Monitorbeurteilung digitalisierter und nachbearbeiteter Feldkontrollaufnahmen im Vergleich zu konventionellen Feldkontrollaufnahmen am Röntgenschaukasten

Purpose

Judgement of image quality and detail recognition of digitized and post-processed portal films presented on a computer monitor compared to the present standard, conventional portal films presented on a light-box.

Material and Methods

Conventional portal films of 3 different tumor sites (10 pelvis, 10 cranium, 10 vertebral column) were presented to a panel of 8 observers in 3 different manners: conventional film presented on a light-box (Conv), digitized non-post-processed images (Dig-1) and digitized post-processed images (Dig-2) presented on a high-resolution computer monitor. Subjective judgement of image quality, detail recognition and time requirement of conventional films compared to monitor presentation were evaluated using a 5-scaled questionnaire (from 1=much better to 5=much worse). Furthermore the observers had to point out predefined anatomical bony structures on the conventional films (Conv) as well as on the digitized post-processed images (Dig-2). Standard deviations of the landmarks outlined by 10 different observers were used as a criterion of objective detail recognition (Figure 1).

Results

Image quality of digitized post-processed images presented on the computer monitor was judged statistical significant better than of conventional films (pelvis 78%, vertebral column 62%, cranium 45% better) (Figure 3). Similar results were found for comparison of detail recognition: digitized post-processed images were scored better for pelvis in 81%, for vertebral column in 57%, for cranium in 40% (Figure 4, Table 1). Most benefit from portal film enhancement was found for pelvic images, where portal films are known to be of poor image quality (Figure 2). In contrast image quality of non-processed digital images compared to conventional films was graded worse (pelvis 69%, vertebral column 53%, cranium 71% worse) (Figure 4). Digital post-processed images were especially for the pelvis judged to require less time (pelvis 68%, vertebral column 26%, cranium 8% less time requirement) (Figure 5). For the pelvis a statistical significant decrease of standard deviations was found for Dig-2 compared to conventional films, indicating an objective increase of image quality and detail recognition (Table 2). In case of vertebral column and cranium no significant differences were evaluated (Table 3).

Conclusions

Digitized enhanced portal films presented on a computer monitor resulted in a quicker assessment and equal to better image quality as well as detail recognition compared to conventional films. Non-processed digitized images were judged to be of less image quality.     

Evaluation of CRT images of digitized film angiographs

X-ray sheet film images of the test chart, the vascular phantom and angiography were digitized at sampling pitch of 0.2 mm and 0.15 mm using film digitizer TFR-01 (Toshiba) and transferred to a device for image storage and display system with 1635-line display monitor (TDF-500AS, Toshiba). Comparison of image qualities between film- and CRT-images was performed in fundamental and clinical studies. Resolution of the test chart image of conventional radiography was worse on CRT than on the original film, although it was improved when film image was digitized at resolution of 0.15 mm/pixel in comparison with that at resolution of 0.2 mm/pixel. Moiré stripes which occurred due to interference were found on CRT images taken using a grid technique. On CRT images of X-ray sheet film using direct magnification technique moiré stripes were not produced because of non grid technique, and the resolution approached that of the original film. In the study using vascular phantom, the optimal image on CRT could be obtained by various image processing procedures, and image quality on CRT with resolution of 0.15 mm approached that of original film. In case of direct magnification CRT images were superior to film images. Subtraction image of the vascular phantom at resolution of 0.2 mm/pixel was obtained on CRT and compared with film subtraction image. On conventional subtraction CRT image moiré stripes impaired the image quality in comparison with the film subtraction. However, magnification subtraction image of the vascular phantom on CRT was superior to the film subtraction. The results obtained in the test chart studies and phantom studies were also confirmed in clinical studies using various kind of angiograms. In addition, ROC study using clinical angiograms showed no significant statistical differences between the original film and CRT image even with 0.2 mm matrix size. Angiographic image on CRT at resolution of 0.15 mm/pixel or less is available for clinical use in place of conventional film image.     

Linear and logarithmic subtraction for detecting enamel subsurface demineralization

OBJECTIVE: To compare the diagnostic performance of linear and logarithmically contrast-enhanced subtraction images, acquired with digital and digitized radiographs, in detecting approximal enamel subsurface demineralization. METHODS: Fifty caries-free human third molars were immersed in a demineralizing solution for 60, 75, 90, and 120 days, in order to induce artificial enamel subsurface demineralization. The teeth were coated with nail varnish, leaving only a circular window of approximately 7 mm2 in one of the approximal surfaces, allowing contact with the solution. Standardized radiographs of the teeth were taken prior to and after the demineralization period with three digital systems, CygnusRay MPS, DenOptix and DIGORA, and InSight film. Conventional, digital and digitized radiographs were assessed by three experienced radiologists. Linear and logarithmically contrast-enhanced subtraction images were acquired and then examined by a fourth independent radiologist. For the validation of the radiographic diagnosis, the enamel test areas were submitted to Knoop microhardness profiling. Radiographic interpretation data was evaluated using ROC analysis. The areas under the ROC curves (Az) were compared by the chi-squared test. The level of significance was set at P=0.05. RESULTS: No significant differences were found between linear and logarithmically contrast- enhanced subtraction images, acquired with the four studied modalities: CygnusRay MPSlinear (Az=0.95), CygnusRay MPSlog (Az=0.98), DenOptixlinear (Az=0.97), DenOptixlog (Az=0.99), DIGORAlinear (Az=0.98), DIGORAlog (Az=0.98), digitized radiographylinear (Az=0.99), digitized radiographylog (Az=0.99). CONCLUSION: Linear and logarithmically contrast-enhanced subtraction images, acquired with digital and digitized radiographs, were diagnostically comparable for assessing enamel subsurface demineralization.     

Quantitative assessment of quality of digitized portal images: receiver operating characteristic analysis applied to imaging in radiation therapy

An objective and quantitative method for the evaluation of the quality of megavoltage portal images was developed by applying receiver operating characteristic analysis. On the basis of therapeutic use of portal images, setup errors were employed as "signals" in this experimental study that compared the original portal films with digitized images. Six readers observed 104 portal images of a chest phantom, half of which were "abnormal" (ie, had setup errors). Digital images (2,048 x 2,048 matrix) were enhanced by means of histogram equalization and then printed with a laser printer for observation. The readers showed a higher discrimination capacity with the digitally enhanced images, although a statistically significant improvement was not demonstrated. The present method of assessment of image quality proved to be both simple and clinically reasonable.     

Anatomy of intrahepatic portal branches visualized by three-dimensional imaging analysis of CT arterial portography

The purpose of this study was to clarify variations in intrahepatic portal branches by means of CT imaging procedures. The subjects were 73 patients, 59 men and 14 women, who ranged in age from 41 to 76 years, with a mean of 63 years. The procedures were as follows. The entire liver was scanned using helical CT during the portal and hepatic venous phases, and 3D images of the portal vein were reconstructed with the volume-rendering technique and the region-growing method. The CT unit was a HITACHI W2000, and the imaging analyzer a Sun Ultra 1. We found that the branching patterns of both the anterior (P5 and P8) and posterior segmental branches (P6 and P7) of the right lobe of the liver could be classified into four types. The caudate branch (P1) and left lateral segmental branches (P2 and P3) were classified into three types, and the interior segmental branch of the left lobe (P4) was classified into two types. The frequency of each pattern was also revealed. These branching types and their frequencies were generally the same as those described in previous reports. Thus, the portal anatomy visualized by these methods indicates that they could be very useful for preoperative examinations or IVR.     

A comparative evaluation of two head and neck immobilization devices using electronic portal imaging

A study was performed to compare the positioning reproducibility and the cost efficiency for two head and neck immobilization devices: the Uvex (Uvex Safety, Smithfield, USA) plastic mask system and the Finesse Frame with Ultraplast System (PLANET Medical, Svendborg, Denmark). 20 patients treated with 3D conformal radiation therapy for head and neck cancers were randomly selected (10 for each of the two different immobilization systems) and electronic portal images acquired during their course of treatment were saved and used in this study. The anatomical landmark coordinates and their shifts in the anteroposterior (AP) and craniocaudal (CC) directions with respect to the digitized simulator films for lateral fields were analysed using an in-house developed portal image registration system. Statistically, no evidence was found to indicate that the systematic components of the displacement for the Uvex system and the Finesse Frame with Ultraplast System were different from each other or from zero. The random component of displacement was slightly smaller in the AP direction for the Uvex than the Ultraplast system (sigma = 1.9 mm and 2.9 mm, respectively, p = 0.007), but larger in the CC direction (sigma = 3.8 mm and 2.2 mm, respectively, p<10(-9)). Production time and required materials for a radiation therapy department were also quantified to assess costs for each system. The overall costs per patient were estimated at 141.50 dollars (CAD) and 82.10 dollars for the Uvex and Ultraplast systems, respectively. The Finesse Frame with Ultraplast System of immobilization for head and neck cancer treatment provides a field placement reproducibility that is equal to, or greater than, that of the Uvex plastic mask immobilization system and, while it requires more expensive materials, the workload and consequently overall cost is greatly reduced.     

正常胰腺小视野高分辨DWI研究

目的:对比研究正常胰腺小视野扩散加权成像(rFOV DWI)和单次激发平面回波成像(SS-EPI)图像质量、ADC值及临床应用价值。方法:对20例胰腺健康志愿者分别行上腹部自由呼吸触发的SS-EPI DWI和rFOV DWI检查(b=600s/mm2)。从形态学方面,分别计算两种方法获得的胰腺头、体及尾部的ADC值,并进行统计学分析。结果:①rFOV DWI及SS-EPI DWI图像分辨力分别为0.55mm×0.55mm和1.56mm×1.56mm。②SS-EPI DWI获得正常胰腺头、体及尾部ADC值分别为(1.61±0.37)×10-3、(1.93±0.43)×10-3和(1.77±0.36)×10-3 mm2/s;rFOV DWI获得正常胰腺头、体及尾部ADC值分别为(1.10±0.48)×10-3、(1.21±0.38)×10-3和(1.11±0.34)×10-3 mm2/s。符号秩检验表明两种方法获得的胰腺头、体及尾部ADC值间差异无统计学意义(s=5,P=0.700>0.05)。③Wilcoxon秩和分析表明SS-EPI DWI获得的胰腺头、体及尾部ADC值间差异具有统计学意义(χ2=6.226,P=0.045<0.05),而rFOV DWI获得的胰腺头、体及尾部ADC值间差异无统计学意义(χ2=1.970,P=0.373>0.05)。结论:rFOV DWI较SS-EPI DWI图像分辨力高,且胰腺组织及总管显示更为清楚;统计学分析表明rFOV DWI获得的胰腺ADC均值不随胰腺形态学区域发生显著变化,具有较好的稳定性,而SS-EPI DWI获得的ADC均值在胰头部最小,胰体部最大,且差异具有统计学意义;较高分辨力和稳定的ADC测量值,将使rFOV DWI在胰腺疾病早期及准确诊断等方面发挥重要作用。     

孤立性肺病变相关支气管的CT最小密度投影与多平面重组对照研究

目的 探讨64层CT的MinIP与MPR在显示孤立性肺病变(SPL)相关支气管中的临床应用价值.方法 回顾性分析64层CT可明确显示SPL相关支气管关系者75例,将0.625 mm薄层重建图像沿SPL相关支气管长轴分别重组为2个斜面的MinIP和MPR图像,重组层厚分为1、2、3和5 mm 4组,对显示支气管和屏蔽肺血管方面进行图像质量评估.采用方差分析及组内相关系数进行统计学分析.结果 (1)两斜面显示SPL相关支气管4组MinIP图像的平均积分(1 mm均为4.85分,2 mm分别为4.77和4.84分,3 mm分别为4.63和4.67分,5 mm分别为4.25和4.28分)和1、2 mm层厚组MPR图像(1 mm分别为4.77和4.76分,2 mm分别为4.04和4.27分)均优良.两斜面MPR图像1 mm层厚组的平均积分与MinIP图像1～3 mm层厚组差异无统计学意义(t值均为0.318,P值均>0.05),明显高于5 mm层厚组(t值分别为6.318和6.610,P值均<0.01);两斜面MPR图像2 mm层厚组的平均积分较MinIP图像1～3 mm层厚组低(t值5.003～8.958,P值均<0.01),与5 mm层厚组差异无统计学意义(t值分别为1.794和0.3181,P值均>0.05).(2)两斜面MinIP图像肺血管屏蔽随层厚增厚效果越好(F值分别为45.312和40.415,P值均<0.01),3、5 mm层厚组平均积分(3 mm分别为4.67和4.64分,5 mm分别为5.00和4.97分)均优良,而2 mm层厚组平均积分(2 mm分别为3.32和3.20分)一般.结论 3 mm层厚的MinIP可清晰显示孤立性肺病变相关支气管.

Abstract：

Objective To investigate the clinical value of 64-slice computed tomography with MinIP and MPR for imaging the bronchus related to a solitary pulmonary lesion (SPL). Methods Seventy-five subjects with solitary pulmonary lesions underwent chest 64-slice CT and their bronchi were analyzed retrospectively. All images of thin-section (0.625 mm) were reconstructed with MPR and MinIP into images of 1, 2, 3, and 5 mm thickness and 1 mm gap in two orthogonal planes along the long axis of bronchus related to the SPL. The image quality of four series of MinIP and MPR images was evaluated in the aspect of bronchus visibility and pulmonary vascular masking. One-way ANOVA with Bonferroni correction and interclass correlation coefficient were used in the statistical analysis. Results (1) The mean scores of display of the bronchi on MinIP images of four series (4.85, 4.77 and 4.84, 4.63 and 4.67, 4.25 and 4.28, in 1, 2, 3, and 5 mm thickness, respectively) and on MPR images of 1 or 2 mm thickness (4.77 and 4.76, 4.04 and 4.27, in 1 and 2 mm thickness, respectively) were good or excellent. MPR images of 1 mm thickness and MinIP images of 1-3 mm thickness showed no significant differences (t=0.318, P> 0.05 for all), but they were superior to MinIP images of 5 mm thickness (t=6.318 and 6.610, P＜0.01). MPR images of 2 mm thickness were inferior to MinIP images of 1-3 mm thickness (t=5.003-8.958, P＜0.01), but there was no significant difference between MPR images of 2 mm thickness and MinIP images of 5 mm thickness (t=1.794 and 0.3181, all P> 0.05). (2) The effect of suppression of pulmonary vascular markings on MinIP images was better with the increase of slice thickness (F=45.312 and 40.415, P＜0.01). The mean scores of MinIP images of 3 mm and 5 mm thickness (4.67 and 4.64, 5.00 and 4.97, for 3 and 5 mm thickness, respectively) were good or excellent, but MinIP images of 2 mm thickness were just acceptable. Conclusion MinIP images of 3 mm thickness may display the bronchus related to SPL more clearly.     

A comparison of 35 mm cine film and digital radiographic image recording: implications for quantitative coronary arteriography. Film vs. digital coronary quantification

To assess potential differences in the intrinsic properties of image recording media and their impact on quantitative coronary arteriography, we used an automatic quantitative arteriography computer program to analyze cine film and digital radiographic images of a radiographic arterial phantom. The phantom consisted of a lucite plate with precision-drilled lumena ranging from 0.5 to 5.0 mm in diameter. Film images were digitized at 2048 X 2048 pixel resolution, and digital radiographic images were acquired at 512 X 512 and 1024 X 1024 resolution. Arterial geometric diameter, percent diameter stenosis, densitometric relative cross-sectional area, and densitometric percent area stenosis were measured. All three techniques were equivalent in measuring diameters with a high degree of overall accuracy (R greater than .992). All methods overestimated diameters below 1.0 mm. Both 512 X 512 and 1024 X 1024 digital images were superior to film for densitometric measurement of relative area (R = .995 vs. R = .940, P = .0032). We conclude that automated analysis of digital radiographic images yields results that are similar in geometric precision but greater in densitometric precision than film analysis.     

Applying computer-assisted detection schemes to digitized mammograms after JPEG data compression: an assessment

RATIONALE AND OBJECTIVES: The authors' purpose was to assess the effects of Joint Photographic Experts Group (JPEG) image data compression on the performance of computer-assisted detection (CAD) schemes for the detection of masses and microcalcification clusters on digitized mammograms. MATERIALS AND METHODS: This study included 952 mammograms that were digitized and compressed with a JPEG-compatible image-compression scheme. A CAD scheme, previously developed in the authors' laboratory and optimized for noncompressed images, was applied to reconstructed images after compression at five levels. The performance was compared with that obtained with the original noncompressed digitized images. RESULTS: For mass detection, there were no significant differences in performance between noncompressed and compressed images for true-positive regions (P = .25) or false-positive regions (P = .40). In all six modes the scheme identified 80% of masses with less than one false-positive region per image. For the detection of microcalcification clusters, there was significant performance degradation (P < .001) at all compression levels. Detection sensitivity was reduced by 4%-10% as compression ratios increased from 17:1 to 62:1. At the same time, the false-positive detection rate was increased by 91%-140%. CONCLUSION: The JPEG algorithm did not adversely affect the performance of the CAD scheme for detecting masses, but it did significantly affect the detection of microcalcification clusters.     

Double arterial phase dynamic MRI with sensitivity encoding (SENSE) for hypervascular hepatocellular carcinomas

PURPOSE: To investigate the efficacy of SENSE MRI, including the double arterial phase dynamic study, to detect hypervascular hepatocellular carcinomas (HCCs). MATERIALS AND METHODS: MRI of the liver was performed in 40 consecutive patients (20 by conventional MRI and 20 by SENSE MRI). The SENSE technique was used to obtain breath-hold T1-weighted FSE images (TR/TE = 556/12 msec), respiratory-triggered T2-weighted FSE images (TR/TE = 1800/90 msec) with and without fat suppression, and dynamic MR images (TR/TE/FA = 160-168/4.6 msec/70 degrees ). In each arterial dominant phase and portal dominant phase, two scans were consecutively performed with one breath-hold, leading to the double arterial phase and double portal phase images with SENSE. RESULTS: The sensitivity of SENSE MRI for HCCs diagnosed from all MR images, including dynamic study, T1-weighted images, and T2-weighted images, was 91.7%, while that of conventional MRI was 76.3%. The positive predictive value of SENSE MRI for HCCs was 91.7%, while that of conventional MRI was 87.9%. In terms of HCCs < or = 10 mm, the sensitivity and positive predictive values of SENSE MRI were 78.6% and 78.6%, respectively, while those of conventional MRI were 27.3% and 60.0%, respectively. The number of detected HCCs < or = 10 mm was significantly larger in SENSE MRI than in conventional MRI (P < 0.05). The cause of false-positive lesions on SENSE MR images was an arterioportal shunt. CONCLUSION: SENSE MRI with double arterial phase dynamic study showed higher sensitivity compared to the conventional technique. Therefore, SENSE MRI is a promising method for the detection of HCC.     

Subtle lung cancers: impact of edge enhancement and gray scale reversal on detection with digitized chest radiographs

The authors studied the impact of edge enhancement and gray scale polarity reversal on the detection of subtle lung cancers. Three experienced readers reviewed 46 biopsy-proved subtle lung cancers and 46 normal controls on chest radiographs that had been digitized into a 1,024 X 1,536-pixel matrix 8 bits deep. Receiver-operating characteristics (ROC) analysis of 1,656 pooled observations indicated that performance was best with the unmodified images (ROC area = 0.83), degraded by moderate enhancement of medium frequencies (ROC area = 0.80), and markedly impaired by severe enhancement of low frequencies (ROC area = 0.69). Gray scale polarity reversal further degraded performance (unenhanced ROC area = 0.74; moderately enhanced ROC area = 0.76; severely enhanced ROC area = 0.76). The authors conclude that edge enhancement and gray scale polarity reversal can impair the detectability of subtle lung cancers on digitized radiographs of medium resolution.     

肝脏MR动态增强扫描：Gd-EOB-DTPA与Gd-DTPA的个体内对照研究

目的：比较钆塞酸二钠（Gd-EOB-DTPA）及钆喷酸葡胺（Gd-DTPA）肝脏 MR动态增强扫描腹腔脏器及血管的强化特点,重点比较Gd-EOB-DTPA移行期与Gd-DTPA平衡期的图像特点。方法：本研究为前瞻性、个体内随机对照研究。25例病理证实为原发直肠癌或结肠癌、怀疑肝转移的患者,3天内行2次肝脏 MR 动态增强检查,分别使用 Gd-EOB-DTPA及Gd-DTPA两种对比剂。动态增强扫描的序列相同,包括平扫、动脉期、门静脉期、平衡期（Gd-DTPA）／移行期（Gd-EOB-DTPA）。图像客观评估中,测量各期相图像上血管及肝脾实质的信号强度。以椎旁肌肉的信号为参考,计算相对信号强度（RS）并比较两组间的差异,以及不同期相时肝实质RS的差异。主观评估：读片者主观评价增强扫描各期相图像上,主动脉、门静脉及肝静脉与肝实质的相对信号强度。结果：肝实质的RS：在动脉期Gd-DTPA 组明显高于Gd-EOB-DTPA组（t＝3．006,P＝0．005）;在门静脉期及平衡期／移行期,两组检查的差异无统计学意义（t＝1．788,P＝0．086;t＝0．781,P＝0．442）。Gd-EOB-DTPA检查时,门静脉期肝实质RS明显高于动脉期（t＝－3．014,P＝0．006）,移行期RS与门静脉期的差异无统计学意义。Gd-DTPA检查时,平衡期肝实质RS明显低于门静脉期（t＝5．827,P＝0．000）。主观评估：Gd-DTPA增强扫描平衡期图像上所有患者的主动脉、门静脉、肝静脉均为高信号（100％）;Gd-EOB-DTPA 增强扫描移行期图像上主动脉、门静脉、肝静脉均以低或等信号为主（84％,92％,92％）。结论：Gd-EOB-DTPA动态增强 MR 检查,肝脏实质在门静脉期及移行期呈持续强化,其移行期的图像特征与Gd-DTPA平衡期的图像特征有明显不同,在影像诊断时应予以关注。     

Development of a semi-automated superimposing image verification system using a template matching algorithm in radiotherapy

To analyze shifts in the isocenter of images, we developed a semi-automated superimposing image-verification system that is capable of automatically quantifying shifts in the isocenter through image analysis with a personal computer (PC). The accuracy and usefulness of this software were examined through a comparison of nine portal images with a simulation image and by comparing nine portal images with a DRR image, using a human pelvic phantom. The difference between the known magnitude of shift and the magnitude of shift detected with this method was analyzed as detection error. When the portal images were compared with the simulation image, the 95% confidence interval (95% CI) of detection errors (mean+/-SD) was 0.57+/-0.36 mm (95% CI: 0.49-0.65 mm). When the portal images were compared with the DRR image, the respective figures were 0.68+/-0.38 mm (95% CI: 0.59-0.77 mm). No significant difference was noted between these two categories of comparison (N.S). The absolute detection error (mean+/-SD) in all directions was 0.34+/-0.34 mm for the comparison of portal images with the simulation image and 0.41+/-0.36 mm for the comparison of portal images with the DRR image. This system seems to be appropriate for verification of the treatment field by improving the accuracy of radiotherapy as a method of computer-assisted landmark recognition during image comparison.     

Portal venous stent placement in patients with pancreatic and biliary neoplasms invading portal veins and causing portal hypertension: initial experience.

PURPOSE: To evaluate the clinical usefulness of portal venous stent placement in patients with pancreatic or biliary neoplasms invading portal veins and causing portal hypertension. MATERIALS AND METHODS: Thirteen patients underwent portal venous stent placement because of gastrointestinal bleeding (n = 8), risk of gastroesophageal varix rupture (n = 4), ascites (n = 4), thrombocytopenia (n = 3), and/or portal venous thrombosis (n = 3). The main portal vein or both the intrahepatic and main portal veins were invaded in six patients (group A). The main portal vein and splanchnic veins were involved in seven patients (group B). Stents were placed across the stenotic (n = 8) or occluded (n = 5) lesions after percutaneous transhepatic portography. Changes in portal venous pressure, stent patency, and survival were evaluated. RESULTS: Mean portal venous pressure decreased significantly immediately after stent placement, from 24.9 mm Hg +/- 5.9 (SD) to 15.8 mm Hg +/- 4.6 (P <.001). In group A, blood flow through the stent was maintained and the symptoms had subsided at follow-up (mean, 12.5 months). In group B, symptoms were improved in five patients, but the stents were occluded in all but one patient at a mean follow-up of 1.5 months. There was a significant difference in stent patency between the patients with (14%) and those without (100%) splanchnic venous involvement (P <.01). CONCLUSION: Stent placement helped to relieve portal hypertension symptoms. Splanchnic venous involvement was associated with worse stent patency.     

Accuracy of alignment in breast irradiation: a retrospective analysis of clinical practice

The objective of the study was to determine the accuracy of patient positioning in radiotherapy for breast cancer. Portal images were obtained using a fast electronic megavoltage radiotherapy imaging system in 30 cases of breast cancer. Quantitative analysis of 530 megavolt portal images and comparison with 30 digitized simulation films were performed. Five linear measurements were taken for each simulation and verification film. Central lung distance (CLD) is the distance from the dorsomedial beam edge to the inner thoracic wall in the central plane of the beam. Cranial lung distance (CrLD) is the distance from the dorsomedial beam edge to the inner thoracic wall in the plane of the beam at 4 cm from the central plane. Central beam edge to skin distance (CBESD) is the distance from the skin to the ventrolateral beam edge in the central plane of the beam. The central irradiated width (CIW) is defined as the distance from the dorsomedial beam edge to the skin. The craniocaudal distance (CCD) is defined as the distance from a particular landmark to the caudal field border. Concerning patient position in the field, mean standard deviations of the difference between simulation and treatment images were 3.9 mm for the CLD, 3.2 mm at +4 cm, 3.6 mm for the CIW, 3.3 mm for the CBESD, 3.8 mm for the CCD. In 90% of all set-up for treatment, errors were less than 1 cm. The variation of the CLD was the largest set-up error. This parameter is clinically the most significant. Future treatment delivery should be improved by introducing patient positioning devices such as thermoplastic shells. The electronic portal imaging device (EPID) appears to be an adequate tool to study the accuracy of treatment set-ups like this.     

Usefulness of a saline flush for intravenous 3-dimensional computed tomography portography using multidetector-row helical computed tomography

PURPOSE: To evaluate the clinical usefulness of a saline flush technique in improving the imaging quality of 3-dimensional computed tomography portography (3D-CTP). METHODS: To evaluate liver metastases, 58 patients were divided into 2 groups undergoing 3D-CTP with or without a saline flush. The computed tomography (CT) values of the right portal vein (RPV), left portal vein (LPV), main portal vein (MPV), and right hepatic parenchyma (RHP) were assessed. Maximum intensity projection (MIP) 3D-CTP images were evaluated by vessel visualization. RESULTS: Higher mean CT attenuation values in the RPV, LPV, MPV, and RPV-RHP were observed in the saline flush group and were statistically significant (P = 0.04, P = 0.03, P = 0.01, and P = 0.04, respectively). The difference in imaging quality between 2 groups was statistically significant (P = 0.04). In segment VIII, the ability to depict the segmental branches was significantly higher when the saline flush technique was used (P = 0.03). CONCLUSIONS: The saline flush technique increases the CT attenuation values of the portal vein and the difference in values between the portal vein and the tissue around it and improves the MIP imaging quality of 3D-CTP.     

Digital image processing of radiation therapy portal films

Digital image processing has the potential to enhance and improve several functions of a modern radiation oncology department. These functions may include improving perception of information for low contrast films, electronic transfer of images to remote facilities and back, and reducing storage space requirements for archiving once treatment is finished. This paper gives an overview of the digitization process and of image processing fundamentals. The clinical evaluation of digitized portal films is also discussed. The authors conclude that digitizing low contrast radiation therapy portal films is feasible with present technology and will produce images acceptable for routine clinical use in most instances. The role of image enhancement is less well established and remains investigational.     

Analysis of the frequency components of CR portal images and application to multi-objective frequency processing

The image contrast of portal images obtained using computed radiography (CR) is low for radiation therapy, and their noise level is high. In order to improve the image quality of CR portal images, we investigated the relationship between the frequency components of the bone edge and noise area. We used a personal computer, conventional flatbed scanner, and public-domain software (NIH Image). To analyze the frequency components of bone edges, we generated difference images from the original and unsharp mask images of various sizes. In addition, we analyzed the frequency components of noise, after changing the cut-off frequency on the power spectrum to process a low- and high-pass filter. We found that the frequency components of bone edges and noise areas ranged from 0.18 to 0.25 cycle/mm and 1.30 cycles/mm, respectively. We conclude that this process can remove noise from homogeneous areas and preserve bone edges using multi-objective frequency processing.     

Early-enhancing nonneoplastic lesions on gadolinium-enhanced magnetic resonance imaging of the liver following partial hepatectomy

PURPOSE: To assess the frequency, imaging findings, and significance of early-enhancing nonneoplastic (EN) lesions with gadolinium-enhanced magnetic resonance imaging (MRI) of the liver following partial hepatectomy. MATERIALS AND METHODS: We retrospectively reviewed MR images after partial hepatectomy in 30 patients. Postoperative MRI was performed in 1-12 months (mean, 3.7 months) after partial hepatectomy. We defined the EN lesion as a lesion that was ill defined; irregular, wedge shaped, or serpiginous; located along the liver edge; not visible on unenhanced MR images; did not appear hypointense on portal venous- or equilibrium-phase images; or a combination of those imaging findings. RESULTS: A total of 39 EN lesions (size range, 5-60 mm; mean, 25.2 mm) in 19 patients and 17 recurrent tumors (size range, 5-50 mm; mean, 16.8 mm) in 10 patients newly appeared after partial hepatectomy. The EN lesions were diagnosed as pseudolesions by the second postoperative follow-up MRI in 17 patients or contrast-enhanced computed tomography (CT) in two. A total of 13 EN lesions (33%) were located along the liver edge and 20 (51%) were adjacent to the resected area. The shape was circular in 11 (28%), oval in three (8%), irregular in 11 (28%), wedge shaped in five (13%), and serpiginous in nine (23%). No EN lesion showed hypointensity on gadolinium-enhanced portal venous-phase or equilibrium-phase images. A total of 14 EN lesions (36%) showed slight hyperintensity on T2-weighted images. The confidence levels for malignancy probability assigned by blinded radiologists were lower with EN lesions than with recurrent tumors (P < 0.001). CONCLUSION: EN lesions are frequently seen in MRI following partial hepatectomy, and occasionally are slightly hyperintense on T2-weighted images, mimicking malignant tumors. However, most EN lesions can be correctly diagnosed with MRI findings.