[Value of multiplanar reformations (MPR)in multi-slice spiral CT of the lung]

Is the detectability of the spot sign on CT angiography depending on slice thickness and reconstruction type?

OBJECTIVE

The spot sign is a validated imaging marker widely used in CT angiography (CTA) to detect active bleeding and a higher risk of hematoma expansion in patients with intracerebral hemorrhage (ICH). The aim of this study was to investigate the detectability of spot signs on thin multiplanar projection reconstruction (MPR) images compared to thicker maximum intensity projection (MIP) images.

METHODS

In this retrospective analysis, we assessed imaging data of 146 patients with primary hypertensive/microangiopathic ICH who received emergency non-contrast computed tomography (NCCT) and CTA. Two experienced radiologists, blinded to each other, evaluated images of thin (1 mm) MPR images and thick (3 mm) MIP images on the presence of spot signs and performed a consensus reading. Kappa tests were used for data comparison.

RESULTS

In total, spot signs were observed in 27 cases (=18.5 %) in both thin MPR and thick MIP slices. Detectability of the spot sign did not differ in 1 mm MPR images and 3 mm MIP images (Cohen's kappa, 1.0; p = 0.00). Also, when the readings of the two radiologists were analyzed separately, results for MPR and MIP slices were similar (MPR: Cohen's kappa, 0.81, p = 0.00; MIP: Cohen's kappa, 0.74; p = 0.00).

CONCLUSION

No significant difference in the detectability of the spot sign could be demonstrated when comparing 1 mm MPR images with 3 mm MIP images.

OIPAV: an Integrated Software System for Ophthalmic Image Processing, Analysis, and Visualization

Ophthalmic medical images, such as optical coherence tomography (OCT) images and color photo of fundus, provide valuable information for clinical diagnosis and treatment of ophthalmic diseases. In this paper, we introduce a software system specially oriented to ophthalmic images processing, analysis, and visualization (OIPAV) to assist users. OIPAV is a cross-platform system built on a set of powerful and widely used toolkit libraries. Based on the plugin mechanism, the system has an extensible framework. It provides rich functionalities including data I/O, image processing, interaction, ophthalmic diseases detection, data analysis, and visualization. By using OIPAV, users can easily access to the ophthalmic image data manufactured from different imaging devices, facilitate workflows of processing ophthalmic images, and improve quantitative evaluations. With a satisfying function scalability and expandability, the software is applicable for both ophthalmic researchers and clinicians.

CT Imaging of Interstitial Lung Diseases

Until today, computed tomography (CT) is the most important and valuable radiological modality to detect, analyze, and diagnose diffuse interstitial lung diseases (DILD), based on the unsurpassed morphological detail provided by high-resolution CT technique.

In the past decade, there has been a shift from an isolated histopathological diagnosis to a multidisciplinary acquired diagnosis consensus that is nowadays regarded to provide the highest level of diagnostic accuracy in patients with diffuse interstitial lung diseases. The 2002 ATS/ERS statement on classification of idiopathic interstitial pneumonias assigned a central role to high-resolution CT (HRCT) in the diagnostic workup of idiopathic interstitial pneumonias (ATS/ERS consensus classification 2002). The more recent 2013 ERS/ATS statement reinforced that combined clinical data (presentation, exposures, smoking status, associated diseases, lung function, and laboratory findings) and radiological findings are essential for a multidisciplinary diagnosis (Travis et al., Am J Respir Crit Care Med 188(6):733–748, 2013).

The traditional HRCT consisted of discontinuous 1 mm high-resolution axial slices. The primary focus was on visual pattern analysis demanding for the highest possible spatial resolution. Because of the intrinsic high structural contrast of the lung, it has been possible to substantially reduce dose without losing diagnostic information. This development has been supported by new detection and reconstruction techniques. Not only detection of subtle disease and visual comparison of disease stage but also disease classification and quantification nowadays take advantage of continuous volumetric data acquisition provided by multidetector row (MD) CT technique. The following book chapter will focus on acquisition technique with special emphasis on dose and reconstruction, advantages, and new diagnostic options of volumetric MDCT technique for interstitial lung diseases. Based on evidence from the literature, certain diseases will be covered more specifically, but it has to be noted that for the pattern analysis of the various interstitial lung diseases, the plethora of other publications and books is recommended.

Postprocessing in Maxillofacial Multidetector Computed Tomography

Multidetector computed tomography (CT) and volumetric rendering techniques have always been a useful support for the anatomical and pathological study of the maxillofacial district. Nowadays accessibility to multidetector CT scanners allows the achievement of images with an extremely thin collimation and with high spatial resolution, not only along the axial plane but also along the patient's longitudinal axis. This feature is the main theoretical assumption for multiplanar imaging and for an optimal 3-dimensional postprocessing. Multiplanar reconstruction (MPR) techniques permit images along any plane in the space to be obtained, including curved planes; this feature allows the representation in a single bidimensional image of different anatomical structures that develop on multiple planes. For this reason MPR techniques represent an unavoidable step for the study of traumatic pathology as well as of malformative, neoplastic, and inflammatory pathologies. Among 3-dimensional techniques, Maximum Intensity Projection and Shaded Surface Display are routinely used in clinical practice. In addition, volumetric rendering techniques allow a better efficacy in representing the different tissues of maxillofacial district. Each of these techniques give the radiologist an undoubted support for the diagnosis and the characterization of traumatic and malformative conditions, have a critical utility in the neoplastic evaluation of primary or secondary bone involvement, and are also used in the planning of the most modern radiosurgical treatments. The aim of this article is to define the main technical aspects of imaging postprocessing in maxillofacial CT and to summarize when each technique is indicated, according to the different pathologies of this complex anatomical district.

Role of virtual bronchoscopy in the evaluation of bronchial lesions

BACKGROUND

Virtual bronchoscopy (VB) is a type of 3-dimensional reconstruction in which the observation point is placed within the airway to produce an endoscopiclike view.

AIM

To evaluate the diagnostic role of VB in the diagnosis of tracheobronchial lesions, as compared to fiberoptic bronchoscopy (FOB).

SUBJECTS

Fifty patients with tracheobronchial lesions were enrolled (30 patients with bronchogenic carcinomas and 20 patients with tracheobronchial inflammatory lesions).

METHODS

The patients were examined using VB and FOB. Virtual bronchoscopic studies were calculated and reconstructed from cross-sectional images obtained from spiral computed tomographic examination of the chest.

RESULTS

Virtual bronchoscopy provided an excellent overview of the trachea, main stem, and lobar bronchi up to the fourth order. The data obtained by VB and FOB (signs of tumor infiltration including endobronchial mass, stenosis, obstruction, and external indentations) were comparable. However, FOB had the advantage of giving direct cues to color, vascularity, and motility. It also detected early tumor infiltration by picking up subtle mucosal changes. Alternatively, VB was superior in bypassing any obstruction and therefore provided an excellent view distal to the obstructive lesions or stenotic segments. Virtual bronchoscopy also defined the optimum pathway for passing instruments into lesions beyond the field of view.

CONCLUSIONS

Here, we compared the diagnostic capacities of both VB and FOB. The interventional and therapeutic ramifications of our findings await further investigations.

[Usefulness of maximum intensity projections in low-radiation multislice CT lung cancer screening]

OBJECTIVE

To evaluate the diagnostic accuracy of non-overlapping 10-mm-thick axial maximum intensity projections (MIP) in the detection of pulmonary nodules in subjects participating in a lung cancer screening program (LCSP) using multislice computed tomography (MSCT) with a low dose of radiation.

MATERIAL AND METHODS

We evaluated 52 consecutive low-radiation MSCT studies in asymptomatic smokers included in an LCSP (1.25 mm axial images). Axial MIPs with 10mm slice thickness (30 images) were performed and evaluated retrospectively; readers were blind to the initial radiological report. All nodules detected were considered, regardless of their size or consistency. The standard of reference was determined by double reading and consensus for each nodule.

RESULTS

A total of 162 pulmonary nodules (mean size: 3.9 mm, sd: 1.7) were detected. MIP reconstruction detected 150 nodules (S = 92.6%). The initial radiological evaluation detected 108 nodules (S = 66.7%). MIP reconstruction detected 54 (33.3%) nodules that were not reported initially (mean size: 3.4 mm; sd: 1.2) but failed to detect 12 (7.4%) of the nodules reported initially (mean size: 2.91 mm; sd: 0.8). MIP detected all 35 nodules > or = 5 mm, (S =100), whereas the initial radiological evaluation only detected 27 (S = 77%). MIP reconstruction enabled more of the nodules to be detected than the 1.25-mm conventional axial slices (p < 0.01).

CONCLUSION

The introduction of non-overlapping 10-mm-thick axial MIP reconstructions in a low-radiation LCSP using MSCT enabled nodules more accurate and faster detection of pulmonary nodules in comparison with 1.25 mm conventional axial slices.

Comparison between coronal reformatted images and direct coronal CT images of the swine lung specimen: assessment of image quality with 64-detector row CT

The aims of this study were to compare the image quality of coronal multiplanar reconstruction (MPR) images from axial spiral images with that of direct coronal spiral and sequential images, and to estimate and analyse the effect of an incremental change on the image quality using 64-detector row CT. 12 swine lungs were used. Five kinds of images from each lung specimen were obtained using 64-detector row CT. All images were analysed by categories and grades, and the direct coronal sequential images were used as the reference standard for the image quality. Statistical analysis was performed for the following categories: (i) inter-observer reliability, (ii) interaction between the observers and images, (iii) image analysis, (iv) anatomical structural analysis of each observer, (v) stair-step artefact and (vi) background noise. The overall image quality and the image quality of all anatomical structures of coronal MPR images with 0.67 mm slice increments were inferior to the image quality of the other images; this difference was statistically significant (p<0.05). Stair-step artefact was detected on coronal MPR images, and was more prominent on coronal MPR images with 0.67 mm slice increments than on coronal MPR images with 0.34 mm slice increments. The most severe background noise was detected on the direct coronal sequential images, but there was no significant difference between the direct coronal sequential images and the direct coronal spiral images. Background noise was least prominent on coronal MPR images with 0.67 mm slice increments. The increment process is important for improving the image quality of MPR images even when using 64-detector row CT. Coronal MPR images with 0.34 mm slice increments using 64-detector row CT showed a similar image quality to that obtained from the direct coronal images, and can be used instead. This means that the coronal MPR images obtained with 64-detector row CT could be as useful for evaluating the lung parenchyma as the axial high-resolution CT images.

Primary Interpretation of Thoracic MDCT Images Using Coronal Reformations

OBJECTIVE

The objective of this study was to evaluate the accuracy and efficiency of primary interpretation of thoracic MDCT using coronal reformations as compared with transverse images.

SUBJECTS AND METHODS

Fifty patients (18 females, 32 males; age range, 15-93 years; mean age, 63.6 years) underwent 4-MDCT of the chest (detector width, 1 mm; beam pitch, 1.5). Contrast material was administered in 20 of the 50 patients. Coronal and transverse sections were reformatted into 5-mm-thick sections at 3.5-mm intervals. All available image and clinical data consensually reviewed by two thoracic radiologists served as the reference standard. Subsequently, three other thoracic radiologists independently evaluated reformatted coronal and transverse images at two separate review sessions. Each image set was assessed in 58 categories for abnormalities of the lungs, mediastinum, pleura, chest wall, diaphragm, abdomen, and skeleton. Interpretation times and number of images assessed were recorded. Sensitivity, specificity, and interobserver concordance were calculated. Differences in mean sensitivities and specificities were evaluated with Wilcoxon's signed rank test.

RESULTS

The most common findings identified were pulmonary nodules (n = 73, transverse images; n = 72, coronal images) and emphysema (n = 45, transverse; n = 40, coronal). The mean detection sensitivity of all lesions was significantly (p = 0.001) lower on coronal (44% +/- 26% [SD]) than on transverse (51% +/- 22%) images, whereas the mean detection specificity was significantly (p = 0.005) higher (96% +/- 5% vs 95% +/- 6%, respectively). Reporting findings for significantly (p < 0.001) fewer coronal images (mean, 63.0 +/- 4.6 images) than transverse images (mean, 91.9 +/- 8.8 images) took significantly (p = 0.025) longer (mean, 263 +/- 56 sec vs 238 +/- 45 sec, respectively).

CONCLUSION

Primary interpretation of thoracic MDCT is less sensitive and more time-consuming using 5-mm-thick coronal reformations as compared with transverse images.

Value of axial and coronal maximum intensity projection (MIP) images in the detection of pulmonary nodules by multislice spiral CT: comparison with axial 1-mm and 5-mm slices

The purpose of this study was to investigate the diagnostic accuracy of non-overlapping 10-mm axial and coronal maximum intensity projections (MIP) in comparison with standard axial 1-mm and 5-mm slices in the detection of pulmonary nodules. Sixty patients with suspected nodules who underwent multislice spiral CT of the chest were evaluated. Axial 1-mm and 5-mm slices as well as non-overlapping 10-mm axial/coronal MIPs were interpreted independently by three blinded radiologists. After initial review, a retrospective consensus session was performed for agreement on final nodule counts using the axial 1-mm slices as gold standard. Small nodules of less than 5 mm in size were most accurately detected by the axial MIPs. Receiver operating characteristic (ROC) analysis of these small nodules showed that 5-mm slices were not capable of a statistically significant differentiation of nodules from other focal lesions in two observers (p=0.034 and p=0.012, respectively) whereas 1-mm slices and coronal/axial MIPs did allow a statistically significant differentiation in all observers (p<0.001). Nodules larger than 5 mm were equally well depicted with all modalities. Non-overlapping 10-mm axial MIPs improve the accuracy in the detection of small pulmonary nodules.

Multislice computed tomography in staging lung cancer: the role of multiplanar image reconstruction

OBJECTIVE

The role of multiplanar image reconstruction (MPR) in staging lung cancer was investigated using multislice helical computed tomography (CT), which allows high-quality volumetric imaging.

METHODS

Forty-one consecutive patients with lung cancer (mean age = 71 years) underwent multislice CT of the thorax. The scans were acquired using contiguous 4-mm x 2.5-mm slices from the lung apex to the diaphragm in a single breath hold after injection of 100 mL intravenous contrast media. Contiguous axial, coronal, and sagittal images (5-mm slice thickness) were reconstructed in the lung and mediastinal windows. The axial images with and without multiplanar reformatted images were reviewed on a workstation on 2 separate occasions (a minimum of 6 weeks apart) by 2 experienced chest radiologists. The films were assessed for features relating to the primary lesion (size; location; and invasion of the chest wall, mediastinum, diaphragm, and/or fissures) and secondary features (mediastinal lymphadenopathy and lung metastases). The diagnostic confidence of each feature was expressed on a 4-point scale.

RESULTS

A significant increase in confidence was seen on the part of both observers when diagnosing features relating to the primary lesion. The mean confidence score increased from 1.68 to 2.08 (P = 0.038) for observer A and from 1.50 to 1.80 (P = 0.020) for observer B. Confidence in assessing invasion of fissures was increased from 1.70 to 2.30 (P = 0.022) for observer A and from 1.67 to 2.27 (P = 0.006) for observer B. Improvement in interobserver agreement (kappa-value from 0.61 to 0.75) was observed with multiplanar reconstruction (MPR) in the assessment of tumor location. No statistical difference was demonstrated in the diagnosis of mediastinal lymphadenopathy or lung secondaries.

CONCLUSION

Multiplanar imaging of the thorax is a useful supplementary tool in the staging of lung cancer, particularly in delineating the relation of the primary lesion to fissures and the diaphragm.

Multislice CT in thoracic trauma

The introduction of CT imaging in the 1970s revolutionized all aspects of medical care, perhaps nowhere more so than in the evaluation of acutely injured patients. Just as single-slice helical scanning was a great advance over conventional CT, the capabilities of MSCT are proving to be dramatically superior to single-slice methods. Improved contrast bolus imaging, thinner slices, and isotropic voxels should enable the trauma radiologist to identify both major organ system disruption and subtle injuries more promptly. Multiplanar and three-dimensional reconstructions, a forte of MSCT, facilitate rapid communication of disease states with surgeons and others involved in the care of injured patients. In many centers, whole-body CT is beginning to supplant plain films of the chest and spine in the evaluation of severe trauma victims; the cost-effectiveness of such methods is still under evaluation.