Chest tomosynthesis: technical and clinical perspectives.

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Chest Tomosynthesis: Technical and Clinical Perspectives Jenny Vikgren, MD, PhD1,2

1 Department of Radiology, Sahlgrenska University Hospital,

Gothenburg, Sweden 2 Department of Radiology, Institute of Clinical Sciences, Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden 3 Department of Medical Physics and Biomedical Engineering, Sahlgrenska University Hospital, Gothenburg, Sweden 4 Department of Radiation Physics, Institute of Clinical Sciences, Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden

Magnus Bath, PhD3,4

Address for correspondence Ase Allansdotter Johnsson, MD, PhD, Department of Radiology, Institute of Clinical Sciences, Sahlgrenska Academy at the University of Gothenburg, Bruna Straket 1113, 413 45 Gothenburg, Sweden (e-mail: [email protected]).

Semin Respir Crit Care Med 2014;35:17–26.

Abstract

Keywords

► ► ► ►

chest radiography tomosynthesis computed tomography

The recent implementation of chest tomosynthesis is built on the availability of large, dose-efficient, high-resolution flat panel detectors, which enable the acquisition of the necessary number of projection radiographs to allow reconstruction of section images of the chest within one breath hold. A chest tomosynthesis examination obtains the increased diagnostic information provided by volumetric imaging at a radiation dose comparable to that of conventional chest radiography. There is evidence that the sensitivity of chest tomosynthesis may be at least three times higher than for conventional chest radiography for detection of pulmonary nodules. The sensitivity increases with increasing nodule size and attenuation and decreases for nodules with subpleural location. Differentiation between pleural and subpleural lesions is a known pitfall due to the limited depth resolution in chest tomosynthesis. Studies on different types of pathology report increased detectability in favor of chest tomosynthesis in comparison to chest radiography. The technique provides improved diagnostic accuracy and confidence in the diagnosis of suspected pulmonary lesions on chest radiography and facilitates the exclusion of pulmonary lesions in a majority of patients, avoiding the need for computed tomography (CT). However, motion artifacts can be a cumbersome limitation and breathing during the tomosynthesis image acquisition may result in severe artifacts significantly affecting the detectability of pathology. In summary, chest tomosynthesis has been shown to be superior to chest conventional radiography for many tasks and to be able to replace CT in selected cases. In our experience chest tomosynthesis is an efficient problem solver in daily clinical work.

Chest tomosynthesis refers to the technique of acquiring several discrete projection radiographs of the chest over a limited angular range and using these radiographs for reconstructing the chest in section images.1–4 These reconstructed slices contain much less of the superimposed anatomy than the original radiographs, suggesting an improvement in detection of pathology. Initial investigations have also shown

Issue Theme Thoracic Imaging; Guest Editor, Martine Remy-Jardin, MD, PhD

that the detection of pathology is substantially increased compared with conventional chest radiography.5,6 As opposed to computed tomography (CT), the radiation dose from a chest tomosynthesis examination is comparable to that from a conventional chest radiography examination and —depending on the system used—effective doses in the order of 0.1 to 0.2 mSv have been reported.7–9 Additionally, as the

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DOI http://dx.doi.org/ 10.1055/s-0033-1363448. ISSN 1069-3424.

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Ase Allansdotter Johnsson, MD, PhD1,2

Chest Tomosynthesis: Technical and Clinical Perspectives

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financial cost for a chest tomosynthesis examination usually is much lower than for a corresponding CT examination10 (existing chest tomosynthesis systems are modified digital chest radiography systems) and the patient throughput is higher,11,12 it may be beneficial for healthcare if chest tomosynthesis can be used for certain tasks for which CT is used today. The aims of the present article are to describe the fundamental principles of chest tomosynthesis, provide details about its implementation in available systems, give an overview of recent clinical evaluations and share our experience of the clinical use of chest tomosynthesis in daily routine.

ography. The patient setup for a chest tomosynthesis examination also closely resembles that of a conventional chest radiography examination. The difference is that as the tomosynthesis projection images are acquired in a time period of several seconds, during which the X-ray tube performs a continuous motion, the patient is required to be still and hold his or her breath longer in order not to introduce motion artifacts. Normally, a chest tomosynthesis examination is performed with the patient standing in the posteroanterior (PA) or anteroposterior (AP) position, leading to coronal section images. However, by imaging the patient in the lateral direction, the technique can also be used to obtain sagittal section images. In the same way as the lateral projection results in a substantially higher radiation dose to the patient than the PA projection, a lateral chest tomosynthesis examination results in a higher radiation dose than a normal chest tomosynthesis examination. In the last years the technique has developed and today a chest tomosynthesis can also be performed with the patient in supine (or prone) position, which is advantageous for patients unable to stand. The recent successful implementation of chest tomosynthesis is built on the availability of flat-panel detectors; large, dose-efficient, high-resolution detectors that enable the acquisition of the necessary number of radiographs within one breath hold. Further, as the reconstruction algorithms are demanding and the total amount of data used is large, the hardware requirements are high. Even with modern computers, the reconstruction of a single examination may take several minutes. Nevertheless, the technical developments in this area in recent years have enabled the introduction of commercial chest tomosynthesis systems into healthcare. The most common technique for reconstructing tomosynthesis section image after the acquisition of the projection radiographs is a filtered back projection algorithm. Other algorithms for reconstruction in tomosynthesis exist,1,31–37 but have not yet been implemented in commercially available chest tomosynthesis systems. In theory, section images can be reconstructed with an arbitrary separation. However, as the slice thickness of the reconstructed images is in the order of 5 mm, section images are normally reconstructed with a separation of 3 to 5 mm.10,38,39 A typical chest tomosynthesis examination thus results in approximately 60 coronal section images, covering the entire chest of the patient.

Limitations with Conventional Chest Radiography Today, conventional chest radiography is a fundamental examination in chest radiology as it gives an instant overview of the cardiopulmonary status of the patient. Important characteristics, such as heart size, pulmonary vascular pattern, and radiodensity of the lungs, as well as contours of the mediastinum, diaphragm, pleura, and chest wall, can quickly be determined. This allows for detection of a variety of different pathological changes in the chest and for several patients chest radiography is the only radiological examination performed before the treatment. This includes patients with pneumothorax, pneumonia, and pulmonary edema. Important advantages of chest radiography include short examination time, easy accessibility, low radiation dose, and low cost.13,14 However, chest radiography is a projection imaging technique, and the overlapping of anatomy in an image may hinder the detection of pathology. For example, several studies have shown that it is the overlapping of anatomy, and not the presence of noise in the images, that mainly limits the detection of pulmonary nodules in chest radiography.15–21 Also for many other tasks the overlapping anatomy is the dominating source of uncertainty, resulting in low sensitivity and specificity.22–27 CT to a large extent solves the problem of reduced detectability caused by overlapping anatomy. However, CT has disadvantages, such as high radiation dose and high cost, compared with chest radiography.28–30 Although, developments of CT technology and reconstruction algorithms in recent years have aimed to reduce the radiation doses associated with CT, the effective dose for most clinical tasks are still up to several mSv. Obtaining the increased diagnostic information provided by volumetric imaging at the low radiation doses associated with conventional projection radiography would be of high value.

Principles of Chest Tomosynthesis Chest tomosynthesis is built on the principle of acquiring a relatively large number of projection radiographs of the chest at slightly different angles and using these radiographs to reconstruct section images.1–4 Despite sometimes being referred to as limited-angle CT, the projection radiographs are acquired using equipment used for conventional chest radiSeminars in Respiratory and Critical Care Medicine

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Available Systems Technical Specifications In December 2013, at least three systems for chest tomosynthesis were commercially available. The manufacturers of these three systems are GE Healthcare (66, Chalfont St. Giles, UK); Shimadzu (Kyoto, Japan); and Fujifilm (Tokyo, Japan). The GE and Fujifilm flat-panel detectors are based on indirect conversion (CsI) whereas the Shimadzu detector is based on direct conversion (a:Se). All systems employ a linear movement of the X-ray tube for acquiring projection radiographs at different angles. In the GE and Fujifilm systems, the detector is stationary whereas the Shimadzu detector performs a linear movement in the opposite direction of the X-ray


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Radiation Dose The radiation doses reported (effective dose) for chest tomosynthesis are in the order of 0.1 to 0.2 mSv.6–9,42 These are values close to the 0.1 mSv typically reported for conventional chest radiography,43 although it is not rare that the effective dose for conventional chest radiography, including a PA and a lateral projection, rather is half of that, 0.05 mSv.8 However, as chest tomosynthesis is a relatively new technique, there has been limited work attempting to further reduce the radiation dose associated with the examination.44 Nevertheless, a recent study showed that by optimizing the acquisition parameters, an effective dose as low as 0.06 mSv could be reached without a significant decrease in image quality.45 To put these numbers in perspective, the average effective dose for a standard-dose chest CT has been reported to be 7 mSv,43 although the use of automatic tube current modulation and dedicated low-dose CT protocols for selected examination— such as visualization of the lung parenchyma—can result in effective doses as low as 1 mSv46,47 and the recent introduction of model-based iterative reconstruction techniques has a potential for reducing the doses even further.48 Regarding the determination of radiation doses in chest tomosynthesis, conversion factors that can be used to estimate the effective dose from the registered kerma-area product have been published.49

Clinical Evaluations Initial evaluations of chest tomosynthesis focused on its use for detection of pulmonary nodules,5,6 although experiences of its use for other purposes were also described.50 However, as the technique has become more established, recent years

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have seen a steady increase in the number of clinical evaluations of the technique and a broadening of the topics being investigated. Here, an overview of evaluations of chest tomosynthesis for several clinical applications will be given.

Detection of Pathology Several studies have investigated the use of chest tomosynthesis for detection of pulmonary nodules and have shown that the sensitivity of chest tomosynthesis may be up to three times higher than for conventional chest radiography for nodules within the clinically important size range of 8 to 10 mm diameter, with an even larger difference between the modalities for smaller nodules 4 to 6 mm.5,6,51 ►Fig. 1 shows a nodule clearly visible on chest tomosynthesis that cannot be detected on chest radiography. The sensitivity regarding nodule detection increases with nodule size and CT attenuation value and decreases for nodules with subpleural location.9 Also for other types of important pathology, a substantial increase in detectability compared with conventional chest radiography has been reported. For example, a study by Kim et al52 reported that only 19% of cavities found on chest CT were detected on chest radiography while 77% of the cavities were detected on chest tomosynthesis, indicating a four-fold increase in sensitivity for cavities in favor of chest tomosynthesis. Detection of cavities is an important radiological task for identification of mycobacterial disease. In tuberculosis, the presence of a cavity indicates more advanced and possibly contagious disease and the report of such findings should lead to improved identification and treatment of active cases which are essential for tuberculosis control. Chest tomosynthesis has also been shown to be substantially more sensitive than chest radiography for detection of pleural plaques in the diagnosis of asbestosis.53 Detection of pulmonary emphysema has also been reported as superior in comparison to chest radiography.42 This could lead to earlier recommendation of pulmonary function testing and smoking cessation, resulting in a beneficial effect in terms of disease progression.54

Lung Cancer Screening The cost of a chest tomosynthesis examination has been reported to be only slightly higher than that of conventional chest radiography and only one-third of a chest CT.10 In

Fig. 1 (A–C) The chest tomosynthesis examination (A) clearly reveals a nodule in the left upper lobe (arrow), which is impossible to identify on the corresponding chest radiograph (B). Coronal CT image (C) verifies the presence of the nodule. CT, computed tomography. Seminars in Respiratory and Critical Care Medicine

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tube. With the GE system, typically today 60 low-dose projection images are acquired in 10 seconds,6 whereas the faster Shimadzu system acquires 74 projections in 6 seconds.40 On the Fujifilm system, the acquisition time ranges from 4 to 12 seconds depending on the number of projections acquired (20–60). The sweep angle (angular range used for the acquisition) varies from 8 to 60 degrees, although the typical sweep angle used is 30 or 40 degrees. In principle, a larger sweep angle results in decreased slice thickness and improved depth resolution.41

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combination with the low radiation doses associated with chest tomosynthesis and the improved detectability compared with conventional chest radiography, this has led to an interest in using the technique for screening purposes. In a recent study, it was concluded that the detection rate of lung cancer with chest tomosynthesis is comparable to that of lowdose CT and that experimental studies support the use of tomosynthesis to select those suitable for CT among high-risk people.39 The study included subjects 45 to 75 years of age being at risk for developing lung cancer (current and former smokers > 20 pack years) and chest tomosynthesis was performed at baseline and after 1 year in cases with benign nodules or nodules being 5 mm or less in size at baseline. Subjects with nodules > 5 mm or multiple nodules underwent further evaluation with CT and, if applicable, positron emission tomography-CT and/or biopsy. Although the study reported that the percentage of nodules and lung cancer detected with chest tomosynthesis was comparable to that reported for low-dose CT, one could argue that additional cases of lung cancer might have remained undetected considering the known difficulties in detecting nodules of low attenuation9 and the short follow-up time of 1 year. Followup of 3 to 5 years has been suggested for subsolid pulmonary nodules55 as these nodules can be slow growing lung cancers. Subsolid nodules represent an important part in lung cancer screening, and therefore one might hesitate to introduce chest tomosynthesis as a screening tool. In an additional phantom study,40 the use of chest tomosynthesis as a screening method for pulmonary nodules was evaluated and compared with CT and the authors concluded that chest tomosynthesis may be a useful alternative to CT for this purpose. However, since the results are based on a detection study performed using an anthropomorphic phantom they should be treated with caution. A recent report from the Dutch-Belgian Randomized Lung Cancer Multi-Slice Screening Trial56 pointed out that no perifissural nodules turned out to be malignant after 5.5 years of follow-up and recognition of these nodules can reduce the number of follow-up examinations. Perifissural nodules was also the example of a false positive nodule elaborated in the study on chest tomosynthesis by Rystedt et al.57 However, according to our experience it is possible to identify morphological properties of a perifissural nodule on chest tomosynthesis, when the nodule and fissure is depicted in the same image.

overestimated nodule size in comparison to the true nodule sizes.58 However, the difference was small and a recent study on patient nodules showed no systematic difference in manual nodule size measurements between CT and chest tomosynthesis.59 Additionally, it was shown that the repeatability of the measurements is comparable for the two modalities, with limits of agreement (LOA) for intraobserver variability of approximately 1.5 mm. However, the LOA between the modalities were larger than the LOA for intraobserver variability, suggesting that the two modalities should not be used interchangeably during the follow-up. Finally, in a nonblinded feasibility study on follow-up of incidentally detected nodules with chest tomosynthesis, in 29 out of 36 cases (nodules ranging from 4.5–8 mm), follow-up with chest tomosynthesis rendered the same result as follow-up with chest CT. Regarding the remaining seven cases, six nodules could not be identified on the baseline chest tomosynthesis (one ground glass opacity, i.e., GGO and five solid nodules) and additionally one nodule was incorrectly judged as growing due to motion artifacts in the follow-up chest tomosynthesis.60

Follow-up of Pulmonary Nodules In the previously described detection study by Vikgren et al,6 it was additionally found that 28% of the nodules could be identified in retrospect in the chest radiography images, while almost all the nodules (92%) were retrospectively visible in the chest tomosynthesis images. Furthermore, all nodules larger than 6 mm were reported as visible on chest tomosynthesis. This indicates that there is a potential for using chest tomosynthesis instead of CT for follow-up of incidentally detected parenchymal nodules. A phantom study of measurement accuracy on chest tomosynthesis indicated that tomosynthesis slightly underestimated and CT slightly Seminars in Respiratory and Critical Care Medicine

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Follow-up of Cystic Fibrosis In patients with cystic fibrosis, lung disease is the predominant cause of morbidity and mortality. To enable early intervention and treatment it is important to monitor the onset and progression of lung disease at an early stage. The Cystic Fibrosis Foundation recommended that chest radiographs should be obtained every 2 to 4 years for routine monitoring of clinically stable patients with cystic fibrosis and at least annually for patients who have frequent infections or declining lung function.61 Although CT has been shown to be more sensitive for detection of disease progression (e.g., increased bronchiectasis) than chest radiography or pulmonary tests62–65 the Cystic Fibrosis Foundation has not specified the use of CT to monitor the progression of lung disease due to radiation dose concerns.66 The use of chest tomosynthesis as an alternative to chest radiography has been evaluated by Vult von Steyern et al,67 who showed that chest tomosynthesis is more sensitive to cystic fibrosis changes, in particular bronchiectasis and mucus plugging, and shows them in more detail than chest radiography. An illustration of this is given in ►Fig. 2. The question whether chest tomosynthesis may replace CT remains to be answered, but concern with the radiation exposure from repeated CT scanning in follow-up of cystic fibrosis has been raised by several groups.68–70

Problem Solving When suspected pathology is detected on conventional chest radiography, the significance of which cannot be directly determined, the patient is often sent to CT for problem solving. Often, this leads to additional waiting times and recall of the patient, delaying the diagnostic procedure. The ability of chest tomosynthesis to characterize a suspected pulmonary lesion detected on chest radiography has therefore been investigated.12,71,72 The studies have shown that tomosynthesis improves diagnostic accuracy and confidence


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Fig. 2 (A–C) In the chest tomosynthesis examination (A) the bronchiectasis ~ and mucus plugging ~ are more clearly visualized than in the corresponding chest radiograph (B). A coronal CT image (C) is shown for comparison. CT, computed tomography.

in the diagnosis of suspected pulmonary lesions found on chest radiography. For example, the accuracy in classifying a lesion as pulmonary or extra pulmonary was lower than 50% for chest radiography but as high as 90% for chest tomosynthesis, using CT as reference method.71 Chest tomosynthesis also allowed excluding most pseudolesions initially considered as potential thoracic lesions on chest radiography and allowed excluding pulmonary lesions in a majority of the patients, avoiding the need for CT in 75% of the patients.12,72

of clinical use showed no additional increase in detectability, indicating that experienced thoracic radiologists are able to exploit the benefits of chest tomosynthesis for nodule detection already after a few months of clinical experience with the technique.73 In the study by Asplund et al38 it was also found, regarding the task of nodule detection, that inexperienced readers could reach a performance at the level of an experienced thoracic radiologist after participating in a dedicated learning session, described in detail in Rystedt et al.57

Learning to Use a New Modality

Use of Chest Tomosynthesis in Clinical Routine at Sahlgrenska University Hospital

The review process of a chest tomosynthesis is very similar to reading a chest CT, scrolling through the section images in cine mode. It is more time-consuming than reading a conventional chest radiography but takes less time than reading a CT.11,12 The reconstructed section images show a resemblance to both conventional chest radiographs and CT images and an observer accustomed to reading such images should with relatively moderate effort be able to take advantage of chest tomosynthesis. Several studies have focused on the learning aspects associated with chest tomosynthesis, mainly regarding the use of the technique for detecting pulmonary nodules.38,57,73 The study by Zachrisson et al73 is a follow-up study to a previous study by Vikgren et al,6 in which the performance of chest tomosynthesis was evaluated by comparing the detectability of parenchymal nodules with this method and conventional chest radiography. In a patient material containing a total of 131 nodules identified in 87 patients using CT, experienced chest radiologists managed to detect on average only 16% of the nodules using chest radiography, while the corresponding percentage using chest tomosynthesis was 56%. This substantial increase was obtained although the observers only had a limited clinical experience (6 mo) and no formal training of the new technique. The follow-up study performed after an additional year

At our hospital, chest tomosynthesis accounts for approximately 10% of the PA chest radiography production, that is, 3,000 chest tomosynthesis examinations on yearly basis. Currently there is an even distribution among clinical and radiological referrals for chest tomosynthesis, the proportion of clinical referrals having increased from just a few percent in 2007 to approximately 40% in 2009.50 As part of our clinical routine, the patient stays at the department until the initial chest radiography has been reviewed so that supplemental projections or chest tomosynthesis can be performed directly as problem solving (radiological referral). Regarding clinical referrals chest tomosynthesis is chosen as staging or followup modality in selected cases. As described above the sensitivity for detection of pathology is increased with the use of chest tomosynthesis. We have found chest tomosynthesis especially beneficial in evaluating perceived opacities on chest radiography, for rejection or confirmation of the existence of a true lesion. The apex of the lung is a known difficult region, mainly due to the overlaying skeletal structures. This region is also a common location for lung cancer. With chest tomosynthesis the region is much better visualized and an example of this scenario is given in ►Fig. 3. Another illustration, where chest tomosynthesis Seminars in Respiratory and Critical Care Medicine

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Fig. 3 (A–C) A patient with a subtle opacity in the left upper lobe seen on chest radiography (A) (arrow). The chest tomosynthesis (B) revealed the tumor (). The corresponding coronal CT image (C) is shown for comparison. CT, computed tomography.

revealed that a rounded opacity detected in the left hilum represented an intrabronchial tumor, is presented in ►Fig. 4. Occasionally a parenchymal consolidation might obscure a concurrent tumor. ►Fig. 5 shows an example of such a case where chest tomosynthesis delineated a tumor from surrounding parenchymal infiltration. Regarding pathologic changes with low density one might expect chest tomosynthesis to be less sensitive. However, our experience is that the technique might provide valuable help, for instance in detection of a pneumothorax in the presence of subcutaneous emphysema as shown in ►Fig. 6. As pointed

out by Kim et al,52 detection of cavities is improved by the use of chest tomosynthesis. ►Fig. 7 illustrates a case where even the subtle cysts of a patient with pneumothorax and lymphangioleiomyomatosis could be delineated by chest tomosynthesis. An example where chest tomosynthesis could verify the presence of cavitating lesions due to septic embolization is given in ►Fig. 8; in this case chest tomosynthesis obviated the need for CT. The patient throughput at a chest radiography/chest tomosynthesis laboratory is higher than at a CT laboratory. In our experience, performing a chest tomosynthesis for

Fig. 4 (A–C) A rounded opacity in the left hilum (A) was proven to be an intrabronchial tumor ( ) in the left main bronchus by chest tomosynthesis (B). The corresponding coronal CT image (C) is shown for comparison. CT, computed tomography. Seminars in Respiratory and Critical Care Medicine

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Fig. 5 (A and B) In the chest radiograph (A) multiple opacities in the right upper lobe were identified (arrow). The complementary chest tomosynthesis (B) delineated a tumor ( ) from the surrounding parenchymal consolidation.

problem solving provides a powerful tool for optimizing the use of CT resources as the time allocated for a chest tomosynthesis examination is roughly comparable to a chest radiography examination and the reading time for a chest tomosynthesis is shorter compared with CT.

Limitations of Chest Tomosynthesis As the projection images in tomosynthesis are acquired over a limited angular range (and not > 180 degrees as in CT), the depth resolution in the reconstructed section images is

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limited and a complete removal of superimposed tissue cannot be obtained. The limited depth resolution may lead to difficulties correctly localizing structures in the depth direction, in turn complicating clinical tasks. The difficulty in correctly localizing pleural and subpleural nodular lesions has been identified as a major problem in chest tomosynthesis images, especially in the anterior and posterior parts of the lungs, where this task is mainly affected by the limited depth resolution.38 For example, in the study by Quaia et al,71 where the higher accuracy in classifying a lesion as pulmonary or extra pulmonary for tomosynthesis than for chest radiography was shown, all pulmonary lesions misinterpreted on tomosynthesis images were located in the anterior part of the lung parenchyma close to the thoracic wall and the majority of the extrapulmonary lesions classified as pulmonary lesions on chest tomosynthesis were pleural plaques. The distinction between pleural and subpleural lesions is an important clinical task, since a pleural nodule or plaque is less likely to represent a pulmonary neoplasm than a pulmonary nodule and follow-up of pleural nodules is thus not considered mandatory. There are other difficulties associated with the limited depth resolution of chest tomosynthesis. For example, lymph nodes in hilar and mediastinal node stations may be perceived as pulmonary nodules and pulmonary nodules close to the hilum may be misinterpreted as lymph nodes. Also, small nodules located closely to vessels, especially at branching points, might be regarded as part of a somewhat tortuous vessel. Furthermore, the limited depth resolution may lead to artifacts, as objects will show up in section images they ideally should not be present in. This is of special concern when high-density objects are superimposed on tissue with low density. Asplund et al38 identified several pitfalls associated with the limited depth resolution and proposed several tips aiming at aiding the interpretation of chest

Fig. 6 (A–C) In a patient with extensive subcutaneous emphysema postoperatively and a clinical suspicion of pneumothorax, the chest radiography examination (A) could not accurately delineate the pneumothorax. The chest tomosynthesis examination (B) revealed a localized anterior pneumothorax (arrow heads), which was confirmed by CT scan (C). CT, computed tomography. Seminars in Respiratory and Critical Care Medicine

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Fig. 7 (A–C) In a patient with a pneumothorax seen on the chest radiograph (A), the cystic pattern of lymphangioleiomyomatosis could be delineated by chest tomosynthesis (arrows) (B). The corresponding coronal CT image (C) is shown for comparison. CT, computed tomography.

Fig. 8 (A–C) In a septic patient the chest radiograph (A) delineated a suspected cavitating lesion in the right upper lobe (arrow). Chest tomosynthesis confirmed the finding (B) (arrow) and depicted additional lesions (arrows) (C).

tomosynthesis images. One key finding worth mentioning is that the location of a finding should always be related to the location where the nearest skeletal structure is in focus, to evaluate whether the finding is skeletal, pleural or within the lung parenchyma. Another concern in chest tomosynthesis is motion artifacts, which are the result of the facts that the acquisition of the original projection images takes several seconds, that all projection images are used for the reconstruction of each section image, and that the chest contains organs with substantial movement (mainly the heart). Motion artifacts therefore can be relatively common in chest tomosynthesis examinations, even if the projection images are collected within one breath hold. Additionally, breathing during the image acquisition may result in severe artifacts in the section images. Kim et al74 showed that in tomosynthesis examinations with motion artifacts, the detectability of pulmonary Seminars in Respiratory and Critical Care Medicine

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nodules may not be higher than in conventional chest radiography. It is therefore of utmost importance that the radiographer before performing the chest tomosynthesis examination ensures that the patient can hold his/her breath for the time needed, in order for the examination not to result in nondiagnostic imaging due to severe breathing artifacts, exposing the patient to unnecessary radiation.

Conclusions In summary, chest tomosynthesis has proven to be a valuable imaging technique, complementing conventional chest radiography by providing section images of the patient at a very low radiation dose. The technique has been shown to be superior to chest conventional radiography for many tasks and to be able to replace CT in selected cases. It has also been shown to be an efficient problem solver in daily clinical work,


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Copyright of Seminars in Respiratory & Critical Care Medicine is the property of Thieme Medical Publishing Inc. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.

Digital tomosynthesis of the chest: current and emerging applications.

Wavelet denoising for quantum noise removal in chest digital tomosynthesis.

Functional neuroimaging: technical, logical, and social perspectives.

Ovulation induction with pulsatile gonadotropin-releasing hormone: technical modalities and clinical perspectives.

Comparison of Digital Tomosynthesis and Chest Radiography for the Detection of Noncalcified Pulmonary and Hilar Lesions.

Pulmonary nodule size evaluation with chest tomosynthesis and CT: a phantom study.

Evaluation of accuracy and precision of manual size measurements in chest tomosynthesis using simulated pulmonary nodules.

Clinical implementation of digital breast tomosynthesis.

Comparison of chest radiography, chest digital tomosynthesis and low dose MDCT to detect small ground-glass opacity nodules: an anthropomorphic chest phantom study.

Catalases as biocatalysts in technical applications: current state and perspectives.

Stationary chest tomosynthesis using a carbon nanotube x-ray source array: a feasibility study.

Effect of radiation dose level on the detectability of pulmonary nodules in chest tomosynthesis.

OVERVIEW OF A DIGITAL TOMOSYNTHESIS DEVELOPMENT: NEW APPROACHES FOR LOW-DOSE CHEST IMAGING.

Correlation of clinical and physical-technical image quality in chest CT: a human cadaver study applied on iterative reconstruction.

Digital breast tomosynthesis from concept to clinical care.

Lung cancer detection with digital chest tomosynthesis: first round results from the SOS observational study.

A dual-view digital tomosynthesis imaging technique for improved chest imaging.

Cell encapsulation: technical and clinical advances.

Robotic thoracic surgery: from the perspectives of European chest surgeons.

Image quality dependency on system configuration and tube voltage in chest tomosynthesis—a visual grading study using an anthropomorphic chest phantom.

Amebiasis: clinical and laboratory perspectives.

Comparison of patient specific dose metrics between chest radiography, tomosynthesis, and CT for adult patients of wide ranging body habitus.

VISIBILITY OF STRUCTURES OF RELEVANCE FOR PATIENTS WITH CYSTIC FIBROSIS IN CHEST TOMOSYNTHESIS: INFLUENCE OF ANATOMICAL LOCATION AND OBSERVER EXPERIENCE.

A comparison of digital tomosynthesis and chest radiography in evaluating airway lesions using computed tomography as a reference.