Generative AI in Medical Imaging: Applications, Challenges, and Ethics.

Medical imaging is playing an important role in diagnosis and treatment of diseases. Generative artificial intelligence (AI) have shown great potential in enhancing medical imaging tasks such as data augmentation, image synthesis, image-to-image translation, and radiology report generation. This commentary aims to provide an overview of generative AI in medical imaging, discussing applications, challenges, and ethical considerations, while highlighting future research directions in this rapidly evolving field.

Primary results of the randomized trial of metformin administration in polycystic kidney disease (TAME PKD).

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by growth of kidney cysts and glomerular filtration rate (GFR) decline. Metformin was found to impact cystogenesis in preclinical models of polycystic disease, is generally considered safe and may be a promising candidate for clinical investigation in ADPKD. In this phase 2 two-year trial, we randomly assigned 97 patients, 18-60 years of age, with ADPKD and estimated GFR over 50 ml/min/1.73 m2, in a 1:1 ratio to receive metformin or placebo twice daily. Primary outcomes were medication safety and tolerability. Secondary outcomes included estimated GFR decline, and total kidney volume growth. Thirty-eight metformin and 39 placebo participants still received study product at 24-months. Twenty-one participants in the metformin arm reduced drug dose due to inability to tolerate, compared with 14 in the placebo arm (not significant). Proportions of participants experiencing serious adverse events was similar between the groups. The Gastrointestinal Symptoms Rating Scale score was low at baseline and did not significantly change over time. The annual change for estimated GFR was -1.71 with metformin and -3.07 ml/min/1.73m2 per year with placebo (mean difference 1.37 {-0.70, 3.44} ml/min/1.73m2), while mean annual percent change in height-adjusted total kidney volume was 3.87% in metformin and 2.16% per year in placebo, (mean difference 1.68% {-2.11, 5.62}). Thus, metformin in adults with ADPKD was found to be safe and tolerable while slightly reducing estimated GFR decline but not to a significant degree. Hence, evaluation of efficacy requires a larger trial, with sufficient power to detect differences in endpoints.

Prognostic Value of Fibroblast Growth Factor 23 in Autosomal Dominant Polycystic Kidney Disease.

INTRODUCTION: Autosomal dominant polycystic kidney disease (ADPKD) is characterized by progressive cyst growth and a loss of functioning renal mass, but a decline in glomerular filtration rate (GFR) and onset of end-stage renal disease (ESRD) occur late in the disease course. There is therefore a great need for early prognostic biomarkers in this disorder. METHODS: We measured baseline serum fibroblast growth factor 23 (FGF23) levels in 192 patients with ADPKD from the Consortium for Radiologic Imaging Studies of PKD (CRISP) cohort that were followed for a median of 13 years and tested the association between FGF23 levels and change over time in height-adjusted total kidney volume (htTKV), GFR, and time to the composite endpoints of ESRD, death, and doubling of serum creatinine. RESULTS: Patients in the highest quartile for baseline FGF23 level had a higher rate of increase in htTKV (0.95% per year, P = 0.0016), and faster rate of decline in GFR (difference of -1.03 ml/min/1.73 m2 per year, P = 0.005) compared with the lowest quartile, after adjusting for other covariates, including htTKV and genotype. The highest quartile of FGF23 was also associated with a substantial increase in risk for the composite endpoint of ESRD, death, or doubling of serum creatinine (hazard ratio [HR] of 2.45 in the fully adjusted model, P = 0.03). CONCLUSION: FGF23 is a prognostic biomarker for disease progression and clinically important outcomes in ADPKD, and has additive value to established imaging and genetic biomarkers.

Long-term trajectory of kidney function in autosomal-dominant polycystic kidney disease.

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by cyst and kidney growth, which is hypothesized to cause loss of functioning renal mass and eventually end-stage kidney disease. However, the time course of decline in glomerular filtration rate (GFR) is poorly defined. The Consortium for Radiologic Imaging Studies of Polycystic Kidney Disease study is a 14-year observational cohort study of 241 adults with ADPKD. As an estimate of the rate of kidney growth, participants were stratified into 5 subclasses based on baseline age and magnetic resonance imaging measurements of total kidney volume (TKV) according to the method of Irazabal. GFR trajectories spanning over four decades of life were reconstructed and fitted using mixed polynomial models, which were validated using data from the HALT-PKD study. GFR trajectories were nonlinear, with a period of relative stability in most participants, followed by accelerating decline. The shape and slope of these trajectories were strongly associated with baseline Irazabal class. Patients with PKD1 mutations had a steeper GFR decline than patients with PKD2 mutations or with no detected mutation, largely mediated by the effect of genotype on Irazabal class. Thus, GFR decline in ADPKD is nonlinear, and its trajectory throughout adulthood can be predicted from a single measurement of kidney volume. These models can be used for clinical prognostication, clinical trial design, and patient selection for clinical interventions. Our findings support a causal link between growth in kidney volume and GFR decline, adding support for the use of TKV as a surrogate endpoint in clinical trials.

Relationship between caffeine intake and autosomal dominant polycystic kidney disease progression: a retrospective analysis using the CRISP cohort.

BACKGROUND: Caffeine has been proposed, based on in vitro cultured cell studies, to accelerate progression of autosomal dominant polycystic kidney disease (ADPKD) by increasing kidney size. Since ADPKD patients are advised to minimize caffeine intake, we investigated the effect of caffeine on disease progression in the Consortium for Radiologic Imaging Studies of Polycystic Kidney Disease (CRISP), a prospective, observational cohort study. METHODS: Our study included 239 patients (mean age = 32.3 ± 8.9 ys; 188 caffeine consumers) with a median follow-up time of 12.5 years. Caffeine intake reported at baseline was dichotomized (any vs. none). Linear mixed models, unadjusted and adjusted for age, race, sex, BMI, smoking, hypertension, genetics and time, were used to model height-adjusted total kidney volume (htTKV) and iothalamate clearance (mGFR). Cox proportional hazards models and Kaplan-Meier plots examined the effect of caffeine on time to ESRD or death. RESULTS: Caffeine-by-time was statistically significant when modeling ln(htTKV) in unadjusted and adjusted models (p <  0.01) indicating that caffeine consumers had slightly faster kidney growth (by 0.6% per year), but htTKV remained smaller from baseline throughout the study. Caffeine consumption was not associated with a difference in mGFR, or in the time to ESRD or death (p > 0.05). Moreover the results were similar when outcomes were modeled as a function of caffeine dose. CONCLUSION: We conclude that caffeine does not have a significant detrimental effect on disease progression in ADPKD.

AI and Clinicians: Not a Mutually Exclusive Zero-Sum Game.

Recent bold, eye-catching headline predictions made by nonradiologists, e.g., "in a few years, radiology will disappear" and "stop training radiologists now," are not only far from reality but also irresponsible and a disservice to the appropriate implementation and adoption of artificial intelligence (AI) technology to health care. It is highly likely and foreseeable that AI will enhance the quality and efficiency of the current clinical practice across many specialties and even render some activities in clinical practice obsolete.

Development of a 7 T RF coil system for breast imaging.

In ultrahigh-field MRI, such as 7 T, the signal-to-noise ratio (SNR) increases while transmit (Tx) field (B1+ ) can be degraded due to inhomogeneity and elevated specific absorption rate (SAR). By applying new array coil concepts to both Tx and receive (Rx) coils, the B1+ homogeneity and SNR can be improved. In this study, we developed and tested in vivo a new RF coil system for 7 T breast MRI. An RF coil system composed of an eight-channel Tx-only array based on a tic-tac-toe design (can be combined to operate in single-Tx mode) in conjunction with an eight-channel Rx-only insert was developed. Characterizations of the B1+ field and associated SAR generated by the developed RF coil system were numerically calculated and empirically measured using an anatomically detailed breast model, phantom and human breasts. In vivo comparisons between 3 T (using standard commercial solutions) and 7 T (using the newly developed coil system) breast imaging were made. At 7 T, about 20% B1+ inhomogeneity (standard deviation over the mean) was measured within the breast tissue for both the RF simulations and 7 T experiments. The addition of the Rx-only array enhances the SNR by a factor of about three. High-quality MR images of human breast were acquired in vivo at 7 T. For the in vivo comparisons between 3 T and 7 T, an approximately fourfold increase of SNR was measured with 7 T imaging. The B1+ field distributions in the breast model, phantom and in vivo were in reasonable agreement. High-quality 7 T in vivo breast MRI was successfully acquired at 0.6 mm isotropic resolution using the newly developed RF coil system.

Prognostic enrichment design in clinical trials for autosomal dominant polycystic kidney disease: the HALT-PKD clinical trial.

BACKGROUND: Patients with mild autosomal dominant polycystic kidney disease (ADPKD) are less likely to be informative in randomized clinical trials (RCTs). We previously developed an imaging classification of ADPKD (typical diffuse cyst distribution Class 1A-E and atypical cyst distribution Class 2) for prognostic enrichment design in RCTs. We investigated whether using this classification would have increased the power to detect a beneficial treatment effect of rigorous blood pressure (BP) control on HALT-PKD participants with early disease (Study A). METHODS: Post hoc analysis of the early disease HALT-PKD study, an RCT that studied the effect of rigorous versus standard BP control on rates of total kidney volume (TKV) increase and estimated glomerular filtration rate (eGFR) decline in ADPKD patients with eGFR >60 mL/min/1.73 m2. RESULTS: Five hundred and fifty-one patients were classified by two observers (98.2% agreement) into Class 1A (6.2%), 1B (20.3%), 1C (34.1%), 1D (22.1%), 1E (11.8%) and 2 (5.4%). The TKV increase and eGFR decline became steeper from Class 1A through 1E. Rigorous BP control had been shown to be associated with slower TKV increase, without a significant overall effect on the rate of eGFR decline (faster in the first 4 months and marginally slower thereafter). Merging Classes 1A and 2 (lowest severity), 1B and 1C (intermediate severity) and 1D and 1E (highest severity) detected stronger beneficial effects on TKV increase and eGFR decline in Class 1D and E with a smaller number of patients. CONCLUSIONS: Strategies for prognostic enrichment, such as image classification, should be used in the design of RCTs for ADPKD to increase their power and reduce their cost.

Experimental and numerical analysis of B1(+) field and SAR with a new transmit array design for 7T breast MRI.

Developing a radiofrequency (RF) coil system that produces a uniform B1(+) field (circularly polarized component of the transverse magnetic field responsible for excitation) and low specific absorption rate (SAR) is critical for high performance ultrahigh field human imaging. In this study, we provide the design of a new eight channel radiofrequency (RF) transmit (Tx) array for breast MRI at 7T. A numerical analysis utilizing an in-house finite difference time domain (FDTD) package was carried out in (1) four breast models, (2) homogeneous spherical model and (3) full body model to calculate the B1(+) intensity (µT) and homogeneity represented by coefficient of variation (CoV=standard deviation/mean) in the proposed RF array design. The numerical results were compared with that measured in breast phantom (Bphantom) and homogeneous spherical phantom at 7T MRI and showed very good agreement. Average and peak SARs were also calculated in the four breast models and the temperature rises due to the operation of the RF array were also measured in the Bphantom. The proposed RF array; which can operate in a single or multi transmit modes, demonstrates homogeneous RF field excitation with acceptable local/average SAR levels for breast MRI at 7T.

Mapping blood flow directionality in the human brain.

Diffusion properties of tissue are often expressed on the basis of directional variance, i.e., diffusion tensor imaging. In comparison, common perfusion-weighted imaging such as arterial spin labeling yields perfusion in a scalar quantity. The purpose of this study was to test the feasibility of mapping cerebral blood flow directionality using alternate ascending/descending directional navigation (ALADDIN), a recently-developed arterial spin labeling technique with sensitivity to blood flow directions. ALADDIN was applied along 3 orthogonal directions to assess directional blood flow in a vector form and also along 6 equally-spaced directions to extract blood flow tensor matrix (P) based on a blood flow ellipsoid model. Tensor elements (eigenvalues, eigenvectors, etc) were calculated to investigate characteristics of the blood flow tensor, in comparison with time-of-flight MR angiogram. While the directions of the main eigenvectors were heterogeneous throughout the brain, regional clusters of blood flow directionality were reproducible across subjects. The technique could show heterogeneous blood flow directionality within and around brain tumor, which was different from that of the contralateral normal side. The proposed method is deemed to provide information of blood flow directionality, which has not been demonstrated before. The results warrant further studies to assess changes in the directionality map as a function of scan parameters, to understand the signal sources, to investigate the possibility of mapping local blood perfusion directionality, and to evaluate its usefulness for clinical diagnosis.

Inter-Slice Blood Flow and Magnetization Transfer Effects as A New Simultaneous Imaging Strategy.

The recent blood flow and magnetization transfer (MT) technique termed alternate ascending/descending directional navigation (ALADDIN) achieves the contrast using interslice blood flow and MT effects with no separate preparation RF pulse, thereby potentially overcoming limitations of conventional methods. In this study, we examined the signal characteristics of ALADDIN as a simultaneous blood flow and MT imaging strategy, by comparing it with pseudo-continuous ASL (pCASL) and conventional MT asymmetry (MTA) methods, all of which had the same bSSFP readout. Bloch-equation simulations and experiments showed ALADDIN perfusion signals increased with flip angle, whereas MTA signals peaked at flip angle around 45°-60°. ALADDIN provided signals comparable to those of pCASL and conventional MTA methods emulating the first, second, and third prior slices of ALADDIN under the same scan conditions, suggesting ALADDIN signals to be superposition of signals from multiple labeling planes. The quantitative cerebral blood flow signals from a modified continuous ASL model overestimated the perfusion signals compared to those measured with a pulsed ASL method. Simultaneous mapping of blood flow, MTA, and MT ratio in the whole brain is feasible with ALADDIN within a clinically reasonable time, which can potentially help diagnosis of various diseases.

Investigation of inter-slice magnetization transfer effects as a new method for MTR imaging of the human brain.

We present a new method for magnetization transfer (MT) ratio imaging in the brain that requires no separate saturation pulse. Interslice MT effects that are inherent to multi-slice balanced steady-state free precession (bSSFP) imaging were controlled via an interslice delay time to generate MT-weighted (0 s delay) and reference images (5-8 s delay) for MT ratio (MTR) imaging of the brain. The effects of varying flip angle and phase encoding (PE) order were investigated experimentally in normal, healthy subjects. Values of up to ∼50% and ∼40% were observed for white and gray matter MTR. Centric PE showed larger MTR, higher SNR, and better contrast between white and gray matter than linear PE. Simulations of a two-pool model of MT agreed well with in vivo MTR values. Simulations were also used to investigate the effects of varying acquisition parameters, and the effects of varying flip angle, PE steps, and interslice delay are discussed. Lastly, we demonstrated reduced banding with a non-balanced SSFP-FID sequence and showed preliminary results of interslice MTR imaging of meningioma.

Fully automated segmentation of cartilage from the MR images of knee using a multi-atlas and local structural analysis method.

PURPOSE: To develop a fully automated method to segment cartilage from the magnetic resonance (MR) images of knee and to evaluate the performance of the method on a public, open dataset. METHODS: The segmentation scheme consisted of three procedures: multiple-atlas building, applying a locally weighted vote (LWV), and region adjustment. In the atlas building procedure, all training cases were registered to a target image by a nonrigid registration scheme and the best matched atlases selected. A LWV algorithm was applied to merge the information from these atlases and generate the initial segmentation result. Subsequently, for the region adjustment procedure, the statistical information of bone, cartilage, and surrounding regions was computed from the initial segmentation result. The statistical information directed the automated determination of the seed points inside and outside bone regions for the graph-cut based method. Finally, the region adjustment was conducted by the revision of outliers and the inclusion of abnormal bone regions. RESULTS: A total of 150 knee MR images from a public, open dataset (available atwww.ski10.org) were used for the development and evaluation of this approach. The 150 cases were divided into the training set (100 cases) and the test set (50 cases). The cartilages were segmented successfully in all test cases in an average of 40 min computation time. The average dice similarity coefficient was 71.7%±8.0% for femoral and 72.4%±6.9% for tibial cartilage. CONCLUSIONS: The authors have developed a fully automated segmentation program for knee cartilage from MR images. The performance of the program based on 50 test cases was highly promising.

Quantitative sodium MR imaging of native versus transplanted kidneys using a dual-tuned proton/sodium (1H/ 23Na) coil: initial experience.

OBJECTIVES: To compare sodium ((23)Na) characteristics between native and transplanted kidneys using dual-tuned proton ((1)H)/sodium MRI. METHODS: Six healthy volunteers and six renal transplant patients (3 normal function, 3 acute allograft rejection) were included. Proton/sodium MRI was obtained at 3 T using a dual-tuned coil. Signal to noise ratio (SNR), sodium concentration ([(23)Na]) and cortico-medullary sodium gradient (CMSG) were measured. Reproducibility of [(23)Na] measurement was also tested. SNR, [(23)Na] and CMSG of the native and transplanted kidneys were compared. RESULTS: Proton and sodium images of kidneys were successfully acquired. SNR and [(23)Na] measurements of the native kidneys were reproducible at two different sessions. [(23)Na] and CMSG of the transplanted kidneys was significantly lower than those of the native kidneys: 153.5 ± 11.9 vs. 192.9 ± 9.6 mM (P = 0.002) and 8.9 ± 1.5 vs. 10.5 ± 0.9 mM/mm (P = 0.041), respectively. [(23)Na] and CMSG of the transplanted kidneys with normal function vs. acute rejection were not statistically different. CONCLUSIONS: Sodium quantification of kidneys was reliably performed using proton/sodium MRI. [(23)Na] and CMSG of the transplanted kidneys were lower than those of the native kidneys, but without a statistically significant difference between patients with or without renal allograft rejection. KEY POINTS: Dual-tuned proton/sodium RF coil enables co-registered proton and sodium MRI. Structural and sodium biochemical property can be acquired by dual-tuned proton/sodium MRI. Sodium and sodium gradient of kidneys can be measured by dual-tuned MRI. Sodium concentration was lower in transplanted kidneys than in native kidneys. Sodium gradient of transplanted kidneys was lower than for native kidneys.

Quantitative (23) Na MRI of human knee cartilage using dual-tuned (1) H/(23) Na transceiver array radiofrequency coil at 7 tesla.

PURPOSE: To develop quantitative dual-tuned (DT) (1) H/(23) Na MRI of human knee cartilage in vivo at 7 Tesla (T). MATERIALS AND METHODS: A sensitive (23) Na transceiver array RF coil was developed at 7T. B1 fields generated by the transceiver array coil were characterized and corrected in the (23) Na images. Point spread function (PSF) of the (23) Na images was measured, and the signal decrease due to partial-volume-effect was compensated in [(23) Na] quantification of knee cartilage. SNR and [(23) Na] in anterior femoral cartilage were measured from seven healthy subjects. RESULTS: SNR of (23) Na image with the transceiver array coil was higher than that of birdcage coil. SNR in the cartilage at 2-mm isotropic resolution was 26.80 ± 3.69 (n = 7). B1 transmission and reception fields produced by the DT coil at 7T were similar to each other. Effective full-width-half-maximum of (23) Na image was ∼5 mm at 2-mm resolution. Mean [(23) Na] was 288.13 ± 29.50 mM (n = 7) in the anterior femoral cartilage of normal subjects. CONCLUSION: We developed a new high-sensitivity (23) Na RF coil for knee MRI at 7T. Our (1) H/(23) Na MRI allowed quantitative measurement of [(23) Na] in knee cartilage by measuring PSF and cartilage thickness from (23) Na and (1) H image, respectively.

Part 1: Dual-tuned proton/sodium magnetic resonance imaging of the lumbar spine in a rabbit model.

STUDY DESIGN: Development of a dual-tuned proton/sodium radiofrequency (RF) coil for magnetic resonance imaging (MRI) of the rabbit spine and quantification of sodium concentration in intervertebral discs. OBJECTIVE: To develop the dual-tuned proton/sodium MRI of rabbit lumbar spine to investigate proteoglycan matrix content and intervertebral disc degeneration (IDD). SUMMARY OF BACKGROUND DATA: IDD is a common chronic condition that may lead to back pain, limited activity, and disability. Early-stage IDD involves the loss of proteoglycan matrix and water content in the disc. Sodium MRI is a promising noninvasive technique for quantitative measurement of proteoglycan changes associated with IDD. The combined structural (proton) and biochemical (sodium) MRI facilitates the investigation of morphological and molecular changes associated with degeneration of discs. METHODS: Multichannel dual-tuned proton/sodium transceiver RF coil of the rabbit spine was developed and optimized at 3T human scanner-8 channels allocated for the sodium coil and 4 channels for the proton coil. High-resolution anatomy proton images of the discs were acquired using turbo spin echo and dual echo steady state sequence. Sodium concentration of the discs was quantified from sodium magnetic resonance (MR) images that were calibrated for signal attenuation because of RF field inhomogeneity, sodium MR relaxation times, and disc thickness. Twelve rabbits (~1-yr old, female, 5.2 ± 0.4 kg) were used for measuring disc sodium concentration. RESULTS: High-resolution in vivo proton and sodium MR images of rabbit discs (≤2-mm thickness) were successfully obtained using an in-house dual-tuned proton/sodium RF coil at 3T. The total acquisition time for each set of images was approximately 40 minutes. Sodium concentration of normal rabbit lumbar discs was measured at 269.7 ± 6.3 mM, and this measurement was highly reproducible, with 5.3% of coefficient of variation. CONCLUSION: Sodium concentrations of rabbit lumbar discs were reliably measured using our newly developed dual-tuned multichannel proton/sodium RF coil at 3T.

Part 2: Quantitative proton T2 and sodium magnetic resonance imaging to assess intervertebral disc degeneration in a rabbit model.

STUDY DESIGN: Comparison of sodium concentration ([Na]) and proton T2 relaxation time between normal and degenerated discs in a rabbit model. OBJECTIVE: The purpose of this article was to evaluate quantitative [Na] and T2 characteristics of discs associated with degenerative changes. SUMMARY OF BACKGROUND DATA: Intervertebral disc degeneration is a common chronic condition that may lead to back pain, limited activity, and disability. Noninvasive imaging method to detect early intervertebral disc degeneration is vital to follow disease progression and guide clinical treatment and management. METHODS: Dual-tuned magnetic resonance imaging of rabbit discs was performed using 3T. Thirteen rabbits were included in the study; 6 control rabbits (24 normal discs) and 7 rabbits with annular puncture-induced disc degeneration (9 degenerated discs, 19 intact internal-control discs). Dual-tuned magnetic resonance imaging of discs was performed at baseline and 12-week poststab. [Na] and T2 were measured and compared among 3 groups of discs. RESULTS: The mean [Na] were 274.8 ± 40.2 mM for the normal discs, 247.2 ± 27.7 mM for the internal-control discs, and 190.6 ± 19.1 mM for the degenerated discs. The corresponding T2 for 3 groups were 97.1 ± 12.1 ms, 93.7 ± 11.9 ms, and 79.0 ± 9.1 ms, respectively. The [Na] is highly correlated with the T2 in the degenerated discs (r = 0.90, P < 0.01). The mean percent decreases from the normal to degenerated discs were in 30.6% in [Na] and 18.6% in T2, whereas those from the internal-control to degenerated discs were 22.9% in [Na] and 15.6% in T2. CONCLUSION: Although both [Na] and T2 changes in discs were associated with the disc-punctured rabbits, greater change in [Na] is observed at 12-week poststab compared with T2 change. Because T2 and [Na] reflect different disc properties, performing both imaging under same condition will be helpful in the evaluation of disc degeneration.

Kidney volume and functional outcomes in autosomal dominant polycystic kidney disease.

BACKGROUND AND OBJECTIVES: Autosomal dominant polycystic kidney disease (ADPKD) is characterized by increased total kidney volume (TKV) and renal failure. This study aimed to determine if height-adjusted TKV (htTKV) predicts the onset of renal insufficiency. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: This prospective, observational, longitudinal, multicenter study included 241 adults with ADPKD and preserved renal function. Magnetic resonance imaging and iothalamate clearance were used to measure htTKV and GFR, respectively. The association between baseline htTKV and the attainment of stage 3 CKD (GFR <60 ml/min per 1.73 m(2)) during follow-up was determined. RESULTS: After a mean follow-up of 7.9 years, stage 3 CKD was attained in 30.7% of the enrollees. Using baseline htTKV, negative correlations with GFR increased from -0.22 at baseline to -0.65 at year 8. In multivariable analysis, a baseline htTKV increase of 100 cc/m significantly predicted the development of CKD within 8 years with an odds ratio of 1.48 (95% confidence interval: 1.29, 1.70). In receiver operator characteristic curve analysis, baseline htTKV of 600 cc/m most accurately defined the risk of developing stage 3 CKD within 8 years with an area under the curve of 0.84 (95% confidence interval: 0.79, 0.90). htTKV was a better predictor than baseline age, serum creatinine, BUN, urinary albumin, or monocyte chemotactic protein-1 excretion (P<0.05). CONCLUSIONS: Baseline htTKV ≥600 cc/m predicted the risk of developing renal insufficiency in ADPKD patients at high risk for renal disease progression within 8 years of follow-up, qualifying htTKV as a prognostic biomarker in ADPKD.

Suppression of effects of gradient imperfections on imaging with alternate ascending/descending directional navigation.

Alternate ascending/descending directional navigation (ALADDIN) is a new imaging technique that provides interslice perfusion-weighted and magnetization transfer (MT) asymmetry images. In this article, we investigated the effects of gradient imperfections on ALADDIN MT asymmetry (MTA) signals. Subtraction artifacts increasing with readout offsets were detectable in ALADDIN MTA images from an agarose phantom but not from a water phantom. Slice-select offsets had no significant effect on the artifacts in MTA. The artifacts were suppressed by averaging signals over the readout gradient polarities independent of scan parameters. All these results suggested that the subtraction artifacts were induced by readout eddy currents. With suppression of the artifacts, ALADDIN signals in human brain and skeletal muscle varied less with scan conditions. Percent signal changes of MTA in human skeletal muscle (0.51 ± 0.11%, N = 3) were about 30% of those in white matter. The new averaging scheme will allow for more accurate MTA imaging with ALADDIN, especially at off-center positions.