Microwave Ablation of Symptomatic Benign Thyroid Nodules: Energy Requirement per ml Volume Reduction.

Purpose: Microwave ablation (MWA) represents a novel thermal ablative treatment of benign thyroid nodules. The aim was to determine the energy required per ml volume reduction in order to match the required energy to the volume-of-interest (VOI). Materials and Methods: 25 patients with 25 nodules (6 solid, 13 complex and 6 cystic) were treated by microwave ablation (MWA). The transmitted energy (E) was correlated with the volume change (∆ V) after 3 months. The energy required per ml volume reduction after 3 months was calculated by E/∆ V. Results: MWA resulted in a significant (p < 0.0001) volume reduction (∆ V) with a mean of 12.4 ±â€Š13.0 ml (range: 1.5 - 63.2 ml) and relative reduction of 52 ±â€Š16 % (range: 22 - 77 %). There was a positive correlation between E and ∆ V (r = 0.82; p < 0.05). The mean E/∆ V was 1.52 ±â€Š1.08 (range: 0.4 - 4.6) kJ/ml for all nodules and 2.30 ±â€Š1.5 (0.9 - 4.6), 1.5 ±â€Š0.9 (0.4 - 3.6), 0.75 ±â€Š0.25 (0.4 - 1.2) kJ/ml, respectively, for solid, complex and cystic nodules with a significant difference in E/∆ V for solid and cystic (p < 0.03). Conclusion: The energy required per volume depends on the nodule consistency. Solid nodules require more energy than cystic ones. The estimation of the energy needed per volume-of-interest as an additional parameter should help to avoid under- or overtreatment. Key Points: • The estimated required energy for a volume-of-interest depends on the nodule consistency• In solid nodules a higher energy transmission than in cystic nodules is recommended• The energy transmission as an additional marker to ultrasound is helpful for improving periprocedural monitoring Citation Format: • Korkusuz Y, Kohlhase K, Gröner D et al. Microwave Ablation of Symptomatic Benign Thyroid Nodules: Energy Requirement per ml Volume Reduction. Fortschr Röntgenstr 2016; 188: 1054 - 1060.

Bipolar Radiofrequency Ablation of Benign Symptomatic Thyroid Nodules: Initial Experience.

PURPOSE: To determine the safety and efficacy of bipolar radiofrequency ablation (RFA) in benign thyroid nodules. METHODS: 23 patients with 24 symptomatic benign thyroid nodules (21 regressive, 3 adenomas) ranging in volume from 0.5 to 112 ml (mean ± sd: 18 ±â€Š24.4 ml) underwent bipolar RFA. Pain during the procedure was measured on a 10-point scale. Side-effects revealed by ultrasound or patients' complaints were documented. Periablative efficacy was measured 24 hours after RFA as change (Δ) in serum thyreoglobulin (Tg) and sonographic criteria (echogenity, Doppler blood flow and elasticity) categorized on a 3-point scale (echogenity, Doppler blood flow) or 4-point scale (elasticity). Efficacy in the 3 autonomous adenomas was measured as normalization of (99 m)Tc-pertechnate scintigraphy. RESULTS: Bipolar RFA was well tolerated by all patients with a median pain score of 3 ±â€Š1.5 (range: 1 - 7). Side-effects were hematomas in 4 of 23 patients (17 %). Bipolar RFA resulted in a significant (p < 0.01) decrease in echogenity, blood flow, elasticity (Δ = 1 ±â€Š0.28, 1 ±â€Š0.46 and 1 ±â€Š0.85 points, respectively), a median increase in Tg of 403 ±â€Š2568 ng/ml as well as in a normalization of scintigraphy. CONCLUSION: Bipolar RFA is a safe and effective treatment option for symptomatic benign thyroid nodules. KEY POINTS: • Bipolar RFA is a safe and effective treatment for benign thyroid nodules.• Ultrasound imaging allows guidance during bipolar radiofrequency ablation.• (99 m)Tc-pertechnetate is able to detect the ablation area of autonomous adenomas. Citation Format: • Korkusuz Y, Erbelding C, Kohlhase K et al. Bipolar Radiofrequency Ablation of Benign Symptomatic Thyroid Nodules: Initial experience with Bipolar Radiofrequency. Fortschr Röntgenstr 2016; 188: 671 - 675.

Benefits of sinogram-affirmed iterative reconstruction in 0.4 mSv ultra-low-dose CT of the upper abdomen following transarterial chemoembolisation: comparison to low-dose and standard-dose CT and filtered back projection technique.

AIM: To evaluate the advantage of sinogram-affirmed iterative reconstruction (SIR) compared to filtered back projection (FBP) in upper abdomen computed tomography (CT) after transarterial chemoembolisation (TACE) at different tube currents. MATERIALS AND METHODS: The study was approved by the institutional review board. Written informed consent was obtained from all patients. Post-TACE CT was performed with different tube currents successively varied in four steps (180, 90, 45 and 23 mAs) with 40 patients per group (mean age: 60±12 years, range: 23-85 years, sex: 70 female, 90 male). The data were reconstructed with standard FBP and five different SIR strengths. Image quality was independently rated by two readers on a five-point scale. High (Lipiodol-to-liver) as well as low (liver-to-fat) contrast-to-noise ratios (CNRs) were intra-individually compared within one dose to determine the optimal strength (S1-S5) and inter-individually between different doses to determine the possibility of dose reduction using the Kruskal-Wallis test. RESULTS: Subjective image quality and objective CNR analysis were concordant: intra-individually, SIR was significantly (p<0.001) superior to FBP. Inter-individually, regarding different doses (180 versus 23 ref mAs), there was no significant (p=1.00) difference when using S5 SIR at 23 mAs instead of FBP. CONCLUSION: SIR allows for an 88% dose reduction from 3.43 to 0.4 mSv in unenhanced CT of the liver following TACE without subjective or objective loss in image quality.

Seventy kilovolt ultra-low dose CT of the paranasal sinus: first clinical results.

AIM: To evaluate the diagnostic image quality and radiation dose of low-dose 70 kV computed tomography (CT) of the paranasal sinus in comparison to 100 and 120 kV CT. MATERIALS AND METHODS: CT of the paranasal sinus was performed in 127 patients divided into three groups using different tube voltages and currents (70 kV/75 mAs, ultra-low dose protocol, n = 44; 100 kV/40 mAs, standard low-dose protocol, n = 42; 120 kV/40 mAs, standard protocol, n = 41). CT dose index (CTDIvol), dose-length product (DLP), attenuation, image noise and signal-to-noise ratio (SNR) were compared between the groups using Wilcoxon-Mann-Whitney U-test. Subjective diagnostic image quality was compared by using a five-point scale (1 = non-diagnostic, 5 = excellent, read by two readers in consensus) and Cohen's weighted kappa analysis for interobserver agreement. RESULTS: Radiation dose was significantly lower with 70 kV acquisition than 100 and 120 kV (DLP: 31 versus 52 versus 82 mGy·cm; CTDI 2.33 versus 3.95 versus 6.31 mGy, all p < 0.05). Mean SNR (70 kV: 0.37; 100 kV: 0.21; 120 kV: 0.13; p < 0.05) and organ attenuation increased significantly with lower voltages. All examinations showed diagnostic image quality. Subjective diagnostic image quality was higher with standard protocols than the 70 kV protocol (120 kV: 5.0; 100 kV: 4.5; 70 kV: 3.5, p < 0.05) without significant differences with substantial interobserver agreement (κ > 0.59). CONCLUSION: The ultra-low dose (70 kV) CT imaging of the paranasal sinus allowed for significant dose reduction by 61% and an increased attenuation of organ structures in comparison to standard acquisition while maintaining diagnostic image quality with a slight reduction in subjective image quality.

Determination of the optimal MRI sequence for the detection of malignant lung nodules.

OBJECTIVE: For staging, follow-up and even screening (www.screening.info) an "all-in-one" imaging examination is desirable. In the concept of whole body MRI, lung imaging prevails as the weakest link. The purpose of our study was to determine the optimal MRI sequences for the detection of malignant lung nodules. PATIENTS AND METHODS: On the basis of 6 lung cancer, 46 metastases and one tuberculoma in 13 patients eight MRI sequences--HASTE, IR-HASTE, fat saturated TrueFISP, STIR, VIBEipat = 2, and contrast-enhanced (CE) VIBE (with ipat = 2, 0, 4) performed with parallel imaging and 12 matrix coil elements--were compared in terms of contrast-to-noise ratio (CNR) and quality in the visualization of the lung nodules using multidetector CT as standard of reference. The parameters of the sequences were pragmatically selected to minimize the imaging time to allow for imaging the entire lung within one breathold interval. RESULTS: The STIR sequence was found to be the best for detecting malignant lung nodules (p<0.01) followed by the FS TrueFISP, CE VIBE subsetipat = 0, CE VIBE subsetipat = 2, IR-HASTE, HASTE, CE VIBE subsetipat = 4, and VIBE. The STIR sequence visualized malignant nodules down to 2 mm in size and did not display the 19 mm tuberculoma. CONCLUSION: The STIR sequence should be included in future studies investigating if MRI can compete with CT in the early identification (detection and classification) of malignant lung nodules.

Automated mass detection in contrast-enhanced CT colonography: an approach based on contrast and volume.

The purpose of this feasibility study was to design and test an algorithm for automating mass detection in contrast-enhanced CT colonography (CTC). Five patients with known colorectal masses underwent a pre-surgical contrast-enhanced (120 ml volume 1.6 g iodine/s injection rate, 60 s scan delay) CTC in high spatial resolution (16-slice CT: collimation: 16x0.75 mm, tablefeed: 24 mm/0.5 s, reconstruction increment: 0.5 mm). A CT-density- and volume-based algorithm searched for masses in the colonic wall, which was extracted before by segmenting and dilating the colonic air lumen and subtracting the inner air. A radiologist analyzed the detections and causes of false positives. All masses were detected, and false positives were easy to identify. Combining CT density with volume as a cut-off is a promising approach for automating mass detection that should be further refined and also tested in contrast-enhanced MR colonography. More information under http://www.screening.info.

Phase- and size-adjusted CT cut-off for differentiating neoplastic lesions from normal colon in contrast-enhanced CT colonography.

A computed tomography (CT) cut-off for differentiating neoplastic lesions (polyps/carcinoma) from normal colon in contrast-enhanced CT colonography (CTC) relating to the contrast phase and lesion size is determined. CT values of 64 colonic lesions (27 polyps <10 mm, 13 polyps > or =10 mm, 24 carcinomas) were determined by region-of-interest (ROI) measurements in 38 patients who underwent contrast-enhanced CTC. In addition, the height (H) of the colonic lesions was measured in CT. CT values were also measured in the aorta (A), superior mesenteric vein (V) and colonic wall. The contrast phase was defined by xA + (1-x)V using x as a weighting factor for describing the different contrast phases ranging from the pure arterial phase (x=1) over the intermediate phases (x=0.9-0.1) to the pure venous phase (x=0). The CT values of the lesions were correlated with their height (H), the different phases (xA+(1-x)V) and the ratio [xA+(I-x)V]/H. The CT cut-off was linearly adjusted to the imaged contrast phase and height of the lesion by the line y=m[xA+(1-x)V]H+y(0). The slope m was determined by linear regression in the correlation (lesion approximately [xA+(i-x)V]/H) and the Y-intercept y(0) by the minimal shift of the line needed to maximize the accuracy of separating the colonic wall from the lesions. The CT value of the lesions correlated best with the intermediate phase: 0.4A + 0.6V (r=0.8 for polyps > or =10 mm, r=0.6 for carcinomas, r=0.4 for polyps <10 mm). The accuracy in the differentiation between lesions and normal colonic wall increased with the height implemented as divisor, reached 91% and was obtained by the dynamic cut-off described by the formula: cut-off (A,V,H)=1.1 [0.4A+0.6V]/H+69.8. The CT value of colonic polyps or carcinomas can be increased extrinsically by scanning in the phase in which 0.4A + 0.6V reaches its maximum. Differentiating lesions from normal colon based on CT values is possible in contrast-enhanced CTC and improves when the cut-off is adjusted (normalized) to the contrast phase and lesion size.

[Importance of CT and MRI in the follow-up of patients with rectal cancer]. / Wertigkeit der CT und MRT bei der Rezidivdiagnostik des kolorektalen Karzinoms.

INDICATION: Presentation and evaluation of diagnostic procedures for the follow-up in patients with suspected local recurrence of rectal cancer. METHODS: Follow-up usually is performed using endoscopy and endosonography. Imaging techniques applied are also contrast enema as well as helical CT,MR imaging (MRI), and positron emission tomography (PET). RESULTS: The results demonstrate the difficulty of all available modalities to differentiate between early tumor recurrences from post-therapeutic alterations. Especially the differentiation of scar tissue and local tumor recurrence, the detection of lymph node as well as pulmonary or hepatic metastasis requires a large diagnostic effort with employment of various imaging modalities. Values determined for sensitivity and specificity for CT are 84% and 91% with a positive predictive value (PPV) of 78%. For MRI and PET the sensitivity are 94% and 98%,and the specificity 92% and 90% with a PPV of 93% for the PET. CONCLUSION: The results demonstrate the increasing importance of CT and MRI in the follow-up of patients with rectal cancer and enable an accurate and early diagnosis through employment of new examination strategies and sequence protocols.PET remains an add-on examination in uncertain local lesions.

[Diagnosis of colorectal tumors]. / Diagnostik von kolorektalen Tumoren. Mehrschichtcomputertomographie.

With the introduction of multislice CT extensive volumetric data sets can be quickly acquired in high spatial resolution. The high spatial resolution reduces partial volume effects and enables multiplanar reconstructions. Regarding the colorectum this means that the colon can be assessed if the colon is sufficiently cleaned and distended, and that transmural infiltration of colorectal carcinoma and liver metastases can be better detected. T-staging of colon cancer is less important than T-staging of rectal cancer. Based on the higher contrast MRI is superior to CT in T-staging of rectal cancer and in the differentiation between scarring tissue and recurrence of carcinoma.

[Early detection of colorectal tumors: CT or MRI?]. / Früherkennung von kolorektalen Tumoren: CT oder MRT?

Cancer screening is currently offered for the organs breast, prostate, cervix and colorectum. With progressing technique in computerized tomography (CT) and magnetic resonance imaging (MRI) the colorectum can be increasingly better assessed. Because in CT and MRI also other organs are imaged with the colorectum, a colorectal screening automatically becomes a multiorgan screening. CT and MRI protocols designed for early detection of colorectal tumors are presented and discussed with regard to monoorganscreening (in CT: low dose, no i.v. contrast) and multiorganscreening (in CT: diagnostic dose for neighboured organs with i.v. contrast). More information under http://www.multiorganscreening.org.

Multidetector CT of the colon.

Multidetector technology, enabling faster imaging, higher spatial resolution and reduction in radiation dose, increases the role of CT in colonic diagnostic. The higher spatial resolution in the z-direction also changes the way to analyze the images. Instead of reading axial sections, now the colon can be systematically assessed in 3D by scrolling through multiplanar reconstructions or in CT colonography by virtual endoscopy. With ongoing improvements in computer-aided diagnosis CT colonography becomes an alternative to fiberoptic colonocopy for screening (http://www. multiorganscreening.org). In this article we propose a CT examination protocol for the colon, describe the typical imaging findings of different colonic diseases, and summarize the current status of CT colonography.

[Contrast-enhanced multislice CT in detection and evaluation of abdominal neoplasms]. / Kontrastverstärkte Mehrschicht-Computertomographie in der Detektion und Evaluation abdomineller Neoplasien.

PURPOSE: Demonstration of clinical value of contrast-enhanced multislice CT (MS-CT) for evaluating abdominal neoplasias with focus on primary liver tumors, pancreatic carcinoma and colorectal carcinoma. MATERIAL AND METHODS: Optimized examination protocols for multislice CT are presented using oral and intravenous application of contrast agent. RESULTS: For primary liver tumors like hepatocellular carcinoma and cholangiocellular carcinoma diagnostic accuracies are achieved from 82 to 94% and for pancreatic carcinomas from 85 to 96%. For diagnosis of colorectal carcinoma results are relevant for staging of primary tumor, lymph node metastases and further metastases in liver and lung. The results achieve values from 86 to 92% for sensitivity, specificity and diagnostic accuracy. CONCLUSION: Contrast-enhanced multislice CT proves to be a quick and reliable examination technique for detection and staging of abdominal neoplasms with a focus on the epigastric region and colorectal carcinoma.

MR colonography: status and perspective.

With further improvements in multislice CT, enabling now the combination of lung and colon imaging within one breathhold with automated dose optimization, MR colonography has almost been given up. But similar to angiography, we are optimistic that MR can be compatible to CT in colonography and report in this article on the current status and perspective of MR colonography. For more information see www.multiorganscreening.org.

[Hybrid 3-D rendering of the thorax and surface-based virtual bronchoscopy in surgical and interventional therapy control]. / Hybride 3D-Visualisierung des Thorax und oberflächenbasierte virtuelle Bronchoskopie in der operativen und interventionellen Therapiekontrolle.

PURPOSE: The aim of this study was to demonstrate the possibilities of a hybrid rendering method, the combination of a color-coded surface and volume rendering method, with the feasibility of performing surface-based virtual endoscopy with different representation models in the operative and interventional therapy control of the chest. MATERIAL AND METHOD: In 6 consecutive patients with partial lung resection (n = 2) and lung transplantation (n = 4) a thin-section spiral computed tomography of the chest was performed. The tracheobronchial system and the introduced metallic stents were visualized using a color-coded surface rendering method. The remaining thoracic structures were visualized using a volume rendering method. For virtual bronchoscopy, the tracheobronchial system was visualized using a triangle surface model, a shaded-surface model and a transparent shaded-surface model. RESULTS: The hybrid 3D visualization uses the advantages of both the color-coded surface and volume rendering methods and facilitates a clear representation of the tracheobronchial system and the complex topographical relationship of morphological and pathological changes without loss of diagnostic information. Performing virtual bronchoscopy with the transparent shaded-surface model facilitates a reasonable to optimal, simultaneous visualization and assessment of the surface structure of the tracheobronchial system and the surrounding mediastinal structures and lesions. CONCLUSIONS: Hybrid rendering relieve the morphological assessment of anatomical and pathological changes without the need for time-consuming detailed analysis and presentation of source images. Performing virtual bronchoscopy with a transparent shaded-surface model offers a promising alternative to flexible fiberoptic bronchoscopy.

Hybrid rendering of the chest and virtual bronchoscopy [corrected].

Thin-section spiral computed tomography was used to acquire the volume data sets of the thorax. The tracheobronchial system and pathological changes of the chest were visualized using a color-coded surface rendering method. The structures of interest were then superimposed on a volume rendering of the other thoracic structures, thus producing a hybrid rendering. The hybrid rendering technique exploit the advantages of both rendering methods and enable virtual bronchoscopic examinations using different representation models. Virtual bronchoscopic examinations with a transparent color-coded shaded-surface model enables the simultaneous visualization of both the airways and the adjacent structures behind of the tracheobronchial wall and therefore, offers a practical alternative to fiberoptic bronchoscopy. Hybrid rendering and virtual endoscopy obviate the need for time consuming detailed analysis and presentation of axial source images.

Differentiation of malignant from benign solitary pulmonary lesions using chest radiography, spiral CT and HRCT.

OBJECTIVE: The aim of this prospective study was to summarize all of the qualitative and quantitative imaging criteria for the differentiation of solitary pulmonary lesions (SPLs) as malignant (MSPLs) or benign (BSPLs) described in the literature and to critically analyze the different characteristics in order to evaluate their clinical importance and usefulness as criteria for a discrimination during the primary diagnostic assessment of SPLs using chest radiography, spiral computed tomography (SCT) and high-resolution computed tomography (HRCT). MATERIALS AND METHODS: SPLs were examined, evaluated and then completely removed by surgery in 104 consecutive patients (MSPLs n=81, BSPLs n=23). No SPL was excluded by size. Chest radiography was performed with frontal and lateral views, SCT was carried out with a slice thickness of 8 mm and HRCT with a slice thickness of 1 mm and a 12-cm field of view. RESULTS: All the characteristics which enabled a reliable differentiation of MSPLs from BSPLs were characteristics which were observed significantly more frequently in MSPLs than BSPLs. Useful characteristics for the differentiation of MSPLs from BSPLs (1) using chest radiography were the indistinct edge (P<0.0001) and a ground-glass opacity of the lung parenchyma adjacent to the SPL (P<0. 05); (2) using SCT the presence of spicules (P<0.0005), the vessel sign (P<0.0005), necrotic areas (P<0.001), spicules extending to the visceral pleura (P<0.005), circumscribed pleural thickening (P<0. 005), inhomogeneity (P<0.01), a ground-glass opacity of the lung parenchyma adjacent to the SPL (P<0.01), the lesion density (P<0.05), pleural retraction (P<0.05) and the bronchus sign (P<0.05); and (3) using HRCT the presence of spicules (P<0.00005), spicules extending to the visceral pleura (P<0.0005), the vessel sign (P<0.0005), pleural retraction (P<0.001), circumscribed pleural thickening (P<0. 001), the bronchus sign (P<0.005), a ground-glass opacity of the lung parenchyma adjacent to the SPL (P<0.01), the lesion density (P<0.05) and the length of spicules (P<0.05). Using any one of the characteristics with a significance level of P<0.01, the identification of MSPLs (1) using chest radiography showed a sensitivity of 64.2% and a specificity of 82.6% (accuracy of 68.3%); (2) using SCT a sensitivity of 88.9% and a specificity of 60.9% (accuracy of 82.7%); and (3) using HRCT a sensitivity of 91.4% and a specificity of 56.5% (accuracy of 83.7%). CONCLUSIONS: Using chest radiography, SCT and HRCT, a precise morphological assessment of the periphery of the pulmonary lesion and the adjacent visceral pleura is necessary to distinguish MSPLs from BSPLs. In this respect SCT and HRCT are useful in differentiation of MSPLs from BSPLs. However, metastases strongly resembled benign lesions in terms of size and edge type and chronic inflammatory pseudotumors as a group mimic MSPLs.

Synergistic effect between iron and gadolinium in MRI.

Different combinations of iron glycerophosphate (Fe) and gadolinium-diethylene triamine pentaacetic acid (DTPA) (Gd) were imaged with a three-dimensional (3D) gradient-recalled echo (GRE), a 2D GRE, and a HASTE sequence on a 1.5-T MR scanner. A combination of Fe and Gd results in a synergistic effect, which improves the signal gain for selective 3D imaging of the colon and simultaneously decreases the endoluminal signal on the HASTE and 2D GRE images for better visualization of water and Gd-enhanced structures in the gut wall.

Colonic masses: detection with MR colonography.

PURPOSE: To assess magnetic resonance (MR) colonography as a method for detection of colorectal masses, with conventional colonoscopy as the reference standard. MATERIALS AND METHODS: MR colonography was performed in 132 patients referred for colonoscopy because of the possible presence of a mass. After rectal filling with a gadopentetate dimeglumine and water enema, T1-weighted three-dimensional gradient-echo MR studies were acquired with the patient in the prone and supine positions. Water-sensitive single-shot fast spin-echo MR images were also obtained. Surface-rendered virtual endoscopic endoluminal views, orthogonal sections in three planes, and water-sensitive MR images were interactively assessed for presence of colorectal masses by two radiologists. RESULTS: MR colonography was well tolerated without sedation or analgesia. MR image quality was sufficient for diagnosis in 127 (96%) patients. Most small (10-mm) lesions were correctly identified. For these large masses, MR colonography had a sensitivity of 93%, specificity of 99%, positive predictive value of 92%, and negative predictive value of 98% for detection of masses. CONCLUSION: MR colonography is a promising modality for help in detecting colorectal mass lesions larger than 10 mm in diameter.