Measurement of half-value layer in x-ray CT: a comparison of two noninvasive techniques

The purpose of this paper is to determine the accuracy and reproducibility of two noninvasive methods of measuring half-value layer (HVL), ring and localization, compared with an invasive technique (suspending tube rotation). The ring method uses concentric aluminum rings about a CTDI ionization chamber at isocenter. Data were acquired using axial CT protocols (rotating x-ray tube, stationary patient table). The localization technique uses square aluminum sheets secured to the gantry shroud to filter the radiation beam, and a CTDI chamber suspended externally at isocenter. Data were acquired using localization image protocols (stationary x-ray tube, moving patient table). The invasive technique was similar to the localization technique except that the ion chamber was placed on the patient table and the tube rotation disabled using service software. Data for all techniques were collected on the same CT system. Independent data sets were collected to determine reproducibility. Sensitivity to ionization chamber lateral displacement from isocenter was investigated. Measured HVLs (mm aluminum, mean+/-std, n=4) were 7.19+/-0.03 (ring); 7.17+/-0.04 (localization); and 7.24+/-0.02 (service mode), which were not significantly different (p = 0.05). Displacing the chamber from isocenter changes the HVL, depending on the bow-tie filter, by as much as 5 mm aluminum. Aluminum filter to ion chamber distances of 25-35 cm provided accurate results. Both noninvasive techniques were accurate and reproducible at isocenter. However, the measured HVL was dependent upon the bow-tie filter and the lateral displacement of the ionization chamber with respect to isocenter. Greater than 2 cm off of isocenter, the ring technique did not provide accurate HVL measurements.     

Acquiring 4D thoracic CT scans using a multislice helical method

Respiratory motion degrades anatomic position reproducibility during imaging, necessitates larger margins during radiotherapy planning and causes errors during radiation delivery. Computed tomography (CT) scans acquired synchronously with the respiratory signal can be used to reconstruct 4D CT scans, which can be employed for 4D treatment planning to explicitly account for respiratory motion. The aim of this research was to develop, test and clinically implement a method to acquire 4D thoracic CT scans using a multislice helical method. A commercial position-monitoring system used for respiratory-gated radiotherapy was interfaced with a third generation multislice scanner. 4D cardiac reconstruction methods were modified to allow 4D thoracic CT acquisition. The technique was tested on a phantom under different conditions: stationary, periodic motion and non-periodic motion. 4D CT was also implemented for a lung cancer patient with audio-visual breathing coaching. For all cases, 4D CT images were successfully acquired from eight discrete breathing phases, however, some limitations of the system in terms of respiration reproducibility and breathing period relative to scanner settings were evident. Lung mass for the 4D CT patient scan was reproducible to within 2.1% over the eight phases, though the lung volume changed by 20% between end inspiration and end expiration (870 cm3). 4D CT can be used for 4D radiotherapy, respiration-gated radiotherapy, 'slow' CT acquisition and tumour motion studies.     

Measurement techniques for melanoma: a statistical comparison.

Inter- and intra-observer variation in measuring the depth of invasion of malignant melanomas was assessed using three different techniques: eye-piece graticule, stage Vernier, and projection image analysis. Significant variation was found for all methods but was least pronounced with the stage Vernier. It is recommended that this should be the preferred technique for routine use.     

Interobserver agreement for estrogen receptor immunohistochemical analysis in breast cancer: a comparison of manual and computer-assisted scoring methods

Differences in scoring methods for estrogen receptor (ER) immunohistochemistry may cause significant variation in the results. Scoring practices differ within the United States and internationally and include semiquantitative scoring formulas, manual estimations, and computer-assisted techniques. The goal of this study was to determine the rate of interobserver variability for manual ER scoring at our institution and compare the ER scores obtained by manual scoring with those obtained using image-analysis software (QCA, Lake Bluff, IL). In a series of 70 consecutive invasive breast cancers, ER was assayed using standard immunohistochemical techniques and the monoclonal antibody 6F11. Scoring was performed independently by three breast pathologists, and the scores were compared with those obtained using the QCA image-analysis system, using 10% nuclear staining as the cutoff for positivity. We found that 43 cases (61%) were ER positive, 25 cases (36%) were ER negative, and two cases (3%) showed ER staining of less than 10%. The consensus scores for the 70 cases showed a high level of agreement with the ER scores determined by image analysis (kappa = 0.84). Interobserver variability was low. The kappa scores for each observer showed strong agreement with the consensus score, the image-analysis score, and between the observers. Our findings show that interobserver agreement for manual scoring of ER is strong, and that manual or computer-aided scoring techniques are comparable.     

Cataract surgery outcomes: comparison of the extracapsular cataract extraction and manual small incision cataract surgery techniques

BackgroundBlindness and visual impairment are public health problems and constitute an important socio-economic burden in sub-Saharan Africa. Understanding the outcomes of cataract surgery will improve our knowledge of risk factors for poor outcomes. Previous studies have focused exclusively on the phacoemulsification technique with limited attention to the extracapsular cataract extraction (ECCE) and manual small incision cataract surgery (MSICS) techniques.ObjectivesTo compare the cataract surgery outcomes between the ECCE and MSICS techniques.MethodsThe study was an observational research design that used the LogMAR visual acuity (VA) chart, subjective refraction, slit lamp and ophthalmoscope to collect data. The participants were followed for a period of six-weeks post-surgery and outcomes were recorded. Data were presented using frequencies, percentages and means ± standard deviation.ResultsThe sample included 101 participants, with a mean age of 66.32 ± 15.99 years. Fifty and 51 participants had undergone the ECCE and MSICS techniques respectively. Overall, one-hundred participants had poor pre-surgery VA and subjective refractions were generally not possible due to the severity of cataracts present. The mean aided post-surgery VA was 0.31 LogMAR and 0.13 LogMAR in the ECCE and MSICS groups respectively (p < 0.001). The mean post-surgery refractive astigmatism was similar in the ECCE (-2.06 D) and MSICS (-1.80 D) groups (p = 0.110). The spherical equivalence was approximately -0.50 D higher in the MSICS group, but not statistically significant (p = 0.330). Approximately one out of every five participants (n = 21) had post-surgery ocular complications such as corneal opacity and haziness as well as posterior capsular absence.ConclusionsThe MSICS technique showed better post-surgery outcomes than the ECCE technique.     

Fusion of respiration-correlated PET and CT scans: correlated lung tumour motion in anatomical and functional scans

Lower lobe lung tumours in particular can move up to 2 cm in the cranio-caudal direction during the respiration cycle. This breathing motion causes image artefacts in conventional free-breathing computed tomography (CT) and positron emission tomography (PET) scanning, rendering delineation of structures for radiotherapy inaccurate. The purpose of this study was to develop a method for four-dimensional (4D) respiration-correlated (RC) acquisition of both CT and PET scans and to develop a framework to fuse these modalities. The breathing signal was acquired using a thermometer in the breathing airflow of the patient. Using this breathing signal, the acquired CT and PET data were grouped to the corresponding respiratory phases, thereby obtaining 4D CT and PET scans. Tumour motion curves were assessed in both image modalities. From these tumour motion curves, the deviation with respect to the mean tumour position was calculated for each phase. The absolute position of the centre of the tumour, relative to the bony anatomy, in the RCCT and gated PET scans was determined. This 4D acquisition and 4D fusion methodology was performed for five patients with lower lobe tumours. The peak-to-peak amplitude range in this sample group was 1-2 cm. The 3D tumour motion curve differed less than 1 mm between PET and CT for all phases. The mean difference in amplitude was less than 1 mm. The position of the centre of the tumour (relative to the bony anatomy) in the RCCT and gated PET scan was similar (difference <1 mm) when no atelectasis was present. Based on these results, we conclude that the method described in this study allows for accurate quantification of tumour motion in CT and PET scans and yields accurate respiration-correlated 4D anatomical and functional information on the tumour region.     

Automated screening versus manual screening: a comparison of the ThinPrep imaging system and manual screening in a time study

The ThinPrep Imaging System (TIS) is an automated system that assists cytotechnologists in the primary screening of ThinPrep liquid based cervical samples. Between June 1, 2004, and April 1, 2005, four experienced cytotechnologists participated in the study in which the duration of the screening procedure was timed for each of the 11,354 slides included. In every slide 22 fields of view were reviewed, and the samples that contained potentially abnormal cells were fully screened. The screening time was reduced by 42% (mean) (p < 0.001). By manual rescreening of the negative TIS samples, abnormal cells were found in 10 samples (false negative rate 0.14%). In every case the abnormal cells had been identified by the scanner, but misinterpreted by the cytotechnologist. These findings stressed the importance of carefulness in the interpretation of the marked fields and beyond that helped the cytotechnologists and pathologists to have more confidence in the automated system.     

Malignant mesothelioma: a comparison of biopsy and postmortem material by light microscopy and immunohistochemistry

AIMS: The diagnosis of malignant mesothelioma in pleural biopsies can be difficult. Survival is short and consequently many of these cases are submitted to necropsy to assist with medicolegal claims. This study compares the histological appearances and immunohistochemical profile of nine biopsy specimens with corresponding postmortem specimens. METHODS: Archival, formalin fixed, paraffin wax embedded material was obtained from nine biopsy and corresponding postmortem cases of malignant mesothelioma. The specimens were examined by light microscopy and stained with an immunohistochemical panel of 12 commercially available antibodies including CAM5.2, HBME-1, and Ber-EP4, and antibodies to thrombomodulin, calretinin, CD44H, WT-1, carcinoembryonic antigen, Leu-M1, epithelial membrane antigen and p53. RESULTS: There was greater variation in the range of histological appearances of mesotheliomas in postmortem specimens compared with biopsy specimens. There was also variability in the immunohistochemical staining pattern for certain antibodies including HBME-1, and Ber-EP4 and antibodies to calretinin, CD44H, WT-1, and p53. CONCLUSIONS: All available information should be taken into account in the histological diagnosis of malignant mesothelioma. Interpretation of the immunohistochemical profile should be regarded with some caution when only postmortem material is available. When reporting a postmortem case of suspected mesothelioma, the pathologist should seek to review all available biopsy material in conjunction with the necropsy.     

Automated detection of lung nodules in CT scans: preliminary results

We have developed a fully automated computerized method for the detection of lung nodules in helical computed tomography (CT) scans of the thorax. This method is based on two-dimensional and three-dimensional analyses of the image data acquired during diagnostic CT scans. Lung segmentation proceeds on a section-by-section basis to construct a segmented lung volume within which further analysis is performed. Multiple gray-level thresholds are applied to the segmented lung volume to create a series of thresholded lung volumes. An 18-point connectivity scheme is used to identify contiguous three-dimensional structures within each thresholded lung volume, and those structures that satisfy a volume criterion are selected as initial lung nodule candidates. Morphological and gray-level features are computed for each nodule candidate. After a rule-based approach is applied to greatly reduce the number of nodule candidates that corresponds to nonnodules, the features of remaining candidates are merged through linear discriminant analysis. The automated method was applied to a database of 43 diagnostic thoracic CT scans. Receiver operating characteristic (ROC) analysis was used to evaluate the ability of the classifier to differentiate nodule candidates that correspond to actual nodules from false-positive candidates. The area under the ROC curve for this categorization task attained a value of 0.90 during leave-one-out-by-case evaluation. The automated method yielded an overall nodule detection sensitivity of 70% with an average of 1.5 false-positive detections per section when applied to the complete 43-case database. A corresponding nodule detection sensitivity of 89% with an average of 1.3 false-positive detections per section was achieved with a subset of 20 cases that contained only one or two nodules per case.     

Paraprotein estimation: a comparison of immunochemical and densitometric techniques.

Paraproteins have been estimated by both immunochemical methods and densitometric analysis of electrophoretic strips. Correlation between the results obtained by these two methods, although generally good for assessing trends, varied between patients.