Experience with gated cardiac software phantoms for quality control of applications programmes

Ten gated cardiac software phantoms, representing normal and abnormal clinical conditions, were transferred to 9 different computer systems and tested with 11 cardiac programmes. Problems of inappropriate data format were encountered when analysing the phantoms on other systems. The global left ventricular ejection fraction (LVEF) values resulting from the different programmes were compared. Significant programme differences were found, the programmes falling generally into two groups. Few LVEF outlier values were identified. Full functional assessment of cardiac phantoms requires a set of different views which together form the phantom. Application of software phantoms for programme assessment and training requires prudence and attention to the acquired data format, frame time, and gating method for the appropriate use of phantoms.     

Experience with gated cardiac software phantoms for quality control of applications programmes

Ten gated cardiac software phantoms, representing normal and abnormal clinical conditions, were transferred to 9 different computer systems and tested with 11 cardiac programmes. Problems of inappropriate data format were encountered when analysing the phantoms on other systems. The global left ventricular ejection fraction (LVEF) values resulting from the different programmes were compared. Significant programme differences were found, the programmes falling generally into two groups. Few LVEF outlier values were identified. Full functional assessment of cardiac phantoms requires a set of different views which together form the phantom. Application of software phantoms for programme assessment and training requires prudence and attention to the acquired data format, frame time, and gating method for the appropriate use of phantoms.     

A comparison of digital and screen-film mammography using quality control phantoms

AIM: To compare the performance of a direct digital mammography system with normal-view and magnified-view conventional screen-film methods using quality control phantoms. MATERIALS AND METHODS: Using a Siemens Mammomat((R))3000 and an Opdima((R))digital spot imaging and biopsy attachment, film and direct digital images of two phantoms [DuPont and TOR (MAM)] were obtained under normal operating conditions. These were assessed by three groups of observers with differing expertise - radiologists, radiographers and medical physicists. Each observer was asked to compare the direct digital image with films taken in standard view and magnified view, providing scores for object visibility and confidence. For the digital images, observers were allowed to vary the image presentation parameters. RESULTS: Both phantoms showed that overall the direct digital view and the magnified view film performed significantly better (P < 0.05) than standard view film. For certain small or low contrast objects the differences became very highly significant (P < 0.001). CONCLUSION: Only the TOR (MAM) phantom showed any significant difference between digital and magnified modalities, with magnified views performing better for fine, faint filaments and digital acquisition better for low contrast objects. Almost no difference existed between the three observer groups. Undrill, P. E. (2000). Clinical Radiology53, 782-790.     

Diagnostic significance of high-filtration xeromammography in relation to radiation hazard and image quality (author's transl)

The use of additional filtration through 3 mm aluminium enables significant reduction of the radiation dose in xeromammography with the Senographe, compared with conventional xerography, by a factor of 2-3, and, compared with film not requiring an intensifying screen, by a factor of 10-12. The applied tissue doses are between 0.14 and 0.30 rad per exposure. Hence, the radiogenic carcinoma risk, which is still largely hypothetic, is very low as far as this mammographic system is concerned. The high quality of the mammographs guarantees absolute diagnostic safety.     

Clinical dosimetry in xeromammography using the low dose system

The results obtained by utilizing low-dose plates in xeromammography are reported. Phantom experimental examinations and dosimetric measurements were made before using these plates. The new exposition data were then compared to those obtained with the old plates. Findings prove low-dose plates to be more sensitive--thus granting very good iconographic results with reduction of skin dose (about 30%) at FFD of 110 cm. The skin dose has been compared to that obtained with the most modern mammographs.     

Statistical analysis of correlation of gamma passing results for two quality assurance phantoms used for patient-specific quality assurance in volumetric modulated arc radiotherapy

Patient-specific quality assurance (QA) data must be migrated from outdated QA systems to new ones to produce objective results that can be understood by oncologists. We aimed to evaluate a method for obtaining a high correlation of dose distributions according to various gamma passing rates among two types of 2D detectors for the migration of patient-specific QA data of volumetric modulated arc therapy (VMAT). The patient-specific QA of 20 patients undergoing VMAT was measured in two different modes: standard single measurement (SM) mode and multiple merged measurements (MM) techniques using ArcCHECK (AC) and OCTAVIUS (OT). The correlation of the measured and calculated dose distributions was evaluated according to varying gamma passing rates (3%/3 mm, 2%/3 mm, 2%/2 mm, and 1%/1 mm). The gamma passing rates were analyzed using the Anderson–Darling normality test. Treatment plan dose distributions were calculated by intentionally shifting the calculation isocenter position (x,y,z ± 0.5, ± 1.0, ± 1.5, and ± 2.0 mm). The highest correlation between the SM and MM was observed with a gamma passing rate of 1%/1 mm with AC (r = 0.866) and 3%/2 mm with OT (r = 0.916). However, SM and MM did not follow a normal distribution with a rate of 3%/2 mm in OT. The second-highest correlation was obtained with a rate of 2%/2 mm (r = 0.900). Among the two 2D detectors, the highest correlation between the calculated and measured dose distributions was obtained for a gamma passing rate of 1%/1 mm using SM in AC and 2%/2 mm using MM in OT (r = 0.716). Adjusting the gamma passing rate and measurement mode of AC and OT resulted in higher correlations between measured and calculated dose distributions. The high correlation between different 2D detectors objectively indicated a potential migration method. This enabled the sharing of more accurate patient-specific QA data from 2D detectors with different phantoms. A high correlation was observed between the two types of detectors in this study (r = 0.716); therefore, the proposed method should be useful for oncologists to share information regarding patient-specific QA for VMAT.     

Development of small adenocarcinoma phantoms for comparison of image quality among various chest X-ray systems

The aim of our study was to develop a phantom of lung adenocarcinoma for use in a comparative evaluation of image quality among various chest X-ray systems. In this study, we developed type A, B, and C phantoms of lung adenocarcinoma according to Noguchi's classification. The shape of lung adenocarcinoma was assumed to be spherical with a different density in the core. The shapes of the phantoms were obtained by calculating equivalent thickness to X-ray transmission, leading to the same shadow as the sphere in order to perform practical visual evaluation using a chest lung phantom to which the phantoms were attached. The phantoms were tough water phantoms made by Kyoto Kagaku Co., Ltd. The performance of the phantoms was validated for chest radiographs of the phantoms attached to the surface of the chest lung phantom. The results of visual evaluation of tumor detectability by 13 radiologists and technicians showed generally good agreement with previous clinical data.     

Screen-film mammography versus xeromammography in the detection of breast cancer

There are two common methods of obtaining high-quality screening mammography: screen-film mammography (more simply, mammography) using a dedicated unit, and xeromammography. We studied the accuracy of the two techniques in detecting breast cancer by a retrospective study, analysing accuracy of interpretation in cases where both mammography and xeromammography were performed. Seventy-six patients were considered with 86 biopsies and mammograms resulting in detection of 32 cancers and 54 benign lesions. There was no difference in accuracy of interpretation between mammography and xeromammography. The sensitivities were: mammography 0.91, xeromammography 0.88. The specificities were: mammography 0.63, xeromammography 0.75. We conclude that both modalities are comparable in detecting cancer when optimal technique and experienced personnel are used.     

Subjective and objective comparisons of image quality between ultra-high-resolution CT and conventional area detector CT in phantoms and cadaveric human lungs

Objectives

To compare the image quality of the lungs between ultra-high-resolution CT (U-HRCT) and conventional area detector CT (AD-CT) images.

Methods

Image data of slit phantoms (0.35, 0.30, and 0.15 mm) and 11 cadaveric human lungs were acquired by both U-HRCT and AD-CT devices. U-HRCT images were obtained with three acquisition modes: normal mode (U-HRCT_N: 896 channels, 0.5 mm × 80 rows; 512 matrix), super-high-resolution mode (U-HRCT_SHR: 1792 channels, 0.25 mm × 160 rows; 1024 matrix), and volume mode (U-HRCT_SHR-VOL: non-helical acquisition with U-HRCT_SHR). AD-CT images were obtained with the same conditions as U-HRCT_N. Three independent observers scored normal anatomical structures (vessels and bronchi), abnormal CT findings (faint nodules, solid nodules, ground-glass opacity, consolidation, emphysema, interlobular septal thickening, intralobular reticular opacities, bronchovascular bundle thickening, bronchiectasis, and honeycombing), noise, artifacts, and overall image quality on a 3-point scale (1 = worst, 2 = equal, 3 = best) compared with U-HRCT_N. Noise values were calculated quantitatively.

Results

U-HRCT could depict a 0.15-mm slit. Both U-HRCT_SHR and U-HRCT_SHR-VOL significantly improved visualization of normal anatomical structures and abnormal CT findings, except for intralobular reticular opacities and reduced artifacts, compared with AD-CT (p < 0.014). Visually, U-HRCT_SHR-VOL has less noise than U-HRCT_SHR and AD-CT (p < 0.00001). Quantitative noise values were significantly higher in the following order: U-HRCT_SHR (mean, 30.41), U-HRCT_SHR-VOL (26.84), AD-CT (16.03), and U-HRCT_N (15.14) (p < 0.0001). U-HRCT_SHR and U-HRCT_SHR-VOL resulted in significantly higher overall image quality than AD-CT and were almost equal to U-HRCT_N (p < 0.0001).

Conclusions

Both U-HRCT_SHR and U-HRCT_SHR-VOL can provide higher image quality than AD-CT, while U-HRCT_SHR-VOL was less noisy than U-HRCT_SHR.

Key Points

? Ultra-high-resolution CT (U-HRCT) can improve spatial resolution. ? U-HRCT can reduce streak and dark band artifacts. ? U-HRCT can provide higher image quality than conventional area detector CT. ? In U-HRCT, the volume mode is less noisy than the super-high-resolution mode. ? U-HRCT may provide more detailed information about the lung anatomy and pathology.

     

舒芬太尼与瑞芬太尼用于儿童扁桃体和腺样体切除术后麻醉恢复质量的比较

目的 观察舒芬太尼与瑞芬太尼在儿童扁桃体和腺样体切除术中及术后镇痛镇静作用,比较两种药物对麻醉恢复质量的影响。方法 选择择期进行扁桃体和腺样体切除术患儿80例,随机分为舒芬太尼组（S组,n=40）和瑞芬太尼组（R组,n=40）。S组以舒芬太尼0.2μg/kg快速诱导,以0.2μg·kg-1·h-1术中维持,手术结束前30分钟停药。R组以瑞芬太尼2μg/kg快速诱导,以6μg·kg-1·h-1术中维持,手术结束前5分钟停药。分别观察两组术中术后血流动力学指标及术后患儿镇痛镇静程度。结果 两组在术中血流动力学指标无明显差异（P〉0.05）。拔管后5分钟时S组MAP较基础值无明显差异;R组MAP较基础值明显增高（P〈0.05）。S组患儿在术后Ramsay评分较适宜,VAS评分较低。结论 两种药物均适用于儿童扁桃体和腺样体切除术,舒芬太尼可提高术后麻醉恢复质量。     

In-vitro phantoms for estimating diffusion tensor tractography

No literature has reported on in-vitro diffusion tensor tractography, although it is a useful method to visualize neuronal fiber projections in the living human brain. We applied this technique to phantoms of asparagus stems and bundled polyester yarn, and obtained tractography with high-quality images. On the asparagus stem phantom, straight tracts along the axis were displayed. On the polyester phantom, these tracts followed the course of the bundle whether it was straight or curved. These phantoms are useful for in-vitro evaluation of diffusion tensor tractography.