In vivo MRSI of hyperpolarized [1-(13)C]pyruvate metabolism in rat hepatocellular carcinoma

Hepatocellular carcinoma (HCC), the primary form of human adult liver malignancy, is a highly aggressive tumor with average survival rates that are currently less than 1 year following diagnosis. Most patients with HCC are diagnosed at an advanced stage, and no efficient marker exists for the prediction of prognosis and/or response(s) to therapy. We have reported previously a high level of [1-(13)C]alanine in an orthotopic HCC using single-voxel hyperpolarized [1-(13)C]pyruvate MRS. In the present study, we implemented a three-dimensional MRSI sequence to investigate this potential hallmark of cellular metabolism in rat livers bearing HCC (n = 7 buffalo rats). In addition, quantitative real-time polymerase chain reaction was used to determine the mRNA levels of lactate dehydrogenase A, nicotinamide adenine (phosphate) dinucleotide dehydrogenase quinone 1 and alanine transaminase. The enzyme levels were significantly higher in tumor than in normal liver tissues within each rat, and were associated with the in vivo MRSI signal of [1-(13)C]alanine and [1-(13)C]lactate after a bolus intravenous injection of [1-(13)C]pyruvate. Histopathological analysis of these tumors confirmed the successful growth of HCC as a nodule in buffalo rat livers, revealing malignancy and hypervascular architecture. More importantly, the results demonstrated that the metabolic fate of [1-(13)C]pyruvate conversion to [1-(13)C]alanine significantly superseded that of [1-(13)C]pyruvate conversion to [1-(13)C]lactate, potentially serving as a marker of HCC tumors.

Abstract 4881: A novel method of tumor characterization by protein and microRNA biomarker release using ultrasound

Earlier cancer diagnosis and monitoring of therapy could be improved by the earlier detection of circulating biomarkers. Ultrasound at low frequencies is known to permeabilize cell membranes and has been used for delivery of molecules into the cell. We hypothesize and prove that this bioeffect of ultrasound also causes the release of both protein and nucleic acid biomarkers from cells in culture and mice. The ability to focus ultrasonic waves allows for the localization of the potential biomarker source in vivo. This novel strategy could lead to the earlier identification, characterization and localization of incidental lesions, cancer and other disease.

Methods: The colon cancer cell line LS174T that produces protein biomarkers (carcinoembryonic antigen-CEA and cancer antigen 19-9 – CA19-9) and microRNAs (miRNA – miR -16 and miR-141) was exposed to low frequency ultrasound (1 MHz) in culture using varying intensities (0, 0.1, 0.3. 0.5, 0.7, 1.0 W/cm2) and time (0, 10, 30 min). Subcutaneous tumors of LS174T in mice were also exposed to ultrasound (2 W/cm2; 6 min), directly over the tumors or at a non-tumor bearing site. Samples were collected pre and post-ultrasound treatment and compared for changes in biomarker levels. Protein biomarkers were detected using an enzyme-linked immunosorbant assay and miRNAs were detected using quantitative reverse-transcription polymerase chain reaction. Cell death was studied using Trypan blue staining.

Results: LS174T cells treated with 1 MHz ultrasound in culture (n=4) at a low intensity of 0.3 W/cm2 released both CEA and CA19-9 with an increase in time (0, 10, 30 min; p<0.05). Ultrasound treatment increased the abundance of cell-free miRNAs released into the media in a time and intensity dependent manner. This release was seen to increase relative to pre-treatment levels, from 15-fold (0.1 W/cm2) to >1000-fold (1.0 W/cm2) for miR-16 and 100-fold (0.1 W/cm2) to 500-fold (1 W/cm2) for miR-141, within 30 min of ultrasound treatment. Cell death was less than 5% across all conditions. Subcutaneous tumors (n=10) showed an increase release of protein biomarkers when treated with ultrasound at 2 W/cm2 (CEA p<0.04; CA19-9 p<0.002), when comparing pre- and post-ultrasound measurements. Controls treated with no ultrasound or on non-tumor bearing sites of tumor-bearing mice did not show any significant increase in the release of biomarkers.

Conclusions: Increase in protein and miRNA biomarkers were observed when ultrasound was directly applied to cells. We have developed a simple non-invasive method to amplify and spatially localize the biomarker signal from tumors. This method has implications in diagnosis and monitoring of therapy and has a clear pathway into clinical applications uniting the fields of imaging and in vitro diagnostics.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4881. doi:10.1158/1538-7445.AM2011-4881

Advancing radiology through informed leadership: summary of the proceedings of the Seventh Biannual Symposium of the International Society for Strategic Studies in Radiology (IS(3)R), 23-25 August 2007

The International Society for Strategic Studies in Radiology (IS³R) brings together thought leaders from academia and industry from around the world to share ideas, points of view and new knowledge. This article summarizes the main concepts presented at the 2007 IS³R symposium, providing a window onto trends shaping the future of radiology. Topics addressed include new opportunities and challenges in the field of interventional radiology; emerging techniques for evaluating and improving quality and safety in radiology; and factors impeding progress in molecular imaging and nanotechnology and possible ways to overcome them. Regulatory hurdles to technical innovation and drug development are also discussed more broadly, along with proposals for addressing regulators’ concerns and streamlining the regulatory process.

Practical approaches to the evaluation of signal-to-noise ratio performance with parallel imaging: application with cardiac imaging and a 32-channel cardiac coil

In this work, two practical methods for the measurement of signal-to-noise-ratio (SNR) performance in parallel imaging are described. Phantoms and human studies were performed with a 32-channel cardiac coil in the context of ultrafast cardiac CINE imaging at 1.5 T using steady-state free precession (SSFP) and TSENSE. SNR and g-factor phantom measurements using a "multiple acquisition" method were compared to measurements from a "difference method". Excellent agreement was seen between the two methods, and the g-factor shows qualitative agreement with theoretical predictions from the literature. Examples of high temporal (42.6 ms) and spatial (2.1x2.1x8 mm3) resolution cardiac CINE SSFP images acquired from human volunteers using TSENSE are shown for acceleration factors up to 7. Image quality agrees qualitatively with phantom SNR measurements, suggesting an optimum acceleration of 4. With this acceleration, a cardiac function study consisting of 6 image planes (3 short-axis views, 3 long-axis views) was obtained in an 18-heartbeat breath-hold.

A model for faculty mentoring in academic radiology

RATIONALE AND OBJECTIVES

The purpose of this report is to describe the development and implementation of a faculty mentoring program in radiology designed to promote the career development of junior faculty and enhance communication in the department.

MATERIALS AND METHODS

The mentoring program was implemented in five stages: organizational readiness, participant recruitment, mentor matching and orientation, implementation, and evaluation. Evaluations were based on Likert scale ratings and qualitative feedback. A retrospective analysis was also conducted of the annual performance reviews of junior faculty in the areas of research, teaching, patient care, and overall performance.

RESULTS

An average of 83% (19 of 23) of the junior faculty participated in the pilot phase of the mentoring program. During five rounds of testing, the median rating (1 indicates not important; 10, extremely important) from responding junior faculty was 10 for overall value of individual mentoring meetings; the median rating for the mentors responding was 8.75. Research and academic development were identified as the areas of greatest importance to the faculty. Research and patient care were most improved as assessed by faculty peers during performance reviews. The schedule of semiannual formal mentoring meetings was reported to be optimal.

CONCLUSION

The program was implemented to the satisfaction of junior faculty and mentors, and longitudinal performance suggests positive effects. Issues to be contended with include confidentiality and the time needed for mentoring beyond already saturated schedules. Overall, the authors propose that mentoring programs can be an asset to academic radiology departments and a key factor in maintaining their vitality.

Lung herniation through a postthoracoscopy chest wall defect: demonstration with spiral CT

The incidence of complications following thoracoscopy is approximately 10%, the most prevalent being prolonged air leak and chest pain. We report two cases of lung herniation through the chest wall defect created by thoracoscopy. Use of the Valsalva maneuver during CT scanning is recommended as a diagnostic imaging method in cases with suspected lung herniation.

Preoperative staging of non-small-cell carcinoma of the lung: imaging methods

Preoperative tumor staging in patients with non-small-cell lung cancer is important for selecting those patients with localized disease who are likely to benefit from surgical resection. The TNM staging system of the American Joint Committee on Cancer is the most widely accepted and used classification system for preoperative and postoperative staging [1] (Table 1). Small-cell carcinoma has a very different biologic behavior and is classified and treated differently; it will not be discussed in this imaging review. Chest radiography is the preferred initial imaging technique for patients with known or suspected lung cancer because of its availability, low cost, low radiation dose, and sensitivity [2]. CT and MR imaging of the chest and abdomen are often used to stage a known or suspected lung carcinoma. Various nuclear medicine procedures may be used to aid in the staging process and to assess the patient's medical status for surgery, including cardiac and pulmonary function. This article reviews the major imaging techniques that are currently used to stage primary non-small-cell carcinoma of the lung. Although evaluation of distant metastatic disease is highly important in these patients, discussion of the imaging methods used for this purpose is beyond the scope of this article.

Scintigraphic evaluation of clinically silent adrenal masses

We studied 229 patients with abnormal adrenal anatomy depicted by CT who were without biochemical evidence of endocrine dysfunction using the presence of 131I-6 beta-iodomethyl-nor-cholesterol (NP-59) adrenal gland uptake as an index of differential adrenal function in the evaluation of the clinically "silent" adrenal mass lesion.

METHODS

NP-59 (1 mCi) was injected intravenously with posterior and lateral abdominal images obtained 5-7 days postinjection.

RESULTS

One-hundred and fifty-nine of 185 patients with unilateral adrenal enlargement on CT had scintigraphic evidence that the mass represented a functioning (NP-59 avid) but not hypersecretory, (biochemically normal) adrenal cortical adenoma (concordant imaging pattern). Forty-one of 44 patients with intra-adrenal neoplasms were depicted on scintigraphy as decreased or absent NP-59 accumulation on the side of the adrenal mass (discordant imaging pattern). In this study, sensitivity was 71% (41 of 58 patients; 95% confidence interval (CI), 58% to 88%); specificity was 100% (171 of 171 patients; 95% CI, 95% to 100%) and accuracy was 93% (212 of 229 patients; 95% CI, 88% to 96%).

CONCLUSIONS

These data confirm our earlier observations that the functional information depicted by scintigraphy complements the morphological evaluation by CT and in the absence of hormonal dysfunction, the presence of concordant CT and 131I-NP-59 scans are characteristic of functioning, but not hypersecretory, benign adrenocortical adenomas. Conversely, discordant CT and 131I-NP-59 scans are suggestive of nonfunctioning, space-occupying, adrenal lesions.

Dynamic breath-hold multiplanar spoiled gradient-recalled MR imaging with gadolinium enhancement for differentiating hepatic hemangiomas from malignancies at 1.5 T

PURPOSE

To compare the enhancement patterns of focal liver lesions at dynamic breath-hold gadolinium-enhanced multiplanar spoiled gradient-recalled (SPGR) magnetic resonance (MR) imaging with T2 relaxation times in the differentiation of liver hemangiomas from malignancies.

MATERIALS AND METHODS

Forty-seven patients with focal liver lesions underwent MR imaging with spin-echo and gadolinium-enhanced multiplanar SPGR techniques. T2 relaxation times and enhancement patterns were compared for accuracy in liver lesion characterization.

RESULTS

Enhancement patterns allowed better characterization of liver lesions than did T2 relaxation times. Only specific patterns of contrast enhancement indicated a hemangioma. Although 18 of the 33 malignancies and 10 of the 12 hemangiomas showed progressive centripetal hyperintense enhancement, only hemangiomas filled in with hyperintense peripheral nodules. Malignancies often filled in with hyperintense thick rinds.

CONCLUSION

Gadolinium-enhanced multiplanar SPGR imaging allows more accurate characterization of liver lesions than does T2 relaxation time.

Interobserver variability in CT and MR staging of lung cancer

OBJECTIVE

Our goal was to assess the interobserver variability in staging non-small cell lung cancer using CT and MRI.

MATERIALS AND METHODS

As part of the Radiologic Diagnostic Oncology Group (RDOG) study of lung cancer staging, the CT and MR examinations of 40 patients suspected of having non-small cell bronchogenic carcinoma were blindly interpreted by four expert observers. The primary tumor and lymph node stages in the 40 study subjects were similar to the final proportions reported in the RDOG study. Assessed abnormalities included the presence of a lung nodule, chest wall invasion, mediastinal invasion, bronchial involvement, lymph node metastasis in specific node stations, and T and N classifications. Percent agreement and kappa-values were calculated for each of these determinations.

RESULTS

Depending on the finding assessed and the method of analysis, average agreement rates ranged from 58 to 90% for CT and from 61 to 96% for MRI. Average kappa-values were largely between 0.40 and 0.60 when dichotomous analysis was used; weighted kappa-values were similar. With a single exception, no significant differences were found for kappa-values calculated for CT and MRI.

CONCLUSION

Although interobserver agreement rates are good for determining T and N classification in patients with lung cancer, variability in image interpretation is frequent, even among experienced observers.

Positive bowel contrast agent for MR imaging of the abdomen: phase II and III clinical trials

PURPOSE

To evaluate the efficacy and safety of two dose levels of an orally administered ferric ammonium citrate-based contrast agent for bowel enhancement on T1-weighted spin-echo magnetic resonance (MR) images in 222 patients with known or suspected abnormality of the upper abdomen.

MATERIALS AND METHODS

Adverse reactions were graded for intensity, frequency, duration, and relationship to the contrast agent. Twelve unblinded readers compared enhanced with unenhanced images; all MR images were evaluated by two independent offsite radiologists in a blinded review.

RESULTS

No statistically significant changes in mean vital signs or laboratory values were seen. Forty-eight of 220 patients (22%) reported minor side effects. The readers found increased intraluminal signal intensity and improved contrast enhancement of the gastrointestinal tract and distention and improved signal homogeneity in 101-107 cases (89%-98%) after ingestion; the blinded reviewers' findings were similar.

CONCLUSION

The contrast agent provided new or additional radiologic information in 142 patients (64%), specific additional information in a detected abnormality in 46 of 142 patients (32%), and information that changed diagnosis, management, or surgical approach in 22 of 142 patients (15%).

Fast multiplanar spoiled gradient-recalled imaging of the liver: pulse sequence optimization and comparison with spin-echo MR imaging

OBJECTIVE

The purpose of this study was to optimize a new rapid-acquisition MR pulse sequence, called fast multiplanar spoiled gradient-recalled (FMPSPGR) imaging, for breath-hold imaging of the liver and to compare unenhanced and contrast-enhanced FMPSPGR with standard spin-echo imaging in detecting liver tumors.

MATERIALS AND METHODS

The pulse sequence was optimized at 1.5 T with a healthy volunteer. Various scanning parameters were evaluated, and liver-spleen signal difference/noise measurements were used to estimate lesion contrast-to-noise ratios. We examined 24 patients with hepatic masses using the optimized sequence with spin-echo T1-weighted and T2-weighted imaging as well as unenhanced and gadopentetate dimeglumine-enhanced FMPSPGR imaging. The contrast-to-noise ratio for the hepatic tumors was determined for each sequence. Three radiologists who did not know the biopsy or test results reviewed all images for lesion conspicuity, lesion tissue specificity, and overall image quality.

RESULTS

A comparison of unenhanced FMPSPGR images with spin-echo T1-weighted images showed a 40% improvement in mean contrast-to-noise ratio and a 70% improvement in liver signal-to-noise ratio for the FMPSPGR images. A comparison of gadopentetate dimeglumine-enhanced FMPSPGR images with spin-echo T1- and T2-weighted images showed a superior contrast-to-noise ratio for the enhanced FMPSPGR images in 17 (68%) of 25 hepatic lesions, which included all hepatic cysts (n = 3) and all hepatomas (n = 6), and in six of 12 patients with other liver tumors. The results of contrast-to-noise ratio for four patients with hemangiomas were mixed. For the remaining eight lesions, the contrast-to-noise ratio for spin-echo T1- and T2-weighted images predominated in three and five cases, respectively. Contrast-enhanced FMPSPGR images revealed a 40% and 300% increase in contrast-to-noise ratio compared with T2- and T1-weighted images, respectively. All three radiologists preferred the contrast-enhanced FMPSPGR images for overall image quality. For lesion conspicuity and specificity, however, the three radiologists differed, with a preference for the FMPSPGR images in 52%, 80%, and 40% of cases for lesion conspicuity and in 68%, 40%, and 60% of cases for lesion specificity.

CONCLUSION

FMPSPGR is a new, ultrafast MR sequence that provides T1-weighted images of the liver during suspended respiration. Contrast-to-noise ratio and liver signal-to-noise ratio are significantly improved over those on conventional spin-echo T1-weighted images. The combination of breath-hold FMPSPGR with gadopentetate dimeglumine is an excellent technique that can be used to rapidly evaluate the liver with superior overall image quality. Contrast-to-noise ratios are generally superior to T2-weighted spin-echo images, making this technique a useful adjunct to conventional spin-echo MR imaging.

Malignant hepatic tumors: P-31 MR spectroscopy with one-dimensional chemical shift imaging

To determine the clinical feasibility and applicability of phosphorus-31 magnetic resonance (MR) spectroscopy and to assess its potential for characterization of human hepatic tissue, one-dimensional chemical shift imaging (CSI) was performed in 37 patients with various malignant hepatic neoplasms (30 metastases from a variety of primary tumors and seven hepatocellular carcinomas) and seven healthy volunteers. Tumors were grouped according to the percentage of the analyzed section that was occupied by tumor: less than 50% (group A) or more than 50% (group B). In group B, all phosphomonoester/beta-adenosine triphosphate ratios were significantly higher than normal (P less than .001). Hepatocellular carcinomas and metastases from various primary neoplasms could not be differentiated on the basis of spectral characteristics and metabolite ratios. Limitations of one-dimensional surface coil CSI prevented separation of spectra of small tumors and tumors deep within the liver parenchyma from spectra of normal liver parenchyma.

Clinical significance of the large adrenal mass

Current clinical teaching indicates that large (greater than 5 cm in diameter) adrenal masses are often malignant. In a retrospective analysis of patients studied between 1977 and 1988 with computed tomography (CT), adrenal scintigraphy, and when available, magnetic resonance imaging (MRI) 45 were found to have adrenal masses greater than 5 cm (range 5-19 cm) in diameter. Thirty were benign (16 phaeochromocytomas, six adrenocortical adenomas, four adrenal cysts, two myelolipomas, an adrenal hematoma and a ganglioneuroma). Of 15 malignant masses, there were seven adrenocortical carcinomas, five adrenal metastases and three adrenal lymphomas. With the exception of the adrenal myelolipomas, cysts, and the ganglioneuroma neither CT nor MRI demonstrated sufficient diagnostic specificity to distinguish benign from malignant lesions. Functional scintigraphy with 131I-6-beta-iodomethyl-19-norcholesterol for suspected adrenocortical lesions and 131I-metaiodobenzylguanidine for suspected phaeochromocytomas frequently provided useful information.

CT and MR imaging in staging non-small cell bronchogenic carcinoma: report of the Radiologic Diagnostic Oncology Group

The accuracies of magnetic resonance (MR) imaging and computed tomography (CT) in determining tumor classification and assessing mediastinal node metastases were compared in a prospective cooperative study of 170 patients with non-small cell bronchogenic carcinoma. The sensitivity of CT in distinguishing T3-T4 tumors from T0-T2 tumors was 63%; specificity was 84%. These values for MR imaging were not significantly different (56% and 80%). With receiver operating characteristic (ROC) analysis, no difference existed between the accuracies of CT and MR imaging in diagnosis of bronchial involvement or chest wall invasion, but MR imaging was significantly more accurate than CT (P = .047) in diagnosis of mediastinal invasion. Lymph node sampling was performed in 155 patients (642 node stations). Cancerous nodes were found in 14% of stations in 21% of patients. There was no significant difference between the accuracies of CT and MR imaging in detecting mediastinal node metastases (N2 or N3); the sensitivities were 52% and 48%, respectively, and specificities were 69% and 64%. ROC analysis also showed no difference between CT and MR imaging.

Carcinoma of the prostate: MR images obtained with body coils do not accurately reflect tumor volume

MR imaging with a body coil is unreliable in directly demonstrating tumor spread through the prostatic capsule. However, the likelihood of extracapsular spread of prostatic cancer rises with increasing tumor volume. The aim of our study was to assess the accuracy of MR with a body coil in diagnosing capsular penetration indirectly via an estimation of prostatic tumor volumes. Twenty-six patients with proved prostatic cancer that was clinically confined to the gland underwent MR imaging before radical prostatectomy and whole-mount pathologic sectioning of the specimen. Twenty of 31 lesions prospectively outlined on the MR images corresponded to cancers outlined on the pathology slides, and tumor volumes were calculated by using a voxel summation technique. On MR, tumor volume was underestimated in 11 of 20 cases and overestimated in nine of 20 cases. Only two of 20 size estimates based on MR findings were within 10% of actual tumor volume. Overlap in MR tumor volumes was significant between lesions with and without capsular penetration at microscopy. Factors contributing to inaccuracies in measurements of tumor volume on MR images included the variable histologic make-up of the tumors. Our results show that, although knowledge of the size of a prostatic lesion is important in predicting the behavior of the tumor, MR imaging with a body coil is not reliable for accurate estimation of tumor volume.

Sarcoidosis: abdominal manifestations at CT

There are few data in the literature on the abdominal manifestations of sarcoidosis at computed tomography (CT). To determine whether differences in nodal distribution and appearance can be reliably used to distinguish between sarcoidosis and non-Hodgkin lymphoma (NHL), the authors retrospectively reviewed the abdominal and pelvic CT scans of 16 patients with biopsy-proved sarcoidosis and 20 patients with biopsy-proved NHL. Eleven of the 16 patients with sarcoidosis had abdominal and/or pelvic lymphadenopathy, which was common at all nodal sites except for the retrocrural and pelvic locations. There was a statistically significant lower frequency of retrocrual adenopathy in sarcoidosis than in NHL. Mean nodal size was significantly greater in NHL. Nodes tended to be confluent in NHL and discrete in sarcoidosis. Hepatomegaly was seen in six of the 16 patients (38%) with sarcoidosis and splenomegaly was present in nine of 15 (60%). CT depicted hepatic lesions in only three of eight patients (38%) with biopsy-proved hepatic involvement. Splenic lesions were seen at CT in five of the 15 patients (33%). The authors believe that the overlap in nodal appearance and distribution poses a limitation for use of these criteria in accurate disease characterization.

Three dimensional CT of central lung tumors

Three-dimensional computed tomography (CT) reconstructions and conventional CT were compared with surgical/pathological findings in seven patients with central lung tumors, in order to assess accuracy in predicting the lobectomy/pneumonectomy decision. Although conventional CT surpassed 3D CT in diagnosing bronchial tumor invasion, 3D CT appeared to be better for central arterial invasion. Despite problems due to motion effects, partial volume averaging and the time consuming nature of the reconstruction process, 3D CT is probably useful in this setting and promises to have similar applications throughout the body.

CT-angiographic correlation of collateral venous pathways in isolated splenic vein occlusion: new observations

The computed tomographic (CT) findings in 18 patients with angiographically proved, isolated splenic vein occlusion (SVO) were retrospectively analyzed. The distribution of venous collateral vessels and the frequency of their occurrence in these patients were then compared with CT findings in 17 patients with proved portal hypertension and normal CT findings in 20 patients. Short gastric and coronary collateral vessels were seen in 61% and 83%, respectively, of patients with SVO and in 71% each in patients with portal hypertension. However, a large gastroepiploic vein was seen only in patients with SVO (11 of 18 patients [61%]). Recanalization of umbilical/paraumbilical veins was seen only in patients with portal hypertension (seven of 17 patients [41%]). Results suggest that collateral vessels in SVO often have a characteristic and distinctive appearance on abdominal CT scans.

The detection of adrenal tumors and hyperplasia in patients with primary aldosteronism: comparison of scintigraphy, CT, and MR imaging

We retrospectively reviewed the imaging studies in 17 proved cases of primary aldosteronism to determine the value of the procedures used to detect adrenal tumors or adrenal hyperplasia. The procedures included CT with 3-, 5-, and/or 10-mm-thick sections (17 patients), 131I-6 beta-iodomethyl-19-norcholesterol (NP-59) scintigraphy (16 patients), and MR imaging (six patients). Proof of the adrenal abnormality was established in cases of tumor (seven adenomas, one carcinoma) by surgery and in cases of adrenal hyperplasia by surgery (three cases); venous sampling (three cases); or combined clinical, biochemical, and imaging data (three cases). Both CT and scintigraphy detected six of the seven adenomas and the adrenal carcinoma (88%). Regarding hyperplasia, CT was correct in five of six and scintigraphy was correct in two of four cases proved by surgery or venous sampling. CT and NP-59 were concordant and suggested the diagnosis of hyperplasia in the remaining three cases without surgical or venous sampling proof. MR detected both cases of adenoma in which it was performed and showed evidence of hyperplasia in one of the four cases of hyperplasia in which it was performed. Although the number of patients in this series is too small to have much statistical power, these results suggest that CT and NP-59 scintigraphy are equivalent in the detection of adrenal abnormalities in patients with primary aldosteronism. The value of MR in the detection of small adrenal contour abnormalities was limited by slice thickness capabilities.

Calculating radiation absorbed dose for pheochromocytoma tumors in 131-I MIBG therapy

A protocol for calculating radiation absorbed dose to pheochromocytoma tumors during treatment with 131I-labeled metaiodobenzylguanidine (MIBG) is described. The technique calls for (a) obtaining tumor volumes from Computed Tomography and/or Magnetic Resonance Imaging, (b) computing energy absorbed by assuming complete beta-particle absorption and a standard shape for gamma-ray absorption and (c) scaling from tracer to therapy dose rate by the ratio of administered activities. Also a 131I time-activity curve is obtained from planar, Anger-camera, conjugate-view images of the tumor and a known-strength source, both over a series of days. In addition, to correct for any systematic errors in the calculated uptakes, a larger activity of 123I MIBG is administered separately and quantitative Single Photon Emission Computed Tomography (SPECT) is undertaken. A known-strength source also undergoes SPECT to calibrate the tomograms. Correction for Compton scattering is accomplished by the dual-energy-window technique. The subtraction fraction was found to be 0.7 for the 1/2" crystal camera and the mean reduction in tumor counts for seven tumors from Compton correction was 0.76. The normalization factor needed to bring the conjugate-view activities into agreement with the SPECT values ranged from 0.74 to 1.06. A test study on an anthropomorphic phantom indicated that the error in resultant activities might be estimated as +/- 13%. Application of the protocol led to the calculation of real, or potential (when decision was finally made to not administer therapy) radiation absorbed dose to seven tumors in three patients from an administration of about 8 GBq of MIBG. For two metastatic tumors in a 19-year old patient who did not have her primary cancer resected, the calculated radiation absorbed dose was 170 and 180 Gy. For the four metastatic deposits evaluated in two older patients, both of whom had their primary tumor surgically removed, the values ranged from 18 to 31 Gy.

Hyperfunctioning and nonhyperfunctioning benign adrenal cortical lesions: characterization and comparison with MR imaging

The authors evaluated the potential of magnetic resonance (MR) imaging at 0.35 T to permit differentiation of nine hyperfunctioning adrenal cortical lesions from 21 nonhyperfunctioning adrenal cortical adenomas. Both qualitative data (visual assessment) and quantitative data (signal intensity ratios, T1, and T2) were used for tissue characterization. With a 2,000/56-100 sequence (repetition time msec/echo time msec), the majority of lesions were visually isointense to liver. Of 34 quantitative measures, only lesion-liver and lesion-kidney intensity ratios at 2,000/150 showed statistically significant differences among nonhyperfunctioning adenomas, aldosterone-producing lesions, and corticosteroid-producing lesions; however, the authors question the significance of these differences because of the abundant noise associated with the 2,000/150 sequence. The results suggest that nonhyperfunctioning adrenal cortical adenomas cannot be distinguished from benign hyperfunctioning cortical lesions with use of MR imaging at 0.35 T.

Adrenal magnetic resonance imaging in Addison's disease

Magnetic resonance imaging of the adrenal glands was performed in 9 patients with Addison's disease to evaluate the role of magnetic resonance (MR) in this entity. All patients had bilateral adrenal masses demonstrated by computed tomography (CT); etiologies included adrenal hemorrhage (2 patients), granulomatous disease (1 patient), adrenal lymphoma (3 patients), and adrenal metastases (3 patients). Spin-echo axial images were obtained at repetition times (TR) 0.5, 2.0 s and TE 28, 56 ms, using a Diasonics superconducting magnet operating at 0.35 T. In the patients with lymphoma, metastases, and granulomatous disease, the adrenal masses appeared hypointense or isointense with liver on the T1-weighted images (TR 0.5 s, TE 28 ms). In cases of adrenal hemorrhage, areas of hyperintensity were seen on TR 0.5, TE 56 ms sequences, due to shortening of T1 values. In both groups of patients the masses were hyperintense on T2 weighted sequences. Mean calculated T1 of the hemorrhagic glands was 449 ms, compared with a mean of 782 ms for metastases and lymphoma. While MR is not capable of distinguishing between acute inflammatory and metastatic diseases of the adrenal glands, it may be equally efficacious as CT in suggesting the diagnosis of adrenal hemorrhage in patients with Addison's disease.

In vivo and in vitro MR imaging of renal tumors: histopathologic correlation and pulse sequence optimization

Magnetic resonance (MR) imaging has given mixed results in the detection of renal masses. To identify the reasons for this and to determine the optimal pulse sequences for evaluating renal tumors, the authors imaged 12 primary renal tumors in vivo and 17 in vitro at 0.35 T. Histopathologic findings for each specimen were closely correlated with the MR images. Four of seven solid tumors imaged in vivo were isointense with surrounding normal renal parenchyma at all pulse sequences. The other three tumors were hyperintense in vivo at T2-weighted sequences. At heavily T2-weighted sequences eight solid tumors were hyperintense in vitro and four were hypointense. There was no correlation between signal intensity and specific tissue type or histologic pattern for solid tumors. The five cystic tumors were well seen both in vivo and in vitro on T2-weighted images. However, the signal intensity of the cyst fluid was an unreliable indicator of benignancy. SE MR imaging at 0.35 T has significant limitations in the detection of solid renal masses.

Distinction of hepatic cavernous hemangioma from hepatic metastases with MR imaging

Twenty-four hepatic cavernous hemangiomas and 91 metastases from a variety of hypovascular and hypervascular primary neoplasms were prospectively studied with magnetic resonance (MR) imaging. In addition to qualitative analysis, quantitative analysis of signal intensity ratios of lesion to normal liver was performed with images obtained with 500/28-30 (repetition time msec/echo time msec) and 2,000/28-150 sequences. Quantitative data did not improve the ability to distinguish hemangiomas from metastases in our series compared with qualitative analysis. Hypovascular metastases, such as colon carcinoma, could be differentiated from hemangioma more frequently (97.5%) than hypervascular endocrine metastases, such as islet cell tumor, carcinoid, and pheochromocytoma (61%). These findings indicate that the utility of MR imaging in differentiating hemangiomas from metastases is dependent on the histologic type of the primary neoplasm.

Distinguishing benign from malignant euadrenal masses

STUDY OBJECTIVE

To determine the efficacy of 131I-6-beta-iodomethylnorcholesterol (NP-59) adrenal scintigraphy in distinguishing benign from malignant euadrenal masses.

DESIGN

Case series of patients with incidentally discovered unilateral, euadrenal masses.

SETTING

Referral-based nuclear medicine clinics at university and affiliated Veterans Administration medical centers.

PATIENTS

Consecutive sample of 119 euadrenal patients with unilateral adrenal masses discovered on computed tomographic (CT) scans for reasons other than suspected adrenal disease.

INTERVENTIONS

Adrenal scintiscans done using 1 mCi of NP-59 intravenously, and gamma camera imaging 5 to 7 days later.

MEASUREMENTS AND MAIN RESULTS

Mean lesion diameter was 3.3 +/- 1.9 cm (SD) (95% CI: 2.9 to 3.6 cm). In 76 patients, NP-59 uptake lateralized to the abnormal adrenal seen on CT scans (concordant imaging), and in all of these patients, a diagnosis of adenoma was made by needle-aspiration biopsy, adrenalectomy, or extended follow-up with repeat CT scans that were unchanged at 6 months or later. Twenty-six patients had absent or markedly reduced NP-59 uptake in the glands identified as abnormal on CT scans (discordant imaging). These adrenal masses proved to be metastatic malignancies in 19 patients, primary adrenal neoplasms other than adenoma in 4, and adrenal cysts in 3. Bilateral, symmetric accumulation of NP-59 was seen in 17 patients, in whom the adrenal masses were shown to be metastatic malignancies in 2, and adenomas in 6 (the lesions in these cases being 2 cm or less in diameter), and lesions not truly involving the adrenal in the rest (periadrenal metastases in 4 and pseudoadrenal masses in 5). Sensitivity was 76% (26 of 34 patients; CI, 58% to 88%); specificity, 100% (85 of 85 patients; CI, 95% to 100%), and accuracy, 93% (111 of 119 patients: CI, 88% to 98%).

CONCLUSIONS

Functional NP-59 scintigraphy can be used to accurately and noninvasively characterize many euadrenal masses; concordance of CT and NP-59 scans can be used to exclude the presence of a malignancy or other space-occupying adrenal lesion.

Adrenal localization in the adrenocorticotropic hormone-independent Cushing syndrome

STUDY OBJECTIVE

To assess the efficacy of 131I-6-beta-iodomethylnorcholesterol scintigraphy in the adrenocorticotropic hormone-independent Cushing syndrome and to compare this with computed tomography.

DESIGN

Retrospective analysis of case series from 1977 to 1987.

SETTING

Referral to the Division of Nuclear Medicine at a tertiary-care university medical center.

PATIENTS

Twenty-four patients with a pathologically-confirmed diagnosis of the adrenocorticotropic hormone-independent Cushing syndrome had 131I-6-beta-iodomethylnorcholesterol scintigraphy and, in most cases, computed tomography.

MEASUREMENTS AND MAIN RESULTS

Using 131I-6-beta-iodomethylnorcholesterol scintigraphy, adenomas were accurately seen as focal, unilateral tracer uptake in 14 of 14 patients. In carcinoma, the classic scintigraphic pattern of bilateral nonvisualization was observed in 3 of 4 patients, with ipsilateral uptake of tracer in 1 patient with a histologically well-differentiated malignancy. Computed tomography done during the same interval depicted abnormal adrenals in all cases of adenoma and carcinoma. In cortical nodular hyperplasia, however, computed tomography identified abnormal pairs of adrenals in only one of four cases studied, whereas scintigraphy showed typical patterns of bilateral increased uptake in all of the cases.

CONCLUSION

131I-6-beta-iodomethylnorcholesterol scintigraphy accurately shows the location and nature of adrenal dysfunction in the adrenocorticotropic hormone-independent Cushing syndrome and may be particularly useful in identifying the bilateral adrenal involvement in cortical nodular hyperplasia.

Radiologic evaluation of the subcarinal lymph nodes: a comparative study

Subcarinal lymph nodes are commonly involved by metastases from cancers of both the right and left lungs. No data exist on the relative accuracy of radiologic methods for evaluating subcarinal nodes. We prospectively studied lung cancer patients who were surgical candidates with CT, MR imaging (0.35 T), esophagography, and anteroposterior tomography. Forty-six patients who subsequently underwent thoracotomy had excision or sampling of subcarinal nodes at mediastinoscopy. All 46 had CT scans, 27 had MR imaging, 23 had esophagography, and 21 had anteroposterior tomography. Receiver-operating characteristic curves were constructed for each technique, and the area under each curve was calculated. MR and CT were nearly identical in subcarinal evaluation, with areas under the receiver-operating characteristic curves of 0.90 and 0.86, respectively; both were superior to esophagography (0.55) and anteroposterior tomography (0.61). The size threshold at which subcarinal nodes were considered abnormally enlarged in this lung cancer population was 11 mm in short axis for CT, agreeing with the size threshold previously reported for a normal population. The size threshold for abnormal nodal enlargement with MR imaging was 18 mm in short axis. We conclude that CT and MR imaging are comparable in the detection of subcarinal lymphadenopathy and are superior to both tomography and esophagography. Different size thresholds for metastatic subcarinal nodes are needed for CT and MR imaging to be comparable in overall performance.

Mediastinal lymph nodes: relaxation time/pathologic correlation and implications in staging of lung cancer with MR imaging

The authors measured the T1 and T2 relaxation times of freshly excised human mediastinal lymph nodes to determine whether the times are clinically useful in distinguishing benign from malignant nodes. All measurements were performed at 20 MHz and 40 degrees C, within 45 minutes of lymph node excision. Mean T1 and T2 relaxation times of 99 benign nodes were 566 msec (standard deviation [SD], 117 msec) and 92 msec (SD, 29 msec), respectively. For the 16 malignant nodes, these times were 640 msec (SD, 138 msec) and 105 msec (SD, 26 msec), respectively (P less than .05 for difference in T1 times, P greater than .05 for difference in T2 times). Histograms showed considerable overlap in the relaxation times of benign and malignant nodes such that absolute measurement of these times will likely be of limited clinical value.

IV contrast material for abdominal CT: comparison of three methods of administration

Despite a decade of experience, there is still no consensus as to the optimal IV contrast regimen for use in combined abdominal and pelvic CT scanning. In order to determine which regimen is most effective, 90 patients undergoing CT were prospectively randomized into one of three groups, depending on the method by which IV contrast material was administered: (1) a single bolus (150 ml or 175 ml, depending on the patient's weight) started when scans were made at the level of the dome of the diaphragm; (2) a split bolus delivered by means of a power injector, with the first bolus (100 or 125 ml) given when scans were made at the level of the dome of the diaphragm and the second bolus (50 ml) given when scans were made at the level of the iliac crest; (3) an initial hand-delivered bolus (100 or 125 ml) given when scans were made at the level of diaphragm, followed by rapid IV drip infusion of 50 ml throughout the remainder of the study. Quantitative comparison of pre- and postcontrast scans was performed at two levels: at the mid-liver to assess hepatic enhancement and 1 cm above the sacrosciatic notch to assess pelvic vascular enhancement. The single bolus provided better mean liver enhancement (46 H) than did either the split-bolus (36 H) or the bolus-drip (32 H) method (p less than .05). The last two methods achieved a sufficient aortocaval difference (greater than 10 H) to allow for evaluation of the liver in the nonequilibrium phase of contrast enhancement in which lesion detection is thought to be optimal. Mean enhancement of pelvic vessels was significantly better with the split bolus (arterial enhancement of 56 H, venous enhancement of 47 H) than with the single bolus (34 H, 31 H) or bolus-drip infusion (38 H, 35 H) (p less than .05). We conclude that the split-bolus method is optimal for routine combined abdominal and pelvic CT scanning. The bolus-drip method is the least effective method for administering the contrast material.

Small renal cell carcinomas: resolving a diagnostic dilemma

Thirty-nine patients with pathologically proved renal cell carcinomas 3 cm or les in diameter were examined. Results of intravenous urography (n = 30) were true positive in 20 patients and false negative in ten (sensitivity, 67%). Renal ultrasound (US) (n = 29) had true-positive results in 23 patients and false-negative results in six (sensitivity, 79%); computed tomography (CT) (n = 36) had true-positive results in 34 and false-negative results in two (sensitivity, 94%). For selective renal angiography (n = 35%), the results were true positive in 26 and false negative in nine (sensitivity, 74%), with typical hypervascular renal cell carcinomas demonstrated in 17. Finally, the findings of percutaneous fine-needle aspiration biopsy were true positive in one of five patients when US guidance was used (sensitivity, 20%) and in five of eight when CT guidance was used (sensitivity, 62%). Small renal cell carcinomas are more frequently encountered in clinical practice than heretofore realized, and they are best imaged by CT.

MR diagnosis of pancreatic transplant rejection

To determine the role of MR imaging in the assessment of pancreatic transplant rejection, we prospectively obtained 13 MR scans in nine transplant patients. The presence of rejection was verified pathologically by pancreatic transplant biopsies in five patients. In two additional patients, rejection was proved by concordant renal transplant biopsy as well as by compatible clinical and laboratory data. In the remaining two patients, in whom no biopsy was done, clinical and laboratory data showed no evidence of rejection. The mean T2 of the seven pancreata undergoing rejection was significantly elevated (86 msec) compared with the mean T2 of the two transplants not undergoing rejection (59 msec) (p less than .002). These preliminary results suggest that MR may be useful in the noninvasive diagnosis of pancreatic rejection.

Adrenal masses in oncologic patients: functional and morphologic evaluation

The role of adrenocortical scintigraphy in the evaluation of unilateral adrenal masses detected with computed tomography (CT) in 28 oncologic patients with normal adrenal function was studied prospectively with the use of NP-59 (iodine-131-6-iodomethyl-19-norcholesterol). The diagnosis was proved by means of percutaneous fine-needle aspiration cytologic examination in 20 patients, surgical biopsy in one, and clinical and CT follow-up in seven. In 14 of the 28 patients, there was increased uptake of the NP-59 on the side of the adrenal mass detected at CT (concordant uptake). Thirteen of the 14 masses with concordant uptake were greater than 2 cm in diameter, and one was 1.5 cm; all were found to be adenomas. In 11 of 28 patients there was decreased uptake on the side of the mass detected at CT (discordant uptake). None of these 11 masses were adenomas; nine were metastases and two were adrenal cysts. Uptake was indeterminate (symmetric) in three patients, two of whom had adrenal adenomas and one an adrenal metastasis; each mass with indeterminate uptake was less than 2 cm in diameter.

MR evaluation of liver iron overload

Children and young adults with hemolytic anemias requiring frequent transfusions develop increased liver iron content. We evaluated 15 chronically transfused children with sickle cell disease to determine whether spin-echo magnetic resonance (MR) imaging was useful in assessing the degree of iron overload. Quantitative MR parameters were correlated with liver biopsy iron determinations and serum ferritin levels. The best predictor of liver iron was the ratio of the intensities between the liver and paraspinal musculature on somewhat T1 weighted sequence (repetition time 0.5 s, echo time 28 ms), R2 = 0.58. Magnetic resonance was able to separate those patients with liver iron levels greater than 100 micrograms/mg (intensity ratios approximately 0.4), from those with levels less than 100 micrograms/mg (intensity ratios near 1). However, MR was unable to quantitate liver iron in patients with values ranging from 100 to 400 micrograms/mg since similar intensity ratios were present in this range. Thus, MR provides a qualitative rather than quantitative assessment of liver iron overload.

Ischemic or infarcted bowel: CT findings

Computed tomography (CT) has been used in the evaluation of patients with suspected bowel ischemia or infarction. To assess its efficacy in this setting, the CT scans and medical records of 23 patients with proved bowel ischemia or infarction were retrospectively reviewed. Surgery or autopsy revealed that the colon was involved in 17 patients, the small bowel in 13, and the stomach in one (some patients had multiple sites of involvement). The prospective CT interpretation enabled a specific diagnosis of bowel ischemia or infarction in only six of 23 patients (26%). However, in 13 patients (56%), the CT scans were considered useful in patient treatment. A retrospective review of CT scans indicated that bowel dilatation was present in 13 of 23 patients (56%); however, it was not always restricted to the ischemic area. Six of 23 patients (26%) had bowel wall thickening greater than 3 mm, but two had thickening in areas that were not ischemic at surgery. Pneumatosis intestinalis and portal venous gas were seen in only five patients (22%) and three patients (13%), respectively. Superior mesenteric artery thrombosis and free intraperitoneal gas were each found in only one patient (4%).

Bronchogenic carcinoma metastatic to normal-sized lymph nodes: frequency and significance

CT staging of mediastinal lymph node metastases from bronchogenic carcinoma is a subject of considerable controversy. The frequency of metastases to normal-sized lymph nodes is a critical issue related to the sensitivity of CT. The authors prospectively examined 42 patients with bronchogenic carcinoma with CT; in 39, careful surgical-pathologic correlation of mediastinal lymph node status was possible. Only 7% had metastases limited to mediastinal lymph nodes that were normal-sized at CT. This reflected a low overall frequency of metastases to normal-sized nodes and several diagnostic factors that converted potentially false-negative studies into true-positive CT studies. In this small series, metastases to enlarged nodes were more likely to have extracapsular spread of tumor, a poor prognostic factor. Overall, the authors do not consider metastases to normal-sized mediastinal lymph nodes to be a major problem in CT staging of non-small cell lung cancer.

Central lung masses: prediction with CT of need for pneumonectomy versus lobectomy

To assess the possible role of computed tomography (CT) in predicting the need for pneumonectomy rather than lobectomy, the authors retrospectively analyzed the CT scans of 26 patients requiring pneumonectomy (n = 21) or lobectomy (n = 5) for resection of central pulmonary abnormality. Twenty-three patients had primary lung cancer, two had metastatic carcinoma, and one had a massive granuloma. Scans were evaluated for tumor involvement of bronchi and pulmonary arteries and veins and for evidence of tumor extension across a fissure. Findings were compared with detailed surgical and pathologic data. Pneumonectomy was necessary most commonly because of proximal bronchial tumor invasion (13 patients). CT showed poor sensitivity (50%-54%) in depicting central bronchial and central pulmonary artery involvement as well as transfissural tumor extent. The results suggest that CT is not highly accurate in predicting the lobectomy/pneumonectomy decision in patients with central lung masses.

MR imaging in hydatid disease of the liver

We describe the appearance on MR of hydatid disease of the liver in 2 patients. The lesions were well demonstrated using spin-echo pulse sequences, and could be easily seen with either T1 or T2 weighting; however, maximum information was obtained using both. In these 2 cases, a thin, low signal boundary was noted around the cysts; this finding may prove useful in differential diagnosis.

The varied appearances of hepatic cavernous hemangiomas with sonography, computed tomography, magnetic resonance imaging and scintigraphy

The incidental detection of an hepatic cavernous hemangioma may create a problem in differential diagnosis. The authors here review the characteristics of hemangiomas as recorded by various types of imaging.

Pheochromocytoma and paraganglioma: comparison of MR imaging with CT and I-131 MIBG scintigraphy

To ascertain the magnetic resonance (MR) imaging characteristics of pheochromocytomas and paragangliomas and to compare MR with computed tomography (CT) and iodine-131 metaiodobenzylguanidine (I-131 MIBG), 19 patients (18 with pheochromocytomas, one with a paraganglioma) were studied. The 18 patients with pheochromocytomas had had positive findings with I-131 MIBG scintigraphy. Abdominal pheochromocytomas were generally hypointense compared with normal liver on T1-weighted MR images and extremely hyperintense on T2-weighted MR images. MR imaging was preferable to CT in the evaluation of primary pheochromocytomas due to superior tissue characterization, particularly in the patient with hypertension and borderline catecholamine levels. For patients with recurrent or metastatic disease, the data suggest that I-131 MIBG scintigraphy is the examination of choice.