Planning treatment for patients with cancer relies heavily on imaging information to establish tumor stage at presentation and to assess tumor response to treatment. It is also becoming increasingly desirable to define precisely the tumor target to deliver various forms of local treatment as accurately as possible. Because different imaging modalities have different inherent soft tissue contrast properties, use of several imaging modalities in a stepwise approach is common.
Computed tomography (CT) is the most commonly used technology in the evaluation of patients with cancer. Advances in technology of spiral CT with multiple detectors has significantly improved its efficacy and allows for rapid image acquisition of large parts of the body with thin slices during a single breath hold and, if desired also for whole-body scanning. However, the soft tissue contrast properties of CT for tumor staging are limited in terms of tumor delineation and metastases detection, even when intravenous contrast enhancement is used.1 The introduction of integrated positron emission tomography (PET) and CT (PET/CT) scanners is a potentially ideal solution to circumvent this limitation. This technology adds functional tumor information obtained through injection of radiolabeled metabolites, most notably the glucose analog tracer [18F]-fluorodeoxyglucose. Areas of increased metabolic uptake identified by PET can now be combined with superior spatial resolution of CT. The strength of this approach is further augmented if combined whole-body scanning can be performed in an acceptable imaging time.
Magnetic resonance imaging (MRI) has traditionally been regarded as a strictly directed examination performed to answer focused clinical questions in limited anatomical areas of the body. Recent improvements in MRI software and hardware have extended the applicability of this diagnostic technology. The introduction of phased-array surface coils that allow for high-resolution imaging has become a standard for MRI.2 However, due to magnetic field homogeneity requirements, the acquisition of magnetic resonance images is still limited to a field of view of no more than 50 cm in one patient table position. The introduction of a rolling bed patient platform permits scanning of larger parts of the body in different series of images in consecutive anatomical positions and even enables whole-body imaging to be performed without time-consuming stepwise manual repositioning of the patient. This approach is used for single session whole-body contrast-enhanced magnetic resonance angiography,3 whole-body skeletal metastases screening,4 magnetic resonance autopsy,5 -Â 6 or whole-body tumor staging.7
The day in which futuristic movies show a patient lying on a table, entering a tunnel-like device with blinking lights, only to return a few moments later with a rapid diagnosis and a specific treatment plan, does not seem as far away as once thought. Based on the article by Antoch and colleagues8 in this issue of THE JOURNAL, it appears that the wheels of progress already have been set in motion to realize this futuristic diagnostic approach.
The dual-imaging modality PET/CT is a relatively new investigation method that has not been extensively studied. PET/CT has been studied mostly in patients with lung cancer. A few studies have evaluated local recurrence of different tumors and primary head and neck tumors.9 Only a limited number of studies have reported use of whole-body MRI in malignancy.10 -Â 14 Only 2 studies4 ,15 have compared whole-body MRI with other imaging modalities.
The article by Antoch et al is the first to report a side-by-side comparison of 2 whole-body imaging modalities in patients with a heterogeneous group of tumors with the aim to detect metastases at any site. Furthermore, it is the first study that includes some elements of local staging (ie, T- and N-staging) when the final results are evaluated. The study was performed in a university hospital setting by experienced investigators who have carefully studied 98 patients with different forms of malignancy. Antoch et al present the classification of primary tumor, regional lymph nodes, and distant metastasis (overall TNM stage) and its impact on patient treatment planning. The authors conclude that PET/CT seems to be more efficacious than MRI in TNM staging and should be regarded as the first choice for whole-body tumor staging.
This study includes a large proportion of patients with lung cancer and it is possible that some of the greater accuracy observed with PET/CT compared with MRI is explained by inclusion of the high number of patients with pulmonary tumors. T-staging in lung cancer is based primarily on 3 factors: tumor size, localization (in relation to bronchial tree and hilus), and involvement of adjacent structures. The presence of air as a favorable contrast medium, the dependence of the T-staging on simple factors such as tumor size and proximity to the hilus, the lower cost of CT (in comparison with MRI), and the relative immunity to different types of motion artifacts with ultrafast scanners have made CT the imaging choice for detecting lung cancer.16
In addition to using rather thick sections (7 mm), the MRI protocol in this study was quite extensively designed with both T1- and T2-weighted images as well as whole-body postcontrast images. However, the authors used thinner sectioning with CT (5 mm) compared with MRI. Future studies that use state-of-the-art MRI at the site of primary tumor might show different results in T-staging.
One of the most important, if not the only, indication for whole-body imaging is the search for metastases. Somewhat surprisingly, results of MRI reported by Antoch et al were comparable with PET/CT. Only a handful of articles have dealt with whole-body MRI as a tool to detect distant metastasis.4 ,10 ,17 Most if not all of the published work on whole-body MRI reports on the comparison between bone-scintigraphy and whole-body MRI in bone metastasis.10 ,17
Decisions about use of imaging modalities also involve cost considerations. At the institution where the authors work, the cost for the 2 diagnostic investigations was almost identical. The costs reported by the authors are those charged for each individual examination. However neither PET/CT nor whole-body MRI is available at most centers, and even more rarely are they both available at the same center. Costs for installation and maintenance are not trivial and are not included in this cost analysis, and differ greatly depending on country and continent.
Radiologists are also interested in knowing the amount of time spent for image analysis. While this variable is difficult to measure, especially in the setting of a clinical trial, it seems that interpretation of images produced by MRI generally would take a longer time than PET/CT.
The article by Antoch et al is the first comparative study of 2 relatively new imaging modalities, PET/CT and whole-body MRI. For most clinicians accustomed to step-by-step or multimodality approaches, introduction of PET/CT or whole-body MRI as the first line of investigation would lead to significant changes in the management of patients with cancer. While these results are intriguing, additional studies are needed to establish the role of whole-body imaging for tumor staging in oncology practice.
Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature
Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
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