Imaging of prostate carcinoma.

BACKGROUND: Imaging of prostate carcinoma is an important adjunct to clinical evaluation and prostate specific antigen measurement for detecting metastases and tumor recurrence. In the past, the ability to assess intraprostatic tumor was limited. METHODS: Pertinent literature was reviewed to describe the capabilities and limitations of the currently available imaging techniques for assessing prostate carcinoma. Evaluation of primary tumor and metastatic disease by ultrasonography, computed tomography (CT), magnetic resonance imaging (MRI), and nuclear medicine techniques is discussed. RESULTS: Ultrasonography and MRI have limited usefulness for local staging of prostate cancer because of suboptimal sensitivity and specificity for identifying tumor extent and capsular penetration. Additional MRI techniques such as magnetic resonance-based perfusion imaging, diffusion imaging, and spectroscopy may provide incremental benefit. CT and bone scanning provide an assessment of metastatic disease but are also limited by the poor sensitivity of lymph node size as a criterion for detecting metastases. Novel imaging techniques such as hybrid imaging devices in the form of single-photon emission CT/CT gamma cameras, positron emission tomography/CT cameras, and, in the near future, positron emission tomography/MRI combined with tumor specific imaging radiotracers may have a significant impact on tumor staging and treatment response. CONCLUSIONS: Cross-sectional imaging and scintigraphy have an important role in assessing prostate carcinoma metastases and treatment response. Increasingly, the incremental value of primary tumor imaging through MRI is being realized.

Imaging of the liver for hepatocellular cancer.

BACKGROUND: Imaging of the liver is a key component in the detection, diagnosis, management, and follow-up of patients with hepatocellular carcinoma. METHODS: The author uses his own experience as well as a review of pertinent literature to describe the capabilities and the limitations of the principal currently available imaging techniques for the liver. RESULTS: Ultrasound is widely available, but sensitivity and specificity for small nodules are limited. Computed tomography effectively demonstrates extrahepatic lesions and can differentiate between cysts or hemangiomas and hepatocellular carcinomas. Magnetic resonance imaging better characterizes hepatic lesions, but positron emission tomography is of limited value. CONCLUSIONS: Cross-sectional imaging with ultrasound, CT, or MRI is critical for nodule characterization in the cirrhotic liver, surgical planning of HCC, and treatment response evaluation.

Improved characterization of focal liver lesions with liver-specific gadoxetic acid disodium-enhanced magnetic resonance imaging: a multicenter phase 3 clinical trial.

OBJECTIVES: To evaluate the safety of gadoxetic acid disodium (Gd-EOB-DTPA) magnetic resonance imaging (MRI) and its efficacy in characterizing liver lesions. METHODS: Lesion characterization and classification using combined (unenhanced and Gd-EOB-DTPA-enhanced) MRI were compared with those using unenhanced MRI and contrast-enhanced spiral computed tomography (CT) using on-site clinical and off-site blinded evaluations for patients with focal liver lesions. RESULTS: Gadoxetic acid disodium was well tolerated in this study. For the clinical evaluation, more lesions were correctly characterized using combined (unenhanced and Gd-EOB-DTPA-enhanced) MRI than using unenhanced MRI and spiral CT (96% vs 84% and 85%, respectively; P < or = 0.0008). For the blinded evaluation, more lesions were correctly characterized using combined MRI compared with using unenhanced MRI (61%-76% vs 48%-65%, respectively; P < or = 0.0012 for 2/3 readers); when compared with spiral CT, a similar proportion of lesions were correctly characterized. CONCLUSIONS: Gadoxetic acid disodium-enhanced MRI is of clinical benefit relative to unenhanced MRI and spiral CT for a radiological diagnosis of liver lesions.

Rapid water and lipid imaging with T2 mapping using a radial IDEAL-GRASE technique.

Three-point Dixon methods have been investigated as a means to generate water and fat images without the effects of field inhomogeneities. Recently, an iterative algorithm (IDEAL, iterative decomposition of water and fat with echo asymmetry and least squares estimation) was combined with a gradient and spin-echo acquisition strategy (IDEAL-GRASE) to provide a time-efficient method for lipid-water imaging with correction for the effects of field inhomogeneities. The method presented in this work combines IDEAL-GRASE with radial data acquisition. Radial data sampling offers robustness to motion over Cartesian trajectories as well as the possibility of generating high-resolution T(2) maps in addition to the water and fat images. The radial IDEAL-GRASE technique is demonstrated in phantoms and in vivo for various applications including abdominal, pelvic, and cardiac imaging.

MRI diagnosis of brown tumor based on magnetic susceptibility.

A 56-year-old male with chronic renal failure was incidentally found to have lytic bone lesions in the pubic symphysis, left femoral head, left acetabulum, left iliac bone, and L1 vertebra on computed tomography (CT). Subsequent magnetic resonance imaging (MRI) of the abdomen was performed (for evaluation of a renal lesion) which demonstrated marked loss of signal intensity in the L1 bone lesion on increasing TE gradient echo images, consistent with magnetic susceptibility effect due to hemosiderin. Brown tumor was confirmed at biopsy. The susceptibility imaging probes one particular histological characteristic of tissues and allows a restricted differential of lytic tumors that contain significant hemosiderin, including brown tumor.

Dual-energy X-ray absorptiometry is a valid tool for assessing skeletal muscle mass in older women.

Assessing skeletal muscle mass (SMM) is critical in studying and detecting sarcopenia. Direct measurements by MRI or computerized tomography are expensive or high in radiation exposure. Dual-energy X-ray absorptiometry (DXA) is promising for body composition assessments, but the validity of DXA for predicting SMM in the elderly is still under investigation. The objective of this study was to assess the relationship between DXA-derived measurements of lean soft tissue mass (LSTM) and SMM in older women. Study participants were postmenopausal women (n = 101) recruited in southern Arizona. Total and regional body composition was measured using MRI and DXA (QDR4500w). The participants' mean age was 70.7 +/- 6.4 y and their mean BMI was 27.4 +/- 5.1 kg/m2. DXA-derived LSTM was highly correlated with MRI-derived SMM for the whole body (r = 0.94; P < 0.001) and leg region (r = 0.91; P < 0.001). In multivariate models, adjusting for age and DXA-derived percent fat slightly increased the amount of variance in SMM that can be explained by the DXA-derived LSTM assessments for the leg region but not for the total body. In conclusion, although the relationships between DXA measures and MRI-derived SMM vary by region of interest, the overall prediction of SMM by DXA is excellent. We conclude that DXA is a reliable method for cross-sectional assessments of SMM in older women.

Changes in water mobility measured by diffusion MRI predict response of metastatic breast cancer to chemotherapy.

The goal of oncology is the individualization of patient care to optimize therapeutic responses and minimize toxicities. Achieving this will require noninvasive, quantifiable, and early markers of tumor response. Preclinical data from xenografted tumors using a variety of antitumor therapies have shown that magnetic resonance imaging (MRI)-measured mobility of tissue water (apparent diffusion coefficient of water, or ADCw) is a biomarker presaging cell death in the tumor. This communication tests the hypothesis that changes in water mobility will quantitatively presage tumor responses in patients with metastatic liver lesions from breast cancer. A total of 13 patients with metastatic breast cancer and 60 measurable liver lesions were monitored by diffusion MRI after initiation of new courses of chemotherapy. MR images were obtained prior to, and at 4, 11, and 39 days following the initiation of therapy for determination of volumes and ADCw values. The data indicate that diffusion MRI can predict response by 4 or 11 days after commencement of therapy, depending on the analytic method. The highest concordance was observed in tumor lesions that were less than 8 cm3 in volume at presentation. These results suggest that diffusion MRI can be useful to predict the response of liver metastases to effective chemotherapy.

Evaluation of neck and body metastases to nodes with ferumoxtran 10-enhanced MR imaging: phase III safety and efficacy study.

PURPOSE: To determine the safety and efficacy of ferumoxtran 10-enhanced magnetic resonance (MR) imaging for diagnosis of metastases to lymph nodes and the clinical usefulness of ferumoxtran 10 in nodal staging. MATERIALS AND METHODS: One hundred fifty-two patients were injected with ferumoxtran 10. Readers independently evaluated precontrast MR images by using node size criteria and subjective assessment of other imaging features. Ferumoxtran 10-enhanced MR images were evaluated alone and paired with precontrast images for comparison. The diagnostic performances of precontrast MR size criteria and postcontrast MR imaging were evaluated with receiver operating characteristic (ROC) analysis. Lymph node signal intensity was correlated with histopathologic findings. MR imaging and histopathologic nodal stages were compared. RESULTS: Node-level sensitivity, specificity, and accuracy of precontrast MR imaging were 54%, 82%, and 68%, respectively, with node size criterion alone; 91%, 51%, and 71%, respectively, with subjective reader assessment; 85%, 85%, and 85%, respectively, with postcontrast MR imaging alone; and 83%, 77%, and 80%, respectively, with paired pre- and postcontrast MR imaging. Compared with size criteria, subjective reader assessment had higher sensitivity but substantially lower specificity. Areas under the ROC curve for pre- and postcontrast MR imaging were 0.76 and 0.83, respectively. Nonmetastatic nodes had significantly lower signal intensity than metastatic nodes on postcontrast T2-weighted MR images (P <.001). Postcontrast nodal staging was significantly more accurate than precontrast nodal staging (P <.01). Headache, back pain, vasodilatation, and urticaria each occurred in 6% of patients. CONCLUSION: Ferumoxtran 10-enhanced MR imaging was safe and effective and facilitated improved diagnostic performance. Use of iron oxide-enhanced MR imaging increased the positive predictive value by 20% and the accuracy by 14% compared with reader assessment. Differentiating patients with no nodal metastatic involvement was more reliable with ferumoxtran 10-enhanced MR imaging than with precontrast MR imaging.

Hepatic MR imaging with ferumoxides: multicenter study of safety and effectiveness of direct injection protocol.

PURPOSE: To compare the safety and effectiveness of an undiluted direct injection of ferumoxides with those of a diluted slow infusion of ferumoxides during 30 minutes in patients with known liver lesions or in those suspected of having them. MATERIALS AND METHODS: Two hundred thirty-three patients at 16 institutions were randomized to receive either an undiluted direct injection of 0.56 mg of iron per kilogram of body weight of ferumoxides administered during 2 minutes (2 mL/min) or a diluted slow infusion administered during 30 minutes. Safety was assessed with monitoring for adverse events and laboratory tests. For sensitivity, specificity, and accuracy analysis, two independent blinded observers identified and classified lesions as benign or malignant with precontrast images and with pre- and postcontrast images combined. RESULTS: There was no statistically significant difference in adverse events in the group with direct injection compared with those in the group with infusion (21 [18%] of 114 patients vs 19 [17%] of 112 patients, respectively). No serious adverse events were observed. The most common adverse events in the group with direct injection versus the group with infusion were headache (five [4%] of 114 vs three [3%] of 112, respectively) and back pain (five [4%] of 114 vs three [3%] of 112, respectively). Overall, in 68 (62%) of 109 patients with direct injection and 71 (66%) of 108 patients with infusion, additional magnetic resonance (MR) imaging information was obtained after ferumoxides administration (P =.67). Sensitivity, specificity, and accuracy for the diagnosis of malignancy were significantly improved by adding images obtained after ferumoxides administration to the images obtained before contrast agent administration (P <.05 for all comparisons). CONCLUSION: Direct injection of ferumoxides has safety and effectiveness profiles similar to those of slow infusion of the agent. Further findings indicate that the addition of ferumoxides increases the sensitivity and specificity of hepatic MR evaluation when compared with unenhanced MR imaging.

Location, size, and distribution of mediastinal lymph node enlargement in chronic congestive heart failure.

PURPOSE: The purpose of this study is to identify the prevalence, location, and size of enlarged mediastinal lymph nodes in patients with chronic congestive heart failure and to correlate the presence of lymph node enlargement with cardiac ejection fraction. METHODS: Sixty-six consecutive, retrospectively identified patients underwent computer tomography (CT) imaging of the thorax as part of a routine work-up prior to cardiac transplantation from 1993 to 1996. CT images of 44 of these patients were independently examined by 3 radiologists for evidence of pulmonary edema, pleural effusions, and the presence, size, and location of lymph nodes >1 cm in short axis. Multigated acquisition (MUGA) scans were available for cardiac ejection fraction assessment in 38 of the 44 patients. RESULTS: Twenty-nine (66%) patients had at least 1 mediastinal lymph node >1 cm. The mean ejection fraction was significantly less for patients with lymph node enlargement when compared with patients without lymph node enlargement (20% versus 35%; P < 0.01). Adenopathy was observed in 81% of patients with a calculated ejection fraction of <35%. No patient with an ejection fraction of >35% had lymph node enlargement. There was no correlation between pulmonary edema and the frequency of lymph node appearance. Sixty-three percent of the enlarged nodes were pretracheal, with a mean short axis diameter for all the enlarged nodes of 1.3 cm. CONCLUSIONS: Enlarged mediastinal lymph nodes were observed in 81% of patients with a calculated ejection fraction of <35%, most commonly in the pretracheal group. The presence of the lymph nodes did not correlate with CT evidence of pulmonary edema.

Radial fast spin-echo method for T2-weighted imaging and T2 mapping of the liver.

PURPOSE: To evaluate a multishot radial fast-spin echo (RAD-FSE) method developed to improve the quality of abdominal T2-weighted imaging as well as the characterization of focal liver lesions. MATERIALS AND METHODS: The RAD-FSE sequence used in this work consisted of a preparatory period followed by a short echo train (ETL = 16). A novel radial k-space trajectory was used to minimize streaking artifacts due to T2 variations and motion. Small diffusion gradients (b = 1.2 mm/s(2)) were used to improve flow suppression. The quality of images obtained with RAD-FSE was compared to multishot 2DFT fast spin-echo (2DFT-FSE) and half-Fourier acquisition single-shot turbo-spin-echo (HASTE) images using data from 16 patients. A postprocessing algorithm was used to generate multiple high-resolution images (at different effective TE values) as well as a T2 map from a single RAD-FSE data set. The T2 maps were used to differentiate malignant from benign lesions for a set of 33 lesions ranging from 0.8-194 cm(3). RESULTS: RAD-FSE produces high-resolution images of the liver in a breath-hold without the motion artifacts of 2DFT-FSE methods, and without the blurriness and loss of small lesion detectability of HASTE. The inclusion of diffusion weighting in RAD-FSE decreases the signal from blood in hepatic vessels, which improves lesion visualization. The T2 values obtained by postprocessing a single RAD-FSE data set can differentiate malignant from benign lesions. The mean T2 values obtained for malignancies, hemangiomas, and cysts are 108 +/- 30 msec, 240 +/- 14 msec, and 572 +/- 334 msec, respectively. CONCLUSION: These results indicate that RAD-FSE produces abdominal images of higher quality than 2DFT-FSE and HASTE. In addition, lesions can be characterized using T2 maps generated from a single RAD-FSE data set.

Overexpression of the HMGA2 gene in transgenic mice leads to the onset of pituitary adenomas.

Overexpression of the HMGA2 gene is a common feature of neoplastic cells both in experimental and human models. Intragenic and extragenic HMGA2 rearrangements responsible for HMGA2 gene overexpression have been frequently detected in human benign tumours of mesenchymal origin. To better understand the role of HMGA2 overexpression in human tumorigenesis, we have generated transgenic mice carrying the HMGA2 gene under the transcriptional control of the cytomegalovirus promoter. High expression of the transgene was demonstrated in all the mouse tissues analysed, whereas no expression of the endogenous HMGA2 gene was detected in the same tissues from wild-type mice. In this study, two independent lines of transgenic mice have been generated. By 6 months of age, 85% of female animals of both transgenic lines developed pituitary adenomas secreting prolactin and growth hormone. The transgenic males developed the same phenotype with a lower penetrance (40%) and a longer latency period (about 18 months). Therefore, these data demonstrate that the overexpression of HMGA2 leads to the onset of mixed growth hormone/prolactin cell pituitary adenomas. These transgenic mice may represent an important tool for the study of this kind of neoplasia.