Evaluation of adipose tissue volume quantification with IDEAL fat-water separation

PURPOSE

To validate iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) for adipose tissue volume quantification. IDEAL allows MRI images to be produced only from adipose-containing tissues; hence, quantifying adipose tissue should be simpler and more accurate than with current methods.

MATERIALS AND METHODS

Ten healthy controls were imaged with 1.5 Tesla (T) Spin Echo (SE), 3.0T T1-weighted spoiled gradient echo (SPGR), and 3.0T IDEAL-SPGR. Images were acquired from the abdomen, pelvis, mid-thigh, and mid-calf. Mean subcutaneous and visceral adipose tissue volumes were compared between the three acquisitions for each subject.

RESULTS

There were no significant differences (P>0.05) between the three acquisitions for subcutaneous adipose tissue volumes. However, there was a significant difference (P=0.0002) for visceral adipose tissue volumes in the abdomen. Post hoc analysis showed significantly lower visceral adipose tissue volumes measured by IDEAL versus 1.5T (P<0.0001) and 3.0T SPGR (P<0.002). The lower volumes given by IDEAL are due to its ability to differentiate true visceral adipose tissue from other bright structures like blood vessels and bowel content that are mistaken for adipose tissue in non-fat suppressed images.

CONCLUSION

IDEAL measurements of adipose tissue are equivalent to established 1.5T measurement techniques for subcutaneous depots and have improved accuracy for visceral depots, which are more metabolically relevant.

A simple noniterative principal component technique for rapid noise reduction in parallel MR images

The utilization of parallel imaging permits increased MR acquisition speed and efficiency; however, parallel MRI usually leads to a deterioration in the signal-to-noise ratio when compared with otherwise equivalent unaccelerated acquisitions. At high accelerations, the parallel image reconstruction matrix tends to become dominated by one principal component. This has been utilized to enable substantial reductions in g-factor-related noise. A previously published technique achieved noise reductions via a computationally intensive search for multiples of the dominant singular vector which, when subtracted from the image, minimized joint entropy between the accelerated image and a reference image. We describe a simple algorithm that can accomplish similar results without a time-consuming search. Significant reductions in g-factor-related noise were achieved using this new algorithm with in vivo acquisitions at 1.5 T with an eight-element array.

Robust multipoint water-fat separation using fat likelihood analysis

Fat suppression is an essential part of routine MRI scanning. Multiecho chemical-shift based water-fat separation methods estimate and correct for Bo field inhomogeneity. However, they must contend with the intrinsic challenge of water-fat ambiguity that can result in water-fat swapping. This problem arises because the signals from two chemical species, when both are modeled as a single discrete spectral peak, may appear indistinguishable in the presence of Bo off-resonance. In conventional methods, the water-fat ambiguity is typically removed by enforcing field map smoothness using region growing based algorithms. In reality, the fat spectrum has multiple spectral peaks. Using this spectral complexity, we introduce a novel concept that identifies water and fat for multiecho acquisitions by exploiting the spectral differences between water and fat. A fat likelihood map is produced to indicate if a pixel is likely to be water-dominant or fat-dominant by comparing the fitting residuals of two different signal models. The fat likelihood analysis and field map smoothness provide complementary information, and we designed an algorithm (Fat Likelihood Analysis for Multiecho Signals) to exploit both mechanisms. It is demonstrated in a wide variety of data that the Fat Likelihood Analysis for Multiecho Signals algorithm offers highly robust water-fat separation for 6-echo acquisitions, particularly in some previously challenging applications.

T(1) independent, T(2) (*) corrected chemical shift based fat-water separation with multi-peak fat spectral modeling is an accurate and precise measure of hepatic steatosis

PURPOSE

To determine the precision and accuracy of hepatic fat-fraction measured with a chemical shift-based MRI fat-water separation method, using single-voxel MR spectroscopy (MRS) as a reference standard.

MATERIALS AND METHODS

In 42 patients, two repeated measurements were made using a T(1) -independent, T 2*-corrected chemical shift-based fat-water separation method with multi-peak spectral modeling of fat, and T(2) -corrected single voxel MR spectroscopy. Precision was assessed through calculation of Bland-Altman plots and concordance correlation intervals. Accuracy was assessed through linear regression between MRI and MRS. Sensitivity and specificity of MRI fat-fractions for diagnosis of steatosis using MRS as a reference standard were also calculated.

RESULTS

Statistical analysis demonstrated excellent precision of MRI and MRS fat-fractions, indicated by 95% confidence intervals (units of absolute percent) of [-2.66%,2.64%] for single MRI ROI measurements, [-0.81%,0.80%] for averaged MRI ROI, and [-2.70%,2.87%] for single-voxel MRS. Linear regression between MRI and MRS indicated that the MRI method is highly accurate. Sensitivity and specificity for detection of steatosis using averaged MRI ROI were 100% and 94%, respectively. The relationship between hepatic fat-fraction and body mass index was examined.

CONCLUSION

Fat-fraction measured with T(1) -independent T 2*-corrected MRI and multi-peak spectral modeling of fat is a highly precise and accurate method of quantifying hepatic steatosis.

The predictive value of urinary vanillylmandelic acid testing in the diagnosis of phaeochromocytoma at the University Hospital of the West Indies

OBJECTIVE

To investigate the positive predictive value (PPV) of urinary vanillylmandelic acid (VMA) testing in the diagnosis of phaeochromocytoma and to describe the features associated with phaeochromocytoma at the University Hospital of the West Indies (UHWI).

SUBJECTS AND METHODS

There were 551 VMA tests performed from January 2003 to June 2009 and 122 tests in 85 patients were elevated (ie > or = 35 micromol/24 hr). The study patients were categorized as: (i) 'surgical' (5 patients who underwent surgery) or (ii) 'non-surgical' (remaining 80 patients). Forty medical charts (out of 85) were reviewed using a standardized data extraction form.

RESULTS

The median age for patients in the non-surgical group (with charts reviewed, n = 35) was 36 years (range 9-70) and the median VMA was 43 micromol/24 hr (IQR 38-51). Of these patients, 83% had one or no symptom typical of phaeochromocytoma. In the surgical group the median VMA was 58 micromol/24 hr (IQR 44-101); phaeochromocytoma was confirmed histologically in 3 patients, all of whom had several symptoms typical of catecholamine excess. VMA testing had a PPV of 8%, specificity of 79% and sensitivity of 100%.

CONCLUSIONS

VMA testing at UHWI has poor specificity and high sensitivity. These results contrast with international data showing that VMA testing is poorly sensitive but highly specific. The use of assays with higher specificity (eg plasma or urinary metanephrines) may represent a more cost-effective approach to biochemical screening at UHWI.

Combination of complex-based and magnitude-based multiecho water-fat separation for accurate quantification of fat-fraction

Multipoint water-fat separation techniques rely on different water-fat phase shifts generated at multiple echo times to decompose water and fat. Therefore, these methods require complex source images and allow unambiguous separation of water and fat signals. However, complex-based water-fat separation methods are sensitive to phase errors in the source images, which may lead to clinically important errors. An alternative approach to quantify fat is through "magnitude-based" methods that acquire multiecho magnitude images. Magnitude-based methods are insensitive to phase errors, but cannot estimate fat-fraction greater than 50%. In this work, we introduce a water-fat separation approach that combines the strengths of both complex and magnitude reconstruction algorithms. A magnitude-based reconstruction is applied after complex-based water-fat separation to removes the effect of phase errors. The results from the two reconstructions are then combined. We demonstrate that using this hybrid method, 0-100% fat-fraction can be estimated with improved accuracy at low fat-fractions.

Quantification of hepatic steatosis with T1-independent, T2-corrected MR imaging with spectral modeling of fat: blinded comparison with MR spectroscopy

PURPOSE

To prospectively compare an investigational version of a complex-based chemical shift-based fat fraction magnetic resonance (MR) imaging method with MR spectroscopy for the quantification of hepatic steatosis.

MATERIALS AND METHODS

This study was approved by the institutional review board and was HIPAA compliant. Written informed consent was obtained before all studies. Fifty-five patients (31 women, 24 men; age range, 24-71 years) were prospectively imaged at 1.5 T with quantitative MR imaging and single-voxel MR spectroscopy, each within a single breath hold. The effects of T2 correction, spectral modeling of fat, and magnitude fitting for eddy current correction on fat quantification with MR imaging were investigated by reconstructing fat fraction images from the same source data with different combinations of error correction. Single-voxel T2-corrected MR spectroscopy was used to measure fat fraction and served as the reference standard. All MR spectroscopy data were postprocessed at a separate institution by an MR physicist who was blinded to MR imaging results. Fat fractions measured with MR imaging and MR spectroscopy were compared statistically to determine the correlation (r(2)), and the slope and intercept as measures of agreement between MR imaging and MR spectroscopy fat fraction measurements, to determine whether MR imaging can help quantify fat, and examine the importance of T2 correction, spectral modeling of fat, and eddy current correction. Two-sided t tests (significance level, P = .05) were used to determine whether estimated slopes and intercepts were significantly different from 1.0 and 0.0, respectively. Sensitivity and specificity for the classification of clinically significant steatosis were evaluated.

RESULTS

Overall, there was excellent correlation between MR imaging and MR spectroscopy for all reconstruction combinations. However, agreement was only achieved when T2 correction, spectral modeling of fat, and magnitude fitting for eddy current correction were used (r(2) = 0.99; slope ± standard deviation = 1.00 ± 0.01, P = .77; intercept ± standard deviation = 0.2% ± 0.1, P = .19).

CONCLUSION

T1-independent chemical shift-based water-fat separation MR imaging methods can accurately quantify fat over the entire liver, by using MR spectroscopy as the reference standard, when T2 correction, spectral modeling of fat, and eddy current correction methods are used.

T(2)-weighted 3D fast spin echo imaging with water-fat separation in a single acquisition

PURPOSE

To develop a robust 3D fast spin echo (FSE) T(2)-weighted imaging method with uniform water and fat separation in a single acquisition, amenable to high-quality multiplanar reformations.

MATERIALS AND METHODS

The Iterative Decomposition of water and fat with Echo Asymmetry and Least squares estimation (IDEAL) method was integrated with modulated refocusing flip angle 3D-FSE. Echoes required for IDEAL processing were acquired by shifting the readout gradient with respect to the Carr-Purcell-Meiboom-Gill echo. To reduce the scan time, an alternative data acquisition using two gradient echoes per repetition was implemented. Using the latter approach, a total of four gradient echoes were acquired in two repetitions and used in the modified IDEAL reconstruction.

RESULTS

3D-FSE T(2)-weighted images with uniform water-fat separation were successfully acquired in various anatomies including breast, abdomen, knee, and ankle in clinically feasible scan times, ranging from 5:30-8:30 minutes. Using water-only and fat-only images, in-phase and out-of-phase images were reconstructed.

CONCLUSION

3D-FSE-IDEAL provides volumetric T(2)-weighted images with uniform water and fat separation in a single acquisition. High-resolution images with multiple contrasts can be reformatted to any orientation from a single acquisition. This could potentially replace 2D-FSE acquisitions with and without fat suppression and in multiple planes, thus improving overall imaging efficiency.

A preliminary examination of the effects of genetic variants of redox enzymes on susceptibility to oedematous malnutrition and on percentage cytotoxicity in response to oxidative stress in vitro

BACKGROUND

The causes of oedematous vs non-oedematous childhood malnutrition (OM vs NOM) remain elusive. It is possible that inherited differences in handling oxidant stressors are a contributing factor.

AIMS

To test for associations between polymorphisms in five genes and (i) risk of OM, a case-control study, and (ii) percentage cytotoxicity in peripheral blood mononuclear cells (PBMCs) exposed to hydrogen peroxide (H(2)O(2)), an in vitro cell challenge study.

METHODS

Participants had been admitted previously for treatment of OM (cases, n = 74) or NOM (controls, n = 50), or were an independent set of healthy pregnant women (n = 47) who donated peripheral blood mononuclear cells. We tested for associations between genetic variation and outcome using single markers or a bivariate score constructed by counting numbers of deleterious alleles for each of 15 possible pairs of markers.

RESULTS

In the case-control study there were no significant single-marker associations with OM. We did find that higher bivariate scores were associated with OM for the pair of NAD(P)H:quinone oxidoreductase 1 and catalase (odds ratio 2·00, 95% CI 1·05-3·82). In the cell challenge experiments, there were no significant associations with percentage cytotoxicity.

CONCLUSIONS

Variation in this small set of genes seems unlikely to have a large impact on either risk of OM or cytotoxicity after H(2)O(2) exposure. The use of larger sample sizes to test the effects of a much larger set of genetic variants will be required in order to determine whether genetic variation contributes to the risk of OM. Such studies have potential for improving our understanding of causal pathways in OM.

Noise analysis for 3-point chemical shift-based water-fat separation with spectral modeling of fat

PURPOSE

To model the theoretical signal-to-noise ratio (SNR) behavior of 3-point chemical shift-based water-fat separation, using spectral modeling of fat, with experimental validation for spin-echo and gradient-echo imaging. The echo combination that achieves the best SNR performance for a given spectral model of fat was also investigated.

MATERIALS AND METHODS

Cramér-Rao bound analysis was used to calculate the best possible SNR performance for a given echo combination. Experimental validation in a fat-water phantom was performed and compared with theory. In vivo scans were performed to compare fat separation with and with out spectral modeling of fat.

RESULTS

Theoretical SNR calculations for methods that include spectral modeling of fat agree closely with experimental SNR measurements. Spectral modeling of fat more accurately separates fat and water signals, with only a slight decrease in the SNR performance of the water-only image, although with a relatively large decrease in the fat SNR performance.

CONCLUSION

The optimal echo combination that provides the best SNR performance for water using spectral modeling of fat is very similar to previous optimizations that modeled fat as a single peak. Therefore, the optimal echo spacing commonly used for single fat peak models is adequate for most applications that use spectral modeling of fat.

Association of common DNA sequence variants at 33 genetic loci with blood lipids in individuals of African ancestry from Jamaica

The relevance of loci associated with blood lipids recently identified in European populations in individuals of African ancestry is unknown. We tested association between lipid traits and 36 previously described single-nucleotide polymorphisms (SNPs) in 1,466 individuals of African ancestry from Spanish Town, Jamaica. For the same allele and effect direction as observed in individuals of European ancestry, SNPs at three loci (1p13, 2p21, and 19p13) showed statistically significant association (p < 0.05) with LDL, two loci (11q12 and 20q13) showed association with HDL cholesterol, and two loci (11q12 and 2p24) showed association with triglycerides. The most significant association was between a SNP at 1p13 and LDL cholesterol (p = 4.6 × 10(-8)). This SNP is in a linkage disequilibrium region containing four genes (CELSR2, PSRC1, MYBPHL, and SORT1) and was recently shown to relate to risk for myocardial infarction. Overall, the results of this study suggest that much of the genetic variation which influences blood lipids is shared across ethnic groups.

Phase and amplitude correction for multi-echo water-fat separation with bipolar acquisitions

PURPOSE

To address phase and amplitude errors for multi-point water-fat separation with "bipolar" acquisitions, which efficiently collect all echoes with alternating read-out gradient polarities in one repetition.

MATERIALS AND METHODS

With the bipolar acquisitions, eddy currents and other system nonidealities can induce inconsistent phase errors between echoes, disrupting water-fat separation. Previous studies have addressed phase correction in the read-out direction. However, the bipolar acquisitions may be subject to spatially high order phase errors as well as an amplitude modulation in the read-out direction. A method to correct for the 2D phase and amplitude errors is introduced. Low resolution reference data with reversed gradient polarities are collected. From the pair of low-resolution data collected with opposite gradient polarities, the two-dimensional phase errors are estimated and corrected. The pair of data are then combined for water-fat separation.

RESULTS

We demonstrate that the proposed method can effectively remove the high order errors with phantom and in vivo experiments, including obliquely oriented scans.

CONCLUSION

For bipolar multi-echo acquisitions, uniform water-fat separation can be achieved by removing high order phase errors with the proposed method.

Independent estimation of T*2 for water and fat for improved accuracy of fat quantification

Noninvasive biomarkers of intracellular accumulation of fat within the liver (hepatic steatosis) are urgently needed for detection and quantitative grading of nonalcoholic fatty liver disease, the most common cause of chronic liver disease in the United States. Accurate quantification of fat with MRI is challenging due the presence of several confounding factors, including T*(2) decay. The specific purpose of this work is to quantify the impact of T*(2) decay and develop a multiexponential T*(2) correction method for improved accuracy of fat quantification, relaxing assumptions made by previous T*(2) correction methods. A modified Gauss-Newton algorithm is used to estimate the T*(2) for water and fat independently. Improved quantification of fat is demonstrated, with independent estimation of T*(2) for water and fat using phantom experiments. The tradeoffs in algorithm stability and accuracy between multiexponential and single exponential techniques are discussed.

Quantification of hepatic steatosis with 3-T MR imaging: validation in ob/ob mice

PURPOSE

To validate quantitative imaging techniques used to detect and measure steatosis with magnetic resonance (MR) imaging in an ob/ob mouse model of hepatic steatosis.

MATERIALS AND METHODS

The internal research animal and resource center approved this study. Twenty-eight male ob/ob mice in progressively increasing age groups underwent imaging and were subsequently sacrificed. Six ob/+ mice served as control animals. Fat fraction imaging was performed with a chemical shift-based water-fat separation method. The following three methods of conventional fat quantification were compared with imaging: lipid extraction and qualitative and quantitative histologic analysis. Fat fraction images were reconstructed with single- and multiple-peak spectral models of fat and with and without correction for T2* effects. Fat fraction measurements obtained with the different reconstruction methods were compared with the three methods of fat quantification, and linear regression analysis and two-sided and two-sample t tests were performed.

RESULTS

Lipid extraction and qualitative and quantitative histologic analysis were highly correlated with the results of fat fraction imaging (r(2) = 0.92, 0.87, 0.82, respectively). No significant differences were found between imaging measurements and lipid extraction (P = .06) or quantitative histologic (P = .07) measurements when multiple peaks of fat and T2* correction were included in image reconstruction. Reconstructions in which T2* correction, accurate spectral modeling, or both were excluded yielded lower agreement when compared with the results yielded by other techniques. Imaging measurements correlated particularly well with histologic grades in mice with low fat fractions (intercept, -1.0% +/-1.2 [standard deviation]).

CONCLUSION

MR imaging can be used to accurately quantify fat in vivo in an animal model of hepatic steatosis and may serve as a quantitative biomarker of hepatic steatosis.

T1 independent, T2* corrected MRI with accurate spectral modeling for quantification of fat: validation in a fat-water-SPIO phantom

PURPOSE

To validate a T(1)-independent, T(2)*-corrected fat quantification technique that uses accurate spectral modeling of fat using a homogeneous fat-water-SPIO phantom over physiologically expected ranges of fat percentage and T(2)* decay in the presence of iron overload.

MATERIALS AND METHODS

A homogeneous gel phantom consisting of vials with known fat-fractions and iron concentrations is described. Fat-fraction imaging was performed using a multiecho chemical shift-based fat-water separation method (IDEAL), and various reconstructions were performed to determine the impact of T(2)* correction and accurate spectral modeling. Conventional two-point Dixon (in-phase/out-of-phase) imaging and MR spectroscopy were performed for comparison with known fat-fractions.

RESULTS

The best agreement with known fat-fractions over the full range of iron concentrations was found when T(2)* correction and accurate spectral modeling were used. Conventional two-point Dixon imaging grossly underestimated fat-fraction for all T(2)* values, but particularly at higher iron concentrations.

CONCLUSION

This work demonstrates the necessity of T(2)* correction and accurate spectral modeling of fat to accurately quantify fat using MRI.

Quantification of hepatic steatosis with MRI: the effects of accurate fat spectral modeling

PURPOSE

To develop a chemical-shift-based imaging method for fat quantification that accounts for the complex spectrum of fat, and to compare this method with MR spectroscopy (MRS). Quantitative noninvasive biomarkers of hepatic steatosis are urgently needed for the diagnosis and management of nonalcoholic fatty liver disease (NAFLD).

MATERIALS AND METHODS

Hepatic steatosis was measured with "fat-fraction" images in 31 patients using a multiecho chemical-shift-based water-fat separation method at 1.5T. Fat-fraction images were reconstructed using a conventional signal model that considers fat as a single peak at -210 Hz relative to water ("single peak" reconstruction). Fat-fraction images were also reconstructed from the same source images using two methods that account for the complex spectrum of fat; precalibrated and self-calibrated "multipeak" reconstruction. Single-voxel MRS that was coregistered with imaging was performed for comparison.

RESULTS

Imaging and MRS demonstrated excellent correlation with single peak reconstruction (r(2) = 0.91), precalibrated multipeak reconstruction (r(2) = 0.94), and self-calibrated multipeak reconstruction (r(2) = 0.91). However, precalibrated multipeak reconstruction demonstrated the best agreement with MRS, with a slope statistically equivalent to 1 (0.96 +/- 0.04; P = 0.4), compared to self-calibrated multipeak reconstruction (0.83 +/- 0.05, P = 0.001) and single-peak reconstruction (0.67 +/- 0.04, P < 0.001).

CONCLUSION

Accurate spectral modeling is necessary for accurate quantification of hepatic steatosis with MRI.

Multiecho water-fat separation and simultaneous R2* estimation with multifrequency fat spectrum modeling

Multiecho chemical shift-based water-fat separation methods are seeing increasing clinical use due to their ability to estimate and correct for field inhomogeneities. Previous chemical shift-based water-fat separation methods used a relatively simple signal model that assumes both water and fat have a single resonant frequency. However, it is well known that fat has several spectral peaks. This inaccuracy in the signal model results in two undesired effects. First, water and fat are incompletely separated. Second, methods designed to estimate T(2) (*) in the presence of fat incorrectly estimate the T(2) (*) decay in tissues containing fat. In this work, a more accurate multifrequency model of fat is included in the iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) water-fat separation and simultaneous T(2) (*) estimation techniques. The fat spectrum can be assumed to be constant in all subjects and measured a priori using MR spectroscopy. Alternatively, the fat spectrum can be estimated directly from the data using novel spectrum self-calibration algorithms. The improvement in water-fat separation and T(2) (*) estimation is demonstrated in a variety of in vivo applications, including knee, ankle, spine, breast, and abdominal scans.

Comprehensive quantification of signal-to-noise ratio and g-factor for image-based and k-space-based parallel imaging reconstructions

Parallel imaging reconstructions result in spatially varying noise amplification characterized by the g-factor, precluding conventional measurements of noise from the final image. A simple Monte Carlo based method is proposed for all linear image reconstruction algorithms, which allows measurement of signal-to-noise ratio and g-factor and is demonstrated for SENSE and GRAPPA reconstructions for accelerated acquisitions that have not previously been amenable to such assessment. Only a simple "prescan" measurement of noise amplitude and correlation in the phased-array receiver, and a single accelerated image acquisition are required, allowing robust assessment of signal-to-noise ratio and g-factor. The "pseudo multiple replica" method has been rigorously validated in phantoms and in vivo, showing excellent agreement with true multiple replica and analytical methods. This method is universally applicable to the parallel imaging reconstruction techniques used in clinical applications and will allow pixel-by-pixel image noise measurements for all parallel imaging strategies, allowing quantitative comparison between arbitrary k-space trajectories, image reconstruction, or noise conditioning techniques.

Multiecho reconstruction for simultaneous water-fat decomposition and T2* estimation

PURPOSE

To describe and demonstrate the feasibility of a novel multiecho reconstruction technique that achieves simultaneous water-fat decomposition and T2* estimation. The method removes interference of water-fat separation with iron-induced T2* effects and therefore has potential for the simultaneous characterization of hepatic steatosis (fatty infiltration) and iron overload.

MATERIALS AND METHODS

The algorithm called "T2*-IDEAL" is based on the IDEAL water-fat decomposition method. A novel "complex field map" construct is used to estimate both R2* (1/T2*) and local B(0) field inhomogeneities using an iterative least-squares estimation method. Water and fat are then decomposed from source images that are corrected for both T2* and B(0) field inhomogeneity.

RESULTS

It was found that a six-echo multiecho acquisition using the shortest possible echo times achieves an excellent balance of short scan and reliable R2* measurement. Phantom experiments demonstrate the feasibility with high accuracy in R2* measurement. Promising preliminary in vivo results are also shown.

CONCLUSION

The T2*-IDEAL technique has potential applications in imaging of diffuse liver disease for evaluation of both hepatic steatosis and iron overload in a single breath-hold.

Prospective evaluation and characteristics of patients with suspected primary hyperaldosteronism

Primary hyperaldosteronism (PH), resulting in hypokalaemic hypertension, may be due to an aldosterone-producing adenoma (APA) or bilateral zona glomerulosa hyperplasia. Six patients with suspected PH were identified at the University Hospital of the West Indies and standardized screening was carried out. Plasma renin activity (PRA) and serum aldosterone concentrations (SAC) were measured, followed by confirmatory intravenous saline suppression test. The patients were all women, of median age 48 years (interquartile range, IQR: 41-51.7 years). They tended to be overweight with suboptimal blood pressure control. Median serum potassium was 3.1 mmol/L (IQR 2.7 - 3.3 mmol/l) and kaliuresis was elevated or inappropriately normal. All individuals had suppressed PRA (< 0.6 ng/ml/hr) and elevated SAC (> 30 ng/dl), with SAC/PRA ratios > 50. Five patients had confirmed PH (ie post-saline SAC > 10 ng/dl); PH could not be definitely excluded in the sixth patient (ie post-saline SAC 5 - 10 ng/dl). Imaging studies revealed normal adrenal glands in one patient, unilateral adrenal enlargement in three patients, and unilateral adrenal masses in two patients. Only one of these latter two patients was shown to have an adrenal adenoma on histological examination. In this series, there appears to be fewer cases of the APA subtype of PH than expected. It remains to be seen whether the distribution of PH subtypes in Jamaica is actually different from elsewhere. This, and the cost-effectiveness of different approaches to screening, identification and management of patients suspected of having PH in Jamaica are areas for further study.