Proximal splenic artery embolization for treatment of refractory ascites, a single-center experience.

AIM: Refractory ascites from portal hypertension can be managed with regular large-volume paracentesis (LVP) or transjugular intrahepatic portosystemic shunt (TIPS). Large-volume paracentesis is clinically unsatisfactory and many patients are ineligible or relatively contraindicated for TIPS or Denver shunt. Proximal splenic artery embolization (PSAE) using coils or plugs reduces but does not completely stop splenic arterial inflow, differing from distal splenic artery embolization techniques. By reducing splenic arterial inflow, splenic vein outflow is also decreased, lowering portal pressure and thus treating refractory ascites. METHODS: In this institutional review board-approved single-center retrospective study, electronic medical records were reviewed to obtain demographics and baseline clinical and laboratory data, paracentesis data before and after PSAE, PSAE procedural details, and follow-up imaging up to 12 months post-PSAE. Mixed-effects models were used for statistical analysis. RESULTS: Ten patients with LVP-dependent ascites meeting inclusion criteria underwent PSAE for refractory ascites from 2017 to 2024. Prior to PSAE, four patients had TIPS, three had liver transplants, and the remaining three were neither TIPS nor transplant candidates. In the month before PSAE, patients averaged 3.8 ± 1.7 paracentesis sessions, draining a total of 20.84 ± 10.39 L of fluid monthly. Post-PSAE, the number of paracentesis sessions decreased to 2.1 ± 2.7, 1.0 ± 1.7, 0.4 ± 1.1, and 0.0 ± 0.0 at 1, 3, 6, and 12 months, respectively (p = 0.03). Corresponding ascitic volume drained decreased to 8.7 ± 10.3, 2.7 ± 6.4, 2.0 ± 5.4, and 0.0 ± 0.0 L (p = 0.01). Over the 12-month follow-up period, 6 of 10 patients became LVP-independent. CONCLUSION: Proximal splenic artery embolization can improve refractory ascites in certain patients with portal hypertension, thus providing safe and effective treatment as an alternative to TIPS.

Safety and Effectiveness of Abre Self-Expanding Venous Stent for Treatment of Superior Vena Cava Syndrome.

PURPOSE: Superior vena cava (SVC) syndrome is a constellation of symptoms that results from partial or complete SVC obstruction. Endovascular SVC stenting is an effective treatment for SVC syndrome with rapid clinical efficacy and low risk of complications. In this study, we assess the technical and clinical outcomes of a cohort of patients with SVC syndrome treated with the AbreTM self-expanding venous stent (Medtronic, Inc, Minneapolis, MN, USA). METHODS: An institutional database was used to retrospectively identify patients with SVC syndrome treated with AbreTM venous self-expanding stent placement between 2021-2023. Patient demographic data, technical outcomes, treatment effectiveness, and adverse events were obtained from the electronic medical record. Nineteen patients (mean age 58.6) were included in the study. Thirteen interventions were performed for malignant compression of the SVC, 5 for central venous catheter-related SVC stenosis, and 1 for HD fistula-related SVC stenosis refractory to angioplasty. RESULTS: Primary patency was achieved in 93% of patients (17/19). Two patients (7%) required re-intervention with thrombolysis and angioplasty within 30 days post-stenting. Mean duration of clinical and imaging follow-up were 228.7 ± 52.7 and 258.7 ± 62.1 days, respectively. All patients with clinical follow-up experienced significant improvement in clinical symptoms post-intervention. No stent related complications were identified post-intervention. CONCLUSIONS: Treatment of SVC syndrome with the AbreTM self-expanding venous stent has high rates of technical and clinical success. No complications related to stent placement were identified in this study.

Provocative mesenteric angiography for occult gastrointestinal bleeding: a systematic review.

Occult gastrointestinal bleeding (GIB) is a challenge for physicians to diagnose and treat. A systematic literature search of the PubMed and Embase databases was conducted up to January 1, 2023. Eligible studies included primary research studies with patients undergoing provocative mesenteric angiography (PMA) for diagnosis or localization of occult GIB. Twenty-seven articles (230 patients) were included in the review. Most patients (64.8%) presented with lower GIB. The average positivity rate for provocative angiography was 48.7% (58% with heparin and 46.7% in thrombolytics). Embolization was performed in 46.4% of patients, and surgical management was performed in 37.5%. Complications were rare. PMA can be an important diagnostic and treatment tool but studies with high-level evidence and standardized protocols are needed to establish its safety and optimal use.

Quadrilateral space syndrome.

The quadrilateral space is a confined area through which the axillary nerve and posterior circumflex humeral artery (PCHA) travel in the shoulder. Both structures are susceptible to impingement and compression as they travel though this space resulting in a constellation of symptoms known as quadrilateral space syndrome (QSS). Patients may experience paresthesias, loss of motor function, pain and vascular complications. Individuals who perform repetitive overhead arm movements such as elite athletes are at greater risk of developing QSS. The diagnosis can be difficult, but in the setting of clinical suspicion, physical exam and imaging studies can provide specific findings. On MRI, patients may have atrophy of the deltoid or teres minor muscles and angiography may show aneurysm or vascular occlusion of the PCHA. Treatment is initially conservative, with physiotherapy. Surgical decompression is effective in patients with severe or progressive symptoms. Causes of external compression such as fibrous bands, scarring, or other space occupying lesion may be addressed at that time. Neurolysis and aneurysm resection may also be performed. In some cases, emboli from the PCHA can cause ischemia in the involved upper extremity resulting in an acute presentation. Catheter directed therapy such as thrombolysis or thrombectomy may performed emergently in these cases. Though rare, in patients presenting with arm weakness, paresthesia, pain and/or arterial thrombosis in the arm, QSS is an important entity to consider.

Arterial thoracic outlet syndrome.

Thoracic outlet syndrome (TOS) is used to describe the constellation of symptoms arising from neurovascular compression of the thoracic outlet. The structures passing through the thoracic outlet include the subclavian artery, subclavian vein and trunks of the brachial plexus. Patients may experience symptoms related to compression of any one or various combinations of these structures. Arterial pathology as the cause of TOS is rare, though repetitive overhead arm motion, such as seen in athletes, is a risk factor for developing arterial TOS (aTOS). Symptoms include chronic findings, such as pallor, arm claudication or cool arm. Currently diagnosis of aTOS is made using clinical and imaging parameters which include focused history and physical including provocative maneuvers and imaging follow-up ranging from angiography to MRI. Occasionally, acute thrombosis can result in limb threatening ischemia requiring emergent catheter directed thrombolysis. Outside of acute limb ischemia, management of aTOS is variable, however typically begins with conservative measures such as physical therapy. In patients who do not respond or progress on conservative management, surgical decompression may be performed. Open or endovascular treatment of subclavian artery pathology may be necessary for recalcitrant cases. In this article, the aim is to review the elements involving diagnosis and management of aTOS.

Microwave Ablation as Bridging Therapy for Patients with Hepatocellular Carcinoma Awaiting Liver Transplant: A Single Center Experience.

PURPOSE: To determine the pathologic response of computed tomography-guided percutaneous microwave ablation as bridging therapy for patients with hepatocellular carcinoma awaiting liver transplant, and its subsequent effect on survival. MATERIALS AND METHODS: A single-center retrospective analysis was conducted on 62 patients (M:F = 50:12) with mean age of 59.6 years ± 7.2 months (SD). Sixty-four total MWA procedures were performed for hepatocellular carcinomas within Milan criteria as bridging therapy to subsequent orthotopic liver transplant between August 2014 and September 2018. The pathology reports of the explanted livers were reviewed to assess for residual disease. Residual disease was categorized as complete or incomplete necrosis. Patient demographics, tumor/procedural characteristics, and laboratory values were evaluated. Survival from time of ablation and time of transplantation were recorded and compared between cohorts using log rank tests. RESULTS: The mean tumor size was 2.4 cm ± 0.7 cm (SD), (range = 1-4.6 cm). 32 (50%) cases required hydrodissection. Histopathologic necrosis was seen in 66% of cases at time of liver transplantation. Median time to liver transplant post-MWA was 12.6 months. [IQR = 8.6-14.8 months]. The median survival from ablation was 60.8 months [IQR = 45.5-73.7 months], and the median survival from transplant was 49.3 months [IQR = 33.7-60.1 months]. There was no significant difference in survival for patients with complete versus incomplete necrosis from ablation or liver transplant (p = 0.49, p = 0.46, respectively). CONCLUSIONS: Computed tomography-guided percutaneous microwave ablation is an effective bridge to orthotopic liver transplantation for patients with hepatocellular carcinoma. CEBM LEVEL OF EVIDENCE: Level 3, non-randomized controlled cohort study/follow-up study.

Interventional Radiology in Renal Trauma.

Traumatic injuries to the kidney and collecting system can range widely from small lacerations to significant bleeding and its sequelae. Urinary obstruction can occur in the renal pelvis, ureters, or urethra. Interventional radiology plays a significant role in treatment and management, in many cases requiring emergent action. Endovascular embolization is frequently the first-line approach to treating hemorrhage. Percutaneous interventions for urinary obstruction include nephrostomy and suprapubic catheter placement. In this article, we outline the clinical approach and interventional methods used in the evaluation and treatment of renal trauma. Several case presentations demonstrate the role of interventional radiology in renal trauma.

Yttrium-90 Hepatic Radioembolization for Advanced Chemorefractory Metastatic Colorectal Cancer: Survival Outcomes Based on Right- Versus Left-Sided Primary Tumor Location.

BACKGROUND. Primary colon cancer location affects survival of patients with metastatic colorectal cancer (mCRC). Outcomes based on primary tumor location after salvage hepatic radioembolization with 90Y resin microspheres are not well studied. OBJECTIVE. The objectives of this study are to assess the survival outcomes of patients with advanced chemorefractory mCRC treated with 90Y radioembolization, as stratified by primary tumor location, and to explore potential factors that are predictive of survival. METHODS. A total of 99 patients who had progressive mCRC liver metastases while receiving systemic therapy and who were treated with 90Y radioembolization at a single center were retrospectively analyzed. For 89 patients, tumor response on the first imaging follow-up examination (CT or MRI performed at a mean [± SD] of 1.9 ± 0.9 months after 90Y radioembolization) was evaluated using RECIST. Overall survival (OS), OS after 90Y radioembolization, and hepatic progression-free survival (PFS) were calculated using the Kaplan-Meier method. Outcomes and associations of outcomes with tumor response were compared between patients with left- and right-sided tumors. RESULTS. A total of 74 patients had left-sided colon cancer, and 25 patients had right-sided colon cancer. Median OS from the time of mCRC diagnosis was 37.2 months, median OS after 90Y radioembolization was 5.8 months, and median hepatic PFS was 3.3 months. Based on RECIST, progressive disease on first imaging follow-up was observed in 38 patients (43%) after 90Y radioembolization and was associated with shorter OS after 90Y radioembolization compared with observation of disease control on first imaging follow-up (4.0 vs 10.5 months; p < .001). Patients with right-sided primary tumors showed decreased median OS after 90Y radioembolization compared with patients with left-sided primary tumors (5.4 vs 6.2 months; p = .03). Right- and left-sided primary tumors showed no significant difference in RECIST tumor response, hepatic PFS, or extrahepatic disease progression (p > .05). Median survival after 90Y radioembolization was significantly lower among patients with progressive disease than among those with disease control in the group with left-sided primary tumors (4.2 vs 13.9 months; p < .001); however, this finding was not observed in the group with right-sided primary tumors (3.3 vs 7.2 months; p = .05). CONCLUSION. Right-sided primary tumors were independently associated with decreased survival among patients with chemorefractory mCRC after 90Y radioembolization, despite these patients having a similar RECIST tumor response, hepatic PFS, and extrahepatic disease progression compared with patients with left-sided primary tumors. CLINICAL IMPACT. Primary colon cancer location impacts outcomes after salvage 90Y radioembolization and may help guide patient selection.

Repeat Evaluation of Lung Shunt Fraction is Unnecessary: A Retrospective Observational Study of Successive Lung Shunt Fractions from Variable Arterial Distributions in Patients Undergoing Radioembolization of Primary and Secondary Liver Tumors.

PURPOSE: To evaluate whether the recalculation of lung shunt fraction (LSF) is necessary prior to next-stage or same lobe repeat radioembolization. MATERIALS AND METHODS: Retrospective chart review was performed for patients who underwent radioembolization between February 2008 and December 2018. Eighty of 312 patients had repeat mapping angiograms and LSF calculations. A total of 160 LSF calculations were made using planar imaging (155, [97%]) and single-photon emission computed tomography (5 [3%]) technetium-99m macroaggregated albumin hepatic arterial injection imaging. The mean patient age was 61.8 years ± 12.7; 69 (86%) patients had metastatic disease and 11 (14%) had hepatocellular carcinoma. RESULTS: Patients had a median LSF of 5% (interquartile range [IQR] 3%-9%) with a median absolute difference of 1.25 (IQR 0.65-3.4) and a median of 76 days (IQR 42.5-120 days) between repeat LSF calculations. There was a median change in LSF of 0.2% between mapping studies (P = .11). There was no statistical significance between the repeat LSFs regardless of the arterial distribution (P = .79) or between tumor types (P = .75). No patients exceeded lung dose limits using actual or predicted prescribed dose amounts. The actual median lung dose was 2.6 Gy (IQR 1.8-4.4 Gy, maximum = 20.5) for the first radioembolization and 2.0 Gy (IQR 1.3-3.7 Gy, maximum = 10.1) for the second radioembolization. CONCLUSIONS: No significant difference in LSF was identified between different time points and arterial distributions within the same patient undergoing repeat radioembolization. In patients who receive well under 30-Gy lung dose for the initial treatment and a 50-Gy cumulative lung dose, repeat radioembolization treatments in the same patient may not require a repeat LSF calculation.

ACR Appropriateness Criteria® Thoracic Outlet Syndrome.

Thoracic outlet syndrome (TOS) is the clinical entity that occurs with compression of the brachial plexus, subclavian artery, and/or subclavian vein at the superior thoracic outlet. Compression of each of these structures results in characteristic symptoms divided into three variants: neurogenic TOS, venous TOS, and arterial TOS, each arising from the specific structure that is compressed. The constellation of symptoms in each patient may vary, and patients may have more than one symptom simultaneously. Understanding the various anatomic spaces, causes of narrowing, and resulting neurovascular changes is important in choosing and interpreting radiological imaging performed to help diagnose TOS and plan for intervention. This publication has separated imaging appropriateness based on neurogenic, venous, or arterial symptoms, acknowledging that some patients may present with combined symptoms that may require more than one study to fully resolve. Additionally, in the postoperative setting, new symptoms may arise altering the need for specific imaging as compared to preoperative evaluation. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Same-Day Yttrium-90 Radioembolization: Feasibility with Resin Microspheres.

PURPOSE: To evaluate the feasibility of a same-day yttrium-90 (90Y) radioembolization protocol with resin microspheres (including pretreatment angiography, lung shunt fraction [LSF] determination, and radioembolization) for the treatment of hepatocellular carcinoma (HCC) and liver metastases. MATERIALS AND METHODS: All same-day radioembolization procedures performed over 1 y (February 2017 to January 2018) were included in this single-institutional retrospective analysis, in which 34 procedures were performed in 26 patients (median age, 63 y; 13 women), 19 with liver metastases and 7 with HCC. Yttrium-90 treatment activities were calculated by body surface area method. Tumor imaging response was assessed by Response Evaluation Criteria In Solid Tumors (RECIST) 1.1 for liver metastases and modified RECIST for HCC. Clinical side effects and adverse events were graded per Common Terminology Criteria for Adverse Events version 4.0. RESULTS: All planned cases were technically successful, and no cases were canceled for elevated LSF or vascular anatomic reasons. Pretreatment angiography modified the planned 90Y treatment activity in 1 case in which vascular anatomy required a lobar-dose split into 2 for segmental infusions. In 18% of cases, patients were briefly admitted after the procedure for observation or symptom management. Imaging evaluation of initial efficacy at 1 month demonstrated partial response in 25% and stable disease in 67% of patients with liver metastases and partial/complete response in 43% and stable disease in 14% of patients with HCC. Grade ≥ 3 adverse events occurred in 6% of cases, with no systemic therapy-limiting toxicities. The mean total procedure time was 4.2 hours. CONCLUSIONS: A same-day 90Y radioembolization protocol with resin microspheres is feasible in select patients, which can expedite cancer therapy.

Safety and Efficacy of Catheter-Directed Therapies as a Supplement to Surgical Decompression in Venous Thoracic Outlet Syndrome.

OBJECTIVE: The purpose of this study is to evaluate the role of endovascular therapy in the management of venous thoracic outlet syndrome (TOS), with an emphasis on its role after surgical decompression. MATERIALS AND METHODS: This single-center retrospective review identified all patients who underwent conventional contrast-enhanced venography as a component of the imaging evaluation of clinically suspected venous TOS from January 2004 through September 2015. Eighty-one patients were identified, with a mean (± SD) age of 33 ± 12 years, of whom 59% (48/81) were women. After imaging confirmation of venous TOS, a standardized treatment protocol combining surgical and endovascular intervention was used for management. RESULTS: Of the 81 patients included in the study, 73 (90%) had angiographic evidence of venous TOS; 41 of these 73 patients (56%) underwent endovascular venous intervention (e.g., thrombolysis or angioplasty before surgical) decompression. A total of 67 patients (67/73; 92%) with venous TOS underwent surgical decompression, with 56 of these (56/73; 77%) undergoing postoperative venography. Of these 56 patients who underwent postoperative venography, 48 (86%) required venoplasty, four had normal-appearing subclavian veins (7%) and had no intervention, and four of 48 (8%) had chronic total venous occlusions that could not be recanalized. Only four of the 48 of the patients (8%) who underwent postdecompression venoplasty required subsequent repeat venography and intervention for management of persistent or recurrent symptoms, whereas all others (44/48; 92%) remained symptom free on clinical follow-up. No complications were identified that were related to the endovascular interventions. CONCLUSION: Combining venography and endovascular venous intervention with surgical decompression in managing patients with clinically suspected venous TOS is safe and effective. Postdecompression venoplasty appears to be highly effective, with a low rate of symptom recurrence.

Angiographic Evaluation and Management of Nonvariceal Gastrointestinal Hemorrhage.

OBJECTIVE: The purpose of this article is to review the roles of angiography, embolization, and various ancillary techniques in evaluating and managing gastrointestinal hemorrhage. CONCLUSION: Nonvariceal gastrointestinal hemorrhage typically resolves spontaneously or responds to medical or endoscopic management. Refractory hemorrhage may require angiography and transcatheter intervention. Noninvasive imaging evaluation may be useful for characterizing the bleeding source and confirming the presence of active hemorrhage before angiography. If a bleeding source is angiographically identified, superselective catheterization with embolization is typically effective in controlling hemorrhage while minimizing complications.

Digital diffraction analysis enables low-cost molecular diagnostics on a smartphone.

The widespread distribution of smartphones, with their integrated sensors and communication capabilities, makes them an ideal platform for point-of-care (POC) diagnosis, especially in resource-limited settings. Molecular diagnostics, however, have been difficult to implement in smartphones. We herein report a diffraction-based approach that enables molecular and cellular diagnostics. The D3 (digital diffraction diagnosis) system uses microbeads to generate unique diffraction patterns which can be acquired by smartphones and processed by a remote server. We applied the D3 platform to screen for precancerous or cancerous cells in cervical specimens and to detect human papillomavirus (HPV) DNA. The D3 assay generated readouts within 45 min and showed excellent agreement with gold-standard pathology or HPV testing, respectively. This approach could have favorable global health applications where medical access is limited or when pathology bottlenecks challenge prompt diagnostic readouts.

Beyond hepatocellular carcinoma and colorectal metastasis: the expanding applications of radioembolization.

As a relatively safe outpatient procedure, radioembolization can potentially be used to treat any type of tumor within the liver, primary or metastatic. The safety and effectiveness of radioembolization in the treatment of hepatocellular carcinoma (HCC) and metastatic colorectal cancer (mCRC) has led many groups to explore its application in other malignancies. Moreover, other organs, such as the lungs and kidneys, have been explored as targets for therapy. Although the most data for radioembolization is related to HCC and mCRC, there is increasing experience and data regarding metastatic disease to the liver for other primary tumors. We review the current state of liver-directed therapy with radioembolization outside of HCC and mCRC, including metastatic neuroendocrine, breast, and melanoma, as well as limited experiences with other primary malignancies. Applications of radioembolization related to these other cancers and new trends and future directions will be discussed. With increasing use and availability of radioembolization, it promises to serve an expanding role in the repertoire of tools available for treating and managing oncologic disease.

Treatment of multiple system atrophy using intravenous immunoglobulin.

BACKGROUND: Multiple system atrophy (MSA) is a progressive neurodegenerative disorder of unknown etiology, manifesting as combination of parkinsonism, cerebellar syndrome and dysautonomia. Disease-modifying therapies are unavailable. Activation of microglia and production of toxic cytokines suggest a role of neuroinflammation in MSA pathogenesis. This pilot clinical trial evaluated safety and tolerability of intravenous immunoglobulin (IVIG) in MSA. METHODS: This was a single-arm interventional, single-center, open-label pilot study. Interventions included monthly infusions of the IVIG preparation Privigen®, dose 0.4 gram/kg, for 6 months. Primary outcome measures evaluated safety and secondary outcome measures evaluated preliminary efficacy of IVIG. Unified MSA Rating Scale (UMSARS) was measured monthly. Quantitative brain imaging using 3T MRI was performed before and after treatment. RESULTS: Nine subjects were enrolled, and seven (2 women and 5 men, age range 55-64 years) completed the protocol. There were no serious adverse events. Systolic blood pressure increased during IVIG infusions (p<0.05). Two participants dropped out from the study because of a non-threatening skin rash. The UMSARS-I (activities of daily living) and USMARS-II (motor functions) improved significantly post-treatment. UMSARS-I improved in all subjects (pre-treatment 23.9 ± 6.0 vs. post-treatment 19.0±5.9 (p=0.01). UMSARS-II improved in 5 subjects, was unchanged in 1 and worsened in 1 (pre-treatment 26.1±7.5 vs. post-treatment 23.3±7.3 (p=0.025). The MR imaging results were not different comparing pre- to post-treatment. CONCLUSIONS: Treatment with IVIG appears to be safe, feasible and well tolerated and may improve functionality in MSA. A larger, placebo-controlled study is needed.

Protein-based MRI contrast agents for molecular imaging of prostate cancer.

PURPOSE: The purpose of this study was to demonstrate a novel protein-based magnetic resonance imaging (MRI) contrast agent that has the capability of targeting prostate cancer and which provides high-sensitivity MR imaging in tumor cells and mouse models. PROCEDURE: A fragment of gastrin-releasing peptide (GRP) was fused into a protein-based MRI contrast agent (ProCA1) at different regions. MR imaging was obtained in both tumor cells (PC3 and H441) and a tumor mouse model administrated with ProCA1.GRP. RESULTS: PC3 and DU145 cells treated with ProCA1.GRPs exhibited enhanced signal in MRI. Intratumoral injection of ProCA1.GRP in a PC3 tumor model displayed enhanced MRI signal. The contrast agent was retained in the PC3 tumor up to 48 h post-injection. CONCLUSIONS: Protein-based MRI contrast agent with tumor targeting modality can specifically target GRPR-positive prostate cancer. Intratumoral injection of the ProCA1 agent in the prostate cancer mouse model verified the targeting capability of ProCA1.GRP and showed a prolonged retention time in tumors.

Rational design of protein-based MRI contrast agents.

We describe the rational design of a novel class of magnetic resonance imaging (MRI) contrast agents with engineered proteins (CAi.CD2, i = 1, 2,..., 9) chelated with gadolinium. The design of protein-based contrast agents involves creating high-coordination Gd(3+) binding sites in a stable host protein using amino acid residues and water molecules as metal coordinating ligands. Designed proteins show strong selectivity for Gd(3+) over physiological metal ions such as Ca(2+), Zn(2+), and Mg(2+). These agents exhibit a 20-fold increase in longitudinal and transverse relaxation rate values over the conventional small-molecule contrast agents, e.g., Gd-DTPA (diethylene triamine pentaacetic acid), used clinically. Furthermore, they exhibit much stronger contrast enhancement and much longer blood retention time than Gd-DTPA in mice. With good biocompatibility and potential functionalities, these protein contrast agents may be used as molecular imaging probes to target disease markers, thereby extending applications of MRI.