Usefulness of fat attenuation index in postmortem CT for identifying responsible vessels in acute coronary syndromes: A case report.

Postmortem imaging, particularly unenhanced postmortem computed tomography (PMCT), has been increasingly utilized for pathological or judicial examination as a substitute for conventional autopsy, to compensate very low autopsy rates. While unenhanced PMCT has a limitation in diagnosing acute coronary syndromes, the fat attenuation index (FAI) which is a novel imaging biomarker measured by clinical coronary CT angiography (CCTA), has been known to noninvasively detect coronary artery inflammation. We investigated the postmortem diagnostic usefulness of perivascular FAI measured by CCTA in a 61-year-old male who died suddenly after chest pain. PMCT and autopsy were conducted 92 hours after death. FAI measurement results were -57 Hounsfield units (HU) in the right coronary artery (RCA), -73 HU in the left anterior descending artery (LAD), and -64 HU in the left circumflex artery (LCX). Autopsy revealed significant stenosis in the RCA and LCX, but no significant stenosis was found in the LAD. The elevated FAI in the RCA suggested acute inflammation, which agreed with the autopsy findings. This case is the first to demonstrate effectiveness of FAI measured with PMCT for identifying the vessels responsible for acute coronary syndromes, indicating its potential in postmortem diagnosis.

Optimization of Traction Magnetic Resonance Imaging to Improve Visibility of the Elbow Cartilage.

We previously reported that elbow magnetic resonance imaging (MRI) with 7 kg traction increases the joint space width of the radiocapitellar joint and improves articular cartilage visibility without arthrography. However, the optimal traction weight remains unclear. We assessed the effects of different traction weights on elbow MRI in 30 healthy volunteers. Elbow MRI was performed without traction and with 3, 5, and 7 kg axial tractions. The joint space width, humeral articular cartilage outline visibility, and intraprocedural pain/discomfort were evaluated. The joint and cartilage parameters were measured at the radiocapitellar joint and the lateral and medial thirds of the ulnohumeral joint. At the radiocapitellar joint, the joint space width increased significantly with traction. The cartilage outline visibility significantly increased with traction, with no significant differences among the traction weights. No significant result was observed at the lateral and medial thirds of the ulnohumeral joint. Pain and discomfort significantly increased as we used heavier traction weights. Elbow MRI with 3 kg traction showed sufficient effects similar to those observed with 7 kg traction with minimal pain and discomfort. There was no difference in the effect of traction between male and female participants. This procedure may enable enhanced visualization of intra-articular elbow injuries.

Hip and lumbosacral joint centre locations in asian population: Biases produced by existing regression equations and development of new equations.

The hip and lumbosacral joint centre (HJC and LSJC) predictions are required to analyse the lumbo-pelvic-hip dynamics during various human motions. Some HJC and LSJC regression equations based on pelvic dimension have been developed; however, the pre-existing methods need to be re-evaluated, and methodological reconsideration may improve the regression methods. Here we show that pre-existing methods produce biased predictions of the LSJC and HJC in 23 male and 24 female Japanese adults, and that the biases in the LSJC differ between sexes, using magnetic resonance imaging (MRI) around the pelvis. Compared with directly measured locations on MRI, the pre-existing regression equations predict LSJC to be more posterior in males and more inferior and posterior in females, and HJC to be more medial in both sexes. The better pre-existing regression equation for LSJC height differs between sexes, with pelvic-width-base better in males and pelvic-depth-base better in females, respectively. We suggest the unsuitability of pre-existing methods to our dataset consisting of Japanese adults and the importance of considering sex differences in regression methods. We propose regression equations to predict HJC and LSJC, considering soft-tissue thickness, sex differences, and a height-directional measure, using least absolute shrinkage and selection operator regression. We validate them using leave-one-out cross-validation (LOOCV). LOOCV shows that our model produces negligible biases and smaller absolute errors than the pre-existing regressions; in particular, the anteroposterior absolute error for LSJC is less than half that of the pre-existing regression. Our regression equation can be a powerful solution for accurate motion analysis.

Distal muscle cross-sectional area is correlated with shot put performance.

Shot putters throw a heavy shot by "pushing". Pushing involves the coordinated extension of multiple joints and is a common motor task for both upper and lower limbs. In lower limb musculature, proximal-specific development and association with motor performance have been shown in athletes. However, as the upper limb is not mechanically loaded to support the body during daily locomotion, it may develop differently from the lower limb. We investigated the cross-sectional area of the prime movers of the upper limb and upper trunk (pectoralis major, deltoid, triceps brachii, and palmar flexors) in eleven male shot put athletes and fourteen untrained males by obtaining magnetic resonance images and manually tracing the muscles on the images. All target muscles were significantly larger in athletes than non-athletes (p < 0.01), with "huge" effect sizes for the pectoralis major and palmar flexors (d = 2.74, 2.04). All target muscle cross-sectional areas were positively correlated with season best record (r ≥ 0.62, p ≤ 0.04), with a particularly strong correlation for the palmar flexors (r = 0.96). These results suggest that the distal muscles of the upper limb are also expected to develop and are strongly associated with motor performance. This is especially true for the distal upper limb muscles (palmar flexors) in shot putters. These findings provide insight into potential training interventions for athletic performance in forceful upper limb movements.

Consideration on size, velocity and path of droplets emitted during running.

BACKGROUND: People began to wear face masks during physical activities due to spread of COVID-19. There are no previous studies about the need for wearing masks while running. METHODS: Assuming a citizen runner who runs full marathon in 4 hours, we verified the path and the amount of droplet dispersal, setting a humanoid mannequin with a mask in simulated running environment (Experiment 1). We also had six adults exercise in the same environment to examine droplet behaviors when not wearing a face mask (Experiment 2). Average droplet size was determined, and repeated measures ANOVA was carried out to examine statistical significance. To evaluate observed droplet behaviors, theoretical solutions of the downfall motion of large droplets were then derived, taking air resistance into consideration. RESULTS: Experiment 1: wearing a face mask caused more droplets to adhere to the face; Experiment 2: droplets were emitted in conversation, coughing or sneezing, and they fell within social distancing. Average droplet size was not sensitive to the wind velocity. It could vary with a significant difference for time and wind velocity. Observed velocity and path of droplet can be expressed by the theoretical solutions. CONCLUSIONS: Velocity and path of large droplets can be expressed by the theoretical solution of particles in downfall motion under air resistance. We therefore conclude that wearing a mask while running gives adverse effects in preventing infection. Possibility of droplet transmission while running is considered low even when not wearing a face mask, as long as social distancing is ensured.

Development of a Car-mounted Mobile MR Imaging System for Diagnosis of Sports-related Wrist Injury.

Portable MRI scanners, in which a permanent magnet with a low magnetic field is mounted on a small car, have enabled the performance of MRI examinations in various remote environments. Here, we have modified the portable MRI system to enable the early diagnosis of wrist sports injuries among tennis players. A RF probe specifically designed for the human wrist was developed, and a power supply scheme using a small generator was introduced. The portable MRI system was located at a tennis school and imaging of the wrists of junior tennis players was performed. To demonstrate clinical feasibility, image quality was assessed by a radiologist and clinical evaluations were performed. In most cases, the image quality was sufficient for diagnosis, and triangular fibrocartilage complex damage could be detected. The results indicated that the modified portable MRI system could be applied for an early diagnosis of wrist injuries.

Advances in Bone Joint Imaging-Metal Artifact Reduction.

Numerous types of metal implants have been introduced in orthopedic surgery and are used in everyday practice. To precisely evaluate the postoperative condition of arthroplasty or trauma surgery, periprosthetic infection, and the loosening of implants, it is important to reduce artifacts induced by metal implants. In this review, we focused on technical advances in metal artifact reduction using digital tomosynthesis, computed tomography, and magnetic resonance imaging. We discussed new developments in diagnostic imaging methods and the continuous introduction of novel technologies to reduce metal artifacts; however, these innovations have not yet completely removed metal artifacts. Different algorithms need to be selected depending on the size, shape, material and implanted body parts of an implant. Future advances in metal artifact reduction algorithms and techniques and the development of new sequences may enable further reductions in metal artifacts even on original images taken previously. Moreover, the combination of different imaging modalities may contribute to further reductions in metal artifacts. Clinicians must constantly update their knowledge and work closely with radiologists to select the best diagnostic imaging method for each metal implant.

Two case reports showing a rather striking abnormal finding of unknown origin localized to the cortex of an amputated femur.

MRI scans of patients who have undergone leg amputation are rarely obtained; such scans may be performed when a mass is suspected to be related to the amputation or when inflammation (infection) is suspected, but the number of such cases is not large. In this study, however, we encountered 2 very striking cases in which short-tau inversion recovery coronal images taken for different purposes coincidentally showed a diffuse high signal intensity of the residual femoral cortex on the side wearing the artificial limb. Further examination of these images revealed that the superior margins of the artificial limb cup and the abnormal signal were almost identical and that the signal was only observed in the residual femur of the side using the artificial limb, suggesting that the change was caused by artificial limb usage. Despite the difficulty in imaging-pathologic correlation because the patients were still alive, we considered that the high signal was related to the characteristic microanatomy of the bone cortex and the mechanical changes caused by the effects of artificial limb usage on the residual femur. The 2 patients have not shown any specific events since then. Thus, while the residual femoral cortex may show findings of interest, these findings do not seem to require any specific treatment.

Use of a Small Car-Mounted Magnetic Resonance Imaging System for On-Field Screening for Osteochondritis Dissecans of the Humeral Capitellum.

Mobile magnetic resonance imaging (MRI) using a car is a recent advancement in imaging technology. Specifically, a car-mounted mobile MRI system is expected to be used for medical check-ups; however, this is still in the research stage. This study demonstrated the practicality of a small car-mounted mobile MRI in on-field screening for osteochondritis dissecans (OCD) of the humeral capitellum. In the primary check-up, we screened the throwing elbows of 151 young baseball players using mobile MRI and ultrasonography. We definitively diagnosed OCD at the secondary check-up using X-ray photography and computed tomography or MRI. We investigated the sensitivity and specificity of mobile MRI and ultrasonography for OCD. Six patients were diagnosed with OCD. The sensitivity was 83.3% for mobile MRI and 66.7% for ultrasonography, with specificity of 99.3% vs. 100%, respectively. One patient was detected using ultrasonography but was missed by mobile MRI due to poor imaging quality at the first medical check-up. Following this false-negative case, we replaced a damaged radio frequency coil to improve the image quality, and the mobile MRI could detect all subsequent OCD cases. Two patients were diagnosed by mobile MRI only; ultrasonography missed cases lacking subchondral bone irregularity, such as a healing case, and an early-stage case. Mobile MRI could screen for OCD from the very early stages through the healing process and is therefore a practical tool for on-field screening.

Characteristic MRI findings of the shoulder, elbow, and wrist joints in elite wheelchair basketball players.

BACKGROUND: The health of wheelchair users' upper limbs is directly related to their quality of life. Moreover, para-sport athletes are subjected to a dual load on their upper extremities from competition and daily life, making it even more critical to maintain upper extremity health. This study aimed to investigate the characteristics of joint disorders in elite wheelchair basketball players using magnetic resonance imaging (MRI). METHODS: We scanned MRI images of the bilateral shoulders, elbows, and wrist joints of ten elite wheelchair basketball players and ten general wheelchair users. The elite wheelchair players were athletes who underwent at our institution medical checkup of the candidates for the national team for the international women's tournament and who agreed to this research purpose. The general wheelchair players were recruited from wheelchair users in their 20s and 30s who had no daily exercise habits and who agreed to the study objectives. Two radiologists interpreted the MRI images and diagnosed the diseases of each joint. We compared the number of lesions between the two groups. We used Fisher's exact test to determine whether the lesions diagnosed by MRI were specific to wheelchair basketball players. The significance threshold was set at P < 0.05. RESULTS: Elite wheelchair basketball players had significantly more right-sided, left-sided and bilateral latero-posterior lesions, which are cysts found on the lateral-posterior corner of the capitulum of the humerus than did general wheelchair users (P < 0.05). Severe damage to the right triangular fibrocartilage complex was also observed more frequently (P < 0.05) in wheelchair basketball players. CONCLUSIONS: We believe that the patients' tendency to fall forward in the wheelchair hitting both hands on the ground, thereby injuring the triangular fibrocartilage complex and locking the lateral elbow, may be the cause of the characteristic findings on MRI. High-speed wheelchair operation was also considered a cause of severe triangular fibrocartilage complex injuries. This study's insights can be useful for future solutions to extend players' careers.

Effectiveness of temporal subtraction computed tomography images using deep learning in detecting vertebral bone metastases.

PURPOSE: To assess the clinical effectiveness of temporal subtraction computed tomography (TS CT) using deep learning to improve vertebral bone metastasis detection. METHOD: This retrospective study used TS CT comprising bony landmark detection, bone segmentation with a multi-atlas-based method, and spatial registration of two images by a log-domain diffeomorphic Demons algorithm. Paired current and past CT images of 50 patients without vertebral metastasis, recorded during June 2011-September 2016, were included as training data. A deep learning-based method estimated registration errors and suppressed false positives. Thereafter, paired CT images of 40 cancer patients with newly developed vertebral metastases and 40 control patients without vertebral metastases were evaluated. Six board-certified radiologists and five radiology residents independently interpreted 80 paired CT images with and without TS CT. RESULTS: Records of 40 patients in the metastasis group (median age: 64.5 years; 20 males) and 40 patients in the control group (median age: 64.0 years; 20 males) were evaluated. With TS CT, the overall figure of merit (FOM) of the board-certified radiologist and resident groups improved from 0.848 to 0.876 (p = 0.01) and from 0.752 to 0.799 (p = 0.02), respectively. The sub-analysis focusing on attenuation changes in lesions revealed that the FOM of osteoblastic lesions significantly improved in both the board-certified radiologist and resident groups using TS CT. The sub-analysis focusing on lesion location showed that the FOM of the resident group significantly improved in the vertebral arch (p = 0.04). CONCLUSIONS: TS CT was effective in detecting bone metastasis by both board-certified radiologists and radiology residents.

Characteristic MRI findings of shoulder, elbow, and wrist joints in wheelchair user.

OBJECTIVE: Wheelchair users frequently utilize their upper extremities for moving around in their daily life. Therefore, it is likely they may develop conditions of overuse in their joints, which could affect their activity and daily life. The purpose of this study is to clarify the actual conditions of the joints of wheelchair users using MRI. MATERIAL AND METHODS: Twenty-five wheelchair users and twenty able-bodied control volunteers participated in this study. We scanned MRI images of their right and left shoulders, elbows, and wrists. Two radiologists interpreted the images and made diagnoses for each of the joints. The number of diseases for each joint was compared between wheelchair users and able-bodied volunteers. RESULTS: The number of supraspinatus tendon tears was higher in wheelchair users than controls in the right (Rt.) (P < 0.05), left (Lt.) (P < 0.05), and bilateral (Bil.) (P < 0.05) shoulders. The number of elbow LP lesions (Rt. (P < 0.01), Lt. (P < 0.01), and Bil. (P < 0.05)) and the number of elbow lateral epicondylitis cases (Rt. [P < 0.05] and Lt. [P < 0.05]) were also higher in wheelchair users than that of control volunteers. Additionally, the number of wrist TFCC injuries in wheelchair users (Rt. [P < 0.01], Lt. [P < 0.01], and Bil. [P < 0.01]) was more than that of control volunteers. CONCLUSION: Our results suggest that there are several types of overuse injury in each joint. However, we hypothesize that these are not induced by driving wheelchairs, but instead by the "push up" movement characteristic for wheelchair users, according to the situations caused by each injury.

Investigation of site and frequency of asymptomatic injury in medial structures of the elbow in adolescent baseball players using dedicated magnetic resonance imaging.

PURPOSE: Medial epicondyle (ME) and elbow joint proximal (UCL-p) and distal ulnar collateral ligament (UCL-d) asymptomatic injuries are frequently observed using magnetic resonance imaging (MRI). However, the injury rates vary among these structures in elbow screening of adolescent baseball players, despite being adjacent medial structures of the elbow. This study aimed to retrospectively determine the actual injury site and rate, and investigate the underlying reason for discrepancies anatomically and biomechanically. MATERIALS AND METHODS: Forty-four male adolescent baseball players were scanned using MRI. Two interpreters independently and retrospectively assessed the ME, UCL-p, and UCL-d injuries using the gradient echo axial, sagittal, and coronal planes. RESULTS: The injury prevalence was significantly higher in the ME and UCL-p (> 50% of the participants) than in the UCL-d (22.7%), P < 0.01 and P < 0.01, respectively. Additionally, there was a tendency toward a high-frequency injury rate of the ME or UCL-p. CONCLUSION: The injury site of the medial structures tended to be proximal. The ME and UCL-p were observed to be more frequently injured compared to the UCL-d in adolescent baseball players according to the dedicated MRI findings in this study.

Changes in skeletal muscle diffusion parameters owing to intramyocellular lipid.

INTRODUCTION: Several studies investigated the changes in diffusion of water molecules in skeletal muscle cells of lifestyle-related-disease patients who performed a hybrid training (HYBT) for six months. They reported that the apparent diffusion coefficient (ADC) and all diffusion eigenvalues (λ1, λ2, and λ3) increased after the HYBT, owing to the enlargement of the intramyocellular diffusion space (intracellular space) caused by the muscular hypertrophy. We assumed that the HYBT promoted metabolism of the whole skeletal muscle including lipids, which reduced the amount of intramyocellular lipid (IMCL), and led to a secondary enlargement of the diffusion space in the skeletal muscle cells. However, the IMCL has to be a diffusion limiting factor in order to verify this hypothesis. Until now, there is no report on whether IMCL is a diffusion limiting factor for water molecules. The objective of this study was to examine whether the IMCL is a diffusion limiting factor in skeletal muscle cells. MATERIALS AND METHODS: We performed a three-dimensional quantification of the IMCL in triceps surae muscles of lifestyle-related-disease patients and healthy volunteers. In addition, we measured the ADC in the volume of interest (VOI), diffusion anisotropy (FA), and diffusion eigenvalues (λ1, λ2, and λ3), and evaluated the correlations between these diffusion parameters and IMCL. RESULTS: The results showed that the amount of IMCL was positively and negatively correlated with the FA and λ3, respectively, in lifestyle-related-disease patients. In addition, there was a weak negative correlation between IMCL and ADC, λ1, and λ2. There was no correlation between the amount of IMCL and diffusion parameters of healthy volunteers. DISCUSSION: Above a certain amount, the IMCL correlates with the diffusion parameters. A higher amount of IMCL leads to smaller diffusion eigenvalues. This result suggested that IMCL possibility of influencing diffusion of water molecules in skeletal muscle cells. However, in order for the influence of IMCL to be reflected in the diffusion eigenvalues, it was needed large amount of IMCL existed, and we thought that the influence was smaller than the influence by the already reported cell membrane.

Clinical and anthropometric characteristics of non-obese non-alcoholic fatty liver disease subjects in Japan.

AIM: The underlying mechanism of non-obese non-alcoholic fatty liver disease (NAFLD) has not been fully elucidated. We classified patients with NAFLD by sex and body mass index and compared their clinical features to clarify the background pathophysiology of non-obese NAFLD. METHODS: A total of 404 patients with NAFLD were divided according to their body mass index (<25 [non-obese], 25 to <30 [obese], and ≥30 [severe obese]), and were further compared with 253 patients without obesity and NAFLD (non-NAFLD). RESULTS: The proportion of the individuals with non-obese NAFLD was 25.7% in men and 27.6% in women. The male and female non-obese NAFLD groups had lower skeletal muscle mass and muscle strength than the obese NAFLD groups. The visceral fat area, although low, was ≥100 cm2 in 59.3% of men and 43.8% of women. An increase in liver fat accumulation, hepatic fibrosis, homeostasis model assessment of insulin resistance, and leptin levels was modest in the non-obese NAFLD group compared with a marked increase in the obese NAFLD groups. The muscle mass of the non-obese NAFLD group was similar to that of the non-NAFLD group, but muscle steatosis was particularly common among women. Multivariate analysis revealed that the factors contributing to increased liver fat accumulation in the non-obese NAFLD group were visceral fat area, HbA1c, myostatin, and leptin. CONCLUSIONS: In patients with non-obese NAFLD, a sex difference was observed in the clinical features. In addition to increased visceral fat, decreased muscle mass and muscle strength, muscle atrophy (presarcopenia), and impaired glucose tolerance were considered to be important pathophysiological factors.

Urinary Levels of Titin-N Fragment, a Skeletal Muscle Damage Marker, are Increased in Subjects with Nonalcoholic Fatty Liver Disease.

Sarcopenia is a pathological condition affecting the development and progression of NAFLD. Urinary levels of titin-N fragment, a biomarker reflecting muscle damage, were measured in NAFLD subjects, and analyzed in a retrospective manner for possible correlations with NAFLD pathophysiology to assess their clinical relevance. This study enrolled 153 NAFLD subjects and 100 subjects without NAFLD, obesity or diabetes mellitus (non-NAFLD). NAFLD subjects had more decreased knee extension strength. NAFLD subjects had greater subcutaneous fat thickness and echo intensity (brightness) of the rectus femoris muscle on ultrasound images; higher levels of the intra- and extra-myocellular lipids (IMCL, EMCL) using 1H-MRS. Urinary titin-N fragment levels were increased with increasing age but not different between males and females. NAFLD subjects had higher titin-N fragment levels than non-NAFLD subjects. The levels were negatively correlated with skeletal muscle mass and knee extension strength and positively correlated with muscle echo intensity, EMCL, and liver fibrosis scores (NAFLD fibrosis score, FIB-4 index). Multivariate analysis revealed that factors affecting the levels were skeletal mass index, leg skeletal muscle mass, liver stiffness, and NAFLD fibrosis score. Urinary levels of titin-N fragment reflected skeletal muscle deterioration and functional decline, and was closely associated with hepatic pathological conditions in NAFLD subjects.

Clinical usefulness of temporal subtraction CT in detecting vertebral bone metastases.

PURPOSE: The purpose of this study was to determine whether temporal subtraction (TS) computed tomography (CT) contributes to the detection of vertebral bone metastases. METHOD: The calculation of TS CT was composed of bony landmark detection, bone segmentation with a multiatlas-based method, and spatial registration. Temporal increase and decrease of the CT values were visualized in blue and red, respectively. Paired CT images of 20 patients with cancer and newly-developed vertebral metastases were analyzed. Control CT examinations of 20 different patients were also included. The presence of vertebral metastases on the TS CT was evaluated by two board-certified radiologists. Five additional board-certified radiologists and five radiology residents independently interpreted the 40 paired CT images with and without TS CT. RESULTS: In the lesion conspicuity evaluation, 96% of vertebral metastases were scored as excellent or good. In the image interpretation examination, according to free-response receiver operating characteristics analysis, the overall figure of merit (FOM) of the board-certified radiologist group was 0.892 and 0.898 with and without TS CT, respectively. The FOM of the resident group improved from 0.849 to 0.902 with viewing TS CT. In the sub-analysis focusing on the location of the lesion, the FOM of the resident group significantly improved from 0.75 to 0.92 in vertebral arch lesions (p = 0.001). CONCLUSIONS: The TS CT may be useful to detect vertebral metastases because almost all the vertebral metastases were shown to be favorable visualization. The TS CT was proven to be especially helpful for radiology residents in detecting vertebral arch metastases.

Change in MRI findings of medial collateral ligament injury in adolescent baseball players with no clinical symptoms over time.

OBJECTIVE: Elbow screening of adolescent baseball players began in 2014 using ultrasound, palpation, and dedicated magnetic resonance imaging (MRI). We frequently encountered subjects showing MCL injury on MRI but no clinical symptoms. We assessed variations in asymptomatic MCL injury findings at follow-up MRI, and clarified the pathogenesis of these findings. MATERIALS AND METHODS: Using a 0.2-T-dedicated MRI, 30 subjects with asymptomatic MCL injury at initial MRI who agreed to follow-up MRI were included. We classified the findings at repeat MRI as follows: (a) disappeared, (b) better, and (c) worse. RESULTS: There were 6, 16, and 8 subjects in groups a, b, and c, respectively. The average age at follow-up was 14.0, 12.1, and 12.4 years in groups a, b, and c, respectively. There were significant differences between groups a and b and between groups a and c. Average height at follow-up of groups a, b, and c was 1.64, 1.52, and 1.57 cm, respectively, with a statistically significant difference between groups a and b. The average size of the short axis of the MCL of subjects in group a was 2.0 cm on the dominant side and 1.5 cm on the contradominant side (P < 0.04). CONCLUSION: Players with asymptomatic MCL injury can continue to play baseball with no limitations, as these findings usually disappear around the age of 14.0 years, when the growth spurt occurs. This finding may be a precursor of 'adaptation', which is generally observed in high school baseball players, suggesting that the MCL adapts as growth occurs.

Safety margin of radiofrequency ablation for hepatocellular carcinoma: a prospective study using magnetic resonance imaging with superparamagnetic iron oxide.

PURPOSE: In radiofrequency ablation (RFA) for hepatocellular carcinoma (HCC), it is difficult to assess the ablative margin (AM) precisely by comparing pre- and post-RFA CT images. We prospectively studied the AMs using magnetic resonance imaging (MRI) with pre-administered superparamagnetic iron oxide (SPIO). SPIO is safe for kidney disease patients. MATERIALS AND METHODS: Hepatocellular carcinoma patients were treated with RFA within 8 h of SPIO administration. On T2*-weighted MRI performed 4-7 days later, AM was visualized as a hypointense rim. The ablation status was classified as AM(+) if the rim completely surrounded the tumor, AM(0) if the rim was partly discontinuous without tumor protrusion, and AM(-) if the rim was partly discontinuous with tumor protrusion. The minimal thickness of AM was measured. AM(-) tumors were re-treated consecutively. RESULTS: In total, 85 HCCs ablated in 76 patients were evaluated. The local recurrence rate at 3 years was 2% for AM(+) tumors and 34% for AM(0) tumors (p < 0.01). In addition, no local recurrence was seen in the tumors with an AM of ≥ 2 mm. CONCLUSION: MRI with pre-administered SPIO is useful for determining the AM precisely, and an AM of ≥ 2 mm is recommended for curative RFA. TRIAL REGISTRATION NUMBER: This study was registered with UMIN Clinical Trials Registry (UMIN 000025406).