Mn-DPDP enhanced MR imaging of the liver: analysis of pulse sequence performance

AIM

To compare liver enhancement and lesion-liver contrast on T1-weighted (T1W) gradient recalled echo (GRE), spin-echo (SE) and fat-suppressed SE (FS-SE) pulse sequences at Manganese-DPDP (Mn-DPDP) enhanced magnetic resonance (MR) imaging of the liver. PATIENTS AND METHODS. Twenty-one patients with known liver lesions were administered 5 mumol/kg of Mn-DPDP. TIW GRE (78/2.3/80 degrees), SE and F-SE (300/12) images were obtained before and 15 min after Mn-DPDP. Signal/noise ratio (SNR) and lesion-liver contrast/noise ratio (CNR) were calculated for each pulse sequence.

RESULTS

Liver SNR (n = 21) and lesion-liver CNR (n = 10) increased significantly after Mn-DPDP on all three pulse sequences (P < 0.0001). Liver SNR was highest on the FS-SE and GRE pulse sequences (FS-SE = 43.8, GRE = 38.4, SE = 29.2). Lesion-liver CNR was highest on the FS-SE pulse sequence (FS-SE = -29.3, SE = -23.2, GRE = -19.8), which was significantly higher than the GRE pulse sequence (P < 0.05).

CONCLUSION

The T1-weighted fat-suppressed SE (FS-SE) pulse sequence provides highest liver enhancement and lesion-liver contrast and is recommended for Mn-DPDP enhanced MR imaging.

T2 relaxation times of hypervascular and non-hypervascular liver lesions: do hypervascular lesions mimic haemangiomas on heavily T2-weighted MR images?

AIM

To correlate the T2 relaxation times of liver lesions with their vascularity at angiography and to determine whether hypervascular lesions have similar signal intensity to haemangiomas on heavily T2-weighted MR images.

PATIENTS AND METHODS

Thirty-four patients with histologically proven malignant liver lesions had both angiography and T2W (SE 3000/80,160) MR imaging (1.5 T) of the liver. Angiographically, the lesions were hypervascular in 15 and non-hypervascular in 19 patients. Fifteen additional patients with proven haemangioma also had MR imaging during the same time period. The T2 relaxation time of a representative lesion was calculated for each patient and the results compared.

RESULTS

The mean T2 time for hypervascular lesions was 76 +/- 21 ms compared with 79 +/- 18 ms for non-hypervascular lesions (P = 0.61). The mean T2 relaxation time for haemangiomas was significantly longer than either group: 147 +/- 46 ms (P = 0.0001).

CONCLUSION

The T2 relaxation times of hypervascular and non-hypervascular liver lesions are similar and are significantly shorter than those of haemangiomas. Therefore, hypervascular lesions should not mimic haemangiomas on heavily T2-weighted images.

Localised cutaneous blastomycosis : Response to fluconazole

A case of atypical cutaneous blastomycosis is reported. Patient responded to oral fluconazole 200 mg per day given for 9 months.

Liver. II: Iron oxide-based reticuloendothelial contrast agents for MR imaging. Clinical review

Iron oxide-based compounds are a new class of MR contrast agents that have a wide range of clinical applications. The biodistribution and subsequent influence on the MR image depends on the particle size. Iron oxides can be used to increase contrast-to-noise ratio, facilitating the visibility of focal liver lesions. Other applications include blood-pool imaging and targeting the reticuloendothelial system and cell surface receptors.

Preoperative staging of cancer of the pancreas: value of MR angiography versus conventional angiography in detecting portal venous invasion

OBJECTIVE

The purpose of this study was to compare contrast-enhanced MR angiography with conventional catheter angiography for detecting portal venous invasion in the preoperative staging of pancreatic cancer, using the surgical confirmation of vascular involvement as the standard of truth.

SUBJECTS AND METHODS

MR and conventional angiography were performed in 20 patients with pancreatic carcinoma, with surgical confirmation in all cases. MR angiography was performed at 1.5 T, with coronal (2.9 mm) and axial (6.0 mm) contrast-enhanced breath-hold two-dimensional time-of-flight imaging. Data from each imaging technique were collected prospectively and analyzed in a blinded fashion by expert vascular radiologists. Vascular involvement in each patient and in each vessel (main portal vein, confluence, splenic vein, and superior mesenteric vein) determined whether the tumor was resectable (normal, abutment) or nonresectable (encased, occluded). Surgical confirmation of the vascular involvement of the portal venous structures was used as the standard of truth in all patients.

RESULTS

Among the 20 patients, 11 tumors were surgically resectable and seven were nonresectable with performance of a palliative bypass. MR angiography and conventional angiography had an overall concordance in 65% of patients (13/20; seven resectable, four nonresectable, two false-negatives) on the basis of the vascular status in each patient of the portal venous structures and in 84% (47/56) of the individual vessels surgically confirmed. MR angiography correctly identified 11 of 11 resectable patients and five of nine nonresectable patients, with four false-negative cases. Conventional angiography correctly identified seven of 11 resectable patients and six of nine nonresectable patients, with three false-negative cases and four false-positive cases.

CONCLUSION

The lack of false-positives by MR angiography suggests that MR imaging may provide a noninvasive screen for nonresectability on the basis of vascular involvement, with no patients with potentially resectable tumors being denied surgery by MR angiography in this cohort. However, the presence of false-negatives using MR angiography indicates the procedure would still not fully eliminate unnecessary laparotomies.

Homologues of murine Vh11 gene are conserved during evolution

Since the murine Vh11 gene family shows 75% homology with group III VH gene families and is preferentially expressed in B-1 lymphocytes, we have analyzed if corresponding Vh11 genes existed across phylogenetically distant mammalian lineages. In a Southern blot, homologues of the murine Vh11 gene were detected in the genomic DNA from rats, pigs, sheep, cattle, horses, dogs and man. These observations suggest conservation of corresponding sequences of the Vh11 gene family during evolution, similar to group III VH genes, either because of strong selection pressures essential for species fitness and survival or molecular drive leading to these consequences.

MR contrast material for vascular enhancement: value of superparamagnetic iron oxide

OBJECTIVE

The purpose of this study were to quantify abdominal vascular enhancement and to prove the feasibility of iron oxide-enhanced MR angiography in humans using three doses of superparamagnetic iron oxide agent AMI 227.

SUBJECTS AND METHODS

Sixteen patients randomly received either 0.8, 1.1, or 1.7 mg Fe/kg of ultrasmall superparamagnetic iron oxide agent AMI 227. T1-weighted breath-hold gradient-echo images were obtained before and 45 min after i.v. administration of AMI 227. Signal intensity was measured in the aorta, the inferior vena cava, the portal vein, and muscle on unenhanced and contrast-enhanced images. Signal-to-noise ratios and enhancement [(SNR after contrast-SNR before contrast) / SNR before contrast] were calculated. Vessels were visually graded before and after administration of AMI 227.

RESULTS

All vessels showed statistically significant enhancement 45 min. after administration of AMI 227 by both qualitative and quantitative measures (p < .001). There was no significant increase in noise or signal intensity of muscle after contrast material was administered. The amount of enhancement was not statistically significantly different among the three doses.

CONCLUSIONS

AMI 227, which is currently in phase III clinical trials, demonstrates significant vascular enhancement and may prove useful as an MR angiographic contrast agent.

Alien attractors and memory annihilation of structured sets in Hopfield networks

This paper considers the encoding of structured sets into Hopfield associative memories. A structured set is a set of vectors with equal Hamming distance h from one another, and its centroid is an external vector that has distance h/2 from every vector of the set. Structured sets having centroids are not infrequent. When such a set is encoded into a noiseless Hopfield associative memory using a bipolar outer-product connection matrix, and the network operates with synchronous neuronal update, the memory of all encoded vectors is annihilated even for sets with as few as three vectors in dimension n>5 (four for n=5). In such self-annihilating structured sets, the centroid emerges as a stable attractor. We call it an alien attractor. For canonical structured sets, self-annihilation takes place only if h<n/2. Self-annihilation does not occur and alien attractors do not emerge in dimensions less than five.

[Echo-planar imaging (EPI) of the abdomen]

The time resolution of echoplanar imaging (EPI) allows the acquisition of images < or = 100 ms, thus eliminating motion-related artifacts of the abdomen. Physical limitations are restrictions in signal-to-noise ratio and spatial resolution. Breath-held acquisitions are recommended to avoid spatial misregistrations and to ensure a defined slice position. Clinical studies have demonstrated the usefulness of EPI for the detection and characterization of focal liver lesions. The development of clinical strategies of EPI for abdominal imaging requires the administration of gastrointestinal contrast agents as in computed tomography. Current clinically approved CT contrast agents appear to be applicable for abdominal EPI because of their long relaxation times.

Endoscopic retrograde pancreatography: imaging findings

Endoscopic retrograde pancreatography (ERP) is commonly used in the diagnosis and management of pancreatic disorders. The aim of this pictorial essay is to provide an overview of the common appearances of normal anatomy, anatomic variants, and pancreatic diseases at ERP.

Gadoteridol-enhanced MR imaging of malignant hepatic tumors: effects of triple versus standard doses on lesion-liver contrast

OBJECTIVE

The purpose of this study was to compare liver signal-to-noise ratio (SNR), lesion SNR, and lesion-liver contrast-to-noise-ratio (CNR) in patients with malignant liver lesions after the administration of a standard dose (0.1 mmol/kg of body weight) or a triple dose (0.3 mmol/kg) of a gadolinium chelate (gadoteridol). We hypothesized that the higher dose would produce a higher lesion-liver CNR and therefore increase the conspicuity of hepatic lesions.

MATERIALS AND METHODS

A total of 85 patients with malignant hepatic masses (61 metastases, 22 hepatocellular carcinomas, and two lymphomas) proved by histologic or follow-up studies underwent MR imaging at 1.5 T. T1-weighted spin-echo imaging and gradient-echo imaging were done before and within 1 min after (gradient echo) as well as 5 (spin echo) and 15 (spin echo) min after the injection of 0.1 or 0.3 mmol of gadoteridol per kg, randomized before the start of the study (39 patients received the standard dose, and 46 received the triple dose). The signal intensities of the liver and lesions and the SD of background noise were measured by use of regions of interest to calculate the SNR of the liver and malignant lesions and the lesion-liver CNR.

RESULTS

The lesion-liver CNR was increased significantly at 5 and 15 min after the administration of gadoteridol. No significant differences in the liver SNR, lesion SNR, and lesion-liver CNR (after 1 min: standard dose, -5 +/- 8, and triple dose, -4 +/- 14; after 5 min: standard dose, -1 +/- 5, and triple dose, 2 +/- 8; and after 15 min: standard dose, 1 +/- 5, and triple dose, 6 +/- 20) were found between the doses at all time points.

CONCLUSION

Triple-dose gadoteridol does not improve the lesion-liver contrast of malignant hepatic lesions over that provided by the standard dose and is not warranted for liver MR imaging.

Fast MR imaging: technical strategies

Since the introduction of MR imaging for medical use in the early 1980s, there has been a continuous trend toward reduction in scan times. Whereas it took over 24 hr to acquire and display the earliest MR images [1], scan times of well under a second are now feasible. The trend toward shorter scan times is based on a need to reduce motion-related artifacts, to provide more comprehensive studies in a reasonable examination time (such as those with multiple pulse sequences, multiple planes, or contrast media), or to increase patient throughput to reduce per-patient examination costs.

Hepatocellular adenoma: MR imaging features with pathologic correlation

OBJECTIVE

The purpose of this study was to describe the MR imaging characteristics of hepatic adenomas and to correlate these features with pathologic findings.

MATERIALS AND METHODS

Sixteen patients from four institutions who had 31 hepatocellular adenomas underwent MR imaging with T1- and T2-weighted pulse sequences at 1.5 T. Dynamic gadolinium-chelate-enhanced gradient-recalled-echo (GRE) MR imaging was done in eight patients with 15 lesions. Twenty-three lesions in 15 patients were confirmed by surgical excision. MR images were retrospectively reviewed by three experienced radiologists for signal intensity of lesions relative to liver, heterogeneity, contrast enhancement, and presence of signs of histopathologic correlates. These imaging findings were then compared with histopathologic findings.

RESULTS

Nearly all (29 of 31 lesions) hepatocellular adenomas showed heterogeneous signal intensity on MR images. Most (19/31) were predominantly hyperintense on proton density- or T2-weighted images; the predominant signal intensity on T1-weighted images varied. Thirteen of 15 lesions showed early arterial enhancement relative to liver on dynamic GRE MR images. MR imaging was most successful in showing intratumoral hemorrhage (10 of 12 histopathologically proven lesions), large intratumoral vessels (five of five), fatty change (three of six), and peliosis (three of three cases). In two lesions, capsules (one of five) and central scars (one of three) were detected.

CONCLUSION

Hepatocellular adenomas have a highly variable appearance on MR images because of their varied histologic appearances. Although no definitive MR imaging signal or structural characteristics can be identified, tumor heterogeneity, particularly when related to hemorrhage, and early arterial enhancement can suggest a diagnosis of hepatocellular adenoma in the proper patient population.

Characterization of adrenal masses (< 5 cm) by use of chemical shift MR imaging: observer performance versus quantitative measures

OBJECTIVE

The purposes of this study were to evaluate the ability of chemical shift MR imaging to differentiate 1- to 5-cm adrenal adenomas from metastases and to compare subjective interpretation with several different quantitative measures.

SUBJECTS AND METHODS

Forty-three patients with 46 proved adrenal lesions (28 adenomas and 18 metastases) had MR imaging with a gradient-echo breath-hold technique and echo time varied to obtain in-phase and out-of-phase images. Qualitative analysis of the MR images was done by three experienced observers, who reported their confidence in diagnosing the benignity versus the malignancy of the adrenal masses on the basis of signal loss on out-of-phase images. Quantitative analysis was performed by calculating the difference in signal intensity between in-phase and out-of-phase images by use of regions of interest (signal intensity index) and by use of adrenal-liver, adrenal-spleen, and adrenal-muscle signal intensity ratios. Results between quantitative and qualitative measures were compared by use of receiver operating characteristic (ROC) analysis.

RESULTS

The mean signal intensity was significantly different between adenomas and metastases on out-of-phase images (64 versus 98) (p < .0005) but not in-phase images (130 versus 122) (p = .47). The adrenal-spleen ratio discriminated between adenomas and metastases better than did the adrenal-liver ratio, the adrenal-muscle ratio, or the signal intensity index. No significant difference in interpretation among the three observers was evident (areas under the ROC curves, 0.93, 0.95, and 0.96). The performance of the observers was comparable to the results obtained with the adrenal-spleen ratio measurement (area under the ROC curve, 0.97).

CONCLUSION

Experienced observers were able to differentiate adrenal adenomas from metastases just as well as quantitative measures. The adrenal-spleen ratio is the best quantitative means of distinguishing benign from malignant adrenal masses. Chemical shift MR imaging is a good but imperfect discriminator of adrenal adenomas.

Blood-pool MR contrast material for detection and characterization of focal hepatic lesions: initial clinical experience with ultrasmall superparamagnetic iron oxide (AMI-227)

OBJECTIVE

AMI-227 is an ultrasmall superparamagnetic iron oxide colloid known to enhance tissue T1 and T2 relaxation rates. Animal studies show that AMI-227 has an estimated blood half-life of more than 200 min. In this study, we evaluated the clinical utility of AMI-227 as an MR contrast agent for detection and characterization of focal hepatic lesions, with MR imaging done while the contrast agent is in the intravascular space (blood-pool phase).

SUBJECTS AND METHODS

Twenty-two patients with known or suspected focal hepatic masses underwent T1- and T2-weighted MR imaging of the liver at 1.5 T before and immediately after drip infusion of AMI-227 at doses of 0.8, 1.1, or 1.7 mg Fe/kg. Unenhanced and contrast-enhanced images were analyzed qualitatively (lesion detection and tissue characterization) and quantitatively (lesion-liver contrast-to-noise ratio).

RESULTS

AMI-227 enhanced signal in normal liver and blood vessels on T1-weighted images and decreased signal in these tissues on T2-weighted images. Qualitatively and quantitatively, lesion-liver contrast was increased for solid tumors (non-cyst and nonhemangioma) at all three doses (p < .02) on both T1- and T2-weighted images. Differentiation between blood vessels and small lesions was easier on contrast-enhanced images, which allowed increased confidence in excluding lesions. Unique enhancement patterns were noted for hemangiomas, solid tumors, and cysts.

CONCLUSION

Initial clinical experience suggests that AMI-227 is a useful contrast agent for detection and characterization of focal hepatic lesions.

Secretory symptoms from metastatic adrenal cortical carcinoma responding to octreotide

The prognosis of patients with metastatic adrenal cortical carcinoma is poor, and their disabling symptoms are usually unresponsive to conventional therapy. A patient with Cushing's syndrome secondary to a secretory adrenal cortical carcinoma was treated with octreotide, endocrine therapy and chemotherapy having failed. Treatment led to a dramatic relief of her symptoms with a fall in corticosteroid secretion. Somatostatin analogue therapy for this tumour should be encouraged in view of the lack of alternative palliative treatment.

Do widowers use the health care system differently? Does intervention make a difference?

OBJECTIVE

To describe the health care use patterns of widowers who had participated in a randomized trial of mutual support, and of a matched cohort of married men

DESIGN

Retrospective audit of Ministry of Health use data

SETTING

The family practice unit in a general teaching hospital.

PARTICIPANTS

The 113 new widowers (61 treatment, 52 waiting-list controls) who participated in a randomized trial of mutual support, and 111 married men matched for age

INTERVENTIONS

Mutual support program

MAIN OUTCOME MEASURES

Monthly rates of visits to family physicians, psychiatrists, and all other specialists for the three cohorts

RESULTS

Visit rates to family physicians and specialists (SPs) for the married men were stable for the 20 months of the study; rates for the widowers rose significantly from the time of loss to the end of the intervention (for FPs, f = 13.18, df = 2, P < .01; for SPs, f = 5.34, df = 2, P = .005). Rates for FPs declined after intervention for the treatment group, but kept rising among the controls (f = 4.17, df = 1, P = .044).

CONCLUSIONS

The decreased physician visit rate among those taking part in the mutual support program suggests that this program met some of the widowers' social support needs that would otherwise have led to the use of health care resources.

Adrenal gland enhancement at MR imaging with Mn-DPDP

PURPOSE

To determine adrenal gland enhancement with manganese (II) N,N' dipyridoxylethylenediamine-N,N'-diacetate 5,5'bis(phosphate) (DPDP) at magnetic resonance imaging.

MATERIALS AND METHODS

After phase III trials, fat-suppressed, motion-compensated, T1-weighted spin-echo images (repetition time, 500 msec; echo time, 12 msec) of 13 consecutive patients were obtained at 1.5 T at one site, prior to and approximately 30 minutes after intravenous administration of 5 mumol/kg Mn-DPDP. Images were analyzed visually and by means of region-of-interest measurements, normalized to spleen. With data added from three more sites, enhancement of three adrenal adenomas and two metastases was analyzed.

RESULTS

Twenty-five of 26 adrenal glands were depicted on MR images, and all showed enhancement. Mean adrenal enhancement (38%) was comparable to mean enhancement of liver (46%), pancreas (25%), and renal cortex (58%). Adrenal cortex and medulla could not be distinguished in nonenhanced or enhanced images. All three adrenal adenomas enhanced by more than 40%, but the metastases did not enhance.

CONCLUSION

Functioning adrenal tissue (glands and at least some adenomas) are enhanced with Mn-DPDP.