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British Journal of Radiology [journal]
- Agreement between objective and subjective assessment of image quality in ultrasound abdominal aortic aneurism screening. [JOURNAL ARTICLE]
- Br J Radiol 2014 Dec 11.:20140482.
Objective: To investigate agreement between objective and subjective assessment of image quality of ultrasound scanners used for abdominal aortic aneurysm screening. Methods: Nine ultrasound scanners were used to acquire longitudinal and transverse images of the abdominal aorta. One hundred images were acquired per scanner from which five longitudinal and five transverse images were randomly selected. Thirty-three practitioners scored 90 images blinded to the scanner type and subject characteristics, and were required to state whether or not the image was of adequate diagnostic quality. Odds ratios were used to rank the subjective image quality of the scanners. For objective testing, three standard test objects were used to assess penetration and resolution, and used to rank the scanners. Results: The subjective diagnostic image quality was ten times greater for the highest ranked scanner compared to the lowest ranked scanner. It was greater at depths of <5.0 cm (odds ratio 6.69 [95% CI: 3.56, 12.57]) compared to depths of 15.1 - 20.0 cm. There was a larger range of odds ratios for transverse images than longitudinal images. No relationship was seen between subjective scanner rankings and test object scores. Conclusions: Large variation was seen in the image quality when evaluated both subjectively and objectively. Objective scores did not predict subjective scanner rankings. Further work is needed to investigate the utility of both subjective and objective image quality measurements. Advances in Knowledge: Ratings of clinical image quality and image quality measured using test objects did not agree, even in the limited scenario of AAA screening.
- Correlation between Gamma index passing rate and clinical dosimetric difference for pretreatment 2D and 3D volumetric modulated arc therapy dosimetric verification. [JOURNAL ARTICLE]
- Br J Radiol 2014 Dec 10.:20140577.
Purpose:To investigate comparatively the percent gamma passing rate (%GP) of 2D and 3D pretreatment volumetric modulated arc therapy (VMAT) dosimetric verification, and their correlation and sensitivity with percent dosimetric errors (%DE) Materials and methods: %GP of 2D and 3D pretreatment VMAT QA with different acceptance criteria were obtained by ArcCHECK for twenty nasopharyngeal cancer (NPC) patients and 20 esophageal cancer patients. %DE were calculated from planned dose-volume histogram (DVH) and patients' predicted DVH calculated by 3DVH software. Correlation and sensitivity between %GP and %DE was investigated using Pearson's correlation coefficient (r) and receiver operating characteristics (ROC).
Results:Relatively higher %DE on some DVH based metrics were observed for both NPC and esophageal cancer patients. Except for 2%/2mm criterion, the average %GPs for all VMAT patients was acceptable with average rates of 97.11%±1.54% and 97.39%±1.37% for 2D and 3D 3%/3mm criterion, respectively. The number of correlation of 3D was higher than that of 2D (21 vs.8). However, the general correlation was still poor for all the analyzed metrics (9 out of 26 for 3D 3%/3mm criterion). The average area under curve (AUC) of ROCs were 0.66±0.12 and 0.71±0.21 for 2D and 3D, respectively.
Conclusion:There is a lack of correlation between %GP and %DE for both 2D and 3D pretreatment VMAT dosimetric evaluation. DVH-based dose metrics evaluation obtained from 3DVH will provide more useful analysis. Advances in knowledge: Correlation and sensitivity of %GP with %DE for VMAT QA were studied for the first time.
- Partial-Volume Effect Correction in Positron Emission Tomography Brain Scan Image Using Superresolution Image Reconstruction. [JOURNAL ARTICLE]
- Br J Radiol 2014 Dec 10.:20140119.
The partial-volume effect (PVE) is a consequence of limited (i.e. finite) spatial resolution. PVE can lead to quantitative underestimation of activity concentrations in reconstructed images, which may result in misinterpretation of Positron Emission Tomography (PET) scan images, especially in the brain. The PVE becomes significant when the dimensions of a source region are less than two to three times the full-width at half-maximum (FWHM) spatial resolution of the imaging system.
Objective:In the current study, the ability of superresolution (SR) image reconstruction to compensate for PVE in PET was characterized.
Methods:The ability of the SR image reconstruction technique to recover activity concentrations in small structures was evaluated by comparing images before and after image reconstruction in the NEMA/IEC phantom, the Hoffman brain phantom and in 4 human brain subjects (3 normal subjects and 1 atrophic brain subject) in terms of apparent recovery coefficient (ARC) and percentage yield.
Results:Both the ARC and percentage yield are improved after SR implementation in NEMA/IEC phantom and Hoffman brain phantom. When tested in normal subjects, SR implementation can improve the intensity and justify SR efficiency to correct PVE.
Conclusion:SR algorithm can be used to effectively correct PVE in PET images. Advances in knowledge: The current research focused on brain PET scanning exclusively; future work will extend to whole-body imaging.
- Patients with severe emphysema have a low risk of radiation pneumonitis following stereotactic body radiotherapy. [JOURNAL ARTICLE]
- Br J Radiol 2014 Dec 9.:20140596.
Objectives:To evaluate the risk of radiation pneumonitis (RP) after stereotactic radiotherapy (SBRT) for patients presenting with severe pulmonary emphysema.
Methods:This study included 40 patients with stage I non-small cell lung cancer (NSCLC) who underwent SBRT, 75 Gy given in 30 fractions, at Tokyo Medical University between February 2010 and February 2013. The median age of patients was 79 years (range, 49-90), and the male/female ratio was 24/16. There were 20 T1 and 20 T2 tumors. Seventeen patients had emphysema, 6 had slight interstitial changes on CT images, and the remaining 17 had no underlying lung disease. The level of emphysema was classified into three groups according to the modified Goddard's criteria (severe: 3 patients, moderate: 8 patients, mild: 6 patients). Changes in the irradiated lung following SBRT were evaluated by CT.
Results:On CT images, RP was detected in thirty-four (85%) patients, and not in six (15%) patients, during a median observation period of 313 days. Of the six patients, three had severe emphysema and three had no underlying lung disease. Patients with severe emphysema had less risk of RP than those with moderate emphysema (P = 0.01), mild emphysema (P = 0.04), and no underlying lung disease (P = 0.01).
Conclusions:Patients with severe emphysema had a low risk of RP following SBRT. Advances in knowledge: Little is known about the association between radiation pneumonitis and pulmonary emphysema. Patients with severe emphysema had less risk of radiation pneumonitis than those with no underlying lung disease.
- Effective dose of cone beam CT (CBCT) of the facial skeleton: a systematic review. [Journal Article]
- Br J Radiol 2015 Jan; 88(1045):20140658.
To estimate effective dose of cone beam CT (CBCT) of the facial skeleton with focus on measurement methods and scanning protocols.A systematic review, which adhered to the preferred reporting items for systematic reviews (PRISMA) Statement, of the literature up to April 2014 was conducted. Data sources included MEDLINE®, The Cochrane Library and Web of Science. A model was developed to underpin data extraction from 38 included studies.Technical specifications of the CBCT units were insufficiently described. Heterogeneity in measurement methods and scanning protocols between studies made comparisons of effective doses of different CBCT units and scanning protocols difficult. Few studies related doses to image quality. Reported effective dose varied across studies, ranging between 9.7 and 197.0 μSv for field of views (FOVs) with height ≤5 cm, between 3.9 and 674.0 μSv for FOVs of heights 5.1-10.0 cm and between 8.8 and 1073.0 μSv for FOVs >10 cm. There was an inconsistency regarding reported effective dose of studies of the same CBCT unit with the same FOV dimensions.The review reveals a need for studies on radiation dosages related to image quality. Reporting quality of future studies has to be improved to facilitate comparison of effective doses obtained from examinations with different CBCT units and scanning protocols. A model with minimum data set on important parameters based on this observation is proposed.Data important when estimating effective dose were insufficiently reported in most studies. A model with minimum data based on this observation is proposed. Few studies related effective dose to image quality.
- Cardiac Magnetic Resonance Assessment Of Microvascular Obstruction. [JOURNAL ARTICLE]
- Br J Radiol 2014 Dec 4.:20140470.
Microvascular obstruction is usually seen in a proportion of patients with acute myocardial infarction following reperfusion therapy of an occluded coronary artery. It is characterised by damage and dysfunction of the myocardial microvasculature with a no-reflow phenomenon within the infarct zone. While microvascular obstruction may be demonstrated via a number of different imaging modalities, cardiac magnetic resonance enables accurate identification of microvascular obstruction and also permits assessment of infarct extent and overall left ventricular function during the same imaging examination. We present a pictorial review of the characteristic appearances of microvascular obstruction on cardiac magnetic resonance and highlight the importance of this imaging diagnosis for patient outcome following acute myocardial infarction.
- ADC Values in Diffusion-Weighted MRI and Their Relationship with Age, Gender, and BMI in Healthy People's Pancreas. [JOURNAL ARTICLE]
- Br J Radiol 2014 Dec 4.:20140449.
Objectives:The aim of this study is to use diffusion-weighted MRI to assess the ADC values in the head, body, and tail sections of healthy subjects' pancreas and the relationships between these values and the age, gender, and body mass index (BMI) of the cases.
Methods:This study was conducted on 82 participants who referred to Tabesh Medical Imaging Center, Tabriz during 2013. Echo-planar Diffusion-Weighted Imaging (DWI) of the pancreas was done with b-values of 50, 400, and 800 s/mm(2), and ADC values were assessed for the head, body, and tail of the pancreas.
Results:The ADC values for the pancreas head, body, and tail in the female participants were significantly greater than male subjects (P < 0.05). ADC values for these parts among subjects with different BMI levels were differed significantly (P < 0.05). Regarding age, there were no statistically meaningful differences among the ADC values for the three parts (P > 0.05).
Conclusions:Gender and BMI are effective on the ADC values of these three parts. Thus, regarding special cases and further future studies, knowledge of the basic values based on gender and BMI can help to better diagnostic. Having looked at age factor, it seems that the ADC values were not significantly different. Advances in knowledge: According to mentioned statements it can be clearly said that pancreatic ADC values appear to be influenced by gender and BMI but not by age factor.
- Optimizing geometric accuracy of four dimensional CT scans acquired using the wall and couch mounted Varian Real-Time Position Management camera systems. [JOURNAL ARTICLE]
- Br J Radiol 2014 Dec 3.:20140624.
Objective:The aim of this study was to identify sources of anatomical misrepresentation due to the location of camera mounting, tumour motion velocity and image processing artefacts in order to optimise the 4DCT scan protocol and improve geometrical-temporal accuracy.
Methods:A phantom with an imaging insert was driven with a sinusoidal superior-inferior motion of varying amplitude and period for 4DCT scanning. The length of a high density cube within the insert was measured using treatment planning software to determine the accuracy of its spatial representation. Scan parameters were varied including the tube rotation period and the cine time between reconstructed images. A CT image quality phantom was used to measure various image quality signatures under the scan parameters tested.
Results:No significant difference in spatial accuracy was found for 4DCT scans carried out using the wall mounted or couch mounted camera for sinusoidal target motion. Greater spatial accuracy was found for 4DCT scans carried out using a tube rotation speed of 0.5s rather than 1.0s. The reduction in image quality when using a faster rotation speed was not enough to require an increase in patient dose.
Conclusions:4DCT accuracy may be increased by optimising scan parameters, including choosing faster tube rotation speeds. Peak misidentification in the recorded breathing trace leads to spatial artefacts and this risk can be reduced by using a couch mounted infrared camera. Advances in knowledge: This study explicitly shows that 4DCT scan accuracy is improved by scanning with a faster CT tube rotation speed.
- Qualitative and Quantitative Evaluation of Rigid and Deformable Motion-correction Algorithms Using Dual-energy CT-images in View of Application to CT-perfusion Measurements in Abdominal Organs Affected by Breathing Motion. [JOURNAL ARTICLE]
- Br J Radiol 2014 Dec 3.:20140683.
Objectives:To compare six different scenarios for correcting for breathing-motion in abdominal Dual-Energy (DE) CT-perfusion measurements.
Methods:Rigid (RRComm(80kVp)) and non-rigid (NRComm(80kVp)) registration of commercially available CT-perfusion software, custom non-rigid registration (NRCustom(80kVp), demons algorithm), and a control group (CG(80kVp)) without motion-correction were evaluated using 80kVp images. Additionally, NRCustom was applied to DE-blended (NRCustom(DE)) and virtual non-contrast images (NRCustom(VNC)), yielding six evaluated scenarios. After motion-correction, perfusion maps were calculated using a combined Maximum-Slope/Patlak-model. For qualitative evaluation, three blinded radiologists independently rated motion-correction quality and resulting perfusion maps on a 4-point scale (4=best, 1=worst). For quantitative evaluation, relative changes in metric values, R(2), and residuals of perfusion model fits were calculated.
Results:For motion-corrected images mean ratings differed significantly (NRCustom(80kVp) and NRCustom(DE) 3.3, NRComm(80kVp) 3.1, NRCustom(VNC) 2.9, RRComm(80kVp) 2.7, CG(80kVp) 2.7; all p<0.05), except when comparing NRCustom(80kVp) to NRCustom(DE), and RRComm(80kVp) to CG(80kVp). NRCustom(80kVp) and NRCustom(DE) achieved the highest reduction in metric values (NRCustom(80kVp) 48.5%, NRCustom(DE) 45.6%, NRComm(80kVp) 29.2%, NRCustom(VNC) 22.8%, RRComm(80kVp) 0.6%, CG(80kVp) 0%). Regarding perfusion maps, NRCustom(80kVp) and NRCustom(DE) were rated highest (NRCustom(80kVp) 3.1, NRCustom(DE) 3.0, NRComm(80kVp) 2.8, NRCustom(VNC) 2.6, CG(80kVp) 2.5, RRComm(80kVp) 2.4) and had significantly higher R(2) and lower residuals. Correlation between qualitative and quantitative evaluation was low to moderate.
Conclusions:Non-rigid motion-correction improves spatial alignment of the target region and fit of CT perfusion models. Using DE-blended and DE-VNC images for deformable registration offers no significant improvement. Advances in knowledge: Non-rigid algorithms improve the quality of abdominal CT-perfusion measurements, but do not benefit from DECT post-processing.
- Lung radiofrequency and microwave ablation: A review of indications, techniques and post procedural imaging appearances. [JOURNAL ARTICLE]
- Br J Radiol 2014 Dec 3.:20140598.
Lung ablation can be used to treat both primary and secondary thoracic malignancies. Evidence to support its use, particularly for metastases from colonic primary tumours, is now strong, with survival data in selected cases, approaching that seen after surgery. Because of this the use of ablative techniques (particularly thermal ablation) is growing and the Royal College of Radiologists predict that the number of patients who could benefit from such treatment may reach in excess of 5000 per year in the UK. Treatment is often limited to larger regional centres and general radiologists often have limited awareness of the current indications and the techniques involved. Furthermore radiologists without any prior experience are frequently expected to interpret post treatment imaging, often performed in the context of acute complications which have occurred after discharge. This review aims to provide an overview of the current indications for pulmonary ablation, together with the techniques involved and the range of post procedural appearances.