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Biomedical subjects

J P Earls

Publications and source records attributed to J P Earls.

At least 19 recordsLinked to original sources
PubMed2000

Comparison studies of CT and MRI in patients with hepatic metastases.

The increasing use of systemic and directed liver therapy for patients with hepatic metastases has created a demand for improved accuracy of noninvasive imaging techniques. Computed tomography (CT) and magnetic resonance imaging (MRI) are the most common studies used for imaging the liver in oncology patients. Both modalities have undergone substantial technical improvement in the past decade, and it is often unclear which technique is better suited to specific clinical circumstances. This article will review the major recent developments in each modality, including dual-phase spiral CT, CT angiography, ultrafast MRI, and MRI enhanced with liver-specific contrast agents. Studies that directly compared state-of-the-art CT and MRI will be emphasized. This review will give the reader a better understanding of the capabilities and limitations of these techniques and will clarify which is best used for specific clinical situations.

Contrast Media↗
PubMed1999

Echo-train STIR MRI of the liver: comparison of breath-hold and non-breath-hold imaging strategies.

The purpose of this study was to evaluate echo-train short inversion-time inversion recovery (STIR) sequences and compare the results obtained with breath-hold and non-breath-hold imaging strategies. Forty-one patients referred for hepatic magnetic resonance were imaged with both a breath-hold STIR (BH-STIR; acquisition time [TA] 16-20 seconds x 2) and a non-breath-hold STIR (NBH-STIR; TA 210-256 seconds). Quantitative analysis of the liver, spleen, and up to five hepatic lesions per patient was performed. Three blinded readers recorded the number of focal lesions depicted by each study and qualitatively evaluated overall image quality, lesion conspicuity, and image artifacts. The BH-STIR had greater sensitivity (98.8% vs. 91.6%) for detection of hepatic lesions than the NBH-STIR. The BH-STIR was statistically superior in four measures of image quality and had fewer image artifacts. The NBH-STIR images had statistically higher signal-to-noise (S/N, P < 0.001) and liver-lesion contrast-to-noise (C/N, P = 0.005) ratios. For the evaluation of focal hepatic lesions, a breath-hold echo-train STIR sequence provided superior overall image quality and allowed for detection of more lesions in a shorter amount of time than a non-breath-hold echo-train STIR sequence.

Artifacts↗
PubMed1999

New MR imaging contrast agents.

Many new MR contrast agents are undergoing laboratory development, are in clinical trials, or are being used for routine clinical applications. These agents function by targeting specific receptors that allow the agent to accumulate within the reticuloendothelial system, the hepatobiliary system, or the blood pool. Each agent has unique properties that offer advantages over unenhanced and gadolinium chelate-enhanced MR imaging. Use of these agents, however, requires an understanding of their current and potential clinical indications and inherent limitations. This article reviews the development, evaluation, and clinical application of a number of these agents, including ferumoxides, Mn-DPDP, AMI-227, SHU-555A, Gd-EOB/DTPA, Gd-BOPTA, and MS-325.

Biliary Tract↗
PubMed1998

Gadolinium-enhanced three-dimensional MR angiography of the entire aorta and iliac arteries with dynamic manual table translation.

Spoiled fast three-dimensional gradient-echo magnetic resonance imaging of the aorta and iliac arteries was performed in 13 patients after administration of a single bolus of gadopentetate dimeglumine. The imaging table was moved manually 40-45 cm between two acquisitions. Arterial signal-to-noise ratio did not vary significantly between the thoracic (aortic) and pelvic stations, but venous signal-to-noise ratios increased and arterial contrast-to-noise ratios decreased on the pelvic studies. This method was feasible and increased anatomic coverage.

Adult↗
PubMed1998

Gadolinium-enhanced three-dimensional MR angiography of the aorta and peripheral arteries: evaluation of a multistation examination using two gadopentetate dimeglumine infusions.

OBJECTIVE: Three-dimensional gadolinium-enhanced MR angiography is a rapid and accurate method that can at times image only a limited amount of anatomy during an examination. We evaluated a technique that doubled the anatomy imaged by obtaining two separate gadolinium-enhanced MR angiograms during a single examination. MATERIALS AND METHODS: Twenty-three patients referred for MR evaluation of aortic or peripheral vascular disease underwent two successive gadolinium-enhanced three-dimensional MR angiographic examinations during a single MR examination. An injection of 15 ml of gadopentetate dimeglumine was used for the first MR angiogram, and 25 ml was used for the second MR angiogram. The angiograms were quantitatively and qualitatively evaluated to determine the effect of residual gadolinium from the initial MR angiogram on the second angiogram. RESULTS: The two studies depicted either the entire aorta to the femoral arteries (n = 10) or the distal aorta to the popliteal arteries (n = 13). The total mean gadolinium dose was 0.245 mmol/kg per patient. An average of 15 min elapsed between injections. The value of arterial signal-to-noise ratio (mean, 48.8 versus 56.4) and artery-to-vein contrast-to-noise ratio (mean, 45.5 versus 49.0) increased between the first and second angiograms, respectively. Residual gadolinium elevated the values for venous signal-to-noise ratio (mean, 2.3 versus 7.2) and background-to-muscle signal-to-noise ratio (mean, 5.5 versus 10.1) on the second MR angiogram. Qualitative evaluation by three observers showed no significant differences in diagnostic usefulness or overall image quality between the first and second MR angiograms. CONCLUSION: The use of two low-dose gadolinium-enhanced three-dimensional MR angiograms during a single examination is a feasible approach to increase anatomic coverage when performing gadolinium-enhanced three-dimensional MR angiography of the aorta and peripheral vessels. Although background enhancement is slightly elevated on the second angiogram, such enhancement does not significantly change diagnostic usefulness or overall image quality.

Aged↗
PubMed1998

MR angiography of the thoracic, abdominal, and extremity venous system.

MR angiography is a useful clinical tool for noninvasive evaluation of the abdominal, thoracic, and peripheral venous system. A variety of MR techniques are available, although two-dimensional time-of-flight is used most commonly. MR imaging of the venous system is less hindered by technical limitations and artifacts commonly encountered with imaging of the arterial system. This article reviews the most commonly used techniques and their clinical application.

Abdomen↗
PubMed1997

Suppression of venous signal in time-of-flight MR angiography of the lower extremities after administration of gadopentetate dimeglumine.

PURPOSE: To evaluate a magnetic resonance (MR) angiography time-of-flight technique that can effectively suppress venous signal after gadopentetate dimeglumine administration. MATERIALS AND METHODS: Twelve adult patients underwent MR angiography for the evaluation of peripheral vascular disease. Gradient-echo sequences were performed after the administration of 0.2 mmol/kg gadopentetate dimeglumine. Three sequences were compared: a nontriggered sequence; a gap sequence, an electrocardiographically triggered, segmented sequence with a 7-mm gap between saturation and imaging sections; and a no-gap sequence, a similar sequence as gap but with partially overlapping imaging and saturation sections. For each sequence, identical regions of interest were generated for arterial, venous, and background muscle tissue and noise. A paired Student t test was used to compare the signal-to-noise and contrast-to-noise ratios (C/Ns) among the sequences. In seven patients, the no-gap sequence was used to acquire MR angiograms of the distal lower extremities. RESULTS: The mean artery-muscle C/N was similar for the triggered sequences; both were statistically significantly greater than the ratios for the nontriggered sequence. Venous suppression was much better with the no-gap sequence. Overall, the best artery-vein C/N was also obtained with the no-gap sequence. MR angiograms with effective venous suppression could be obtained only with the no-gap sequence. CONCLUSION: Time-of-flight MR angiograms can be obtained with effective venous suppression after the administration of 0.2 mmol/kg gadopentetate dimeglumine.

Aged↗
PubMed1997

Thoracic aorta: comparison of gadolinium-enhanced three-dimensional MR angiography with conventional MR imaging.

PURPOSE: To evaluate gadolinium-enhanced three-dimensional magnetic resonance (MR) angiography for thoracic aortic disease and to compare this technique with conventional thoracic MR imaging. MATERIALS AND METHODS: One hundred eight consecutive patients underwent 122 thoracic MR examinations, including conventional MR imaging followed by enhanced three-dimensional MR angiography. A gradient-echo sequence was used at 1.5 T (116 examinations) and 1.0 T (6 examinations) during infusion of 0.2 mmol/kg gadopentetate dimeglumine. Two independent readers (A and B), with varied experience in thoracic MR angiography, retrospectively evaluated the images for presence of aortic dissection, aneurysm, arch vessel disease, and protruding atheroma. Correlation with findings of surgery or other imaging modalities was available in 98 cases. RESULTS: Enhanced MR angiography was sensitive (92%-96%) and specific (100%) for acute and chronic aortic dissection (n = 26) and was as useful as conventional MR imaging in the diagnosis of aneurysm (n = 43) and arch vessel disease (n = 7). One of two intramural hematomas were overlooked at MR angiography by reader A, and both were overlooked by reader B. CONCLUSION: Enhanced three-dimensional MR angiography is a rapid and accurate imaging modality in diagnosis of thoracic aortic disease but is insensitive to intramural hematoma.

Adolescent↗
PubMed1997

Hepatic arterial-phase dynamic gadolinium-enhanced MR imaging: optimization with a test examination and a power injector.

To optimize findings at dynamic gadolinium-enhanced hepatic magnetic resonance imaging in the hepatic arterial phase, a timing examination was performed after injection of a 0.5-mL timing bolus of gadopentetate dimeglumine. In the experimental group (n = 28), power injection was used and the imaging delay was determined in each patient on the basis of the results of the timing examination. In the control group (n = 28), hand injection and a fixed 20-second imaging delay were used. Arterial-phase examinations (defined as relative liver enhancement of not more than 30% of peak parenchymal enhancement) were successful in 26 (93%) experimental group patients and in 17 (61%) control group patients.

Adolescent↗
PubMed1996

Dysplastic nodules and hepatocellular carcinoma: thin-section MR imaging of explanted cirrhotic livers with pathologic correlation.

PURPOSE: To evaluate detection and characterization of hepatocellular nodules in fresh whole explanted cirrhotic livers at thin-section magnetic resonance (MR) imaging. MATERIALS AND METHODS: T1-weighted spin-echo and T2-weighted fast spin-echo MR imaging (5-mm-thick sections) were performed in a head coil at 1.5 T in the whole cirrhotic livers of 28 consecutive patients within 4 hours of explantation. MR imaging findings were correlated with findings at pathologic examination, and new international terminology was used to classify the hepatocellular nodules. RESULTS: At pathologic examination, 42 suspect (other than regenerative) nodules were identified in 11 patients. MR imaging depicted 41 of 42 (98%) of these nodules (five of five hepatocellular carcinomas [HCCs {diameter, > or = 2 cm}], 10 of 10 small HCCs [diameter, < 2 cm], two of two dysplastic nodules with subfoci of HCC, three of three high-grade dysplastic nodules, and 21 of 22 low-grade dysplastic nodules. Lesions demonstrated the following combinations of signal intensity characteristics on thin-section T1- and T2-weighted images, respectively: HCC, hyperintense, hypointense (n = 3); hyperintense, hyperintense (n = 1); hypointense, isointense (n = 1). Small HCC, hyperintense, hypointense (n = 7); hypointense, hyperintense (n = 2); hyperintense, hyperintense (n = 1). Both dysplastic nodules with subfoci of HCC, hyperintense, hypointense. All seven nonsiderotic low-grade dysplastic nodules, hyperintense, hypointense. All 14 siderotic low-grade dysplastic nodules, hypointense, hypointense. All three high-grade dysplastic nodules, hyperintense, hypointense. CONCLUSION: The variable signal intensity characteristics of HCCs made reliable diagnosis impossible, but the thinsection unenhanced in vitro MR images were sensitive for detection of HCCs and dysplastic nodules in cirrhotic livers.

Carcinoma, Hepatocellular↗
PubMed1996

Breath-hold single-dose gadolinium-enhanced three-dimensional MR aortography: usefulness of a timing examination and MR power injector.

PURPOSE: To determine the usefulness of a timing examination performed with 1 mL gadopentetate dimeglumine administered with a magnetic resonance (MR) power injector at single-dose three-dimensional (3D) MR aortography. MATERIALS AND METHODS: 3D fast imaging with steady-state precession (repetition time [msec]/echo time [msec] = 5.0/2.0, with 50 degrees flip angle) was performed in 30 patients after administration of 0.1 mmol/kg gadopentetate dimeglumine. In 15 inpatients, a power injector was used and a timing examination was performed (experimental group). In 15 outpatients, manual injection was used and a timing examination was not performed (control group). In the timing examination, 1 mL gadopentetate dimeglumine was followed with 15 mL saline, both at 2 mL/sec, during axial turbo fast low-angle shot imaging (11/4.2/300 [inversion time ¿msec¿], with a 15 degrees flip angle); one image was obtained every 2 seconds for 60 seconds. Aortic signal-to-noise ratios (S/Ns) and contrast-to-noise ratios (C/Ns) were determined on images obtained in the two groups. RESULTS: In the timing examinations, aortic S/N increased significantly (902% +/- 517 [P < .001]) and was sufficient to help determine the timing of arterial enhancement. Findings on experimental images were superior to those on control images (S/N, 29.8 vs 20.5 [P = .003]; C/N, 23.8 vs 12.8 [P < .001], respectively). The time to perform procedures and calculations at the timing examination added a mean of 4.5 minutes to each examination. CONCLUSION: The combined use of a power injector and a timing examination improved S/Ns and C/Ns at breath-hold single-dose gadolinium-enhanced 3D MR aortography.

Aged↗
PubMed1996

Mangafodipir trisodium injection (Mn-DPDP). A contrast agent for abdominal MR imaging.

Mangafodipir trisodium (Mn-DPDP) is one of several recently developed targeted hepatobiliary agents. Contrast-to-noise measurements have shown favorable results for Mn-DPDP-enhanced MR as compared with nonenhanced T1- and T2-weighted images. An improved capability for lesion detection and the ability to characterize tumors of hepatocellular origin have been demonstrated. The prolonged enhancement obtained with Mn-DPDP provides an extended window of time during which effective contrast is maintained as compared with traditional extracellular contrast agents. This report details the experimental and initial clinical experience with Mn-DPDP-enhanced MR imaging of the abdomen.

Adrenal Gland Diseases↗