Dirk Schnapauff

Multisegment and Halfscan Reconstruction of 16-slice Computed Tomography for Detection of Coronary Artery Stenoses

Rationale and Objectives:To compare the diagnostic accuracy and image quality of 2 reconstruction algorithms (multisegment and halfscan) for computed tomography (CT) coronary angiography in patients without beta-blocker medication. Materials and Methods:Thirty-four patients with 42 significant coronary stenoses in 136 main coronary branches were examined using a 16-slice CT scanner (Aquilion, Toshiba, Otawara, Japan). Twenty-seven patients (79%) had heart rates above 65 beats/min. Results:Without exclusion of branches the sensitivity, specificity, accuracy, and rate of nonassessable segments with multisegment versus halfscan reconstruction were 88 versus 74%, 91 versus 71%, 90 versus 72%, and 2 versus 21% (P < 0.01), respectively. Multisegment reconstruction improved the average vessel length free of motion artifacts by 56% compared with halfscan reconstruction (P < 0.01). Image quality in terms of vessel continuity and visibility of side branches (P < 0.005) was significantly better using multisegment reconstruction. Conclusions:Multisegment reconstruction has superior diagnostic accuracy and image quality compared with halfscan reconstruction in patients with normal heart rates.

Diffusion-weighted echo-planar magnetic resonance imaging for the assessment of tumor cellularity in patients with soft-tissue sarcomas

To investigate the eligibility of diffusion‐weighted imaging (DWI) for the evaluation of tumor cellularity in patients with soft‐tissue sarcomas.

Coronary artery stenosis quantification using multislice computed tomography.

Rationale and Objectives:Reliable noninvasive detection of stenoses with multislice computed tomography (MSCT) is feasible. This studys aim was to analyze the agreement, correlation, and reliability of MSCT with conventional coronary angiography as the reference standard for quantification of coronary artery stenoses. Materials and Methods:A total of 118 significant (at least 50%) coronary artery stenoses with a reference vessel diameter of at least 1.5 mm in 62 patients were analyzed by MSCT using 16 detector rows (Aquilion, Toshiba, Otawara, Japan), multisegment reconstruction, and voxel sizes of 0.35 × 0.35 × 0.5 mm3. The degree of stenosis on MSCT and quantitative coronary angiography (QCA) was measured by correlating the difference between the reference vessel diameter (average of 2 measurements directly proximal and distal to the stenosis) and the stenotic vessel diameter to the reference vessel diameter. Results:Correlation between the percent diameter stenosis determined by MSCT (78.2 ± 13.6%) and QCA (76.0 ± 14.8%) was significant (P < 0.001) but only moderately so (R = 0.51). Bland-Altman analysis revealed no systematic under- or overestimation with MSCT but large limits of agreements (±27.6%). Also the limits of agreement for interobserver agreement (reliability) of MSCT data were considerably large (±24.8%). Among the 27 coronary artery stenoses with a reference diameter of at least 3.5 mm, there was improved correlation (R = 0.80) and the limits of agreement between MSCT and QCA were significantly smaller (±17.3%, P < 0.008). The agreement between MSCT and QCA was not significantly different for stenoses with no calcification or only calcium spots (±28.2%) as compared with those with moderate-or-severe calcifications (±27.3%; P = 0.8). MSCT allowed correct classification of coronary stenoses into low-grade (below 75%) and high-grade stenoses (at least 75%), in 62% (73 of 118). Conclusions:The accuracy and reliability of coronary artery stenosis quantification with MSCT using isotropic voxel sizes and multisegment reconstruction is still too low to recommend routine clinical application because of rather low agreement, correlation, and reliability. Despite these limitations, the current results demonstrate the potential of MSCT for reliable and accurate quantification of coronary artery stenoses in the near future provided that further improvements in spatial and temporal resolution will be achieved.

Combination of free-breathing and breathhold steady-state free precession magnetic resonance angiography for detection of coronary artery stenoses

To analyze the incremental diagnostic value of a combination of two approaches (free‐breathing and breathhold) vs. the sole free‐breathing approach to coronary magnetic resonance angiography (CMRA) for detection of significant stenoses.

Multisegment and halfscan reconstruction of 16-slice computed tomography for assessment of regional and global left ventricular myocardial function.

Rationale and Objectives:We sought to prospectively compare multisegment and halfscan reconstruction of 16-slice computed tomography (CT) for the assessment of regional and global left ventricular myocardial function with magnetic resonance imaging (MRI) as the reference standard. Materials and Methods:Forty-two patients underwent CT with 16 × 0.5-mm detector collimation. Electrocardiogram-gated reconstructions were generated with multisegment reconstruction (using up to 4 segments correlated with the raw data of up to 4 heartbeats) and standard halfscan reconstruction. Steady-state free-precession cine MRI was acquired within 24 hours. Results:More normal myocardial segments were identified correctly with multisegment (95%, 620/656) compared with halfscan reconstruction (88%, 582/656) of CT (P < 0.001). Also, the accuracy (92% [657/714] vs. 87% [620/714]) and rate of nondiagnostic segments (0% vs. 5% [33/714]) were significantly better when using multisegment reconstruction (P < 0.001). The image quality with multisegment reconstruction was significantly superior to that achieved with halfscan reconstruction (P < 0.001). In the assessment of global left ventricular function, multisegment and halfscan reconstruction of CT showed high correlations for all parameters with MRI, whereas Bland-Altman analysis revealed smaller limits of agreement for assessment of myocardial mass with multisegment reconstruction (P = 0.025), but no significant differences between both reconstruction techniques in the measurement of left ventricular volumes as compared with MRI. Conclusions:Multisegment reconstruction of 16-detector row CT improves image quality and assessment of regional wall motion compared with standard halfscan reconstruction.

Patient Acceptance of Noninvasive and Invasive Coronary Angiography

Background Noninvasive angiography using multislice computed tomography (MSCT) is superior to magnetic resonance imaging (MRI) for detection of coronary stenoses. We compared patient acceptance of these two noninvasive diagnostic tests and invasive conventional coronary angiography (Angio). Methods and Findings A total of 111 consecutive patients with suspected coronary artery disease underwent MSCT, MRI, and Angio. Subsequently, patient acceptance of the three tests was evaluated with questionnaires in all patients. The main acceptance variables were preparation and information prior to the test, degree of concern, comfort, degree of helplessness, pain (on visual analog scales), willingness to undergo the test again, and overall satisfaction. Preparation for each test was not rated significantly differently, whereas patients were significantly more concerned about Angio than the two noninvasive tests (p<0.001). No pain during MSCT, MRI, and Angio as assessed on visual analog scales (0 to 100) was reported by 99, 93, and 31 patients, respectively. Among the 82 patients who felt pain during at least one procedure, both CT (0.9±4.5) and MRI (5.2±16.6) were significantly less painful than Angio (24.6±23.4, both p<0.001). MSCT was considered significantly more comfortable (1.49±0.64) than MRI (1.75±0.81, p<0.001). In both the no-revascularization (55 patients) and the revascularization group (56 patients), the majority of the patients (73 and 71%) would prefer MSCT to MRI and Angio for future imaging of the coronary arteries. None of the patients indicated to be unwilling to undergo MSCT again. The major advantages patients attributed to MSCT were its fast, uncomplicated, noninvasive, and painless nature. Conclusions Noninvasive coronary angiography with MSCT is considered more comfortable than MRI and both MSCT and MRI are less painful than Angio. Patient preference for MSCT might tip the scales in favor of this test provided that the diagnostic accuracy of MSCT can be shown to be high enough for clinical application.

Low-dose computed tomography to detect body-packing in an animal model

OBJECTIVE To assess the possible extent of dose reduction for low-dose computed tomography (CT) in the detection of body-packing (ingested drug packets) as an alternative to plain radiographs in an animal model. MATERIALS AND METHODS Twelve packets containing cocaine (purity >80%) were introduced into the intestine of an experimental animal (crossbred pig), which was then repeatedly examined by abdominal CT with stepwise dose reduction (tube voltage, 80 kV; tube current, 10-350 mA). Three blinded readers independently evaluated the CT datasets starting with the lowest tube current and noted the numbers of packets detected at the different tube currents used. In addition, 1 experienced reader determined the number of packets detectable on plain abdominal radiographs and ultrasound. RESULTS The threshold for correct identification of all 12 drug packets was 100 mA for reader 1 and 125 mA for readers 2 and 3. Above these thresholds all 3 readers consistently identified all 12 packets. The effective dose of a low-dose CT scan with 125 mA (including scout view) was 1.0 mSv, which was below that of 2 conventional abdominal radiographs (1.2 mSv). The reader interpreting the conventional radiographs identified a total of 9 drug packets and detected 8 packets by abdominal ultrasound. CONCLUSIONS Extensive dose reduction makes low-dose CT a valuable alternative imaging modality for the examination of suspected body-packers and might replace conventional abdominal radiographs as the first-line imaging modality.

Size determination and response assessment of liver metastases with computed tomography—Comparison of RECIST and volumetric algorithms

OBJECTIVE To compare different three-dimensional volumetric algorithms (3D-algorithms) and RECIST for size measurement and response assessment in liver metastases from colorectal and pancreatic cancer. METHODS The volumes of a total of 102 liver metastases in 45 patients (pancreatic cancer, n=22; colon cancer, n=23) were estimated using three volumetric methods (seeded region growing method, slice-based segmentation, threshold-based segmentation) and the RECIST 1.1 method with volume calculation based on the largest axial diameter. Each measurement was performed three times by one observer. All four methods were applied to follow-up on 55 liver metastases in 29 patients undergoing systemic treatment (median follow-up, 3.5 months; range, 1-10 months). Analysis of variance (ANOVA) with post hoc tests was performed to analyze intraobserver variability and intermethod differences. RESULTS ANOVA showed significant higher volumes calculated according to the RECIST guideline compared to the other measurement methods (p<0.001) with relative differences ranging from 0.4% to 41.1%. Intraobserver variability was significantly higher (p<0.001) for RECIST and threshold based segmentation (3.6-32.8%) compared with slice segmentation (0.4-13.7%) and seeded region growing method (0.6-10.8%). In the follow-up study, the 3D-algorithms and the assessment following RECIST 1.1 showed a discordant classification of treatment response in 10-21% of the patients. CONCLUSIONS This study supports the use of volumetric measurement methods due to significant higher intraobserver reproducibility compared to RECIST. Substantial discrepancies in tumor response classification between RECIST and volumetric methods depending on applied thresholds confirm the requirement of a consensus concerning volumetric criteria for response assessment.

Arterial Versus Portal Venous Embolization for Induction of Hepatic Hypertrophy before Extended Right Hemihepatectomy in Hilar Cholangiocarcinomas: A Prospective Randomized Study

PURPOSE To assess the efficacy and safety of portal vein (PV) embolization versus hepatic artery embolization (HAE) for induction of hepatic hypertrophy before extended right hemihepatectomy in patients with hilar cholangiocarcinoma. MATERIALS AND METHODS Fifty patients (female, n = 15; male, n = 35; age range, 37-80 y) with hilar cholangiocarcinomas who were planned to undergo extended right hemihepatectomy were prospectively included in 2003-2006. In addition to biliary decompression of the left liver, patients were randomized to undergo embolization of the right hepatic artery (with transfemoral access and polyvinyl alcohol [PVA] particles plus coils) or right PV branches (with computed tomography [CT]-guided transhepatic access and PVA particles). CT was performed before and approximately 3 weeks after embolization for volumetric assessment of the liver. RESULTS In the HAE group, median growth of the left lateral segments was 40 mL (P < .01), with a median reduction of the whole liver of 10 mL (P = .41); adverse events were observed in two of 25 patients (8%), who each developed an abscess in the right liver lobe. In the PV embolization group, median growth of the left lateral segments was 110 mL (P < .01), with a median growth of the whole liver of 10 mL (P = .92); a subcapsular seroma occurred in one of 25 patients (4%). The median growth of the left lateral segments after PV embolization was significantly greater than after HAE (P = .004). CONCLUSIONS Compared with HAE, PV embolization was significantly superior regarding induction of hepatic hypertrophy of the left lateral segments.

Computed-tomography-guided high-dose-rate brachytherapy (CT-HDRBT) ablation of metastases adjacent to the liver hilum

PURPOSE To evaluate technical feasibility and clinical outcome of computed tomography-guided high-dose-rate-brachytherapy (CT-HDRBT) ablation of metastases adjacent to the liver hilum. MATERIALS AND METHODS Between November 2007 and May 2012, 32 consecutive patients with 34 metastases adjacent to the liver hilum (common bile duct or hepatic bifurcation ≤5 mm distance) were treated with CT-HDRBT. Treatment was performed by CT-guided applicator placement and high-dose-rate brachytherapy with an iridium-192 source. MRI follow-up was performed 6 weeks and every 3 months post intervention. The primary endpoint was local tumor control (LTC); secondary endpoints included time to progression (TTP) and overall survival (OS). RESULTS Patients were available for MRI evaluation for a mean follow-up time of 18.75 months (range: 3-56 months). Mean tumor diameter was 4.3 cm (range: 1.3-10.7 cm). One major complication was observed. Four (11.8%) local recurrences were observed after a local tumor control of 5, 8, 9 and 10 months, respectively. Twenty-two patients (68.75%) experienced a systemic tumor progression during the follow up period. Mean TTP was 12.9 months (range: 2-56 months). Nine patients died during the follow-up period. Median OS was 20.24 months. CONCLUSION Minimally invasive CT-HDRBT is a safe and effective option also for unresectable liver metastases adjacent to the liver hilum that would have been untreatable by thermal ablation.