.

OBJECTIVE: The purpose of this study was to evaluate the efficiency of automatic bone removal in dual-energy CT angiography (CTA) of the trunk. SUBJECTS AND METHODS: Nineteen patients underwent dual-energy CTA of the trunk (tube A, 140 kV; tube B, 100 kV). In addition to the dual-energy dataset, an image equivalent to that of a standard 120-kV single-energy examination was generated with both tubes. Automated bone segmentation was performed on both datasets, and the results were analyzed. The time required for and subjective image quality of the maximum intensity projections (MIPs) generated were evaluated. RESULTS: Errors in bone segmentation were found for 1.5% of bones on dual-energy images and 12.4% of bones on single-energy images (p < 0.01). The most important differences were found in the rib cage, sternum, and pelvis. The times required for postprocessing of MIPs were similar for the dual-energy (113.5 seconds) and single-energy (106.8 seconds) techniques. The subjective image quality of the arteries was considered better for dual-energy CTA (4.5 points) than for single-energy CTA (4.1 points) owing to false cutoff of vessels during the bone removal process on the single-energy images (p = 0.026). CONCLUSION: For CTA of the trunk, the dual-energy postprocessing capabilities for 3D visualization are superior to the threshold-based bone removal of single-energy CT. Dual-energy CTA can generate boneless MIP images of substantial quality.

Evaluation of the thermal sensitivity of porcine liver in CT-guided cryoablation: an initial study.

PURPOSE: To evaluate computed tomography (CT)-based thermometry in cryoablation, the thermal sensitivity of an ex-vivo porcine liver was determined in an initial study design. METHODS: The CT-guided cryoablation was performed in three porcine liver samples over a period of 10 min. Fiber optic temperature probes were positioned parallel to the shaft of the cryoprobe in an axial slice orientation. During ablation, temperature measurements were performed simultaneously with CT imaging at 5 s intervals. On the CT images, the average CT number was calculated for a region of interest of 3 × 3 pixels just below the tip of each temperature probe. A linear regression analysis was performed using eleven data sets to determine the dependence of the CT number on the temperature. RESULTS: With decreasing temperature, an increasing hypodense area around the tip of the cryoprobe was observed on the CT images and decreasing values of the CT number were determined. Starting at a temperature of - 40°C a linear relation between the CT number and the temperature was determined and a thermal sensitivity of 0.95 HU/°C (R2  = 0.73) was obtained. The thermal sensitivity was used to calculate color-coded temperature maps. The calculated temperature distribution corresponds quantitatively to the increasing hypodense area. CONCLUSIONS: A noninvasive CT-based temperature determination during cryoablation in a normal ex vivo porcine liver is feasible. A thermal sensitivity of 0.95 HU/°C was determined by linear regression analysis. A color-coded map of the temperature distribution was presented.

Comparison of thick- and thin-slice images in thoracoabdominal trauma CT: a retrospective analysis.

PURPOSE: To compare thick (5 mm) and thin slice images (1.5 mm) of lung, soft tissue, and bone window in thoracoabdominal trauma computed tomography. MATERIALS AND METHODS: 167 Patients that underwent thoracoabdominal trauma CT between November 2014 and December 2015 were included in the study. CT data were reconstructed in a transverse direction with 5 mm and 1.5 mm slice images of lung, soft tissue, and bone window. Two blinded raters (radiologists) evaluated the collected data by detecting predefined injuries in different organ areas. Reconstruction and evaluation times as well as detected injuries were noted and compared. RESULTS: Reconstruction and evaluation times were significantly higher with 1.5 mm thin-slice images, and the effect strength according to Rosenthal displayed a strong effect of 0.61 (< 0.1 small effect, 0.3 middle effect, and > 0.5 strong effect). Average evaluation time differences were 62.7 s (33.9 s-91.5 s) in bone window between 1.5 mm and 3 mm for rater 1 (p < 0.001) and 71.4 s (43.1 s-99.7 s) for rater 2 (p < 0.001). Average time differences between 1.5 mm and 5 mm were 68,7 s (43.9 s-93.5 s) for rater 1 and 75.3 s (44.7 s-105.9 s) for rater 2 in lung window (p < 0.001) and 66.6 s (28.8 s-104.4 s) for rater 1 and 114 s (74.4 s-153.6 s) for rater 2 in soft-tissue window (p < 0.001). There was no significant difference regarding soft-tissue and lung injuries, except non-significant improvement in the detection of bone fractures. CONCLUSION: Thin-slice images do not bring any significant benefit in thoracoabdominal trauma CT of soft-tissue and lung injuries, but they can be helpful for the diagnosis of bone fractures and incidental findings.

Activation of tumor-specific T lymphocytes after laser-induced thermotherapy in patients with colorectal liver metastases.

PURPOSE: To asses if laser-induced thermotherapy (LITT) induces a specific cytotoxic T cell response in patients treated with LITT for colorectal cancer liver metastases. METHODS: Eleven patients with liver metastases of colorectal cancer underwent LITT. Blood was sampled before and after LITT. Peripheral T cell activation was assessed by an interferon gamma (IFNg) secretion assay and flow cytometry. Test antigens were autologous liver and tumor lysate obtained from each patient by biopsy. T cells were stained for CD3/CD4/CD8 and IFNg to detect activated T cells. The ratio of IFNg positive to IFNg negative T cells was determined as the stimulation index (SI). To assess cytolytic activity, T cells were co-incubated with human colorectal cancer cells (CaCo) and cytosolic adenylate kinase release was measured by a luciferase assay. RESULTS: IFNg secretion assay: before LITT SI was 12.73 (+/-4.83) for CD3+, 4.36 (+/-3.32) for CD4+ and 3.64 (+/-1.77) for CD8+ T cells against autologous tumor tissue. Four weeks after LITT SI had increased to 92.09 (+/-12.04) for CD3+ (P < 0.001), 42.92 (+/-16.68) for CD4+ (P < 0.001) and 47.54 (+/-15.68) for CD8+ T cells (P < 0.001) against autologous tumor tissue. No increased SI was observed with normal liver tissue at any time point. Cytotoxicity assay: before LITT activity against the respective cancer cells was low, with RLU = 1,493 (+/-1,954.68), whereas after LITT cytolytic activity had increased to RLU = 7,260 [+/-3,929.76 (P < 0.001)]. CONCLUSION: Patients with liver metastases of colorectal cancer show a tumor-specific cytotoxic T cell stimulation and a significantly increased cytolytic activity of CD3+, CD4+ and CD8+ T cells after LITT against an allogenic tumor (CaCo cell line).

Diffusion-weighted imaging and ADC mapping of head-and-neck paragangliomas: initial experience.

BACKGROUND: Paragangliomas are rare, hypervascularized benign tumors. In some cases a clear differentiation of paragangliomas and other entities is impossible. PATIENTS AND METHODS: The authors evaluated ten patients with skull base lesions (paraganglioma n = 7, meningioma n = 1, giant cell tumor n = 1, and neurinoma n = 1) in addition to conventional magnetic resonance imaging (MRI) with diffusion-weighted imaging (DWI), and calculation of apparent diffusion coefficient (ADC). RESULTS: Mean ADC values +/- standard deviation of the paragangliomas were 1.304 +/- 0.257 x 10(-3) mm(2)/s and differed from ADC values of the other jugular fossa tumors with 0.743 +/- 0.108 x 10(-3) mm(2)/s and measurement derived from the cerebellum with 0.802 +/- 0.075 x 10(-3) mm(2)/s. CONCLUSION: Due to the difference of ADC values, the authors propose that DWI and ADC mapping could be a promising tool in the diagnostic work-up of paragangliomas.

Ex vivo validation of microwave thermal ablation simulation using different flow coefficients in the porcine liver.

The purpose of the study was to validate the simulation model for a microwave thermal ablation in ex vivo liver tissue. The study aims to show that heat transfer due to the flow of tissue water during ablation in ex vivo tissue is not negligible. Ablation experiments were performed in ex vivo porcine liver with microwave powers of 60 W to 100 W. During the procedure, the temperature was recorded in the liver sample at different distances to the applicator using a fiber-optic thermometer. The position of the probes was identified by CT imaging and transferred to the simulation. The simulation of the heat distribution in the liver tissue was carried out with the software CST Studio Suite. The results of the simulation with different flow coefficients were compared with the results of the ablation experiments using the Bland-Altman analysis. The analysis showed that the flow coefficient of 90,000 W/(K*m3) can be considered as the most suitable value for clinically used powers. The presented simulation model can be used to calculate the temperature distribution for microwave ablation in ex vivo liver tissue.

High-pitch Dual-source CT Angiography before TAVI - the Value of ECG Gating.

PURPOSE: To investigate image quality, and radiation dose between ECG-gated singlesource and dual-source CT Angiography (CTA) protocols for planning of Trans-catheter Aortic Valve Implantation (TAVI) with a reference non ECG-gated single-source protocol. METHODS: A total of 120 patients were included in four groups: Non ECG-gated single-source (SS), ECG-gated single-source (SSECG), ECG-gated dual-source high-pitch (DSECG), or non-ECG-gated dual-source high-pitch mode (DS). Qualitative image quality of the aortic annulus, aortic valve, and coronary ostia as well as presence of motion or stair-step artefacts of the thoracic aorta were independently assessed by two readers. Quantitative image quality was assessed to calculate contrast to noise ratio. RESULTS: Subjective and objective scoring of motion artefacts was significantly reduced in SSECG, DSECG and DS (p= 0.010). The imaging length was comparable between groups. Aortic annulus, aortic valve, and coronary ostia were reliably evaluable in all patients with SSECG, DSECG and DS protocols. CONCLUSION: High-pitch, dual-source CT angiography of the whole aorta with or without ECG gating is a dose-efficient and time-saving examination strategy before TAVI. However acquisition timing within the cardiac cycle needs to be taken into account.

Study on the effect of chemoembolization combined with microwave ablation for the treatment of hepatocellular carcinoma in rats.

PURPOSE: We aimed to evaluate the combining effects of transarterial chemoembolization (TACE) and open local thermal microwave ablation in a hepatocellular carcinoma animal model. METHODS: Tumor cubes were implanted into the liver of 30 male inbred ACI rats. Groups of 10 animals were treated at 13 days (TACE or microwave ablation) and 16 days (microwave ablation) postimplantation with combined therapy of TACE (0.1 mg mitomycin C; 0.1 mg iodized oil; 5.0 mg degradable starch microspheres) and microwave ablation (2450 Mhz; 45 s; 35 W) (study group A), TACE alone (control group B), or microwave ablation alone (control group C). At day 12 and day 25 tumor size was measured via magnetic resonance imaging and the relative growth ratio was calculated. Hepatic specimens were immunohistochemically examined for the expression of vascular endothelial growth factor (VEGF). RESULTS: Mean growth rates were 1.34±0.19 in group A, 3.19±0.13 in group B, and 4.18±0.19 in group C. Compared with control groups B and C, tumor growth rate in group A was significantly inhibited (P < 0.01). The VEGF-antibody reaction in peritumoral tissue (staining intensity at portal triad, percent antibody reaction and staining intensity at central vein) was significantly lower in group A compared with group B (P < 0.01). No significant difference between group A and group C could be observed. CONCLUSION: This investigation shows improved results of TACE followed by microwave ablation as treatment of hepatocellular carcinoma in a rat model, compared with single therapy regimen regarding the inhibition of growth rate and reduction of VEGF-level in peritumoral tissue.

Transarterial administration of integrin inhibitor loaded nanoparticles combined with transarterial chemoembolization for treating hepatocellular carcinoma in a rat model.

AIM: To compare the effect of transarterial chemoembolization (TACE) plus GRGDSP (Gly-Arg-Gly-Asp-Ser-Pro, integrin-inhibitor) loaded nanoparticles with TACE alone or TACE + GRGDSP in a rat model of liver tumor. METHODS: Morris hepatoma 3924A tumors were implanted in the livers of 30 ACI rats. The ACI rats were divided randomly into three groups (10 animals each). Tumor volume before treatment (V1) was examined by magnetic resonance imaging (MRI), and then, after laparotomy and placement of a PE-10 catheter into the hepatic artery, the following interventional protocols were performed: TACE (mitomycin C + lipiodol + degradable starch microspheres) + GRGDSP loaded nanoparticles for group A; TACE + GRGDSP for group B (control group 1); TACE alone for group C (control group 2). Tumor volume (V2) was assessed by MRI and the mean ratio of the post-treatment to pretreatment tumor volumes (V2/V1) was calculated. Immunohistochemical analysis was performed to assess the quantification of matrix metalloprotein 9 (MMP-9) and vascular endothelial growth factor (VEGF) positive tumor cells in each treatment group. RESULTS: The mean tumor growth ratios (V2/V1) were 1.3649 ± 0.1194 in group A, 2.0770 ± 0.1595 in group B, and 3.2148 ± 0.1075 in group C. Compared with groups B and C, group A showed a significant reduction in tumor volume. Lower expression of MMP-9 and VEGF in hepatocellular carcinoma was observed in group A than in groups B and C. The angiogenesis of tumor was evaluated using anti-VEGF antibodies, and the metastasis of tumor was assessed using anti-MMP-9 antibody. MMP-9 and VEGF were expressed in all specimens. The immunoexpression of these proteins was confirmed by the presence of red cytoplasmic staining in tumor cells. Lower expression of MMP-9 and VEGF in hepatocellular carcinoma was observed in group A than in groups B and C. CONCLUSION: Transarterial administration of integrin inhibitor loaded nanoparticles combined with TACE evidently retards tumor growth and intrahepatic metastases compared with TACE alone or TACE plus integrin inhibitor in an animal model of hepatocellular carcinoma.

Magnetic resonance-guided laser-induced interstitial thermotherapy of breast cancer liver metastases and other noncolorectal cancer liver metastases: an analysis of prognostic factors for long-term survival and progression-free survival.

PURPOSE: The purpose of this study was the evaluation of prognostic factors for long-term survival and progression-free survival (PFS) after treatment of noncolorectal cancer liver metastases through MR-guided laser-induced thermotherapy (LITT). PATIENTS AND METHODS: We included 401 patients (mean age, 57.3 years) with liver metastases from different primary tumors who were treated with LITT. Long-term survival and progression-free-survival rates were evaluated using the Kaplan-Meier method. A Cox regression model tested different parameters that could be of prognostic value. The tested prognostic factors were as follows: the location of primary tumor, TNM classification, extrahepatic metastases, hepatic resection or neoadjuvant transarterial chemoembolization or systemic chemotherapy before LITT, the number of initial metastases, the volume of metastases, and the quotient of total volumes of metastases and necroses per patient. RESULTS: The median survival was 37.6 months starting from the date of LITT. The 1-, 2-, 3-, 4-, and 5-year survival rates were 86.5%, 67.2%, 51.9%, 39.9%, and 33.4%, respectively. The median PFS was 12.2 months. The 1-, 2-, 3-, 4-, and 5-year PFS rates were 50.6%, 33.8%, 26%, 20.4%, and 17%, respectively. The initial number of metastases, the volumes of metastases, and the quotient of the volumes of metastases and necroses influenced the long-term survival and the PFS. CONCLUSIONS: Laser-induced thermotherapy is a minimally invasive method in the treatment of hepatic metastases of noncolorectal cancer, and it shows good results in long-term survival and PFS. The initial number of metastases and their volume are the most important prognostic factors. The status of the lymph nodes, the existence of other extrahepatic metastases, the location of the primary tumor, and different neoadjuvant therapies are of nonprognostic value.

Usefulness of ultrafast dynamic 3D-T1w data acquisition in detection of hypervascular lesions of the middle ear: first experience.

OBJECTIVE: To evaluate ultrafast dynamic 3D-T1w acquisition for improved detection of tympanic hypervascularized lesions. METHODS: Retrospective evaluation of a total of 50 patients referred from ENT-Department for suspected tympanic lesion. All underwent magnetic resonance imaging including ultrafast dynamic 3D-T1w acquisition imaging. Quantitative and qualitative evaluation was performed as well as statistical analysis. Comparison with intra-operative results. RESULTS: 12/50 patients showed a hypervascularized lesion proved intraoperative as 8 paragangliomas, 2 adenoms, 1 hemangioma and 1 neurinoma. 8/50 do not show hypervascularization though an enhancement was detected. Intra-operative granulation tissue was found. 30 patients did not show any lesions or enhancement. Sensitivity and specificity was 100%/100% for ultrafast dynamic imaging. CONCLUSION: Additional ultrafast dynamic 3D-T1w imaging is superior to conventional imaging in detection of hypervascularized lesions.

Radiation exposure to operating staff during rotational flat-panel angiography and C-arm cone beam computed tomography (CT) applications.

PURPOSE: To evaluate the radiation exposure for operating personnel associated with rotational flat-panel angiography and C-arm cone beam CT. MATERIALS AND METHODS: Using a dedicated angiography-suite, 2D and 3D examinations of the liver were performed on a phantom to generate scattered radiation. Exposure was measured with a dosimeter at predefined heights (eye, thyroid, breast, gonads and knee) at the physician's location. Analysis included 3D procedures with a field of view (FOV) of 24 cm × 18 cm (8s/rotation, 20s/rotation and 5s/2 rotations), and 47 cm×18 cm (16s/2 rotations) and standard 2D angiography (10s, FOV 24 cm×18 cm). RESULTS: Measurements showed the highest radiation dose at the eye and thyroid level. In comparison to 2D-DSA (3.9 µSv eye-exposure), the 3D procedures caused an increased radiation exposure both in standard FOV (8s/rotation: 28.0 µSv, 20s/rotation: 79.3 µSv, 5s/2 rotations: 32.5 µSv) and large FOV (37.6 µSv). Proportional distributions were measured for the residual heights. With the use of lead glass, irradiation of the eye lens was reduced to 0.2 µSv (2D DSA) and 10.6 µSv (3D technique with 20s/rotation). CONCLUSION: Rotational flat-panel angiography and C-arm cone beam applications significantly increase radiation exposure to the attending operator in comparison to 2D angiography. Our study indicates that the physician should wear protective devices and leave the examination room when performing 3D examinations.

Assessment of shunt volumes in children with ventricular septal defects: comparative quantification of MR flow measurements and invasive oximetry.

The aim of this study was to compare the results of magnetic resonance based shunt volume measurements with the results of the invasive method by the principle of Fick. In 14 children (median age: 16.5 months) with ventricular septal defects the shunt volume was quantified by magnetic resonance flow measurements under spontaneous breathing conditions as well as with invasive angiography during one sedation. A good correlation between both methods was observed (r(2) = 0.8, p <0.0001, CI(95%) = 0.62-1.22). A tendency towards higher values in the noninvasive technique was found in the Bland-Altman plot (bias = 3.79). Magnetic resonance based shunt measurements are a reliable alternative to the invasive shunt measurement by cardiac catheterization.