Benjamin Kaltenbach

Ablation therapy of non-colorectal cancer lung metastases: retrospective analysis of tumour response post-laser-induced interstitial thermotherapy (LITT), radiofrequency ablation (RFA) and microwave ablation (MWA)

Abstract Purpose: To retrospectively compare the local tumour response and survival rates in patients with non-colorectal cancer lung metastases post-ablation therapy using laser-induced thermotherapy (LITT), radiofrequency ablation (RFA) and microwave ablation (MWA). Material and methods: Retrospective analysis of 175 computed tomography (CT)-guided ablation sessions performed on 109 patients (43 males and 66 females, mean age: 56.6 years). Seventeen patients with 22 lesions underwent LITT treatment (tumour size: 1.2–4.8 cm), 29 patients with 49 lesions underwent RFA (tumour size: 0.8–4.5 cm) and 63 patients with 104 lesions underwent MWA treatment (tumour size: 0.6–5 cm). CT scans were performed 24-h post-therapy and on follow-up at 3, 6, 12, 18 and 24 months. Results: The overall-survival rates at 1-, 2-, 3- and 4-year were 93.8, 56.3, 50.0 and 31.3% for patients treated with LITT; 81.5, 50.0, 45.5 and 24.2% for patients treated with RFA and 97.6, 79.9, 62.3 and 45.4% for patients treated with MWA, respectively. The mean survival time was 34.14 months for MWA, 34.79 months for RFA and 35.32 months for LITT. In paired comparison, a significant difference could be detected between MWA versus RFA (p = 0.032). The progression-free survival showed a median of 23.49 ± 0.62 months for MWA,19.88 ± 2.17 months for LITT and 16.66 ± 0.66 months for RFA (p = 0.048). The lowest recurrence rate was detected in lesions ablated with MWA (7.7%; 8 of 104 lesions) followed by RFA (20.4%; 10 of 49 lesions) and LITT (27.3%; 6 of 22 lesions) p value of 0.012. Pneumothorax was detected in 22.16% of MWA ablations, 22.73% of LITT ablations and 14.23% of RFA ablations. Conclusion: LITT, RFA and MWA may provide an effective therapeutic option for non-colorectal cancer lung metastases with an advantage for MWA regarding local tumour control and progression-free survival rate.

Free-breathing dynamic liver examination using a radial 3D T1-weighted gradient echo sequence with moderate undersampling for patients with limited breath-holding capacity

PURPOSE To compare free-breathing radial VIBE with moderate undersampling (us-radial-VIBE) with a standard breathhold T1-weighted volumetric interpolated sequence (3D GRE VIBE) in patients unable to suspend respiration during dynamic liver examination. MATERIAL AND METHODS 23 consecutive patients underwent dynamic liver MR examination using the free-breathing us-radial-VIBE sequence as part of their oncologic follow-up. All patients were eligible for the free-breathing protocol due to severe respiratory artifacts at the planning or precontrast sequences. The us-radial-VIBE acquisitions were compared to the patientś last staging liver MRI including a standard breathhold 3D GRE VIBE. For an objective image evaluation, signal intensity (SI), image noise (IN), signal-to-noise ratio (SNR) and contrast-enhancement ratio (CER) were compared. Representative image quality parameters, including typical artifacts were independently, retrospectively and blindly scored by four readers. RESULTS Us-radial-VIBE had significant lower SNR (p<0.0001) and higher IN (p<0.0001), whereas SI did not differ (p=0.62). Temporal resolution assessed with CER in the arterial phase showed higher values for us-radial-VIBE (p=0.028). Subjective image quality parameters received generally slightly higher scores for 3D GRE VIBE. In a smaller subgroup comprising patients with severe respiratory artifacts also at reference breathhold 3D GRE VIBE examination, us-radial-VIBE showed significantly higher image quality scores. Furthermore, there were generally more severe respiratory artifacts in 3D GRE VIBE, whereas streaking was characteristic in almost all us-radial-VIBE acquisitions but did not affect diagnostic validity. CONCLUSION Free-breathing dynamic liver imaging using us-radial-VIBE delivers accurate temporal resolution, low motion artifact susceptibility and good image quality and represents a promising alternative in patients unable to suspend respiration.

Real-time qualitative MR monitoring of microwave ablation in ex vivo livers

Abstract Purpose: Computed tomography (CT) and ultrasound-guided microwave ablations (MWA) are part of the established treatment of liver tumours. In spite of its potential advantages, magnetic resonance (MR) monitoring of MWA did not enter clinical practice because of the lack of compatible devices. The purpose of the current study was to prove the feasibility of real-time qualitative MR monitoring using a new MR-compatible MWA device. Material and methods: We performed 27 MWA experiments with different durations (5, 10 and 15 min) on an ex vivo bovine liver model using a MR-compatible MWA device. We compared the diameters of the ablation zone as depicted on three T1-based sequences to those of the macroscopic specimen. The volume and the sphericity index of the macroscopic ablation area were calculated in order to characterise the device. Ablation pattern and artefacts on the three sequences were also taken into account. Results: We obtained high-quality real-time images using all three sequences. The diameters as depicted on the MR sequences slightly overestimated the macroscopic ablation area but correlated significantly in all cases (p < 0.05). VIBE provided the best correlation for both short-axis diameter (r = 0.96) and long-axis diameter (r = 0.87), whereas starVIBE (r = 0.85; r = 0.72) and FLASH (r = 0.75; r = 0.84) correlated slightly less. Significantly more severe noise artefacts were observed on starVIBE compared to FLASH and VIBE sequences (p < 0.0001). Conclusion: The current ex vivo liver model experiment suggests that real-time qualitative MR monitoring of MWA is feasible. Further research using in vivo and human models are recommended.

Iodine quantification to distinguish hepatic neuroendocrine tumor metastasis from hepatocellular carcinoma at dual-source dual-energy liver CT

PURPOSE To investigate the value of third-generation dual-source dual-energy computed tomography (DECT) iodine quantification to distinguish hepatic neuroendocrine tumor (NET) metastasis from hepatocellular carcinoma (HCC) in non-cirrhotic liver parenchyma. MATERIAL AND METHODS Forty-six patients (mean age, 64.9 ± 10.1 years; 28 male and 18 female) with either hepatic NET metastasis or HCC, who had undergone liver DECT, were included in this retrospective study. For each lesion, arterial-phase attenuation values and DECT quantitative parameters, including iodine uptake, fat fraction, normalized iodine uptake (NIU), and lesion-to-liver-parenchyma ratio (LPR) were evaluated. Available cumulative data from histopathology, MRI, PET/CT, or interval imaging follow-up served as the reference standard for all liver lesions. In addition, the diagnostic accuracy of contrast-enhanced and material decomposition analysis for the differentiation of hepatic NET metastasis and HCC was assessed using receiver operating characteristics (ROC) curve analysis. RESULTS Hepatic NET metastasis and HCC showed significant differences in arterial attenuation (P = 0.003), iodine uptake (P < 0.001), NIU (P < 0.001), and LPR (P = 0.003). No significant differences were found for unenhanced attenuation and fat fraction values (P = 0.686 and P = 0.892, respectively). NIU showed superior sensitivity (100%; iodine uptake, 71%), while both iodine uptake and NIU revealed superior specificity (100% and 90%, respectively) compared to LPR (sensitivity, 96%; specificity, 80%) and arterial attenuation analysis (sensitivity, 79%; specificity, 80%) (P ≤ 0.016). CONCLUSION Third-generation DECT with assessment of iodine uptake improves the differentiation of hepatic NET metastasis and HCC in non-cirrhotic liver, with NIU showing the strongest diagnostic performance.

Dual-energy CT-based iodine quantification to differentiate abdominal malignant lymphoma from lymph node metastasis

PURPOSE To investigate the value of dual-energy computed tomography (DECT)-derived iodine and fat quantification in differentiating malignant abdominal lymphoma from lymph node metastasis. MATERIALS AND METHODS In this retrospective study, 59 patients (39 men; mean age, 62.7 years) with histopathologically-confirmed diagnosis of either malignant lymphoma or lymph node metastasis were included. For each lesion, contrast-enhanced attenuation, as well as DECT-derived iodine density and fat fraction measurements were recorded. Mean attenuation and material density values were compared between malignant lymphomas and lymph node metastases. The receiver operating characteristic (ROC) curve analysis was adopted to estimate the optimal threshold for discriminating between both entities. A control group (n = 60) was analyzed for comparison of attenuation and material density values of normal abdominal lymph nodes. RESULTS Assessment of DECT-derived iodine density and fat fraction values revealed significant differences between lymph node metastases (1.7 ± 0.4 mg/ml and 15.5 ± 7.3%) and malignant lymphomas (2.5 ± 0.5 mg/ml and 26.7 ± 12.2%) as well as normal lymph nodes (2.4 ± 0.8 mg/ml and 24.1 ± 10.8%) (P ≤ 0.013). An iodine concentration of 2.0 mg/ml represented the optimal threshold to discriminate between lymphoma and lymph node metastasis (sensitivity, 87%; specificity, 89%). Moreover, a significant correlation was found between iodine concentration and fat fraction for both lymphomas and lymph node metastases (P = 0.001). CONCLUSION DECT enables characterization of abdominal masses as derived iodine and fat fraction values differ significantly between malignant abdominal lymphomas and lymph node metastases.

A comparison between 915 MHz and 2450 MHz microwave ablation systems for the treatment of small diameter lung metastases

PURPOSE We aimed to retrospectively compare the local tumor control rates between low frequency (LF) and high frequency (HF) microwave ablation devices in the treatment of <3 cm lung metastases. METHODS A total of 36 patients (55 tumors) were treated with the LF system (915 MHz) and 30 patients (39 tumors) were treated with the HF system (2450 MHz) between January 2011 and March 2016. Computed tomography (CT) scans performed prior to and 24 hours after the ablation were used to measure the size of the ablation zone and to calculate the ablation margin. The subsequent CTs were used to detect local tumor progression. Possible predictive factors for local progression were analyzed. All patients had a minimum follow-up of 3 months with a median of 13.8 months for the LF group and 11.7 months for the HF group. RESULTS The ablation margin (P = 0.015), blood vessel proximity (P = 0.006), and colorectal origin (P = 0.029) were significantly associated with the local progression rate. The local progression rates were 36.3% for LF ablations and 12.8% for HF ablations. The 6, 12, and 18 months local progression-free survival rates were 79%, 65.2% and 53% for the LF group and 97.1%, 93.7%, and 58.4% for the HF group, with a significant difference between the survival curves (P = 0.048). CONCLUSION HF ablations resulted in larger ablation margins with fewer local progression compared with LF ablations.

Dynamic Liver Magnetic Resonance Imaging in Free-Breathing: Feasibility of a Cartesian T1-Weighted Acquisition Technique With Compressed Sensing and Additional Self-Navigation Signal for Hard-Gated and Motion-Resolved Reconstruction

Objectives The aim of this study was to assess the feasibility of a free-breathing dynamic liver imaging technique using a prototype Cartesian T1-weighted volumetric interpolated breathhold examination (VIBE) sequence with compressed sensing and simultaneous acquisition of a navigation signal for hard-gated and motion state–resolved reconstruction. Materials and Methods A total of 43 consecutive oncologic patients (mean age, 66 ± 11 years; 44% female) underwent free-breathing dynamic liver imaging for the evaluation of liver metastases from colorectal cancer using a prototype Cartesian VIBE sequence (field of view, 380 × 345 mm2; image matrix, 320 × 218; echo time/repetition time, 1.8/3.76 milliseconds; flip angle, 10 degrees; slice thickness, 3.0 mm; acquisition time, 188 seconds) with continuous data sampling and additionally acquired self-navigation signal. Data were iteratively reconstructed using 2 different approaches: first, a hard-gated reconstruction only using data associated to the dominating motion state (CS VIBE, Compressed Sensing VIBE), and second, a motion-resolved reconstruction with 6 different motion states as additional image dimension (XD VIBE, eXtended dimension VIBE). Continuous acquired data were grouped in 16 subsequent time increments with 11.57 seconds each to resolve arterial and venous contrast phases. For image quality assessment, both CS VIBE and XD VIBE were compared with the patients last staging dynamic liver magnetic resonance imaging including a breathhold (BH) VIBE as reference standard 4.5 ± 1.2 months before. Representative quality parameters including respiratory artifacts were evaluated for arterial and venous phase images independently, retrospectively and blindly by 3 experienced radiologists, with higher scores indicating better examination quality. To assess diagnostic accuracy, same readers evaluated the presence of metastatic lesions for XD VIBE and CS VIBE compared with reference BH examination in a second session. Results Compared with CS VIBE, XD VIBE showed significantly higher overall image quality for both arterial phase (4.2 ± 0.6 vs 3.8 ± 0.7, P = 0.008) and venous phase (4.7 ± 0.4 vs 4.3 ± 0.7, P < 0.001) imaging. There was no significant difference between XD VIBE and BH VIBE for overall image quality in the venous phase (4.7 ± 0.4 vs 4.8 ± 0.4, P = 0.834), whereas arterial phase images were scored slightly lower for XD VIBE (4.5 ± 0.6 vs 4.2 ± 0.6, P = 0.024). Both XD VIBE and BH VIBE were characterized by a very low level of respiratory artifacts with no significant difference between BH and motion-resolved free-breathing strategy (P = 0.505 for arterial phase; P = 0.496 for venous phase). Compared with CS VIBE, obvious quality improvement could be achieved for the extended XD VIBE reconstruction with significantly reduced motion artifacts for venous phase images (P = 0.007). Generally, arterial phase images were scored slightly lower compared with venous phase images when using the free-breathing protocol. Overall, 98% of all metastatic lesions were identified on XD VIBE images and 92% of all metastases were found on CS VIBE. Conclusions Dynamic liver imaging using the proposed free-breathing Cartesian strategy is feasible in oncologic patients with excellent image quality, high respiratory motion robustness, and accurate lesion detection. Overall, XD VIBE was superior to CS VIBE in our study.

A matrix of morphology and distribution of calcifications in the breast: Analysis of 849 vacuum-assisted biopsies

OBJECTIVE The purpose of this retrospective analysis was to evaluate the likelihood of malignancy in prospectively categorized BI-RADS 4 and BI-RADS 5 calcifications. MATERIAL AND METHODS This analysis included 849 women who underwent vacuum biopsy for BI-RADS 4 (with the subgroups 4A, 4B and 4C) or BI-RADS 5 calcifications between February 2007 and May 2015. Calcifications were classified according to the morphology and distribution descriptors of the BI-RADS lexicon (BI-RADS 4th edition lexicon). A standardized scheme (matrix) was used to combine the characteristics of the grouped calcifications with the BI-RADS assessment category. RESULTS Overall, 275/849 (32%) lesions were found to be malignant. 285/327/208/29 calcified lesions were prospectively classified as BI-RADS 4A/4B/4C/5 indicating a risk for malignancy of 16%/27%/55%/90%, respectively. The morphology descriptors predicted the risk for malignancy as follows: typically benign (n=55): 2%; indeterminate (n=676): 27%; typically malignant (n=118): 80%. The distribution descriptors correlated with a malignant histology as follows: diffuse (n=0); round or oval (n=261): 22%; regional (n=398): 33%; segmental (n=106): 42%; linear or branching (n=85): 55%. There was a significant difference between the descriptor categories (p<0.0001). CONCLUSION A standard scheme combining the morphology and distribution characteristics proved to be a helpful tool in diagnosis of calcifications, bridging the gap between description and classification of these lesions.

Evaluation of Radiation Dose and Image Quality using High-Pitch 70-kV Chest CT in Immunosuppressed Patients

PURPOSE  The aim of the study was to evaluate high-pitch 70-kV CT examinations of the thorax in immunosuppressed patients regarding radiation dose and image quality in comparison with 120-kV acquisition. MATERIALS AND METHODS  The image data from 40 patients (14 women and 26 men; mean age: 40.9 ± 15.4 years) who received high-pitch 70-kV CT chest examinations were retrospectively included in this study. A control group (n = 40), matched by age, gender, BMI, and clinical inclusion criteria, had undergone standard 120-kV chest CT imaging. All CT scans were performed on a third-generation dual-source CT unit. For an evaluation of the radiation dose, the CT dose index (CTDIvol), dose-length product (DLP), effective dose (ED), and size-specific dose estimates (SSDE) were analyzed in each group. The objective image quality was evaluated using signal-to-noise (SNR) and contrast-to-noise ratios (CNR). Three blinded and independent radiologists evaluated subjective image quality and diagnostic confidence using 5-point Likert scales. RESULTS  The mean dose parameters were significantly lower for high-pitch 70-kV CT examinations (CTDIvol, 2.9 ± 0.9 mGy; DLP, 99.9 ± 31.0 mGyxcm; ED, 1.5 ± 0.6 mSv; SSDE, 3.8 ± 1.2 mGy) compared to standard 120-kV CT imaging (CTDIvol, 8.8 ± 3.7mGy; DLP, 296.6 ± 119.3 mGyxcm; ED, 4.4 ± 2.1 mSv; SSDE, 11.6 ± 4.4 mGy) (P≤ 0.001). The objective image parameters (SNR: 7.8 ± 2.1 vs. 8.4 ± 1.8; CNR: 7.7 ± 2.4 vs. 8.3 ± 2.8) (P≥ 0.065) and the cumulative subjective image quality (4.5 ± 0.4 vs. 4.7 ± 0.3) (p = 0.052) showed no significant differences between the two protocols. CONCLUSION  High-pitch 70-kV thoracic CT examinations in immunosuppressed patients resulted in a significantly reduced radiation exposure compared to standard 120-kV CT acquisition without a decrease in image quality. KEY POINTS   · Third-generation dual-source CT units enable high-pitch 70-kV CT examinations of the chest.. · High-pitch 70-kV CT examinations show a significantly reduced radiation dose compared to standard 120-kV CT examinations.. · High-pitch 70-kV CT examinations of the chest show comparable objective and subjective image quality.. · Subjectively deteriorated image noise and sharpness of 70-kV CT did not impact diagnostic confidence.. CITATION FORMAT · Yel I, Martin SS, Wichmann JL et al. Evaluation of Radiation Dose and Image Quality using High-Pitch 70-kV Chest CT in Immunosuppressed Patients . Fortschr Röntgenstr 2019; 191: 122 - 129.

The role of MRI in the early evaluation of lung microwave ablation

Abstract Purpose: To retrospectively investigate the role of a contrast enhanced MRI (ceMRI) performed 24 h after a microwave ablation (MWA) of the lung, in predicting local tumour progression (LTP) and detecting complications compared to an unenhanced CT. Material and methods: Forty-nine patients who underwent MWA of 77 lung metastases between 2008 and 2015 were included. All patients received an unenhanced chest CT and a ceMRI (including T2 and ceT1) 24 h after MWA. The conspicuities of the peripheral rim and the ablated tumour were scored using 1–3 scales and compared between examinations. The safety margin was measured directly (both scores ≥2) and indirectly using a subtraction method. The ability of each imaging modality to predict LTP based on safety margin width was analysed using receiver operating characteristic curves. The MRI ability to detect a pneumothorax was compared to CT. Results: The peripheral rim was best visualised on T2 followed by T1 and CT. The tumour was best visualised on CT, followed by T1 and T2. Direct safety margin measurement was possible on CT, ceT1 and T2 in 68.8%, 64.9% and 27.3% of cases, respectively. Direct CT (AUC = 0.77) and ceT1 (AUC = 0.76) measurements had better diagnostic performance than indirect CT (AUC = 0.72), ceT1 (AUC = 0.70) and T2 (AUC = 0.69) measurements. The MRI sensitivity and specificity for pneumothorax were 60.8% and 87.0%, respectively. Only one pneumothorax >1 cm was missed. Conclusions: A ceMRI performed 24 h after MWA of lung tumours has a similar ability to predict LTP and detect important complications as a CT has.