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Traditional T2 magnetic resonance imaging (MRI) contrast agents have defects inherent to negative contrast agents, while chemical exchange saturation transfer (CEST) contrast agents can quantify substances at trace concentrations. After reaching a certain concentration, iron-based contrast agents can "shut down" CEST signals. The application range of T2 contrast agents can be widened through a combination of CEST and T2 contrast agents, which has promising application prospects. The purpose of this study is to develop a T2 MRI negative contrast agent with a controllable size and to explore the feasibility of dual contrast enhancement by combining T2 with CEST contrast agents. The study was carried out in vitro with HCT-116 human colon cancer cells. A GE SIGNA Pioneer 3.0 T medical MRI scanner was used to acquire CEST images with different saturation radio-frequency powers (1.25/2.5/3.75/5 µT) by 2D spin echo-echo planar imaging (SE-EPI). Magnetic resonance image compilation (MAGiC) was acquired by a multidynamic multiecho 2D fast spin-echo sequence. The feasibility of this dual-contrast enhancement method was assessed by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, dynamic light scattering, ζ potential analysis, inductively coupled plasma, X-ray photoelectron spectroscopy, X-ray powder diffraction, vibrating-sample magnetometry, MRI, and a Cell Counting Kit-8 assay. The association between the transverse relaxation rate r2 and the pH of the iron-based contrast agents was analyzed by linear fitting, and the linear relationship between the CEST effect in different B1 fields and pH was analyzed by the ratio method. Fe3O4 nanoparticles (NPs) with a mean particle size of 82.6 ± 22.4 nm were prepared by a classical process, and their surface was successfully modified with -OH active functional groups. They exhibited self-aggregation in an acidic environment. The CEST effect was enhanced as the B1 field increased, and an in vitro pH map was successfully plotted using the ratio method. Fe3O4 NPs could stably serve as reference agents at different pH values. At a concentration of 30 µg/mL, Fe3O4 NPs "shut down" the CEST signals, but when the concentration of Fe3O4 NPs was less than 10 µg/mL, the two contrast agents coexisted. The prepared Fe3O4 NPs had almost no toxicity, and when their concentration rose to 200 µg/mL at pH 6.5 or 7.4, they did not reach the half-maximum inhibitory concentration (IC50). Fe3O4 magnetic NPs with a controllable size and no toxicity were successfully synthesized. By combining Fe3O4 NPs with a CEST contrast agent, the two contrast agents could be imaged simultaneously; at higher concentrations, the iron-based contrast agent "shut down" the CEST signal. An in vitro pH map was successfully plotted by the ratio method. CEST signal inhibition can be used to realize the pH mapping of solid tumors and the identification of tumor active components, thus providing a new imaging method for tumor efficacy evaluation.
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Background: Rotator cuff retears occur more often at the proximal region with the suture-bridge (SB) technique than at the typical footprint region with the single-row (SR) technique. Few longitudinal clinical trials have focused on the postoperative tendon quality of the repaired rotator cuff at different regions between the 2 techniques. Purpose: To compare tendon healing of the proximal and distal regions between the SB and SR techniques. Study Design: Cohort study; Level of evidence, 3. Methods: Included were consecutive patients who underwent arthroscopic rotator cuff repair and undertook clinical and magnetic resonance imaging (MRI) examinations at 3, 6, and 12 months postoperatively between 2016 and 2017. These patients were divided into the SB and SR groups according to the technique used. The repaired tendon was segmented into distal and proximal regions on ultrashort echo time-T2* mapping images. Clinical outcomes (Constant score, American Shoulder and Elbow Surgeons score, Fudan University Shoulder Score, and visual analog scale for pain) and MRI-based tendon healing (T2* values) of different regions were compared between the 2 groups. The differences in T2* values and clinical scores were determined by 1-way analysis of variance for repeated measurements. Results: A total of 31 patients (17 in SB group and 14 in SR group) were included. At 12-month follow-up, significant improvements from preoperatively were achieved for all patients in all clinical scores (P < .001 for all). No significant between-group differences were found in T2* values of the distal region at any time point; however, the mean T2* value of the proximal region at 3 months was significantly higher in the SB group compared with the SR group (P = .03). This difference became nonsignificant at subsequent follow-up time points. Conclusion: Significant clinical improvements over time can be expected in the first year after arthroscopic rotator cuff repair. In the early postoperative period, higher T2* values in the proximal region of the repaired tendon (representing inferior tendon quality) were seen with the SB technique compared with the SR technique; however, this phenomenon was resolved over time.
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Although the probability of pancreatic cystic neoplasms (PCNs) being detected is raising year by year, their differential diagnosis and individualized treatment are still a challenge in clinical work. PCNs are tumors containing cystic components with different biological behaviors, and their clinical manifestations, epidemiology, imaging features, and malignant risks are different. Some are benign [e.g., serous cystic neoplasms (SCNs)], with a barely possible that turning into malignant, while others display a low or higher malignant risk [e.g., solid pseudopapillary neoplasms (SPNs), intraductal papillary mucinous neoplasms (IPMNs), and mucinous cystic neoplasms (MCNs)]. PCN management should concentrate on preventing the progression of malignant tumors while preventing complications caused by unnecessary surgical intervention. Clinically, various advanced imaging equipment are usually combined to obtain a more reliable preoperative diagnosis. The challenge for clinicians and radiologists is how to accurately diagnose PCNs before surgery so that corresponding surgical methods and follow-up strategies can be developed or not, as appropriate. The objective of this review is to sum up the clinical features, imaging findings and management of the most common PCNs according to the classic literature and latest guidelines.
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BACKGROUND: Quantitative ultrashort echo time-T2* (UTE-T2*) mapping shows promise for the detection of potential tendon biochemical conditions, while validation against established clinical studies in the shoulder is needed. PURPOSE: To evaluate and characterize the healing process of the repaired rotator cuff based on longitudinal changes in UTE-T2* values, clinical outcomes, and repair status in patients after arthroscopic rotator cuff repair (ARCR). STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: Patients with ARCR (n = 25) underwent quantitative MRI and clinical examinations at serial follow-up time points: 3, 6, 12, and 24 months postoperatively. Age-matched healthy controls (n = 15) were evaluated at 3 and 12 months after enrollment. Clinical scores included the Constant, American Shoulder and Elbow Surgeons, and Fudan University Shoulder score, and visual analog scale for pain. The MRI examination included UTE-T2*mapping. UTE-T2* maps were generated for T2* values at the healing site. Sugaya classification was adopted to evaluate the repair status. Longitudinal analyses of clinical outcomes, UTE-T2* changes, and Sugaya classification were conducted. RESULTS: The overall retear rate was 8% (2/25, all Sugaya type IV). All patients (including the ones with retear) achieved satisfactory outcomes at 12 months that lasted to 24 months on the basis of clinical scores. The mean UTE-T2* values at the healing site showed an increase from 3 to 6 months (P = .03) and then decreased to a level similar to that observed in age-matched healthy tendons at 12 months (P = .1). No significant differences were found between UTE-T2* values at 12 and 24 months (P = .6). UTE-T2* values at the healing site significantly varied with the repair status according to Sugaya classification (P < .05). Moreover, significant correlations were noted between clinical scores and UTE-T2* values at 6 months (r = -0.6 to -0.3; all P < .05) and 12 months (r = -0.6 to -0.2; all P < .05). CONCLUSION: This study indicated a healing-related relationship between clinical outcomes and quantitative UTE-T2* values, which highlights the potential of using UTE-T2* mapping to track the tendon-healing process noninvasively. Moreover, the repaired tendon was comparable to age-matched healthy controls at 12-month follow-up based on UTE-T2* values.
