Diagnostic accuracy of nodal enhancement pattern of rectal cancer at MRI enhanced with ultrasmall superparamagnetic iron oxide: findings in pathologically matched mesorectal lymph nodes.

OBJECTIVE: The purpose of this study was to evaluate the diagnostic accuracy of the pattern of nodal enhancement at MRI enhanced with ultrasmall superparamagnetic iron oxide (USPIO) in the nodal classification of rectal cancer in pathologically matched mesorectal lymph nodes. SUBJECTS AND METHODS: Twenty-five patients with adenocarcinoma of the rectum underwent prospective evaluation with 3-mm axial T2-weighted and USPIO-enhanced T2*-weighted MRI before surgery. Mesorectal nodes visible at in vivo MRI were independently scored by two radiologists as malignant or nonmalignant according to morphologic criteria (irregular nodal contour, heterogeneous signal intensity) on T2-weighted MR images and according to USPIO enhancement pattern on T2*-weighted MR images. The sensitivity, specificity, and positive and negative predictive values of morphologic and USPIO criteria in identification of malignancy in the pathologically matched mesorectal nodes were compared by use of the McNemar test. Interobserver agreement was compared by use of kappa statistics. RESULTS: After surgery, radiologic-pathologic comparison of 126 mesorectal nodes (116 benign, 10 malignant) was possible. Use of morphologic criteria resulted in an average sensitivity of 65% (95% CI, 35-88%); specificity, 75% (67-83%); positive predictive value, 19% (8-34%); and negative predictive value, 96% (91-99%). Use of USPIO criteria resulted in an average sensitivity of 65% (95% CI, 35-88%); specificity, 93% (87-96%); positive predictive value, 43% (21-67%); and negative predictive value, 97% (92-99%). Use of USPIO MRI improved diagnostic specificity for both observers (p < 0.01). Interobserver agreement was fair for morphologic criteria (kappa = 0.39) but good for USPIO criteria (kappa = 0.68). CONCLUSION: Use of the pattern of USPIO enhancement had higher diagnostic specificity than but the same sensitivity as morphologic findings in pathologically matched mesorectal lymph nodes.

Diagnostic accuracy of serial CT/magnetic resonance imaging review vs. positron emission tomography/CT in colorectal cancer patients with suspected and known recurrence.

PURPOSE: This study examined the sensitivity and specificity of CT/magnetic resonance imaging serial review compared to fluoro-2-deoxy glucose positron emission tomography-CT scanning to optimize colorectal cancer follow-up. PATIENTS AND METHODS: Using standardized proformas, three blinded radiologists reviewed serial CT and magnetic resonance imaging in suspected cases of colorectal cancer recurrence in patients undergoing fluoro-2-deoxy glucose positron emission tomography-CT imaging. RESULTS: Fifty eligible patients were included in the review. On follow-up, 23 patients had positive and 27 patients had negative diagnoses for colorectal cancer recurrence. Serial imaging review reduced the number of equivocal studies from 20 to 4 and unexplained carcinoembryonic antigen elevations from 17 to 10. Using fluoro-2-deoxy glucose positron emission tomography-CT, the number of equivocal studies reduced from 20 to 6 and unexplained carcinoembryonic antigen elevations reduced from 17 to 10. Fluoro-2-deoxy glucose positron emission tomography-CT altered management in 8 percent of patients (4/50, 95 percent CI, 0-16 percent). No significant differences were found between accuracy, sensitivity and specificity upon comparison of serial imaging review and fluoro-2-deoxy glucose positron emission tomography-CT in detecting recurrent disease. Extra information was demonstrated on 18 fluoro-2-deoxy glucose positron emission tomography-CT compared to serial imaging review in 8 of 50 patients and one patient had a positive incidental finding. CONCLUSIONS: With suspected recurrence, we recommend undertaking serial imaging review with careful correlation of suspicious findings with previous studies. Fluoro-2-deoxy glucose positron emission tomography-CT imaging was useful when findings remain equivocal after serial imaging review for colorectal cancer recurrence.

The role of imaging in the diagnosis, staging, and management of testicular cancer.

OBJECTIVE: The objective of this article is to describe recent developments in imaging patients with testicular germ cell tumors (GCTs). CONCLUSION: Most patients with testicular GCTs can now be expected to be cured, so the focus on management moves toward identifying patients who need more aggressive treatment and avoiding long-term complications. CT remains central in the selection of a management strategy, although the roles of MRI and PET continue to evolve.

Predicting response of colorectal hepatic metastasis: value of pretreatment apparent diffusion coefficients.

OBJECTIVE: The purposes of this study were to determine whether the pretreatment apparent diffusion coefficients (ADCs) of hepatic metastatic lesions from colorectal cancer are predictive of response to chemotherapy and to compare the ADCs of metastatic lesions before and after chemotherapy. SUBJECTS AND METHODS: Twenty patients with potentially operable hepatic lesions larger than 1 cm in diameter metastatic from colorectal carcinoma were prospectively evaluated with diffusion-weighted imaging at three b values before and after chemotherapy. Quantitative ADC maps were calculated with images with b values of 0, 150, and 500 s/mm2 (ADC0-500) and with images with b values of 150 and 500 s/mm2 (ADC150-500). Regions of interest were drawn around metastatic lesions and randomly over liver. The mean ADC0-500 and mean ADC150-500 of metastatic lesions before and after chemotherapy were compared according to response defined by Response Evaluation Criteria in Solid Tumors criteria. RESULTS: Twenty-five responding and 15 nonresponding metastatic lesions were evaluated. Nonresponding lesions had a significantly higher pretreatment mean ADC0-500 and mean ADC150-500 than did responding lesions (Mann-Whitney U test, p < 0.002). There was a linear regression relation (r2 = 0.34, p = 0.02) between percentage size reduction of metastatic lesions and pretreatment mean ADC150-500. After chemotherapy, responding lesions had a significant increase in mean ADC0-500 and ADC150-500 (Wilcoxon's signed rank, p = 0.025). No significant change was observed in nonresponding metastatic lesions (Wilcoxon's signed rank, p > 0.5) or in normal liver parenchyma (Wilcoxon's signed rank, p > 0.4). CONCLUSION: High pretreatment mean ADC0-500 and mean ADC150-500 of colorectal hepatic metastatic lesions were predictive of poor response to chemotherapy. A significant increase in mean ADC0-500 and ADC150-500 was observed in metastatic lesions that responded to chemotherapy. These findings may have implications for development of individualized therapy.

Diagnostic accuracy of rim and segmental MRI enhancement of colorectal hepatic metastasis after administration of mangafodipir trisodium.

OBJECTIVE: The purpose of this study was to determine the diagnostic accuracy of rim and segmental MRI enhancement of hepatic metastasis of colorectal cancer after administration of mangafodipir trisodium (MnDPDP). SUBJECTS AND METHODS: Sixty-one patients with a potentially resectable hepatic metastasis of colorectal cancer consecutively underwent breath-hold T1-weighted MRI in the axial and coronal planes 30 minutes and 24 hours after administration of MnDPDP. For each lesion, the presence or absence of rim enhancement and segmental enhancement 30 minutes and 24 hours after contrast administration was recorded. These features were evaluated separately for lesions 10 mm in diameter or larger and lesions smaller than 10 mm. The nature of each lesion was determined at histopathologic examination (n = 29) and on follow-up imaging (n = 32). RESULTS: Two hundred thirty lesions were identified at MRI: 210 lesions were metastatic, and 20 were benign. Rim enhancement was observed around 22 of 210 (10%) of the metastatic lesions at 30 minutes and 199 of 210 (95%) of metastatic lesions at 24 hours. Rim enhancement at 24 hours had 94.8% (95% CI, 91.8-97.8%) sensitivity, 90.0% (68.3-98.8%) specificity, 99.0% (97.6-100%) positive predictive value, 62.1% (42.3-79.3%) negative predictive value, and 94.3% (91.4-97.3%) diagnostic accuracy for metastasis. Segmental enhancement was infrequently seen (34/210; 16%) at 24 hours but had 100% (89.7-100%) positive predictive value for metastasis. CONCLUSION: Rim and segmental enhancement at MRI 24 hours after MnDPDP administration enabled accurate characterization of hepatic colorectal metastasis. These features may aid in preoperative mapping of hepatic tumor burden and disease distribution in patients with colorectal cancer.

Prediction of clinicopathologic response of breast cancer to primary chemotherapy at contrast-enhanced MR imaging: initial clinical results.

PURPOSE: To prospectively document changes in contrast agent kinetics in patients with primary breast cancer treated with systemic chemotherapy after one or two cycles and to determine whether kinetic measures can be used to predict final clinicopathologic response. MATERIALS AND METHODS: Institutional committees on clinical research and ethics approval and patient consent were obtained. Dynamic magnetic resonance (MR) examinations were performed in 25 women with primary breast cancer before treatment and after the first (n = 21) and second (n = 15) cycle of neoadjuvant chemotherapy. Kinetic parameters (transfer constant, leakage space, and rate constant) were derived for whole tumor regions of interest. Changes in histogram distributions of pixel data (median value and range) and MR imaging-derived size were correlated with final clinical and histologic response by using nonparametric methods. Receiver operating characteristic (ROC) analysis of tumor size and transfer constant changes were used to identify patients in whom no benefit was gained from chemotherapy. RESULTS: After the first cycle of treatment, 12 of 14 clinical responders showed decreases in tumor size, and six of seven nonresponders showed increases or no change in tumor size (P < .001). Transfer constant changes did not differ between responders and nonresponders for either clinical or pathologic assessments. After two cycles of treatment, there were tumor size increases in five of six nonresponders compared with decreases in eight of nine responders (P < .001). Reductions in transfer constant range were also observed in responders for both clinical and pathologic assessments (P = .008 and .02, respectively). No other kinetic parameter change predicted response. Size and transfer constant range were equally accurate for predicting the absence of pathologic response after two cycles of treatment (sensitivity, specificity, and area under ROC curve were 100%, 90%, and 0.93, respectively, for size and 100%, 75%, and 0.94, respectively, for transfer constant range). CONCLUSION: Reductions in MR imaging-determined size of the primary tumor best predict clinicopathologic response of breast cancer after one cycle of neoadjuvant chemotherapy. Transfer constant and size changes are equally sensitive in the identification of patients who would gain no clinical or pathologic benefit after two cycles of treatment.

Population screening for lung cancer.

The feasibility of diagnosing small stage 1 lung cancers using low-dose chest computed tomography in asymptomatic at-risk individuals has been demonstrated in multiple studies. However, it has yet to be proved that the introduction of a chest computed tomography screening programme would do more good than harm at an acceptable cost.

Rectal cancer: mesorectal lymph nodes at MR imaging with USPIO versus histopathologic findings--initial observations.

PURPOSE: To compare histopathologic findings with appearances of mesorectal lymph nodes at magnetic resonance (MR) imaging with ultrasmall particles of iron oxide (USPIO) in rectal cancer. MATERIALS AND METHODS: Mesorectal lymph nodes in 12 patients with adenocarcinoma of the rectum were evaluated with USPIO and high-spatial-resolution MR imaging. Appearance and signal intensity of lymph nodes at T2- and T2*-weighted imaging were recorded before and after USPIO administration. Two radiologists visually assessed pattern of enhancement; interobserver agreement was tested with the kappa statistic. After total mesorectal excision, MR imaging of surgical specimens was performed, and it enabled node-by-node correlation with histopathologic findings. RESULTS: Appearances of 74 nodes at in vivo MR imaging were compared with histopathologic findings. Sixty-eight nodes were nonmalignant (34 were normal, 34 showed reactive changes); six nodes were malignant. Four patterns of USPIO uptake were demonstrated at T2*-weighted imaging: uniform low signal intensity, central low signal intensity, eccentric high signal intensity, and uniform high signal intensity. Two radiologists showed good interobserver agreement (kappa = 0.88, P <.01) in classification of nodes into these four categories. Sixty-five (96%) of 68 nonmalignant nodes showed uniform or central low-signal-intensity patterns; 16 (47%) of 34 reactive nodes showed central low-signal-intensity patterns. Compared with uniform low-signal-intensity pattern, central low-signal-intensity pattern was more commonly observed in reactive nodes (P <.01, chi(2) test; positive predictive value, 67%; 95% CI: 47%, 87%). Eccentric and uniform high-signal-intensity patterns were observed in lymph nodes that contained metastases larger than 1 mm in diameter. CONCLUSION: Mesorectal lymph nodes can be characterized by using USPIO and T2*-weighted MR imaging. Uniform and central low-signal-intensity patterns are features of nonmalignant nodes. Reactive nodes frequently show central low signal intensity at T2*-weighted imaging.

Dynamic MRI of breast hardness following radiation treatment.

PURPOSE: To evaluate functional microvascular characteristics of breast induration several years after radiation treatment using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) techniques. MATERIALS AND METHODS: Fifteen women with moderate or marked breast induration after surgery and radiotherapy for breast cancer (2-15 years) were examined. Images of the irradiated breast (boost and nonboost sites) on short tau inversion recovery (STIR) and DCE-MRI sequences were subjectively evaluated for edema and the presence of enhancement and compared to the contralateral normal breast. Quantitative enhancement parameters-percent enhancing pixels, transfer constant (K(trans)), rate constant (k(ep)), leakage space (v(e)), and maximum contrast medium accumulation (MCMA)-were also compared. RESULTS: No tumor recurrence was seen. Fat necrosis was seen in 2/15 cases. Increased parenchymal edema at the electron boost site was seen in 12/14 patients. Greater enhancement in the irradiated breast was seen in 11/14 evaluable patients. Kinetic parameter estimates including K(trans) were similar except for percent enhancing pixels, which was greater in the irradiated breast at both boost and nonboost sites (P = 0.03 and 0.04, respectively). v(e) and MCMA estimates were greater in breasts with marked induration compared to moderate grades (P = 0.002 and 0.01, respectively). CONCLUSION: Parenchymal edema may be an important contributor to palpable induration several years after breast radiotherapy. Increased fluid content may be related to increased numbers of perfused microvessels and/or impaired lymphatic drainage.

Magnetic resonance imaging of induration in the irradiated breast.

BACKGROUND: The causes of induration (hardness) in the breast many years after tumour excision and whole breast radiotherapy for early stage breast cancer are not well established. The purpose of this study is to describe morphological magnetic resonance imaging (MRI) appearances and MRI-derived microvascular functional characteristics of the indurated breast several years post-treatment. PATIENTS AND METHODS: Fifteen women with moderate or marked induration at the electron boost site after breast preserving surgery and radiotherapy for early breast cancer (median 6 years; range, 2-15 years) underwent MRI, including 6/15 with very marked breast shrinkage and 8/15 with marked induration. Morphological T1- and T2-weighted and STIR images were obtained followed by a dynamic contrast medium enhanced sequence. The breast skin and underlying parenchyma of the irradiated breast were evaluated for thickening, oedema and the presence of enhancement compared to the contralateral breast. Particular note of boost site findings was made. RESULTS: No evidence of tumour recurrence was seen. Fat necrosis was seen in 2/15 cases. Skin thickening and skin oedema not evident clinically were seen in 11/15 patients. Increased parenchymal oedema at the electron boost site was seen in 12/15 patients. The parenchymal oedema was not confined to the electron boost site, but was strongest in this location in 9/12 patients. Post-contrast images in 12/14 patients showed persistent parenchymal enhancement in nine (marked in three, who also had severe breast shrinkage and marked induration), a finding consistent with, but not diagnostic of tissue fibrosis. CONCLUSIONS: Fat necrosis is not likely to contribute to breast induration several years after radiotherapy in more than a minority of patients. Increased fluid content in the breast parenchyma and skin oedema are likely to be more important contributors to palpable induration. Increased fluid content may be related to persistent capillary leakage even many years post-treatment, an expression of radiation-induced vascular injury. Fibrosis cannot be scored directly on MRI, but persistent parenchymal enhancement in a high proportion of post-contrast images is compatible with this pathology.

MR evaluation of normal retroperitoneal and pelvic lymph nodes.

PURPOSE: To establish guidelines for normal retroperitoneal and pelvic lymph node size at magnetic resonance imaging (MRI) by correlation with computed tomographic (CT) and lymphangiographic (LAG) data. MATERIALS AND METHODS: Twelve patients previously studied with pre- and post-LAG CT to determine normal pelvic lymph node size [ 1 ] were examined with MRI. All were on surveillance for stage I testicular tumour (minimum follow-up 10 years). Three observers recorded blind the site, size and number of nodes in the retroperitoneum and pelvis at 11 sites. The results were validated with previous CT imaging. RESULTS: Eight hundred and fifteen nodes in 12 patients were visible on the MRI initially, and a further 44 nodes were identified after comparison with post-LAG CT. More nodes were seen on MRI than on CT. The 95th centile values for maximum short axis diameter (MSAD) of pelvic lymph nodes were common iliac and obturator 4 mm, external and internal iliac 5 mm and hypogastric 6 mm. In the retroperitoneum the 95th centile MSAD values were retrocrural, high left para-aortic, paracaval and interaortocaval 3 mm, post-caval 4 mm and low left para-aortic 5 mm. CONCLUSION: MRI criteria for normal retroperitoneal and pelvic lymph node size are defined. Adoption of these recommendations may improve the sensitivity of MRI for the detection of nodal metastases.