Published online before print August 18, 2004, 10.1148/radiol.2331030777
(Radiology 2004;233:139-148.)
© RSNA, 2004
Whole-Body MR Imaging: Evaluation of Patients for Metastases1
Thomas C. Lauenstein, MD,
Susanne C. Goehde, MD,
Christoph U. Herborn, MD,
Matthias Goyen, MD,
Carsten Oberhoff, MD,
Jörg F. Debatin, MD,
Stefan G. Ruehm, MD and
Jörg Barkhausen, MD
1 From the Departments of Diagnostic and Interventional Radiology (T.C.L., S.C.G., C.U.H., M.G., J.F.D., S.G.R., J.B.) and Obstetrics and Gynecology (C.O.), University Hospital Essen, Hufelandstrasse 55, D-45122 Essen, Germany. Received May 18, 2003; revision requested July 22; final revision received January 9, 2004; accepted February 24. Address correspondence to T.C.L. (e-mail: thomas.lauenstein@uni-essen.de).
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ABSTRACT
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PURPOSE: To compare the results of whole-body magnetic resonance (MR) imaging with staging based on computed tomographic (CT), dedicated MR imaging, and nuclear scintigraphic results as standard of reference.
MATERIALS AND METHODS: Fifty-one patients with known malignant tumors were included in the study. Patients were placed on a rolling table platform capable of moving the patient rapidly through the isocenter of the magnet bore. The thorax and the abdomen were imaged by using fast breath-hold T2-weighted sequences in the transverse plane. After intravenous administration of a paramagnetic contrast agent, three-dimensional gradient-echo data sets were collected in five stations and covered the body from the skull to the knees. Location and size of cerebral, pulmonary, hepatic, and osseous metastases were documented by two experienced radiologists. Whole-body MR imaging findings were compared with results obtained at skeletal scintigraphy, CT, and dedicated MR imaging.
RESULTS: The mean examination time for whole-body MR imaging was 14.5 minutes. All cerebral, pulmonary, and hepatic metastases greater than 6 mm in diameter could be identified with whole-body MR imaging. Small pulmonary metastases were missed with MR imaging, which did not change therapeutic strategies, but MR imaging depicted a single hepatic metastasis that was missed with CT. Skeletal scintigraphy depicted osseous metastases in 21 patients, whereas whole-body MR imaging revealed osseous metastases in 24 patients. The additional osseous metastases seen with MR imaging were confirmed at follow-up examinations but did not result in a change in therapy. Whole-body MR imaging performed on a per-patient basis revealed sensitivity and specificity values of 100%.
CONCLUSION: Whole-body MR imaging for the evaluation of metastases compared well with the reference techniques for cerebral, pulmonary, and hepatic lesions. Whole-body MR imaging was more sensitive in the detection of hepatic and osseous metastases than were the reference techniques.
© RSNA, 2004
Index terms: Cancer screening • Magnetic resonance (MR), comparative studies • Magnetic resonance (MR), technology, **.121411, **.121412, **.121413, **.1214152 • Neoplasms, diagnosis, **.30
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INTRODUCTION
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Malignant tumors are the second most common cause of death and are responsible for more than 12% of all deaths worldwide (1). Mortality rates and the success of therapeutic approaches depend mainly on the type of cancer, but they also depend on the presence of metastases. Therefore, tumor staging plays a key role for further treatment options in patients with malignant tumors. Since metastatic disease can affect different anatomic parts of the body, patients have to undergo several examinations, such as computed tomography (CT), magnetic resonance (MR) imaging, ultrasonography (US), and scintigraphy, for staging of metastases. Thus, the staging process is often both time-consuming and expensive. Furthermore, the diagnostic accuracy remains limited (2).
The high spatial resolution and excellent soft-tissue contrast make MR imaging an ideal tool for the detection of parenchymal and osseous lesions. The limited field of view restricting coverage to a single body region must be considered a major limitation of conventional MR imaging. Recently, whole-body MR imaging has been proposed for evaluation of the presence of metastases and/or for the evaluation of primary cancers (3–7).
Although theoretically highly attractive, MR imaging of tumor and metastases is hampered by severe limitations. Time-consuming repositioning of the patient and the surface coils, which is necessary for the entire body to be imaged, leads to extensively long examination times. The development of the sliding table platform (BodySURF, system for unlimited field of view; MR-Innovation, Essen, Germany) allows the imaging of different anatomic parts in rapid succession. Recently, the rolling table concept has been successfully applied for whole-body MR angiography, as well as for evaluation of the presence of metastases (4,8–11).
Furthermore, some of the proposed whole-body MR imaging approaches either were limited by long acquisition times (6) or provided only poor image quality owing to reduced spatial resolution and artifacts (5). Recently, fat-saturated three-dimensional (3D) gradient-echo sequences with nearly isotropic resolution have become available for parenchymal imaging (12). The 3D data sets are collected within a single breath hold and provide image quality comparable to that of conventional fat-saturated two-dimensional gradient-echo images (13). In a preliminary study that included eight patients, this technique was evaluated in conjunction with whole-body MR imaging (9). Although initial results are promising, there is a need for evaluation in larger patient cohorts. Thus, the purpose of our study was to compare the results of whole-body MR imaging in patients with tumors, with staging based on results of CT, dedicated MR imaging, and nuclear scintigraphy as standards of reference.
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MATERIALS AND METHODS
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From August 2001 to March 2002, 51 patients with known malignant tumors were included in the study (35 women, age range of 22–81 years, mean age of 61.5 years; 16 men, age range of 18–84 years, mean age of 58.5 years). With a Wilcoxon test, age distributions between the male and female groups failed to prove a statistically significant difference. For all patients, the diagnosis of cancer was proved histologically. Primary tumors included breast cancer (n = 16), lung cancer (n = 6), testicular cancer (n = 6), thyroid cancer (n = 5), prostate cancer (n = 4), ovarian cancer (n = 4), uterine cancer (n = 3), pheochromocytoma (n = 3), malignant melanoma (n = 2), osteosarcoma (n = 1), and non-Hodgkin lymphoma (n = 1). Exclusion criteria were based on contraindications to MR imaging, such as the presence of a cardiac pacemaker or other metallic implants. The study was conducted in accordance with guidelines set forth by the approving institutional review board. Informed consent was obtained prior to each examination.
Rapid Table Movement
Patients were examined after being placed on the rolling table platform (4,8,9) (Fig 1). This system can be mounted on top of the original patient table of the MR system (Magnetom Sonata; Siemens Medical Systems, Erlangen, Germany). For easy manual movement in the z direction, the rolling table platform is placed on roller bearings, which are easily installed on the patient table. Signal reception is accomplished by using two elements of the spine coil, which are integrated into the rolling patient table, and the body phased-array coil, which remains stationary because it is attached to the original patient table. Positioned on the BodySURF platform, the patient glides through the isocenter of the magnet bore, as well as over the spine coil and under the body phased-array coil. Hence, different anatomic regions can be imaged with surface coil quality in rapid succession without changing the position of the coils. By means of a rastering device, the data acquisition is possible in defined and reproducible positions.
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Figure 1. Patients are placed in supine position on the rolling table platform (left) that is capable of pulling the patient through the magnet bore and a phased-array surface coil (right). The rolling table platform is mounted on top of the original patient table. Signal reception is accomplished by using two elements of the spine coil integrated in the patient table and the body phased-array coil, which remains stationary because it is attached to the patient table within the bore. For demonstration purposes, the phased-array coil is not placed in the center of the magnet.
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MR Imaging
The thorax and the abdomen were imaged in two subsequent breath holds by means of a T2-weighted half-Fourier rapid acquisition with relaxation enhancement (RARE) (HASTE; Siemens Medical Systems) with fat suppression. After intravenous injection of a paramagnetic contrast agent (gadopentetate dimeglumine, Magnevist; Schering, Berlin, Germany) at a dose of 0.2 mmol per kilogram of body weight and a flow rate of 3 mL/sec, seven breath-hold contrast material–enhanced 3D gradient-echo data sets were acquired in rapid succession (Fig 2). The first two 3D data sets, with a delay of 20 and 60 seconds after contrast agent administration, covered the upper abdomen, encompassing the entire liver. Subsequently, the rolling table platform was moved manually to the chest region where the next 3D data set was collected. The 8 seconds required to move the platform was used to provide breathing instructions. Subsequently, the platform was moved to permit the acquisition of transverse 3D data sets of the pelvis, the proximal femur, and the skull. Finally, the platform was moved back to the upper abdomen, where a third abdominal data set was collected in the equilibrium phase. Since the 3D data set covered 31.4 cm in the z direction, the table was moved in 27-cm steps from one region to another to ensure coverage of the entire body. All imaging parameters are listed in Table 1.
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Figure 2. Imaging protocol of the 3D gradient-echo sequence. After intravenous administration of a paramagnetic contrast agent, 3D data sets of the abdomen are acquired in early arterial and portal venous phases. Subsequently, the rolling table platform is moved to the thorax, pelvis, femur, skull, and back to the abdomen to acquire data sets in an equilibrium contrast phase.
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Reference Standard
For brain imaging, all patients underwent dedicated contrast-enhanced CT. Because of clinical indications, an additional dedicated MR examination of the brain was performed in 22 patients. T1-weighted turbo spin-echo (repetition time msec/echo time msec of 500/14, 70° flip angle, acquisition time of 172 seconds) and T2-weighted turbo spin-echo (5120/104, 150° flip angle, acquisition time of 53 seconds) sequences were performed. A T1-weighted turbo spin-echo (525/17, 70° flip angle, acquisition time of 180 seconds) sequence was performed 8 minutes after the intravenous injection of gadopentetate dimeglumine at a dose of 0.1 mmol/kg. To visualize the thorax and abdomen, dedicated contrast-enhanced CT scans were obtained in all 51 subjects. All CT examinations were performed with a multisection scanner (Somatom Volume Zoom; Siemens Medical Systems). Examination parameters are listed in Table 2.
For imaging of the skeletal system, whole-body skeletal scintigraphy was performed. Standard skeletal radionuclide scintigraphy was performed by using a planar one-phase technique. Three hours after the intravenous administration of technetium 99m-labeled methylene diphosphonate, images were obtained by using a thin-section dual-head whole-body scanner (Body-Scan; Siemens Medical Systems) with a low-energy collimator (full width at half maximum, 5–8-mm resolution). All examinations were performed within 8 days before or after whole-body MR imaging.
Data Analysis
The examination and interpretation times for whole-body MR imaging were measured (T.C.L., S.C.G.) with a stopwatch. Image interpretation was performed by using a postprocessing workstation (Virtuoso; Siemens Medical Systems). Images from the RARE sequences were read in a two-dimensional mode, whereas the 3D data sets were analyzed by using multiplanar reformation. Images were evaluated for the presence of contrast-enhanced lesions on T1-weighted images and/or of high-signal-intensity lesions with use of the RARE sequence, potentially indicating metastatic disease. Metastases were numerically quantified for the lung, the liver, and the brain. Findings were divided into two groups according to each anatomic region: those with 1–10 metastases and those with more than 10 metastases. The diameter of the smallest metastasis of each anatomic region was measured. Apart from the cerebral, pulmonary, and hepatic metastases, images were analyzed for the presence of other metastases, such as adrenal gland or lymph node metastases.
For the assessment of osseous metastases, the skeletal system was divided into six regions: head, sternum/clavicle/scapula, ribs, spine, pelvis, and femur. The evaluation of MR images was performed both on a per-patient and on a per-region basis.
Each whole-body MR imaging examination was evaluated by two radiologists (T.C.L., J.B.) with more than 4 years of experience in MR imaging, who independently read the images. Discrepancies were resolved by a consensus reading. CT scans and bone scintigrams were evaluated by two radiologists (S.G.R., C.U.H.) and two experienced nuclear medicine physicians. All reviewers had access to patient information, which included age, sex, and primary tumor, but they were blinded to the results of the other imaging modalities. Findings of the reference examinations were analyzed according to those of whole-body MR imaging: For brain, thorax, and abdomen, presence of metastases was quantitatively and qualitatively documented. Results of bone scintigraphy were analyzed on a per-patient and per-region basis.
Clinical Follow-up
Information regarding the clinical follow-up of all patients was collected (T.C.L., J.B.) 6 months after inclusion into the study. In addition, all discrepant findings between the reference techniques and whole-body MR imaging were resolved with follow-up examinations that included CT, dedicated MR imaging, and scintigraphy performed 3–9 months after the whole-body MR examination. All follow-up examinations were clinically indicated.
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RESULTS
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The mean examination time for whole-body MR imaging was 14.5 minutes ± 2.8 (standard deviation) and included the time for patient positioning and the acquisition of all data sets. The average interpretation time for the MR data was 11.5 minutes ± 1.6. Figure 3 shows an example of a patient with a malignant melanoma, with metastatic disease in different organs.
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Figure 3. Reformatted coronal images of transverse T1-weighted gradient-echo data sets (3.1/1.17, 30° flip angle) in a 67-year-old man with malignant melanoma. Cerebral metastases (1), pulmonary metastasis (2), and metastasis in the right adrenal gland (3) were detected at whole-body MR imaging.
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Whole-body MR imaging depicted metastases in 43 of 51 patients, whereas the reference techniques depicted metastases in 42 patients. In one patient with thyroid cancer, a single hepatic lesion, which had been missed with CT, could be visualized with whole-body MR imaging. This patient did not show any other metastatic disease. Subsequently, resection was performed, and the diagnosis of a single hepatic metastasis was histologically confirmed. Whole-body MR images or images from the reference techniques did not show any metastatic disease in eight of 51 patients. All of the eight patients had no evidence of metastases at the follow-up 6 months later.
Analysis of Parenchymal Organs
Table 3 provides an overview of all parenchymal metastases detected with whole-body MR imaging and the reference examinations. Whole-body MR imaging and dedicated brain examinations depicted cerebral metastases in eight and seven patients, respectively. Whole-body MR imaging depicted a total of 24 cerebral metastases. The reference examinations confirmed 23 of the 24 metastases (Fig 4). No additional metastases were detected at CT or dedicated MR imaging. In one patient with uterine cancer, whole-body MR imaging depicted a single cerebral metastasis. This lesion was determined to be a large pacchionian granulation at dedicated cerebral MR examination, and results of the follow-up examination showed no evidence of cerebral metastatic disease. However, this patient had abdominal metastases, and therefore the false-positive cerebral lesions did not result in a change in therapeutic strategy based on whole-body MR imaging results.
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Figure 4a. MR images in a 48-year-old woman with breast cancer. A single cerebral metastasis (arrow) was detected on (a) transverse whole-body image (3.1/1.17, 30° flip angle) and was confirmed on (b) dedicated contrast-enhanced image (525/17, 70° flip angle).
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Figure 4b. MR images in a 48-year-old woman with breast cancer. A single cerebral metastasis (arrow) was detected on (a) transverse whole-body image (3.1/1.17, 30° flip angle) and was confirmed on (b) dedicated contrast-enhanced image (525/17, 70° flip angle).
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Pulmonary metastases were seen at whole-body MR imaging and CT in 17 and 18 patients, respectively (Fig 5). In one patient with a single metastasis at CT, MR imaging failed to depict this pulmonary mass. However, additional skeletal metastases were found in this patient. Hence, the false-negative finding at whole-body MR imaging would not have altered the therapeutic concepts. Thoracic CT and whole-body MR imaging depicted more than 10 pulmonary metastases in a total of three patients. In an additional 14 patients, whole-body MR imaging revealed a total of 39 metastases. T2-weighted imaging depicted three pulmonary metastases, which had not been visualized by using the contrast-enhanced gradient-echo sequence (Fig 6). All lesions were confirmed with the reference CT examination, but 12 additional lung lesions were also found. Pulmonary metastases depicted at CT but missed at whole-body MR imaging were confirmed in all cases at clinical follow-up, that is, subsequent examinations in 10 of 12 cases. The two remaining lung lesions were retrospectively rated as scar tissue. All pulmonary metastases missed at MR imaging were smaller than 6 mm in diameter, and therapeutic strategies would not have been changed in these patients owing to the presence of further metastatic disease.
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Figure 5a. Images in a 55-year-old man with thyroid cancer. Pulmonary metastases (arrows) were depicted at transverse whole-body MR imaging by using (a) contrast-enhanced 3D gradient-echo (3.1/1.17, 30° flip angle) and (b) T2-weighted RARE (1200/60, 150° flip angle) sequences. (c) Corresponding CT scan confirms the results.
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Figure 5b. Images in a 55-year-old man with thyroid cancer. Pulmonary metastases (arrows) were depicted at transverse whole-body MR imaging by using (a) contrast-enhanced 3D gradient-echo (3.1/1.17, 30° flip angle) and (b) T2-weighted RARE (1200/60, 150° flip angle) sequences. (c) Corresponding CT scan confirms the results.
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Figure 5c. Images in a 55-year-old man with thyroid cancer. Pulmonary metastases (arrows) were depicted at transverse whole-body MR imaging by using (a) contrast-enhanced 3D gradient-echo (3.1/1.17, 30° flip angle) and (b) T2-weighted RARE (1200/60, 150° flip angle) sequences. (c) Corresponding CT scan confirms the results.
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Figure 6a. Transverse images in a 71-year-old woman with ovarian cancer. (a) While pulmonary metastases were not detected with 3D gradient-echo MR sequence (3.1/1.17, 30° flip angle), (b) single pulmonary metastasis (arrow) was detected with T2-weighted RARE sequence (1200/60, 150° flip angle).
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Figure 6b. Transverse images in a 71-year-old woman with ovarian cancer. (a) While pulmonary metastases were not detected with 3D gradient-echo MR sequence (3.1/1.17, 30° flip angle), (b) single pulmonary metastasis (arrow) was detected with T2-weighted RARE sequence (1200/60, 150° flip angle).
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Whole-body MR imaging and CT depicted hepatic metastatic disease in 18 and 16 patients, respectively. More than 10 hepatic metastases were detected in two patients with both techniques. In an additional 16 patients, whole-body MR imaging depicted a total of 63 hepatic metastases (Fig 7). CT depicted 46 metastases in 14 patients. In two patients with hepatic lesions detected at whole-body MR imaging, CT did not depict any hepatic metastasis. One of these two patients had a single hepatic metastasis, which led to therapeutic changes. In the other patient with three hepatic metastases depicted only at MR imaging, chemotherapy was performed owing to additional metastatic disease. The 17 additional hepatic lesions detected at MR imaging but missed at CT turned out to be metastases at follow-up examinations.
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Figure 7a. Images in a 51-year-old woman with breast cancer. A single hepatic metastasis arrow) was found in the right hepatic lobe at both (a) transverse whole-body MR (3.1/1.17, 30° flip angle) and (b) CT imaging.
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Figure 7b. Images in a 51-year-old woman with breast cancer. A single hepatic metastasis arrow) was found in the right hepatic lobe at both (a) transverse whole-body MR (3.1/1.17, 30° flip angle) and (b) CT imaging.
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Osseous Metastases
Whole-body MR imaging depicted osseous metastases in 24 patients, whereas skeletal scintigraphy revealed metastases in 21 patients (Table 4, Fig 8). Three patients with osseous metastases at the MR examination were determined to be free of osseous metastases at scintigraphy. However, presence of osseous metastases did not alter therapy in these three patients. Main discrepancies between scintigraphic and MR imaging findings were related to the anatomic region of osseous lesions: Whole-body MR imaging did not depict a considerable number of metastases in the skull and the ribs but depicted more lesions in the spine, the pelvis, and the femur (Table 4, Fig 9). A clinical follow-up was not possible in all patients with discrepant findings because of patient death. In four patients with additional metastases in the spine or pelvis, findings of clinical follow-up confirmed the results of whole-body MR imaging.
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Figure 8a. Images in a 49-year-old woman with breast cancer. Transverse T1-weighted whole-body MR images (3.1/1.17, 30° flip angle) depict osseous metastases in (a) the lumbar spine (left arrow) and pelvis (right arrow). (b) Skeletal scintigrams helped confirm the metastases (arrows).
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Figure 8b. Images in a 49-year-old woman with breast cancer. Transverse T1-weighted whole-body MR images (3.1/1.17, 30° flip angle) depict osseous metastases in (a) the lumbar spine (left arrow) and pelvis (right arrow). (b) Skeletal scintigrams helped confirm the metastases (arrows).
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Figure 9a. Images in a 22-year-old woman with thyroid cancer. Osseous metastases (arrows) were visualized as lesions with high signal intensity on transverse T1-weighted whole-body MR images (3.1/1.17, 30° flip angle) in the (a) lumbar spine and (b) pelvis. (c) Skeletal scintigrams do not depict metastases; they were proved at follow-up studies.
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Figure 9b. Images in a 22-year-old woman with thyroid cancer. Osseous metastases (arrows) were visualized as lesions with high signal intensity on transverse T1-weighted whole-body MR images (3.1/1.17, 30° flip angle) in the (a) lumbar spine and (b) pelvis. (c) Skeletal scintigrams do not depict metastases; they were proved at follow-up studies.
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Figure 9c. Images in a 22-year-old woman with thyroid cancer. Osseous metastases (arrows) were visualized as lesions with high signal intensity on transverse T1-weighted whole-body MR images (3.1/1.17, 30° flip angle) in the (a) lumbar spine and (b) pelvis. (c) Skeletal scintigrams do not depict metastases; they were proved at follow-up studies.
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Other Metastases
Apart from cerebral, pulmonary, and hepatic metastases, other lesions presumed to be metastases were detected. Four patients had lesions in the adrenal glands that were assumed to be metastases. Fifteen patients were determined to have lymph node metastases: 10 (4) patients with mediastinal (abdominal) lymph node metastases and one patient with both thoracic and abdominal metastatic disease. All findings were confirmed on the corresponding CT scans. In one additional patient, mediastinal lymph node metastases, which had not been detected at MR imaging, were seen at CT. The additional mediastinal lesion found at CT turned out to be a metastasis owing to an increasing size at follow-up. Six additional metastases in the cutis and/or subcutis were found with MR imaging in two patients, one with malignant melanoma and one with breast cancer. Two of these metastases had been missed at CT.
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DISCUSSION
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On the basis of our study findings, we have two messages we believe to be important. First, whole-body MR imaging in less than 15 minutes is feasible for tumor staging. Second, whole-body MR imaging provides good agreement with the conventional diagnostic methods for depicting metastases and even proved to be more sensitive for hepatic and skeletal metastases than did the corresponding reference examinations.
None of the 43 patients with proved metastatic disease were deemed to be free of metastases with whole-body MR imaging. Eight patients were correctly classified to be free of metastases. Certainly there are differences concerning the sensitivity of metastasis detection, depending on the anatomic region. Thus, more hepatic metastases could be detected with use of whole-body MR images than with related CT scans because our whole-body approach includes breath-hold fat-suppressed T2-weighted imaging of the liver and a dynamic T1-weighted data acquisition after contrast agent injection, which has been shown to be the most accurate tool for noninvasive detection and characterization of hepatic mass lesions (14,15).
In contrast, the presented whole-body approach missed several pulmonary lesions detected at CT. However, all pulmonary nodules missed at MR imaging were smaller than 6 mm in diameter. These small lesions have only a minor effect on therapeutic strategies, because even thin-section CT cannot help in distinguishing between benign and metastatic lesions (16), and the definite diagnosis can frequently be made only by means of increased lesion size at follow-up examinations.
Compared with the results of a previous study in which only T1-weighted images were used (9), the presented whole-body approach provides certain improvements regarding lung imaging. Recently, the effect of fast T2-weighted sequences in MR imaging of the lungs has been documented (17,18). Pulmonary metastases as small as 3 mm in diameter and primary cancers of the lung could be detected (17). Therefore, we added this sequence to our whole-body protocol, and these T2-weighted images helped to detect three pulmonary masses missed with the 3D gradient-echo sequence. A further improvement of MR lung imaging can be achieved in the future by using parallel acquisition techniques such as sensitivity encoding, or SENSE, or simultaneous acquisition of spatial harmonics, or SMASH. These techniques allow data acquisition with an increased spatial and/or temporal resolution but without the need of increasing the acquisition time (19,20). Hence, both 3D gradient-echo and two-dimensional turbo spin-echo sequences might provide a higher sensitivity for pulmonary mass detection when applied in conjunction with parallel acquisition techniques.
Concerning skeletal imaging for osseous metastasis detection, the interpretation of the presented findings is more complex. All results of this trial show that a higher number of osseous metastases was detected with MR imaging than with skeletal scintigraphy. Regarding the detection of osseous metastases, there are distinct regional advantages and disadvantages of both techniques. Scintigraphy provides a rapid overview of the skeletal system. The technique proves more sensitive in the assessment of the ribs, the scapula, and the skull. However, MR imaging permits a better detection of osseous metastases located in the spine and pelvis; even for osseous metastases from primary tumors characterized by increased tracer accumulation, several studies have documented a poor sensitivity of planar skeletal scintigraphy in the spine and pelvis (21,22).
To date, most whole-body MR imaging concepts have failed to be implemented in the clinical routine for metastases depiction. Long examination times and reduced accuracy regarding metastases detection have been the main reasons. Horvath et al (5) proposed a whole-body approach on the basis of the acquisition of T2-weighted echo-planar imaging data. Nineteen patients with newly diagnosed breast cancer were imaged. MR findings were compared with those of chest radiography, CT, US, and skeletal scintigraphy. Metastatic disease was found in six of 19 patients with use of the reference examinations, whereas metastases were depicted in eight patients with use of whole-body MR imaging. However, a low signal-to-noise ratio, which results in reduced spatial resolution owing to data acquisition with a body coil and magnetic susceptibility artifacts, must be considered as a major limitation of this approach.
A different approach of whole-body MR imaging has been proposed by Walker et al (6). Seventeen patients with breast cancer and suspected of having metastatic disease were examined. For MR imaging, a turbo short inversion time inversion-recovery sequence of the thorax, abdomen, and pelvis was performed without any devices for rapid table movement. The brain was imaged with a dedicated T1-weighted spin-echo sequence before and after contrast agent administration. Although this imaging concept provided a good correlation with reference imaging tools, the time-consuming repositioning of the patient and the surface coils, which resulted in a long examination time, casts doubt over the practicability of this approach in a clinical routine.
We are convinced that the presented whole-body concept overcomes the mentioned limitations. Breath-hold 3D gradient-echo data sets combined with the BodySURF device provide high-spatial-resolution images and a short examination time. The sliding table platform with integrated phased-array surface coils provides high image quality, with excellent signal-to-noise ratio throughout all stations. In addition, the examination time is minimized by obviating patient and coil repositioning. Hence, this whole-body MR imaging approach includes all properties needed for metastasis depiction and its clinical implementation; it is fast, provides high-quality MR data, and allows a reliable detection of metastatic disease in different organ systems.
The lack of a true standard is an important limitation of our study because not all metastases were histologically proved. Indeed, it would have been desirable to clarify at least all discrepant findings of whole-body MR imaging and the reference techniques with surgery or biopsy. However, this was not possible for ethical reasons, since most additional findings did not change the therapeutic strategies. Therefore, in the majority of patients, follow-up examinations had to be used to resolve discrepancies.
Of course, whole-body MR imaging cannot replace dedicated MR examinations, which provide different contrast mechanisms for the examination of individual organ systems. However, the described strategy focuses on the detection of metastatic lesions in patients with known primary tumors and on follow-up. Because of the promising results of this study, we are convinced that whole-body MR imaging with use of a rolling table platform in conjunction with fast T2-weighted turbo spin-echo and 3D gradient-echo sequences is a time-saving and accurate alternative to conventional multimodality evaluation of patients with tumors for metastases.
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FOOTNOTES
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2**. Multiple body systems 
Abbreviations: RARE = rapid acquisition with relaxation enhancement,
3D = three-dimensional
Authors stated no financial relationship to disclose.
Author contributions: Guarantors of integrity of entire study, T.C.L., S.C.G., S.G.R., J.B.; study concepts and design, T.C.L., S.C.G., J.F.D., S.G.R., J.B.; literature research, T.C.L.; clinical studies, T.C.L., S.C.G., C.U.H., M.G.; data acquisition, T.C.L., C.U.H., M.G.; data analysis/interpretation, T.C.L., S.C.G., C.U.H., S.G.R., J.B.; statistical analysis, S.C.G., J.B.; manuscript preparation, C.O., T.C.L., C.U.H., M.G.; manuscript editing, T.C.L., S.C.G., S.G.R., J.F.D., J.B.; manuscript definition of intellectual content, revision/review, and final version approval, all authors
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ABSTRACT
INTRODUCTION
