MULTI-parametric MR imaging with fLEXible design (MULTIPLEX).

PURPOSE: To introduce a gradient echo (GRE) -based method, namely MULTIPLEX, for single-scan 3D multi-parametric MRI with high resolution, signal-to-noise ratio (SNR), accuracy, efficiency, and acquisition flexibility. THEORY: With a comprehensive design with dual-repetition time (TR), dual flip angle (FA), multi-echo, and optional flow modulation features, the MULTIPLEX signals contain information on radiofrequency (RF) B1t fields, proton density, T1 , susceptibility and blood flows, facilitating multiple qualitative images and parametric maps. METHODS: MULTIPLEX was evaluated on system phantom and human brains, via visual inspection for image contrasts and quality or quantitative evaluation via simulation, phantom scans and literature comparison. Region-of-interest (ROI) analysis was performed on parametric maps of the system phantom and brain scans, extracting the mean and SD of the T1 , T2∗ , proton density (PD), and/or quantitative susceptibility mapping (QSM) values for comparison with reference values or literature. RESULTS: One MULTIPLEX scan offers multiple sets of images, including but not limited to: composited PDW/T1 W/ T2∗ W, aT1 W, SWI, MRA (optional), B1t map, T1 map, T2∗ / R2∗ maps, PD map, and QSM. The quantitative error of phantom T1 , T2∗ and PD mapping were <5%, and those in brain scans were in good agreement with literature. MULTIPLEX scan times for high resolution (0.68 × 0.68 × 2 mm3 ) whole brain coverage were about 7.5 min, while processing times were <1 min. With flow modulation, additional MRA images can be obtained without affecting the quality or accuracy of other images. CONCLUSION: The proposed MUTLIPLEX method possesses great potential for multi-parametric MR imaging.

Augmented T1 -weighted steady state magnetic resonance imaging.

T1 contrasts obtained using short-TR incoherent steady state gradient echo (GRE) methods are generally suboptimal, to which non-T1 factors in the signals play a major part. In this work, we proposed an augmented T1 -weighted (aT1 W) method to extract the signal ratio between routine GRE T1 W and proton density-weighted signals that effectively removes the non-T1 effects from the original T1 W signals, including proton density, T2 * decay, and coil sensitivity. A recently proposed multidimensional integration (MDI) technique was incorporated in the aT1 W calculation for better signal-to-noise ratio (SNR) performance. For comparison between aT1 W and T1 W results, Monte Carlo noise analysis was performed via simulation and on scanned data, and region-of-interest (ROI) analysis and comparison was performed on the system phantom. For brain scans, the image contrast, noise behavior, and SNR of aT1 W images were compared with routine GRE and inversion-recovery-based T1 W images. The proposed aT1 W method yielded saliently improved T1 contrasts (potentially > 30% higher contrast-to-noise ratio [CNR]) than routine GRE T1 W images. Good spatial homogeneity and signal consistency as well as high SNR/CNR were achieved in aT1 W images using the MDI technique. For contrast-enhanced (CE) imaging, aT1 W offered stronger post-CE contrast and better boundary delineation than T1 MPRAGE images while using a shorter scan time.

A multi-dimensional integration (MDI) strategy for MR T2 * mapping.

MRI signals are intrinsically multi-dimensional, and signal behavior may be orthogonal among different dimensions. Such dimensional orthogonality can be utilized to eliminate unwanted effects and facilitate mathematical simplicity during image processing for improved outcomes. In this work, we will demonstrate and analyze the principles and performance of a newly developed multi-dimensional integration (MDI) strategy in MR T2 * mapping. By constructing a complex signal function to extract the inter-echo signal changes, MDI solves an optimization problem by processing all signal dimensions (eg echoes, flip angles and coil channels) in one integrative step. MDI was compared with routine curve fitting methods on noise behavior, quantification accuracy and computational efficiency. All methods were tested and compared on simulation, phantom and knee data. Monte Carlo simulations were performed on simulation and all MRI data to investigate noise propagation from k space to T2 * maps. For phantom tests, T2 * values in regions of interest were extracted on a voxel-wise basis and analyzed using a paired t-test between scanning parameters and mapping methods, with p < 0.05 being significantly different. MDI facilitated a straightforward processing procedure, yielding homogeneous, high-signal-to-noise-ratio (SNR) and artifact-free T2 * maps without explicit coil combination or additional measures. Compared with routine fitting methods, MDI offered significantly (p < 0.05) improved SNR and quantitative accuracy/robustness, with two to three orders higher computational efficiency. MDI also represented low-SNR signals with low T2 * values, avoiding misinterpretation with long-T2 * species.

Seed prioritized unwrapping (SPUN) for MR phase imaging.

BACKGROUND: Region-growing-based phase unwrapping methods have the potential for lossless phase aliasing removal, but generally suffer from unwrapping error propagation associated with discontinuous phase and/or long calculation times. The tradeoff point between robustness and efficiency of phase unwrapping methods in the region-growing category requires improvement. PURPOSE: To demonstrate an accurate, robust, and efficient region-growing phase unwrapping method for MR phase imaging applications. STUDY TYPE: Prospective. SUBJECTS, PHANTOM: normal human subjects (10) / brain surgery patients (2) / water phantoms / computer simulation. FIELD STRENGTH/SEQUENCE: 3 T/gradient echo sequences (2D and 3D). ASSESSMENT: A seed prioritized unwrapping (SPUN) method was developed based on single-region growing, prioritizing only a portion (eg, 100 seeds or 1% seeds) of available seed voxels based on continuity quality during each region-growing iteration. Computer simulation, phantom, and in vivo brain and pelvis scans were performed. The error rates, seed percentages, and calculation times were recorded and reported. SPUN unwrapped phase images were visually evaluated and compared with Laplacian unwrapped results. STATISTICAL TESTS: Monte Carlo simulation was performed on a 3D dipole phase model with a signal-to-noise ratio (SNR) of 1-9 dB, to obtain the mean and standard deviation of calculation error rates and calculation times. RESULTS: Simulation revealed a very robust unwrapping performance of SPUN, reaching an error rate of <0.4% even with SNR as low as 1 dB. For all in vivo data, SPUN was able to robustly unwrap the phase images of modest SNR and complex morphology with visually minimal errors and fast calculation speed (eg, <4 min for 368 × 312 × 128 data) when using a proper seed priority number, eg, Nsp = 1 or 10 voxels for 2D and Nsp = 1% for 3D data. DATA CONCLUSION: SPUN offers very robust and fast region-growing-based phase unwrapping, and does not require any tissue masking or segmentation, nor poses a limitation over imaging parameters. LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;50:62-70.

A fully flow-compensated multiecho susceptibility-weighted imaging sequence: The effects of acceleration and background field on flow compensation.

PURPOSE: To present a fully flow-compensated multiecho gradient echo sequence that can be used for MR angiography (MRA), susceptibility weighted imaging (SWI), and quantitative susceptibility mapping (QSM) and to study the effects of flow acceleration and background field gradients on flow compensation. METHODS: The quality of flow compensation was evaluated using the data from eight volunteers. The effects of flow acceleration were studied by changing the polarities of the readout gradients in two consecutive scans. The background field was used to estimate the phase errors of flow compensation in the presence of field inhomogeneities. SWI and QSM data were generated with confounding arterial phase removed. T2 * maps were obtained from the multiecho data to estimate T2 * of arterial blood. RESULTS: Reasonable flow compensation was achieved. Nevertheless, background field gradients and acceleration-induced phase errors were found to be as large as π/2 and π/3, respectively, both in agreement with theory. T2 * was measured as 82 ± 4 ms and 74 ± 9 ms for arteries inside and outside the brain, respectively, at 3T. CONCLUSION: High-quality MRA, SWI, and QSM data can be obtained simultaneously. Masking out the arteries to remove the phase due to flow acceleration and background field gradients improves the quality of both SWI and QSM data. Magn Reson Med 76:478-489, 2016. © 2015 Wiley Periodicals, Inc.

Retrobulbar magnetic resonance angiography using binomial off-resonant rectangular (BORR) pulse.

PURPOSE: Applying a newly developed binomial off-resonant rectangular (BORR) pulse method for high resolution three-dimensional MR angiography (MRA) on retrobulbar ocular vessels, which has not been possible with routine MRA due to background fatty tissues. METHODS: BORR pulse was implemented in a gradient echo sequence by replacing the original excitation pulse, and were optimized for robust orbital fat suppression. Several other MRA methods, with or without fat suppression, were also compared, including time-of-flight, contrast enhanced MRA, and hybrid of opposite-contrast MRA. Nine healthy subjects participated with written informed consents. To reduce eye motion, the subjects were instructed to casually stare at a projected cross during each MRA scan. Major vessels were evaluated by three independent radiologists using a 4-point scale. RESULTS: The BORR method yielded the best MRA results for retrobulbar vessels without contrast enhancement, significantly superior than other MRA methods. BORR results had significantly higher visibility scores than all other methods for small vessels. CONCLUSION: We have successfully revealed orbital vessels in retrobulbar space for the first time using MRA, by using the BORR pulse method. With a clear depiction of the vasculature without the need for contrast enhancement, our method has the potential to provide important diagnostic information for ocular vascular diseases.

Susceptibility mapping of air, bone, and calcium in the head.

PURPOSE: To demonstrate the mapping of structures with high susceptibility values, such as the sinuses, bones and teeth, using short echo times. METHODS: Four in vivo datasets were collected with a gradient-echo sequence (TE1 = 2.5 ms, TE2 = 5 ms and TE3 = 7.5 ms). Complex division was performed to remove the phase offset term and generate the phase at TE = 2.5 ms. Susceptibility maps were generated from unwrapped phase images, using a geometry-constrained iterative algorithm, by preserving phase information in the extracerebral tissues. The susceptibility results were improved by updating the missing phase information inside structures with no signal using the predicted phase at each iteration step. Simulated phase images of a three-dimensional brain model and tooth phantom were used to validate the proposed method. RESULTS: Improved susceptibility maps were obtained once the phase information in the extracerebral tissue region was incorporated, for both the model and in vivo data. For in vivo data, the average susceptibilities of air (sphenoid sinus), bone and calcium (teeth) were found to be (in ppm): Δχ(sinus-tissue) = +9.2 ± 1.3, Δχ(bone-tissue) = -2.1 ± 0.6 and Δχ(teeth-tissue) = -3.3 ± 1.2, respectively. CONCLUSION: High susceptibility structures with little or no signal can be imaged using quantitative susceptibility mapping and can be used to improve background field removal.

Robust selective signal suppression using binomial off-resonant rectangular (BORR) pulses.

PURPOSE: To study the selective signal suppression capability of a binomial off-resonant rectangular (BORR) radiofrequency pulse method. MATERIALS AND METHODS: The BORR pulse consists of two consecutive rectangular pulses with a phase difference of π. The exact solution of the Bloch equations was used to simulate its frequency response. The BORR pulse was implemented in a gradient echo sequence and tested on phantoms, the knee, and the breast. RESULTS: The frequency response of the BORR pulse acquired on the phantom confirmed the theory. Broad suppression bands ensured high suppression efficiency and robustness in both in vitro and in vivo scans compared with other saturation pulses. CONCLUSION: The BORR pulse method provides a simple, efficient, and robust selective signal suppression alternative for three-dimensional short TR (repetition time) imaging.

Improved MR venography using quantitative susceptibility-weighted imaging.

PURPOSE: To remove the geometry dependence of phase-based susceptibility weighting masks in susceptibility-weighted imaging (SWI) and to improve the visualization of the veins and microbleeds. MATERIALS AND METHODS: True SWI (tSWI) was generated using susceptibility-based masks. Simulations were used to evaluate the influence of the characteristic parameters defining the mask. In vivo data from three healthy adult human volunteers were used to compare the contrast-to-noise-ratios (CNRs) of the right septal vein and the left internal cerebral vein as measured from both tSWI and SWI data. A traumatic brain injury (TBI) patient dataset was used to illustrate qualitatively the proper visualization of microbleeds using tSWI. RESULTS: Compared with conventional SWI, tSWI improved the CNR of the two selected veins by a factor of greater than three for datasets with isotropic resolution and greater than 30% for datasets with anisotropic resolution. Veins with different orientations can be properly enhanced in tSWI. Furthermore, the blooming artifact due to the strong dipolar phase of microbleeds in conventional SWI was reduced in tSWI for the TBI case. CONCLUSION: The use of tSWI overcomes the geometric limitations of using phase and provides better visualization of the venous system, especially for data collected with isotropic resolution.

Complex multi-dimensional integration for T2* and R2* mapping.

A dual Multi-Dimensional Integration (dMDI) method was proposed and demonstrated for T2* and R2* mapping. By constructing and jointly using both the original MDI term and an inversed MDI term, T2* and R2* mapping can be performed independently with intrinsic background noise suppression and spike elimination, allowing for high quantitative accuracy and robustness over a wide range of T2*. dMDI was compared to original MDI and curve fitting methods in terms of quantitative specificity, accuracy, reliability and computational efficiency. All methods were tested and compared via simulation and in vivo data. With high signal-to-noise-ratio (SNR), the proposed dMDI method yielded T2*and R2* values similar to curve fitting methods. For low SNR and background noise signals, the dMDI yielded low T2* and R2* values, thus effectively suppressing all background noise. Virtually zero spikes were observed in dMDI T2* and R2* maps in all simulation and imaging results. The dMDI method has the potential to provide improved and reliable T2* and R2* mapping results in routine and SNR-challenging scenarios.

Correlation of Ktrans derived from dynamic contrast-enhanced MRI with treatment response and survival in locally advanced NSCLC patients undergoing induction immunochemotherapy and concurrent chemoradiotherapy.

PURPOSE: This study aimed to investigate the prognostic significance of pretreatment dynamic contrast-enhanced (DCE)-MRI parameters concerning tumor response following induction immunochemotherapy and survival outcomes in patients with locally advanced non-small cell lung cancer (NSCLC) who underwent immunotherapy-based multimodal treatments. MATERIAL AND METHODS: Unresectable stage III NSCLC patients treated by induction immunochemotherapy, concurrent chemoradiotherapy (CCRT) with or without consolidative immunotherapy from two prospective clinical trials were screened. Using the two-compartment Extend Tofts model, the parameters including Ktrans, Kep, Ve, and Vp were calculated from DCE-MRI data. The apparent diffusion coefficient was calculated from diffusion-weighted-MRI data. The receiver operating characteristic (ROC) curve and the area under the curve (AUC) were used to assess the predictive performance of MRI parameters. The Cox regression model was used for univariate and multivariate analysis. RESULTS: 111 unresectable stage III NSCLC patients were enrolled. Patients received two cycles of induction immunochemotherapy and CCRT, with or without consolidative immunotherapy. With the median follow-up of 22.3 months, the median progression-free survival (PFS) and overall survival (OS) were 16.3 and 23.8 months. The multivariate analysis suggested that Eastern Cooperative Oncology Group score, TNM stage and the response to induction immunochemotherapy were significantly related to both PFS and OS. After induction immunochemotherapy, 67 patients (59.8%) achieved complete response or partial response and 44 patients (40.2%) had stable disease or progressive disease. The Ktrans of primary lung tumor before induction immunochemotherapy yielded the best performance in predicting the treatment response, with an AUC of 0.800. Patients were categorized into two groups: high-Ktrans group (n=67, Ktrans＞164.3×10-3/min) and low-Ktrans group (n=44, Ktrans≤164.3×10-3/min) based on the ROC analysis. The high-Ktrans group had a significantly higher objective response rate than the low-Ktrans group (85.1% (57/67) vs 22.7% (10/44), p<0.001). The high-Ktrans group also presented better PFS (median: 21.1 vs 11.3 months, p=0.002) and OS (median: 34.3 vs 15.6 months, p=0.035) than the low-Ktrans group. CONCLUSIONS: Pretreatment Ktrans value emerged as a significant predictor of the early response to induction immunochemotherapy and survival outcomes in unresectable stage III NSCLC patients who underwent immunotherapy-based multimodal treatments. Elevated Ktrans values correlated positively with enhanced treatment response, leading to extended PFS and OS durations.

Noncontrast-enhanced magnetic resonance angiography and venography imaging with enhanced angiography.

PURPOSE: To achieve simultaneous high-resolution magnetic resonance angiography and venography (MRAV) imaging in terms of enhanced time-of-flight (TOF) angiography and susceptibility-weighted imaging (SWI), with a clear separation of arteries and veins. MATERIALS AND METHODS: A new flow rephase/dephase interleaved double-echo sequence was introduced that facilitates multiple types of imaging contrast, i.e., TOF, SWI, and dark blood, in a single acquisition. A nonlinear subtraction (NLS) method is proposed and assessed to maximally enhance angiography contrast with minimum venous contamination. RESULTS: Fully flow rephased TOF MRA and SWI MRV data were acquired simultaneously, along with an extra flow dephased dark blood image for angiography enhancement calculation. Compared to linear subtraction methods, the proposed NLS method was able to enhance angiography contrast while effectively eliminating vein-tissue contrast. The NLS method even outperformed low-dose contrast-enhanced MRA for a clean, enhanced angiography map. CONCLUSION: Using the proposed interleaved double-echo sequence along with the NLS postprocessing method, one can simultaneously obtain both high-quality SWI and significantly enhanced TOF MRA with clear separation of arterial and venous maps.

In ovo serial skeletal muscle diffusion tractography of the developing chick embryo using DTI: feasibility and correlation with histology.

BACKGROUND: Magnetic resonance imaging is a noninvasive method of evaluating embryonic development. Diffusion tensor imaging (DTI), based on the directional diffusivity of water molecules, is an established method of evaluating tissue structure. Yet embryonic motion degrades the in vivo acquisition of long-duration DTI. We used a dual-cooling technique to avoid motion artifact and aimed to investigate whether DTI can be used to monitor chick embryonic skeletal muscle development in ovo, and to investigate the correlation between quantitative DTI parameters fractional anisotropy (FA) and fiber length and quantitative histologic parameters fiber area percentage (FiberArea%) and limb length. RESULTS: From 84 normally developing chick embryos, 5 were randomly chosen each day from incubation days 5 to 18 and scanned using 3.0 Tesla magnetic resonance imaging. A dual-cooling technique is used before and during imaging. Eggs were cracked for making histological specimen after imaging. 3 eggs were serially imaged from days 5 to 18. We show that skeletal muscle fibers can be tracked in hind limb in DTI beginning with incubation day 8. Our data shows a good positive correlation between quantitative DTI and histologic parameters (FA vs FiberArea%: r= 0.943, p<0.0001; Fiber_length vs Limb_length: r=0.974, p<0.0001). The result of tracked fibers in DTI during incubation corresponds to the development of chick embryonic skeletal muscle as reported in the literature. CONCLUSION: Diffusion tensor imaging can provide a noninvasive means of evaluating skeletal muscle development in ovo.

The role of susceptibility weighted imaging in functional MRI.

The development of functional brain magnetic resonance imaging (fMRI) has been a boon for neuroscientists and radiologists alike. It provides for fundamental information on brain function and better diagnostic tools to study disease. In this paper, we will review some of the early concepts in high resolution gradient echo imaging with a particular emphasis on susceptibility weighted imaging (SWI) and MR angiography (MRA). We begin with the history of our own experience in this area, followed by a discussion of the role of high resolution in studying the vasculature of the brain and how this relates to the BOLD (blood oxygenation level dependent) signal. We introduce the role of SWI and susceptibility mapping (SWIM) in fMRI and close with recommendations for future high resolution experiments.

Feasibility of in ovo diffusion tractography in the chick embryo using a dual-cooling technique.

PURPOSE: To evaluate the capability of a dual-cooling technique in suppressing motion artifact and to evaluate the feasibility of the noninvasive muscle fibers tracking using DTI during chick embryonic development. MATERIALS AND METHODS: Fifteen eggs were divided into three groups of 5 eggs each (one group for each imaging sequence), and eggs were imaged every 48 h from incubation day 4; embryos were imaged in ovo using three sequences of varying duration (T1, T2, and DTI). For each sequence, three preprocessing methods were used: no-cooling (NC), single-cooling (SC), and dual-cooling (DC). Two independent observers assessed images for motion artifact. The results of different preprocessing methods used for each sequence were compared by the χ(2) test. The Cohen kappa test was used to assess the interobserver variability. RESULTS: For T1 imaging, motion artifact was adequately suppressed by both SC and DC methods (χ(2) test; P > 0.05). For T2 imaging, motion artifact was also sufficiently suppressed by both SC and DC methods (χ(2) test; P > 0.05) except incubation day 19 (χ(2) test; P < 0.001). For DTI, motion artifact was less with DC than SC after 8 days (χ(2) test; P < 0.05). Hindlimb muscle fibers of chick embryo could be serially evaluated with DTI from 8 days using dual-cooling technique. CONCLUSION: The dual-cooling technique enables DTI of chick embryo in ovo with minimal motion artifact, which permits muscle fiber tracking by DTI during chick embryonic development possible, and can improve the imaging quality of conventional MRI with long duration and those sensitive to motion.

The clinical value of diffusion-weighted imaging in combination with T2-weighted imaging in diagnosing prostate carcinoma: a systematic review and meta-analysis.

OBJECTIVE: We aimed to explore the role of diffusion-weighted imaging (DWI) in combination with T2-weighted imaging (T2WI) in detecting prostate carcinoma through a systematic review and meta-analysis. MATERIALS AND METHODS: The MEDLINE, EMBASE, Cancerlit, and Cochrane Library databases were searched for studies published from January 2001 to July 2011 evaluating the diagnostic performance of T2WI combined with DWI in detecting prostate carcinoma. We determined sensitivities and specificities across studies, calculated positive and negative likelihood ratios, and constructed summary receiver operating characteristic curves. We also compared the performance of T2WI combined with DWI with T2WI alone by analyzing studies that had also used these diagnostic methods on the same patients. RESULTS: Across 10 studies (627 patients), the pooled sensitivity of T2WI combined with DWI was 0.76 (95% CI, 0.65-0.84), and the pooled specificity was 0.82 (95% CI, 0.77-0.87). Overall, the positive likelihood ratio was 4.31 (95% CI, 3.12-5.92), and the negative likelihood ratio was 0.29 (95% CI, 0.20-0.43). In seven studies in which T2WI combined with DWI and T2WI alone were performed, the sensitivity and specificity of T2WI combined with DWI were 0.72 (95% CI, 0.67-0.82) and 0.81 (95% CI, 0.76-0.86), respectively, and the sensitivity and specificity of T2WI alone were 0.62 (95% CI, 0.55-0.68) and 0.77 (95% CI, 0.71-0.82), respectively. CONCLUSION: T2WI combined with DWI may be a valuable tool for detecting prostate cancer in the overall evaluation of prostate cancer, compared with T2WI alone. High-quality prospective studies of T2WI combined with DWI to detect prostate carcinoma still need to be conducted.

Cortical calcification in Sturge-Weber Syndrome on MRI-SWI: relation to brain perfusion status and seizure severity.

PURPOSE: To determine the relationship between calcified cortex and perfusion status of white matter and seizure severity in patients with Sturge-Weber Syndrome (SWS), a sporadic neurocutaneous disorder characterized by a leptomeningeal angioma, progressive brain ischemia, and a high incidence of seizures using susceptibility weighted imaging (SWI) and dynamic susceptibility contrast-enhanced perfusion weighted imaging (DSC-PWI). MATERIALS AND METHODS: Fifteen children (ages: 0.9-10 years) with unilateral SWS prospectively underwent magnetic resonance imaging (MRI). The degree of cortical calcification was assessed using SWI while perfusion status was quantified using DSC-PWI images (asymmetries of various perfusion parameters). Comparisons between calcification, perfusion status, and seizure variables were performed. RESULTS: Patients with severely calcified cortex demonstrated significantly lower perfusion in the ipsilateral white matter (mean asymmetry: -0.52 ± 0.22) as compared to patients with only mildly calcified cortex or no calcification (mean asymmetry: 0.08 ± 0.25). Patients with severely calcified cortex also suffered from a higher seizure burden (a composite measure of seizure frequency and epilepsy duration; P = 0.01) and a trend for earlier seizure onset and longer epilepsy duration. CONCLUSION: Severe calcification in the affected hemisphere is related to severely decreased perfusion in underlying white matter and is associated with more severe epilepsy in SWS patients.

Nigral Iron Deposition Is Associated With Levodopa-Induced Dyskinesia in Parkinson's Disease.

OBJECTIVE: To investigate iron deposition in the substantia nigra (SN) of Parkinson's disease (PD) patients associated with levodopa-induced dyskinesia (LID). METHODS: Seventeen PD patients with LID, 17 PD patients without LID, and 16 healthy controls were recruited for this study. The mean QSM values of the whole, left, and right SN were compared among the three groups. A multivariate logistic regression model was constructed to determine the factors associated with increased risk of LID. The receiver operating characteristic curve of the QSM value of SN in discriminating PD with and without LID was evaluated. RESULTS: The mean QSM values of the whole and right SN in the PD with LID were higher than those in the PD without LID (∗ P = 0.03, ∗ P = 0.03). Multivariate logistic regression analysis revealed that the QSM value of whole, left, or right SN was a predictor of the development of LID (∗ P = 0.03, ∗ P = 0.04, and ∗ P = 0.04). The predictive accuracy of LID in adding the QSM value of the whole, left, and right SN to LID-related clinical risk factors was 70.6, 64.7, and 67.6%, respectively. The QSM cutoff values between PD with and without LID of the whole, left, and right SN were 148.3, 165.4, and 152.7 ppb, respectively. CONCLUSION: This study provides the evidence of higher iron deposition in the SN of PD patients with LID than those without LID, suggesting that the QSM value of the SN may be a potential early diagnostic neuroimaging biomarker for LID.