Computerized detection of pulmonary nodules in computed tomography images

RATIONALE AND OBJECTIVES: Interpretation of computed tomographic (CT) scans of the lungs is a time-consuming task that involves visual correlation of possible nodules in one section with those in contiguous sections to distinguish actual nodules from blood vessels. Thus, the authors are developing automated methods to detect nodules on CT images of the thorax. METHODS: The computerized technique uses various computer-vision techniques and a priori information of the morphologic characteristics of pulmonary nodules. In each section, the external thoracic wall and lung boundaries are detected, and the features within the lung boundaries are subjected to gray-level thresholding operations. By analyzing the relationships between features arising at different threshold levels with respect to their shape, size, and location, each feature is assigned a likelihood of being a nodule or a vessel. Features in adjacent sections are compared to resolve ambiguous features. Detected nodule candidates are displayed in three dimensions within the lung. RESULTS: The system provided a sensitivity of 94% for nodule detection and an average of 1.25 false-positive results per case. CONCLUSIONS: Continued development of an automated method for detecting pulmonary nodules in CT scans is expected to aid radiologists in the task of locating nodules in three dimensions.     

Urologic applications of multiplanar and three-dimensional computed tomography

The introduction of helical computed tomography (CT) has resulted in improved quality of multiplanar reformations and three-dimensional reconstructions in the chest and abdomen and has made CT angiography a clinical reality. These imaging techniques are useful for evaluating the urinary tract, adding a new dimension to its display, resulting in improved diagnosis of renal and perirenal disease. This article reviews the indications and techniques utilized for multiplanar and three-dimensional CT for urology. The advantages and limitations are discussed, and normal and pathologic findings in the urinary tract illustrated.     

Virtual and three-dimensional bronchoscopy with spiral and electron beam computed tomography

PURPOSE: To compare spiral computed tomography (CT) and electron-beam CT (EBT) for 3D and virtual CT-bronchoscopy. MATERIALS AND METHODS: 17 patients with various disorders of the tracheobronchial system were examined using fiberoptic bronchoscopy, spiral CT and EBT. 3D images were reconstructed from CT data sets using automated segmentation based on volume-growing methods. Surface-rendered, volume-rendered, and hybrid reconstructions were visualized in real time using a data helmet. RESULTS: All data sets could be processed to high-quality three-dimensional (3D) and virtual reconstructions. The reduction of motion artifacts due to shorter scan times made EBT data sets better suited for automated segmentation and less susceptible to motion artifacts. 3D and virtual reconstructions did not increase the diagnostic sensitivity of CT compared to axial reconstructions alone. CONCLUSIONS: Shorter scan times of CT imaging yield higher-quality 3D and virtual reconstructions. Modern reconstruction techniques are valuable visualization tools for select indications and are the prerequisite for future developments in computer-aided medicine.     

The assessment of the severity of pulmonary edema by computed tomography. A comparison between high-resolution computed tomography, objective evaluation with density masks and functional tests

The results of high-resolution computed tomography (HRCT) were correlated with those of pulmonary function tests, chest films and CT expiratory density mask values in the evaluation of pulmonary emphysema in 33 symptomatic subjects. Emphysema was quantitated with both subjective and objective measurements. Conventional chest films were useful to diagnose severe emphysema but its actual extent was more reliably evaluated with CT scoring systems. HRCT and density mask correlated well with function tests, but the former method exhibited stronger correlation with carbon monoxide diffusion capacity. The opposite was true for hyperinflation and expiratory obstruction variables. Subjective CT estimates, which are quick and easy to perform, were seen to correspond more specifically to the pathophysiologic derangement and should therefore be used to evaluate the anatomic extent of disease. The functional severity of emphysema correlated only with the overall extent of disease and not with its regional distribution in the upper or lower lungs. Finally, in 4 cases (12.1%) with low CT scores, FEV1 was reduced but diffusion capacity values were normal. In one of these patients HRCT showed signs of bronchiolitis. In fact, small airway disease might be a more critical factor in determining functional impairment than the actual anatomical emphysema.     

Successful treatment of a persistent cutaneous fistula to the seminal tract: imaging with three-dimensional computed tomography

The best position for Centers for Disease Control (Atlanta, GA) light traps, in relation to human-occupied bed nets for trapping of host-seeking Anopheles gambiae Giles and Culex quinquefasciatus Say mosquitoes, was determined in Tanzania. Significantly higher catches were recorded for both species when the trap was positioned at the foot end of the bed, near the top of the net. Parity rates were significantly higher near the top of the net than at the level of the host. Since trap position affects the catch size and the proportion of infectious mosquitoes therein, standardized use of this sampling technique for estimating entomologic inoculation rates (i.e., the number of potentially infectious bites received over a certain period of time) is recommended.     

Enhanced accuracy of defect detection by myocardial single-photon emission computed tomography with attenuation correction with gadolinium 153 line sources: evaluation with a cardiac phantom

Moral imagination has been described by Murdoch as 'a way of seeing'. The focus of concern here is the influence of belief upon moral imagination and those attitudes that are needed if moral imagination is to be developed. The perspective adopted endorses a Humean recognition of the potent influence of personal experience upon those beliefs that are held, and therefore upon how we see the world. Kantian commitment to the power of the will, and to the ability of individuals to choose who they wish to be, allows room for optimism, a view which is supported by the findings of Liaschenko.     

High-resolution computed tomography sampling for detection of asbestos-related lung disease

RATIONALE AND OBJECTIVES: We determined whether a limited number of high-resolution computed tomography (HRCT) scans will effectively screen for interstitial lung disease (ILD) in a population of individuals exposed to asbestos. METHODS: We retrospectively reviewed the computed tomography studies of 49 patients exposed to asbestos. HRCT in the supine and prone positions had been performed at specifically preselected levels. Two teams of thoracic radiologists evaluated, on separate occasions: (1) all images, (2) prone images only, and (3) a single prone image through the lung bases for the presence of diffuse ILD. RESULTS: A relatively high level of accuracy was obtained with a single prone scan. However, improvement to 95% or better was found when additional prone images were used. CONCLUSION: A screening study for ILD, in this case patients exposed to asbestos, may be performed by preselected prone HRCT images only. The ease and decreased time of performing the procedure make screening relatively large patient groups for ILD more feasible.     

Helical computed tomography of the liver: evaluation of the different circulatory phases

Perineal war wounds involve the anterior perineum or urogenital perineum and posterior perineum or ano-sphincteric perineum. They are rare in civilian practice and in war practice, as only a small and hidden surface of this anatomical region is exposed to damaging agents. An isolated wound of the perineum is rarely life-threatening, but always threatens the functional prognosis of these patients, who have a mean age less than 30 years. In war practice, these wounds are often associated with lesions of adjacent of sacral, buttock or abdomino-pelvic regions. This article is confined to perineal war wounds in men. Lesions of the urethra and anus and rectum, as well as lesions of the genital appendages and pelvic nerves, leave micturating, gastrointestinal and sexual sequelae, which are sometimes permanent. These sequelae must not be exacerbated during investigation and surgical repair, despite the unfavourable emergency context, associated lesions and the time required to repair them. The basic principles of surgical treatment remain urinary diversion by a large cystostomy tube for urogenital lesions, faecal diversion by terminal colostomy for ano-sphincteric lesions, conservative debridement of the margins of the anal or urethral wound, debridement and drainage of contaminated soft tissues and connective tissue spaces. First-line immediate suture of the urethra or edges of the anal wound must be considered according to the defect, and the septic and haemorrhagic context. When ideal repair cannot be performed, alignment over an urethral catheter, urethrostomy, fixation-identification of the urethral or anal extremities constitute intermediate procedures allowing secondary urological and proctological specialized procedures in these patients.     

High-resolution computed tomography in patients with bronchial asthma: correlation with clinical features, pulmonary functions and bronchial hyperresponsiveness

Phosphopeptides are a useful tool for the investigation of phosphorylation as a reversible posttranslational modification. There is a growing interest in using mimics of phosphoamino acids involved in phosphorylation in order to study the enzymes concerned in these processes. These mimics should contain a non-hydrolysable or isoelectrically modified phosphate moiety to be used as a specific inhibitor of phosphatases and kinases. We introduce sold-phase synthesis of H- and methylphosphonopeptides as a new class of mimics of phosphotyrosyl peptides. The peptides were synthesized on solid phase using the standard fluorenyl-methyloxycarbonyl (Fmoc) strategy. Tyrosine residues were incorporated as allyl-protected derivatives, which were selectively deprotected on the resin by treatment with Pd(PPh3)4. The peptide resin carrying the side-chain unprotected tyrosine of the model peptide Gly-Gly-Tyr-Ala was phosphonylated with di-tert-butyl-N,N-diethyl-phosphoramidite in the presence of 1H-tetrazole, yielding H-phosphonopeptides after trifluoroacetic acid (TFA) cleavage. Alternatively, phosphonylation of the unprotected tyrosine with O-tert-butyl-N,N-diethyl-P-methylphosphonamidite catalysed by 1H-tetrazole and followed by oxidation led to the methyphosphonopeptides after TFA cleavage. We obtained both the H-phosphonopeptides and the methylphosphonopeptides of the tetrapeptide in high yields and purities above 90%, according to reversed-phase high-performance liquid chromatography (RP-HPLC). To investigate the general applicability of our new methodology, we synthesized phosphonopeptides up to 13 amino acids long, corresponding to recognition sequences of tyrosine kinases. After cleavage and deprotection, all phosphonopeptides were obtained in high yields and purities of about 90%, as shown by mass spectrometry. The only by-product found was the unmodified peptide.     

Progressive patterns of degenerative arthritis in scaphoid nonunion demonstrated by three-dimensional computed tomography

PURPOSE: To investigate the kinetics of chromosomal instability induced in clones of Chinese hamster cells following X-irradiation. MATERIALS AND METHODS: X-irradiated clones of GM10115, human-hamster hybrid cells containing a single human chromosome 4 (HC4), have been previously established. These clones were defined as unstable if they contained > or = three subpopulations of cells with unique rearrangements of HC4 as detected by FISH. Stable and unstable clones were analysed by FISH and Giemsa staining at various times post-irradiation. RESULTS: While most of the stable clones continued to show chromosomal stability of HC4 over time, one became marginally unstable at approximately 45 population doublings post-irradiation. Clones exhibiting chromosomal instability had one of several fates. Many of the unstable clones were showed similar levels of instability over time. However, one unstable clone became stable with time in culture, while another became even more unstable over time. Cytogenetic analyses of all clones after Giemsa staining indicated that in some clones the hamster chromosomes were rearranged independent of HC4, demonstrating increased frequencies of chromatid breaks and dicentric chromosomes. The majority of the unstable clones also had higher yields of chromatid gaps. CONCLUSIONS: These data demonstrate the dynamic nature of chromosomal instability as measured by two different cytogenetic assays.     

Thoracic diagnosis with electron-beam computed tomography

Posterior interproximal alveolar bone in 59 women, within 5 years after menopause, was assessed at baseline and after 2 years of supportive periodontal therapy (history of moderate/advanced periodontitis) using digitized image analysis. Baseline lumbar spine bone mineral density, smoking status, and yearly serum estradiol (E2) levels also were obtained to group subjects. An additional 16 non-periodontitis postmenopausal women were followed 2 years for clinical and estrogen status. 2-min GCF IL-1beta levels averaged from 2 baseline periodontal pockets (in periodontitis subjects) and 2 non-periodontitis sites (in non-periodontitis and periodontitis subjects) were determined with an enzyme immunoassay. A progressive and stable site were also monitored every 6 months for GCF IL-1beta in 15 patients. Results after 2 years indicated that 17 subjects had no posterior interproximal sites losing > or =0.4 mm of alveolar crest bone height, while 13 subjects had > or =3 such sites. Using analysis of variance, none of the above clinical groupings resulted in a significant difference in mean baseline or longitudinal GCF IL-1beta levels. However, when subjects who lost alveolar crest bone height were considered, E2-sufficient subjects had significantly depressed baseline GCF IL-1beta (in past-periodontitis sites) compared to E2-deficient patients (9.1+/-2.1 versus 31.7+/-10.2 pg/2-min sample, p<0.05), suggesting E2 influences gingival IL-1beta production in progressive periodontitis patients.     

Attenuation-corrected 99mTc-tetrofosmin single-photon emission computed tomography in the detection of viable myocardium: comparison with positron emission tomography using 18F-fluorodeoxyglucose

OBJECTIVES: The purpose of this study was to assess the efficacy of attenuation-corrected (AC) technetium-99m (99mTc)-tetrofosmin single-photon emission computed tomography (SPECT) in detecting viable myocardium compared to 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET). BACKGROUND: The role of 99mTc-labeled perfusion tracers in the assessment of myocardial viability remains controversial. Attenuation artifacts affect the diagnostic accuracy of SPECT images. METHODS: Twenty-four patients with coronary artery disease (mean left ventricular ejection fraction 30%) underwent resting 99mTc-tetrofosmin SPECT and FDG PET imaging. Both AC and non-attenuation-corrected (NC) SPECT images were generated. RESULTS: Using a 50% threshold for viability by FDG PET, the percentage of concordant segments of viability between 99mTc-tetrofosmin and FDG on the patient basis increased from 79.8%+/-14.0% (mean+/-SD) on the NC images to 90.8%+/-10.6% on the AC images (p=0.002). The percentage of 99mTc-tetrofosmin defect segments within PET-viable segments, an estimate for the degree of underestimation of viability, decreased from 19.8%+/-15.2% on the NC images to 9.7%+/-12.6% on the AC images (p=0.01). Similar results were obtained when a 60% threshold was used to define viability by FDG PET. When the anterior-lateral and inferior-septal regions were separately analyzed, the effect of attenuation correction was significant only in the inferior-septal region. CONCLUSIONS: The results indicate that AC 99mTc-tetrofosmin SPECT improves the detection of viable myocardium mainly by decreasing the underestimation of viability particularly in the inferior-septal region, although some underestimation/overestimation of viability may still occur even with attenuation correction.     

Average African American three-dimensional computed tomography skull images: the potential clinical importance of ethnicity and sex

The production of average 'normative' three-dimensional (3D) computed tomography surface images of the bony skull has only recently been explored. The authors wish to determine the effect of using sex- and ethnicity-specific adult average 3D skull images for comparisons with patient images at various stages of craniofacial surgical management (i.e., diagnosis, treatment planning, prosthetic design, image-guided operative procedures, and outcomes assessment). Craniofacial surgical reconstruction for abnormal patterns of development, cancer resection, or trauma are most likely to benefit from these comparisons. To morphometrically test the significance of separating normative 3D skull data by sex and ethnicity, the authors collected 52 3D, anatomical landmarks from 3D computed tomography scans of dry skulls of 20 Americans of European ethnicity and 20 Americans of primarily African (i.e., primarily African and some European) ethnicity. A Procrustes-based morphometric analysis of shape detects 1.2 times as much interethnic variance as intersex variance. The African American sample presents 4.2% more dolichocephaly, wider orbits, flatter nasal area, larger gnathic anatomy, and more procumbent dentition. Pooling the sexes across both groups, it is seen that men tend to have less bulbous crania, more protruding brows, noses, and masticatory muscle attachments, and relatively less protrusive palettes and anterior mandibles. Despite a small sample size (N = 40), the authors' results are statistically significant (P approximately 0.001 overall) for both of the main factors, sex and ethnicity, separately.     

Evaluation of emphysema progression as measured by computed tomography in patients with chronic obstructive pulmonary disease

It has been difficult to assess the progression of pulmonary emphysema since accurate quantification of the extent of this condition has only previously been possible on post mortem or resected lungs. Previously we have shown that measurements of CT lung density correlated with the degree of emphysema, measured morphometrically in resected lungs. We have therefore employed this technique to assess the progression of emphysema in 17 patients (12M, 5F) with wide range of chronic airflow limitation (FEV1 15-68% predicted). There was little change in the degree of airflow limitation, hyperinflation or arterial blood gas values over 30 +/- 4 months of follow up (p > 0.05). However during this period there was a significant decrease in the lowest 5th percentile of CT density, which fell from -920 +/- 32 to -940 +/- 36 Hounsfield units (p < 0.005) associated with significant fall in the diffusing capacity for carbon monoxide. We believe that these data show the ability of CT scanning to assess the progression of emphysema in patients with chronic obstructive pulmonary disease.     

Effect of contrast concentration on abdominal enhancement in the rabbit: spiral computed tomography evaluation

BACKGROUND: Langerhans' cell histiocytosis (LCH) is an uncommon, poorly understood granulomatous disease, characterized by the idiopathic proliferation of Langerhan's cells or their marrow precursors. In 1985, the Philadelphia Work-shop adopted the term "Langerhans' cell histiocytosis" (LCH) to differentiate it from reactive and neoplastic causes of histiocytosis. METHODS: This study includes 73 pediatric patients diagnosed with this condition in Dublin, Ireland, and Nottingham, England, during a 34-year period (1959 to 1993). These patients are reviewed with respect to clinical presentation, difficulty with making a histological diagnosis, their management, and outcome. RESULTS: A total of 49 patients (67%) had head and neck involvement. Bony involvement was the most frequent sign, most frequently located in the skull. There were 11 deaths (15%) in this series, all associated with multisystem disease, and nine of these deaths were in children younger than 2 years of age. CONCLUSIONS: The role of otolaryngologists is important in the early and accurate evaluation, staging, and diagnosis of LCH. It may mimic more common diseases, such as otitis externa, acute mastoiditis, skin rash, gingivitis, or cervical lymphadenopathy. Patients with multisystem disease may be so ill at presentation that the head and neck lesions may be overlooked. The current management of LCH has become increasingly conservative, and in the 1990s, fewer cases are given chemotherapy or radiotherapy. The prognosis is very good for single-system disease and poor for multisystem disseminated disease with early onset.     

Radiation dose and image quality in spiral computed tomography: multicentre evaluation at six institutions

The purpose of this study was to evaluate the correlation of radiation dose with image quality in spiral CT. Seven clinical protocols were measured in six different radiological departments provided with four different types of high specification spiral CT scanners. Central and surface absorbed doses were measured in acrylic. The practical CT dose index (PCTDI) was calculated for seven clinical examination protocols and one standardized protocol using identical parameters on four different spiral CT scanners with a dedicated ionization chamber inserted into PMMA phantoms. For low contrast measurements, a cylindrical three-dimensional (3D) phantom (different sized spheres of defined contrast) was used. Image noise was measured with a cylindrical water phantom and high contrast resolution with a Perspex hole phantom. Image quality phantoms were scanned using the parameters of the clinical protocols. Images were randomized, blinded and read by six radiologists (one from each institution). PCTDI values for four different scanners varied up to a factor between 1.5 (centre) and 2.2 (surface) for the standardized protocol. A greater degree of variation was observed for seven clinical examination protocols of the six radiological departments. For example, PCTDI varied up to a factor between 1.7 (cerebrum protocol) and 8.3 (abdomen paediatric protocol). Low contrast resolution correlates closely with dose. An improvement in detection from 8 mm to 4 mm sized spheres needs approximately a ten-fold increase in dose. Noise shows a moderate correlation with PCTDI. High contrast resolution of clinical protocols is independent of PCTDI within a certain range. Differences in modern CT scanner technology seem to be of less importance for radiation exposure than selection of protocol parameters in different radiological institutes. Future discussion on guidelines regarding optimal (patient adapted) tube current for clinical protocols is desirable.     

High resolution computed tomography (HRCT) of pulmonary infections in AIDS patients

The Escherichia coli RuvA and RuvB proteins mediate ATP-dependent branch migration of Holliday junctions during homologous genetic recombination. RuvA is a DNA-binding protein with high affinity for Holliday junctions, to which it directs RuvB (a DNA-dependent ATPase). Electron microscopic studies have shown that RuvB forms double hexameric rings on duplex DNA. To determine whether the rings are biologically active, the conditions required for their formation and activity have been analysed. The quaternary structure of RuvB appears to be dependent upon the binding of ATP, magnesium ions, and the presence of RuvA. In the presence of Mg2+ and ATP, RuvB forms hexamers; however, in the presence of Mg2+ alone, dodecamers were observed. Both forms of the protein are stable and have been isolated by gel filtration. Performed dodecamers and, to a lesser extent, hexamers assembled in the absence of DNA lack ATPase activity. Maximal ATPase activity was observed when RuvB assembled directly on DNA in the presence of Mg2+ and ATP. Moreover, under these conditions, a direct interaction between RuvB hexamers and tetramers of RuvA was observed.