Helical Computed Tomography Imaging Research Articles

Multislice helical computed tomography imaging diagnosis and surgical treatment of primary tracheal tumor in cardiothoracic surgery

Multislice helical computed tomography imaging diagnosis and surgical treatment of primary tracheal tumor in cardiothoracic surgery

Three-Dimensional Volumetric Analysis of Frontal Ethmoidal Cells and Evaluation of Influential Factors: A Helical Computed Tomography Study.

In the present study, we aimed to assess frontal ethmoidal cells by using segmentation 3D software to establish a possible correlation between volume variation and both gender and age, as well as a relationship with Keros classification. Helical computed tomography images were obtained from 71 patients for analysis, in which the agger nasi cell, supra agger cell, supra agger frontal cell, supra bulla frontal cell, supraorbital ethmoidal cell, supra bulla cell, and frontal septal cell were identified and segmented to obtain their volume. Significant differences in volume were found for age and gender regarding agger nasi cells (p-value = 0.017), supra agger cells (p-value < 0.001), and frontal septal cells (p-value = 0.049). In the frontal septal cells, an increase of one year in age reduced the volume by 0.309, on average. According to Keros classification, the mean volumes were 10.07 and 25.64, respectively, for types II and III, both being greater than that of type I. Extracting volumetric data by using segmentation software in agger nasi cells, supra agger cells, and frontal septal cells may be useful for obtaining additional information related to age, in addition to possibly contributing to elucidating the anatomical variations in the region and an identification forensic tool.

A new weighting scheme for arc based circle cone-beam CT reconstruction.

In this paper, we present an arc based fan-beam computed tomography (CT) reconstruction algorithm by applying Katsevich's helical CT image reconstruction formula to 2D fan-beam CT scanning data. Specifically, we propose a new weighting function to deal with the redundant data. Our weighting function ϖ(x_,λ) is an average of two characteristic functions, where each characteristic function indicates whether the projection data of the scanning angle contributes to the intensity of the pixel x_. In fact, for every pixel x_, our method uses the projection data of two scanning angle intervals to reconstruct its intensity, where one interval contains the starting angle and another contains the end angle. Each interval corresponds to a characteristic function. By extending the fan-beam algorithm to the circle cone-beam geometry, we also obtain a new circle cone-beam CT reconstruction algorithm. To verify the effectiveness of our method, the simulated experiments are performed for 2D fan-beam geometry with straight line detectors and 3D circle cone-beam geometry with flat-plan detectors, where the simulated sinograms are generated by the open-source software "ASTRA toolbox." We compare our method with the other existing algorithms. Our experimental results show that our new method yields the lowest root-mean-square-error (RMSE) and the highest structural-similarity (SSIM) for both reconstructed 2D and 3D fan-beam CT images.

Helical CT Reconstruction from Sparse-view Data through Exploiting the 3D Anatomical Structure Sparsity

Sparse-view scanning has great potential for realizing ultra-low-dose computed tomography (CT) examination. However, noise and artifacts in reconstructed images are big obstacles, which must be handled to maintain the diagnosis accuracy. Existing sparse-view CT reconstruction algorithms were usually designed for circular imaging geometry, whereas the helical imaging geometry is commonly adopted in the clinic. In this paper, we show that the sparse-view helical CT (SHCT) images contain not only noise and artifacts but also severe anatomical distortions. These troubles reduce the applicability of existing sparse-view CT reconstruction algorithms. To deal with this problem, we analyzed the three-dimensional (3D) anatomical structure sparsity in SHCT images. Based on the analyses, we proposed a tensor decomposition and anisotropic total variation regularization model (TDATV) for SHCT reconstruction. Specifically, the tensor decomposition works on nonlocal cube groups to exploit the anatomical structure redundancy; the anisotropic total variation works on the whole volume to exploit the structural piecewise-smooth. Finally, an alternating direction method of multipliers is developed to solve the TDATV model. To our knowledge, the paper presents the first work investigating the reconstruction of sparse-view helical CT. The TDATV model was validated through digital phantom, physical phantom, and clinical patient studies. The results reveal that SHCT could serve as a potential solution for reducing HCT radiation dose to ultra-low level by using the proposed TDATV model.

Convolutional Neural Network ensembles for accurate lung nodule malignancy prediction 2 years in the future

Convolutional Neural Networks (CNNs) have been utilized for to distinguish between benign lung nodules and those that will become malignant. The objective of this study was to use an ensemble of CNNs to predict which baseline nodules would be diagnosed as lung cancer in a second follow up screening after more than one year. Low-dose helical computed tomography images and data were utilized from the National Lung Screening Trial (NLST). The malignant nodules and nodule positive controls were divided into training and test cohorts. T0 nodules were used to predict lung cancer incidence at T1 or T2. To increase the sample size, image augmentation was performed using rotations, flipping, and elastic deformation. Three CNN architectures were designed for malignancy prediction, and each architecture was trained using seven different seeds to create the initial weights. This enabled variability in the CNN models which were combined to generate a robust, more accurate ensemble model. Augmenting images using only rotation and flipping and training with images from T0 yielded the best accuracy to predict lung cancer incidence at T2 from a separate test cohort (Accuracy = 90.29%; AUC = 0.96) based on an ensemble 21 models. Images augmented by rotation and flipping enabled effective learning by increasing the relatively small sample size. Ensemble learning with deep neural networks is a compelling approach that accurately predicted lung cancer incidence at the second screening after the baseline screen mostly 2 years later.

A Retrospective Comparison Study of Ultrasonography and Computed Tomography Scan in Diagnosis of Acute Appendicitis in the Pediatric Population

Background: Ultrasonography (US) has largely become the primary diagnostic imaging modality for the diagnosis of acute appendicitis (AA) in pediatric patients. The purpose of this study was to determine and compare the diagnostic accuracy of helical computed tomography (CT) scans and graded compression US for the diagnosis of AA in the pediatric population. Methods: Between January 2011 and December 2013, 431 pediatric patients (aged 5 - 18 years) who presented with acute abdominal pain and received either a CT scan, US, or both for the diagnosis of AA were retrospectively reviewed from an IRB-approved institution-wide database. Sensitivities and specificities of both imaging modalities were calculated and compared. Results: Patients were allocated into two cohorts depending on whether they received an US (239/431) or CT (192/431). Clinical symptoms and laboratory values were noted and analyzed for the significance of mesenteric lymphadenitis in conjunction with appendicitis and for differential diagnosis. A total of 182 CT cases and 227 US cases were verified as appendicitis via histopathology report. The overall sensitivity and specificity of CT imaging were determined to be 91.2% and 70%, respectively, while the sensitivity and specificity for US imaging were 52.8% and 83.3%. Conclusion: Helical CT imaging in the pediatric population has provided a higher sensitivity and diagnostic accuracy for AA. However, the diagnostic benefit of US cannot be excluded in this patient population. Further research is needed on whether CT imaging should be used primarily for the diagnostic approach to AA in pediatric patients complaining of acute abdominal pain. J Curr Surg. 2020;10(3):21-27 doi: https://doi.org/10.14740/jcs404

Correlation of displacement vector fields calculated by different deformable image registration algorithms with motion parameters in helical, axial and cone beam CT imaging

AbstractAim:The purpose of this study is to investigate quantitatively the correlation of displacement vector fields (DVFs) from different deformable image registration (DIR) algorithms to register images from helical computed tomography (HCT), axial computed tomography (ACT) and cone beam computed tomography (CBCT) with motion parameters.Materials and methods:CT images obtained from scanning of the mobile phantom were registered with the stationary CT images using four DIR algorithms from the DIRART software: Demons, Fast-Demons, Horn–Schunck and Lucas–Kanade. HCT, ACT and CBCT imaging techniques were used to image a mobile phantom, which included three targets with different sizes (small, medium and large) that were manufactured from a water-equivalent material and embedded in low-density foam to simulate lung lesions. The phantom was moved with controlled cyclic motion patterns where a range of motion amplitudes (0–20 mm) and frequencies (0·125–0·5 Hz) were used.Results:The DVF obtained from different algorithms correlated well with motion amplitudes applied on the mobile phantom for CBCT and HCT, where the maximal DVF increased linearly with the motion amplitudes of the mobile phantom. In ACT, the DVF correlated less with motion amplitudes where motion-induced strong image artefacts and the DIR algorithms were not able to deform the ACT image of the mobile targets to the stationary targets. Three DIR algorithms produce comparable values and patterns of the DVF for certain CT imaging modality. However, DVF from Fast-Demons deviated strongly from other algorithms at large motion amplitudes.Conclusions:The local DVFs provide direct quantitative values for the actual internal tumour shifts that can be used to determine margins for the internal target volume that consider tumour motion during treatment planning. Furthermore, the DVF distributions can be used to extract motion parameters such as motion amplitude that can be extracted from the maximal or minimal DVF calculated by the different DIR algorithms and used in the management of the patient motion.

Tilting fan beam back-projection filtration algorithm for local reconstruction in helical cone-beam computed tomography

Dose reduction becomes one of the hot research fields in the most commonly used helical computed tomography (CT) for clinical diagnostic. Local imaging using a collimator can effectively lower the CT radiation dose by reducing the direct irradiation area. Due to the limitation of the exposing area, the projection data used for local imaging reconstruction are usually truncated, resulting in local reconstruction problems. The key in local image reconstruction is how to deal with the horizontal truncation of the projection data. The helical cone beam back-projection filtration (BPF) algorithm only needs to ensure the integrity of the projections of PI line to realize the reconstruction of the entire PI line, making local reconstruction possible. Due to the complexity and irregularity of the spatial distribution of PI lines, the existing helical BPF algorithms can only realize local surface reconstruction, whereas the local volume reconstruction is difficult. For the BPF algorithm in designing the PI line and the sampling points in helical cone beam CT and the difficulty in local volume reconstruction, the tilted fan-beam back-projection filtration (TFB-BPF) reconstruction algorithm is proposed by utilizing the weighted correction and coordinate expansion, based on the circular fan beam BPF. The algorithm divides the reconstruction area into several slices, constructs the inclined fan beam geometry for each layer, and slice-by-slice reconstruction is conducted by using the weighted modified tilted fan beam BPF algorithm. The most powerful feature of the algorithm is that the filter line, equivalent to the PI line in the original helical BPF algorithm, is selected in a two-dimensional plane. Therefore, it is more concise and efficient and can be applied to the reconstruction of local volume regions. In this paper, the helical cone beam CT imaging geometry and the original helical cone beam BPF algorithm are introduced. Then, the TFB-BPF reconstruction algorithm is deduced. Experimental results show that the algorithm can effectively realize the local volume reconstruction and overall improved image quality without obvious truncation artifacts.

Postoperative pulmonary function changes according to the resected lobe: a 1-year follow-up study of lobectomized patients.

Pulmonary function and patient complaints appear to improve up to 12 months after lobectomy but long-term prospective studies based on clinical data are scarce. Improvement in pulmonary function may depend on the area and extent of the resection and the time from the operation. This prospective study aimed to determine pulmonary function changes according to the resected lobe. This prospective study included 59 patients requiring single lobectomy. Total volume and low-attenuation volume (LAV) for each lobe and the entire lungs were calculated based on helical computed tomography images. Vital capacity (VC), forced expiratory volume in one second (FEV1), percent FEV1 (%FEV1), percent lung diffusion capacity for carbon monoxide (%DLco), %DLco divided by the alveolar volume (%DLco/VA), modified Medical Research Council (mMRC) grades, and COPD Assessment Test (CAT) scores were compared at 3, 6, and 12 months after surgery. VC was higher at 12 months than at 3 months after right upper lobectomy (RUL) or right lower lobectomy (RLL). FEV1 and %FEV1 were higher at 12 months than at 6 months after left lower lobectomy (LLL). %DLco was higher at 12 months than at 3 months after RUL or left upper lobectomy (LUL). DLco/VA, mMRC grades, and CAT scores did not change significantly in the period from 3 to 12 months after any lobectomy procedure. Compared to the predicted postoperative values, the observed values of VC for RUL, RLL, and LUL; FEV1 for RLL; %FEV1 for RLL and LUL; %DLco for LUL; and %DLco/VA for all lobectomy procedures were higher at 12 months. Improvements in pulmonary function and symptoms varied according to the resected lobe. Some of the observed pulmonary function values were higher than the predicted postoperative values. Pulmonary function changes may be related to the location, volume, and extent of emphysematous changes.

Computed tomography imaging parameters of 82 Chinese patients with congenital microphthalmia

Objective: To observe computed tomography (CT) imaging parameters of congenitally blind microphthalmia in Chinese patients and to provide clinical reference data for the Chinese population. Methods: It was a retrospective study for a consecutive case series of congenitally blind microphthalmia from July 2011 to July 2013. All of the patients were diagnosed in the Ocular Plastic Department, Tongren Eye Center, Beijing Tongren Hospital. We employed multi-section helical CT imaging with a computer-aided design system to observe and measure the imaging features in 82 Chinese patients (85 eyes). The paired T-test was applied for comparing the axial lengths, transverse diameters, and vertical diameters between the both sides in patients with congenital microphthalmia. The Pearson correlation was used for analyzing the relationship between the axial length and the age of the patients. Results: In the 82 patients, the age ranged from 1 month to 40 years old. Forty-one patients were male and 41 were female. The disease was unilateral in 96.34% of the patients. The orbital cysts were observed in 12.94% of them, and 76.47% of them presented basic structures on the CT scan. The abnormalities of the lens (62.35% of the eyes) and vitreous (82.35% of the eyes) were observed. The mean maximum axial length of the affected eyes (85 eyes) was (14.52±0.56) mm and the mean axial length of the unaffected eyes (79 eyes) was (22.79±0.36) mm. There was significantly statistical difference in the ocular size between the affected and unaffected eyes (t= 1.156, P<0.001) . Conclusions: Congenitally blind microphthalmia is usually complicated with the abnormalities of the lens and vitreous. The ocular size decreases significantly. The results of the present study provide a clinical reference for evaluating congenitally blind microphthalmia.(Chin J Ophthalmol, 2018, 54: 199-204).

Three-dimensional volumetric analysis of frontal sinus using medical software

Abstract Objective to investigate the volume and linear measurements of the frontal sinuses by means of a three-dimensional software using helical computed tomography images. Materials and methods The samples consisted of 36 tomographic images from 22 women and 14 men aged between 18 and 86 years old. The ITK/SNAP software was used for image segmentation, analysis of volume data, and linear measurements (i.e. height, width and depth). Results The mean volumes of the left and right frontal sinuses were 3.945 mm 3 (SD = 2.803) and 3.423 mm 3 (SD = 2.835). The mean linear measurements were the following: right-side axial depth of 16.1 mm (SD = 7.6), left-side axial depth of 17.0 mm (SD = 5.8), right-side sagittal height of 19.0 mm (SD = 11.1), and left-side sagittal height of 20.5 mm (SD = 9.8), with no statistically significant differences. The right-side axial width of 19.0 mm (SD = 6.8) and left-side axial width of 22.4 mm (SD = 9.1) in women and right-side axial width of 21.6 mm (SD = 12.9) and left-side axial width of 26.5 mm (SD = 9.8) in men, with statistically significant difference ( P = 0.0264) for the left side. Conclusion There was a significant difference only for axial width, with the left side having higher values compared to the right side.

Three-dimensional analysis of third molar development to estimate age of majority

Third molars are one of the few biological markers available for age estimation in undocumented juveniles close the legal age of majority, assuming an age of 18years as the most frequent legal demarcation between child and adult status. To obtain more accurate visualization and evaluation of third molar mineralization patterns from computed tomography images, a new software application, DentaVol©, was developed. Third molar mineralization according to qualitative (Demirjian's maturational stage) and quantitative parameters (third molar volume) of dental development was assessed in multi-slice helical computed tomography images of both maxillary arches displayed by DentaVol© from 135 individuals (62 females and 73 males) aged between 14 and 23years. Intra- and inter-observer agreement values were remarkably high for both evaluation procedures and for all third molars. A linear correlation between third molar mineralization and chronological age was found, with third molar maturity occurring earlier in males than in females. Assessment of dental development with both procedures, by using DentaVol© software, can be considered a good indicator of age of majority (18years or older) in all third molars. Our results indicated that virtual computed tomography imaging can be considered a valid alternative to orthopantomography for evaluations of third molar mineralization, and therefore a complementary tool for determining the age of majority.

Diagnostic performance of reformatted isotropic thin-section helical CT images in the detection of superior semicircular canal dehiscence.

Purpose The purpose of this article is to assess the diagnostic performance of computed tomography (CT) reformatted images for detection of superior semicircular canal (SSC) dehiscence. Material and methods Forty-two patients, with sound- and/or pressure-induced vestibular symptoms, and 42 control participants underwent helical CT examination with a highly collimated beam (0.5 mm). Reformatted images of the vestibular labyrinth were obtained in the standard axial and coronal planes (group A images), and in a plane parallel and perpendicular to the SSC (group B images). Diagnostic performance obtained by evaluating the group A images alone and the group B images alone was analyzed by using the area under the receiver operating characteristic curve (AUC). Results The diagnostic performance of group A images was AUC = 0.929 with an overall accuracy of 92.9%. The diagnostic performance of group B images was AUC = 0.988 with an overall accuracy of 98.8%. The evaluation of group B images alone showed an improved diagnostic performance over the group A images alone. Conclusion Thin-section 0.5-mm collimation CT with reformatted images oriented in the plane parallel and perpendicular to the SSC improves diagnostic accuracy in assessing for SSC dehiscence in comparison to CT images with reconstructions limited to traditional axial and coronal planes.

"High-precision, reconstructed 3D model" of skull scanned by conebeam CT: Reproducibility verified using CAD/CAM data.

Computed tomography (CT) scanning has recently been introduced into forensic medicine and dentistry. However, the presence of metal restorations in the dentition can adversely affect the quality of three-dimensional reconstruction from CT scans. In this study, we aimed to evaluate the reproducibility of a "high-precision, reconstructed 3D model" obtained from a conebeam CT scan of dentition, a method that might be particularly helpful in forensic medicine. We took conebeam CT and helical CT images of three dry skulls marked with 47 measuring points; reconstructed three-dimensional images; and measured the distances between the points in the 3D images with a computer-aided design/computer-aided manufacturing (CAD/CAM) marker. We found that in comparison with the helical CT, conebeam CT is capable of reproducing measurements closer to those obtained from the actual samples. In conclusion, our study indicated that the image-reproduction from a conebeam CT scan was more accurate than that from a helical CT scan. Furthermore, the "high-precision reconstructed 3D model" facilitates reliable visualization of full-sized oral and maxillofacial regions in both helical and conebeam CT scans.

Prevalence and location of accessory foramina in the human mandible

This study aimed to radiographically assess the prevalence and location of accessory foramina in the human mandible using helical computed tomography (CT) images and three-dimensional reconstructions. Helical CT images from 24 males and 22 females aged 66–88 years (mean age: 73.7 ± 5.3 years) were observed. Each image was assessed in the three anatomical planes, and three-dimensional reconstructions were performed with Amira 5.6 software. All subjects (n = 46) presented at least one accessory foramina. A lingual foramen was the most frequently observed foramen and present in 96 % (n = 44) of subjects. Mandibular anterior nutrient canals were clearly observed in 72 % (n = 33) of subjects (71 %, n = 17, of males; 73 %, n = 16, of females). A retromolar foramen was present in 17 % (n = 8) of subjects (21 %, n = 5, of males; 14 %, n = 3, of females). A double mental foramen (DMF) was present in only one subject (2 %). Fifty percent (n = 23) of subjects presented one or more inferior retromental foramen (IRF). No significant correlations were observed between prevalences of accessory foramina and sex. The lingual foramen can be considered a constant finding, and mandibular anterior nutrient canal foramina and IRF were present in the majority of subjects. Retromolar foramina and DMF were less common but can be associated with anesthetic failures and oral surgery complications. Three-dimensional reconstructions provided better understanding of the locations of foramina and their interrelations with the anatomy of the jaw.

Assessment of temporal resolution of multi-detector row computed tomography in helical acquisition mode using the impulse method

The purpose of this study was to propose a method for assessing the temporal resolution (TR) of multi-detector row computed tomography (CT) (MDCT) in the helical acquisition mode using temporal impulse signals generated by a metal ball passing through the acquisition plane. An 11-mm diameter metal ball was shot along the central axis at approximately 5 m/s during a helical acquisition, and the temporal sensitivity profile (TSP) was measured from the streak image intensities in the reconstructed helical CT images. To assess the validity, we compared the measured and theoretical TSPs for the 4-channel modes of two MDCT systems. A 64-channel MDCT system was used to compare TSPs and image quality of a motion phantom for the pitch factors P of 0.6, 0.8, 1.0 and 1.2 with a rotation time R of 0.5 s, and for two R/P combinations of 0.5/1.2 and 0.33/0.8. Moreover, the temporal transfer functions (TFs) were calculated from the obtained TSPs. The measured and theoretical TSPs showed perfect agreement. The TSP narrowed with an increase in the pitch factor. The image sharpness of the 0.33/0.8 combination was inferior to that of the 0.5/1.2 combination, despite their almost identical full width at tenth maximum values. The temporal TFs quantitatively confirmed these differences. The TSP results demonstrated that the TR in the helical acquisition mode significantly depended on the pitch factor as well as the rotation time, and the pitch factor and reconstruction algorithm affected the TSP shape.

Does Computed Tomography Add Information on Radiographic Analysis in Detecting Periprosthetic Osteolysis After Total Ankle Arthroplasty?

The major longer term complications of ankle arthroplasty are periprosthetic osteolysis and aseptic loosening. Follow-up studies of total hip arthroplasties show that measurements of periprosthetic osteolytic lesions on radiographs underestimate the size compared with those made on computed tomography (CT), and some of the lesions may even remain undetected on radiographs. However, it is unclear whether the same applies to total ankle arthroplasty (TAA). We retrospectively reviewed the radiographs of 123 patients who had undergone TAA with the Ankle Evolutive System (AES) implant. Of these, 43 (34.9%) had at least 1 large (greater than 10 mm) osteolytic lesion on radiographs at a minimum follow-up of 14 months (mean, 43.1 months; range, 14-85 months). Forty of the 43 patients underwent helical CT imaging. Computed tomography showed more osteolytic lesions than radiographs around both tibial and talar components. CT also showed larger lesions than radiographs in 9 of 10 zones around prosthetic components. The difference was highly significant in 3 zones around the talar component. Computed tomography showed more and larger periprosthetic lesions than radiographs around an ankle prosthesis. Because osteolysis is progressive in nature, it presumably leads to component failure. Considering our results, we recommend adding CT imaging to postoperative follow-up after TAA for patients with suspected or known periprosthetic lucencies on radiographs. Level III, diagnostic study.

Helical computed tomography application in rabbit liver anatomy: comparison with frozen cross-sectional cuts

Our focus has been to study and compare the anatomical helical computed tomography (CT) features of the normal rabbit liver with its native cross-sectional anatomy. Helical CT was used for scanning the cranial part of the abdominal cavity. The slice thickness was 5 mm. Frozen transversal anatomic cross-sections with a thickness of 10 mm were obtained from the cranial abdominal part of 4 animals following euthanasia. They were compared with the corresponding helical CT scans. At Th9 (thoracic vertebra), the helical CT images showed in the whole aspect a normal liver. It was a massive, heterogeneous, soft tissue, with normal attenuating findings and distinguished edges. The gallbladder was hypoattenuated compared to the liver parenchyma. At the level of Th11 the liver was in sharp distinction to the fundus and body of the stomach. At Th12 the rabbit liver was found in close contact with the stomach, duodenum, and ascending colon. Only the right hepatic lobe was visible at the level of Th13, outlined by the right kidney impression. The right hepatic and caudate lobe were observed at L1 (lumbar vertebra). The frozen cross-sections have analogues to the corresponding helical CT images. That motivated us to conclude that helical CT is an accurate mode for studying the rabbit liver anatomy.

Clear Cell Renal Cell Carcinoma: Multiphasic Multidetector CT Imaging Features Help Predict Genetic Karyotypes

To determine whether imaging characteristics at multiphasic multidetector computed tomography (CT) correlate with common karyotypic abnormalities in patients with clear cell renal cell carcinomas (ccRCCs). Institutional review board approval was obtained, and informed consent was waived for this HIPAA-compliant retrospective study. From January 2000 through September 2007, the prenephrectomy multiphasic (corticomedullary, nephrographic, and excretory phases), multidetector helical CT images of 58 histologically proved and karyotyped ccRCCs were reviewed by two readers with experience in abdominal imaging. Imaging features assessed included degree of attenuation, contour, and presence of calcifications and neovascularity. These features were independently correlated with specific karyotypic abnormalities on the resected specimens. Degree of attenuation data were analyzed with logistic regression for significance (P < .05), and morphologic characteristics were analyzed with odds ratios for assessing their diagnostic power. On unenhanced scans, 7% (two of 28) of ccRCCs with the loss of chromosome 3p were calcified, whereas 37% (11 of 30) of lesions without this anomaly were calcified (odds ratio, 0.13). During the corticomedullary phase, ccRCCs with the loss of chromosome Y enhanced more than those without this anomaly (130.0 vs 102.5 HU, P = .04), and ccRCCs with trisomy 7 enhanced less than those without this anomaly (105.8 vs 139.3 HU, P = .04). During the excretory phase, ccRCCs with trisomy 5 enhanced more than those without this anomaly (115.5 vs 83.4 HU, P = .03). The genetic makeup of ccRCCs affects their imaging features at multidetector CT examinations. Multidetector CT imaging characteristics may help suggest differences at the cytogenetic level among ccRCCs.

Otimização da dose em exames de rotina em tomografia computadorizada: estudo de viabilidade em um Hospital Universitário

OBJETIVO: Estudar a viabilidade de redução da dose de radiação em protocolos de aquisição de imagens de tomografia helicoidal em um hospital universitário. MATERIAIS E MÉTODOS: Foi realizado levantamento de dose de radiação de protocolos de tomografia com objetos simuladores e câmara de ionização. Foram propostas variações de kVp e mAs, determinando-se a média de ruído. Protocolos com valores de ruído menores ou iguais a 1% foram submetidos à avaliação qualitativa de contraste e resolução espacial por três observadores. RESULTADOS: Foram realizados 22 testes de variações para o protocolo de crânio pediátrico, 26 para crânio adulto, 28 para abdome e 18 para tórax. A redução da dose conseguida variou entre 7,4-13% para protocolo de crânio pediátrico, 3,8-25% para crânio adulto, 9,6-34,3% para abdome e 6,4-12% para tórax. Notou-se também que a utilização de ferramentas de janelamento e zoom favoreceu o aceite das imagens pelos observadores. CONCLUSÃO: É possível reduzir os níveis de dose de radiação em até 34,4%, comparativamente aos protocolos utilizados na rotina, mantendo-se o ruído em níveis aceitáveis. O uso de ferramentas de manipulação digital das imagens possibilitou a aceitação de imagens com níveis maiores de ruído, favorecendo o processo de redução de dose de radiação.