Clinical diagnostic value of Fast Dixon technique in MR hip joint scan / 实用放射学杂志

Objective To explore the application value of Fast Dixon technique in MR hip joint scanning.Methods Fifty young volunteers were recruited to perform axial and coronal MR scans of the hip joint.The scanning sequence was Fast Dixon T2WI sequence and conventional Dixon T2WI sequence.A double-blind five-point scale was used to subjectively evaluate the image quality of the two types sequences.The signal-to-noise ratio(SNR)and contrast-to-noise ratio(CNR)of the axial image were measured at the maximum level of the bladder display.Results In the scores of"good contrast between surrounding tissue and femoral head signal"and"overall image quality",the Fast Dixon T2WI sequence was better than the conventional Dixon T2WI sequence,and the difference was statistically significant(P<0.05).There was no significant difference in the average scores of"whether bladder artifacts affected the diagnosis"and"whether the fat suppression effect was good"between Fast Dixon T2WI sequence and conventional Dixon T2WI sequence(P>0.05).In the objective image quality evaluation,the SNR and CNR of Fast Dixon T2WI sequence were better than those of conventional Dixon T2WI sequence,and the difference was statistically significant(P<0.05).Conclusion The image quality score of the hip joint of young volunteers with Fast Dixon T2WI sequence combined with multiple averaging excitation technique is significantly higher than that of conventional Dixon T2WI sequence.The Fast Dixon T2WI sequence can increase the effect of inhibiting fat and motion artifacts without increasing the scanning time,and the joint face ratio is good.Fast Dixon technique can replace the traditional Dixon technique,thus becoming an optimal choice for hip joint MR scanning.

A comparative study of thyroid TSE T2WI at 3.0T:Fast Dixon,Dixon,and BLADE sequences / 实用放射学杂志

Objective To explore the value of Fast Dixon in improving the quality of thyroid turbo spin echo(TSE)T2WI images via comparing the quality of thyroid MR T2WI images based on Fast Dixon,Dixon,and BLADE sequences.Methods The prospective study included 11 healthy volunteers,who underwent neck MR scanning.The evaluation of image quality was performed via a combination of objective measures and subjective ratings.Objective measures included signal-to-noise ratio(SNR)of bilateral thyroid and muscles,and contrast-to-noise ratio(CNR).Subjective measures included overall image quality,uniformity of fat suppression,sharpness of thyroid margins and muscles surrounding the thyroid,image noise in the neck region,image background noise,and image quality of the nasopharynx.Two diagnostic physicians with over 10 years of thyroid diagnostic experience independently evaluated the images via a 5-point scale.Inter-observer agreement was analyzed via Spearman correlation coefficient.Statistical analysis was performed using SPSS 22.0 software,including normality and homogeneity of variance tests for continuous data.Kruskal-Wallis one-way ANOVA was used for statistical analysis of subjective measures,followed by post hoc pairwise comparisons.A significance level of P<0.05 was considered statistically significant.Results Eleven healthy volunteers,the SNR of bilateral thyroid and muscles was significantly higher in Fast Dixon sequence than that in Dixon and BLADE sequences.For bilateral CNR,Fast Dixon sequence was also significantly higher than that of Dixon and BLADE sequences.Fast Dixon sequence also had significant advantages in seven subjective ratings indicators(P<0.001).Conclusion The Fast Dixon sequence shows the highest image quality and important application value in the display and evaluation of thyroid lesions.

Influences of Dixon anus preserving surgery on curative effect, anorectal function and stress response in patients with low rectal cancer / 中国医师进修杂志

Objective:To investigate the influences of Dixon anus preserving surgery on the curative effect, anorectal function and stress response of patients with low rectal cancer.Methods:A total of 150 patients with low rectal cancer admitted to Zhangjiakou Fifth Hospital from May 2016 to March 2019 were retrospective analysis as the study subjects. According to the different surgical methods, the patients were divided into the study group (75 cases) and the control group (75 cases). The patients in the study group received Dixon operation, and the patients in the control group received Miles operation. The general condition of operation, postoperative urination function, stress response [C reactive protein (CRP), interleukin-6 (IL-6), cortisol (Cor) and adrenocorticotropic hormone (ACTH)], anorectal function [anal resting pressure (ARP), maximal squeeze pressure (MSP), anal longest contraction time (ALCT)], quality of life (PAC-QOL score), postoperative complications, local recurrence rate, distant metastasis rate, 3-year tumor free survival rate and 3-year overall survival rate were compared between the two groups.Results:The operation time, intraoperative blood loss and postoperative drainage volume in the study group were lower than those in the control group: (172.28 ± 23.45) min vs. (189.57 ± 23.68) min, (177.39 ± 21.23) ml vs. (191.35 ± 22.67) ml, (342.36 ± 52.89) ml vs. (489.42 ± 63.33) ml, there were statistical differences ( P<0.05). The levels of CRP, IL-6, Cor and ACTH in the study group were lower than those in the control group: (22.35 ± 4.75) mg/L vs. (35.65 ± 5.28) mg/L, (58.74 ± 15.11) μg/L vs. (79.63 ± 20.23) μg/L, (145.36 ± 27.48) ng/L vs. (156.48 ± 32.55) ng/L, (44.58 ± 5.27) ng/L vs. (49.62 ± 5.68) ng/L, there were statistical differences ( P<0.05). The urination function and anorectal function of the patients in the study group were obviously better than those in the control group 6 months after operation, and the PAC-QOL score was obviously lower than that in the control group: (22.53 ± 2.86) scores vs. (27.54 ± 3.21) scores ( P<0.05); there was no obvious difference between the study group and the control group in the incidence of postoperative complications, local recurrence rate, distant metastasis rate, 3-year tumor free survival rate and 3-year total survival rate ( P>0.05). Conclusions:Dixon operation is effective in the treatment of low rectal cancer. It can preserve the anorectal function of patients to the greatest extent, protect urination function, reduce stress reaction of patients, and it is more conducive to rapid rehabilitation of patients.

Applications of the Dixon technique in the evaluation of the musculoskeletal system / Aplicações da técnica Dixon na prática radiológica do sistema musculoesquelético

Abstract The acquisition of images with suppression of the fat signal is very useful in clinical practice and can be achieved in a variety of sequences. The Dixon technique, unlike other fat suppression techniques, allows the signal of fat to be suppressed in the postprocessing rather than during acquisition, as well as allowing the visualization of maps showing the distribution of water and fat. This review of the Dixon technique aims to illustrate the basic physical principles, to compare the technique with other magnetic resonance imaging sequences for fat suppression or fat quantification, and to describe its applications in the study of diseases of the musculoskeletal system. Many variants of the Dixon technique have been developed, providing more consistent separation of the fat and water signals, as well as allowing correction for many confounding factors. It allows homogeneous fat suppression, being able to be acquired in combination with several other sequences, as well as with different weightings. The technique also makes it possible to obtain images with and without fat suppression from a single acquisition. In addition, the Dixon technique can be used as a quantitative method, allowing the proportion of tissue fat to be determined, and, in more updated versions, can quantify tissue iron.

Resumo A aquisição de imagens com supressão do sinal da gordura é um recurso de grande utilidade diagnóstica, existindo várias sequências capazes de realizá-la. A técnica Dixon, ao contrário de outras técnicas de supressão de gordura, permite suprimir a contribuição do sinal de gordura no pós-processamento e não durante a aquisição, além de permitir a visualização de mapas com a distribuição da água e da gordura. Esta revisão sobre a técnica Dixon almeja ilustrar os princípios físicos básicos, comparar a técnica com outras sequências de ressonância magnética para supressão ou quantificação de gordura, e descrever suas aplicações no estudo de doenças do sistema musculoesquelético. Muitas variantes da técnica Dixon foram desenvolvidas, proporcionando separação mais consistente dos sinais de gordura e água e permitindo correção de muitos fatores de confusão. Permite obter supressão homogênea de gordura, podendo ser adquirida de forma combinada com várias outras sequências, bem como com diferentes ponderações. Esta técnica possibilita também a obtenção de imagens com e sem supressão de gordura a partir de uma única aquisição. Adicionalmente, a técnica Dixon pode ser utilizada como recurso quantitativo, pois permite a mensuração do porcentual de gordura e, em versões mais atualizadas, consegue quantificar ferro tecidual.

Diagnostic Value of mDIXON Quant MRI for Vertebral Metastasis / 肿瘤防治研究

Objective To evaluate the diagnostic efficacy of mDIXON Quant for vertebral metastasis. Methods We retrospectively analyzed MRI images of 152 patients with clinically diagnosed malignant tumors and vertebral metastases. Scanning sequence included T1WI, STIR, mDIXON Quant and enhanced T1WI. We compared the diagnostic efficiency between T1WI and FF images for vertebral metastases. FF values between normal vertebral body and vertebral metastases were quantitatively compared, and the diagnostic efficacy of FF value was evaluated by ROC curve. Results The sensitivity, false positive rate, false negative rate, negative predictive value and accuracy of FF images in the diagnosis of vertebral metastases were all higher than those of T1WI images. The FF value of vertebral metastasis was significantly lower than that of normal vertebral body (Z=-21.792, P < 0.05), and the area under ROC curve was 0.987 and the cutoff value was 9.87%. The diagnostic sensitivity and specificity of vertebral metastasis were 99.6% and 92.0%. Conclusion mDIXON Quant can quantitatively determine the fat content of vertebral metastasis and has a high diagnostic efficiency for vertebral metastases.

A Study on Demographic Profile and Risk Factor Association in Pityriasis Versicolor Cases Attending at a Tertiary Care Hospital in Kolkata

Pityriasis versicolor (PV), also known as tinea versicolor, is a chronic, mild, superficial and recurrent infection of the stratum corneum, caused by different Malassezia spp and seen predominantly in young age group and primarily in hot and humid climates. The aim of this study was to analyze epidemiological parameters and risk factors association in clinically diagnosed PV cases and also the mycological evaluation of those PV cases. Methods: A total of 116 patients attending the OPD of Dermatology were included and analysed for detailed history, clinical examination, epidemiological parameters, risk factors and investigations. Skin scrapings collected were processed by direct microscopy with 10% KOH and culture in modified Dixon agar (mDA). Isolates were identified by colony morphology, gram staining, biochemical characteristics & tween assimilation test. Results: Females were more affected (56.03%) than the males (43.97%) with F: M ratio 1.27:1. PV affected most commonly (36.21%) in 11-20 years of age group. Students (32.29%) were affected in maximum. Majority of affected patients (65.52%) used oily body creams, whereas 34.48% cases shared their body towels with others. 10.34% cases were associated with seborrheic dermatitis. Seasonal occurrence mostly seen in May - August. Patients with type III (Medium) complexion (56.03%) with normal skin texture (49.14%) were mostly affected. Maximum patients (74.14%) were associated with excessive sweating. 18.96% patients were associated with Type II DM. Most of the cases presented with macular, scaly hypopigmented, bilaterally asymmetrically distributed and having well defined margin. Neck was the most affected site (28.45%) followed by back (20.69%). Conclusion: M.furfur was the most common isolate (47.06%) followed by M. globosa (24.71%) and M. sympodialis (15.29%).

Fat Quantification in the Vertebral Body: Comparison of Modified Dixon Technique with Single-Voxel Magnetic Resonance Spectroscopy

OBJECTIVE: To compare the lumbar vertebral bone marrow fat-signal fractions obtained from six-echo modified Dixon sequence (6-echo m-Dixon) with those from single-voxel magnetic resonance spectroscopy (MRS) in patients with low back pain. MATERIALS AND METHODS: Vertebral bone marrow fat-signal fractions were quantified by 6-echo m-Dixon (repetition time [TR] = 7.2 ms, echo time (TE) = 1.21 ms, echo spacing = 1.1 ms, total imaging time = 50 seconds) and single-voxel MRS measurements in 25 targets (23 normal bone marrows, two focal lesions) from 24 patients. The point-resolved spectroscopy sequence was used for localized single-voxel MRS (TR = 3000 ms, TE = 35 ms, total scan time = 1 minute 42 seconds). A 2 × 2 × 1.5 cm³ voxel was placed within the normal L2 or L3 vertebral body, or other lesions including a compression fracture or metastasis. The bone marrow fat spectrum was characterized on the basis of the magnitude of measurable fat peaks and a priori knowledge of the chemical structure of triglycerides. The imaging-based fat-signal fraction results were then compared to the MRS-based results. RESULTS: There was a strong correlation between m-Dixon and MRS-based fat-signal fractions (slope = 0.86, R² = 0.88, p 20%). CONCLUSION: Given its excellent agreement with single-voxel-MRS, 6-echo m-Dixon can be used for visual and quantitative evaluation of vertebral bone marrow fat in daily practice.

Parameters Affecting India Ink Artifacts on Opposed-Phase MR Images

PURPOSE: To determine the MR parameters affecting India ink artifacts on opposed-phase chemical shift magnetic resonance (MR) imaging.MATERIALS AND METHODS: The use of a female Sprague-Dawley rat was approved by our Institutional Animal Care and Use Committee. Using an iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) images, which is a modified Dixon method, axial opposed-phase images of the abdominal cavity were obtained with different MR parameters: series 1, different repetition times (TRs; 400, 2000, and 4000 ms); series 2, different echo times (TEs; 10, 50, and 100 ms); series 3, different field of views (FOVs; 6, 8, 16, and 24 cm); series 4, different echo train lengths (ETLs; 2, 4, and 8); series 5, different bandwidths (25, 50, and 85); and series 6, different slice thicknesses (1, 2, 4, 8, and 16 mm). Artifacts on opposed images obtained with different parameters were compared subjectively by two radiologists. For objective analysis, the thickness of the artifact was measured. Spearman's correlation between altered MR parameters and thicknesses of India ink artifact was obtained via objective analysis.RESULTS: India ink artifact was increasingly apparent using shorter TE, larger FOV and ETL, and thicker slices upon subjective analysis. The objective analysis revealed a strong negative correlation between the thickness of the artifact and TE (r = -0.870, P < 0.01); however, strong positive correlations were found between FOV (r = 0.854, P < 0.01) and slice thickness (r = 0.971, P < 0.01).CONCLUSION: India ink artifact was thicker with shorter TE, larger FOV, and larger slice thickness.

The clinica value of low ligaation of inferior mesenteric artery in non Ⅰ mesosigmoid laparoscopic Dixon / 实用肿瘤学杂志

Objective To explore the application value of low ligation of inferior mesenteric artery(IMA) in laparoscopic Dixon of nonⅠsigmoid colon mesangial(SMC). Methods Seventy-one cases of nonⅠSMC rectal cancer patients who evaluated for feasibility of laparoscopic Dixon in the Department of Gastrointestinal Surgery Affiliated Tumor Hospital of Xinjiang Medical University from September 2017 to July 2018 were selected in this study,and they were randomly divided into two groups:the group of left colic artery reserved(low ligation group)and the group of left colic artery not retained(high ligation group). A three-dimensional compu-ted tomography angiography of inferior mesenteric artery was obtained in all patients to guide the intraoperative accurate ligation of vessels. The baseline data,intraoperative and postoperative quantitative parameters of the two groups were compared. Results Three patients in the group of left colic artery reserved were forced to turn to high ligation for it could not meet the requirement of anastomo-sis. The low ligation group showed significant difference to the high ligation group on operation time[170(160,180) vs. 180 (170, 210)](P=0. 026),but there was no significant difference in the aspect of gender,age,BMI,distance between tumor and anal bor-der,TNM stage,intraoperative blood loss,the splenic free rate,prophylactic stoma rate,Length of specimen,maximum diameter of tumor,tissue typing,total lymph node count,D3 lymph node count,postoperative first exhaust time,days in hospital since surgery and anastomotic fistula rate(P>0. 05). Conclusion Low ligation of inferior mesenteric artery can shorten the operation time and signifi-cantly lessen unplanned bowel length and reduce postoperative risk of anastomotic leakage. All of these are beneficial to patients′post-operative recovery and have important clinical guiding value.

Methods for solving the neck two-point T2-DIXON fat-water separation misalignment / 中华放射学杂志

Objective To explore the methods for solving the neck two-point T2-DIXON fat-water separation misalignment. Methods During August 2015 to July 2016, 140 patients with fat-water separation on the nasopharynx and cervical axial T2-DIXON images were prospectively recruited from Sichuan Cancer Hospital. There was no metal implant in the fat-water separation misalignment area. The patients were divided into 7 groups by random number table method with 20 patients in each group for the axial T2-DIXON scan: Group A adopted plan 1( increasing localized shim box on the fat-water separation misalignment area);Group B adopted plan 2(increasing the times of repeated acquisition to 2 of the T2-DIXON sequence);Group C adopted plan 3 (placing the shimming assist device on the inspection area);Group D adopted plan 1+plan 2;Group E adopted plan 1+plan 3;Group F adopted plan 2+plan 3;Group G adopted plan 1+plan 2+plan 3. The images quality of two scans were graded and compared. We compared the signal-to-noise ratio (SNR) of T2-DIXON image on the same muscle tissue between the two scans of each group. The difference of SNR on the two scan images was compared with the paired t test, the difference of SNR among seven groups was conducted with independent sample t test, and the comparison of image quality classification was conducted by rank sum test. Results The image quality of all the seven groups was improved to some different degrees. The cases with image quality reaching level 3 were 12, 15, 15, 16, 17, 18 and 18 in A to G groups, respectively. It was better to use the combination of two or more methods to improve the quality of the image than to use a single method. There were no statistically significant differences in SNR between two scans in A, C and E group (all P>0.05).There were statistically significant differences in SNR between two scans in groups of B, D, F and G(all P<0.05). There were statistically significant differences among the 7 groups, with the best quality in G group (P<0.05). There was no significant difference in the first SNR among the 7 groups (P>0.05);there were significant differences in the second scans among the 7 groups (P<0.05) .Conclusions This study suggests that placing localized shim box, increasing the times of repeated acquisition, and use of shimming assist device in MRI correct the fat-water separation misalignment, help to provide images with high quality. The combination of the above method was better than using the single method. The SNR can be improved when increasing the times of repeated acquisition.

The feasibility study of MRI m-Dixon-Quant technique to rapidly evaluate middle-aged and elderly osteoporosis / 实用放射学杂志

Objective Based on MRI m-Dixon-Quant technique to quickly quantify bone marrow fat content in the vertebral body of middle-aged and elderly patients,and provide a scientific basis for the diagnosis of osteoporosis(OP).Methods A total of 74 middle-aged and elderly patients who were admitted to our hospital from July 2016 to July 2017 were collected.The age,sex and body mass index (BMI)of the patients were collected.All subjects were evaluated for bone mineral density (BMD)and fat fraction (FF)and other indicators of measurement.According to the guidelines for bone mineral density measurement by the American College of Radiology(ACR),the subject was classified by the bone mineral density value,and receiver operating characteristic(ROC)curve was used for the diagnosis and analysis of FF.Results The average age of the subjects was (59.50±8.72)years.There was a positive correlation between MRI m-Dixon-Quant FF and age(r=0.436),which was highly negatively correlated with the average bone density(r=-0.739).By ROC analysis,the sensitivity and specificity were 74.2% and 83.3% for normal and low bone mass groups,92.0% and 88.9% for the normal and OP groups,and 72.0% and 87.1% for the low bone mass and OP groups.FF could be used for the evaluation of OP.If FF<54.60,normal bone mass was considered.If 54.60≤FF≤65.20,low bone mass was considered,if FF>65.20,OP was considered.Conclusion The MRI m-Dixon-Quant FF index can be rapidly and quantitatively used for the diagnosis of OP,which provides a new reference for the diagnosis of OP.

Skull Base Dermoid Cyst in the Right Infratemporal Fossa Diagnosed Using the Dixon Technique: a Case Report and Review of Literature

Dermoid cysts are benign congenital tumors composed of keratinizing squamous epithelium and dermal derivatives. They account for less than 1% of all intracranial tumors and are rarely exhibited at the base of the skull. To the best of our knowledge, only one case report has presented computed tomography and conventional T1-weighted magnetic resonance (MR) findings that revealed an infratemporal dermoid cyst. In the present study, we report an unusual case of a dermoid cyst in the right infratemporal fossa, which was incidentally detected by MR imaging with the Dixon technique. This article also highlights the importance of meticulous radiological review and the usefulness of the Dixon technique in everyday clinical practice.

Skull Base Dermoid Cyst in the Right Infratemporal Fossa Diagnosed Using the Dixon Technique: a Case Report and Review of Literature

Dermoid cysts are benign congenital tumors composed of keratinizing squamous epithelium and dermal derivatives. They account for less than 1% of all intracranial tumors and are rarely exhibited at the base of the skull. To the best of our knowledge, only one case report has presented computed tomography and conventional T1-weighted magnetic resonance (MR) findings that revealed an infratemporal dermoid cyst. In the present study, we report an unusual case of a dermoid cyst in the right infratemporal fossa, which was incidentally detected by MR imaging with the Dixon technique. This article also highlights the importance of meticulous radiological review and the usefulness of the Dixon technique in everyday clinical practice.

High risk factors and treatment analysis of local recurrence after Dixon operation of rectal cancer / 中国综合临床

Objective To investigate the risk factors and treatment of local recurrence after Dixon operation of rectal cancer.Methods The clinical data of forty-seven patients who had local recurrence after Dixon operation of rectal cancer in our hospital from January 2011 to December 2013 was analyzed retrospectively.According to literature review,the high risk factors and treatment methods of local recurrence of rectal cancer in China and abroad were analyzed.Results The treatment methods of patients with local recurrence after anterior resection were radical resection,palliative resection and chemotherapy.The prognosis of patients with radical resection whose overall survival time was (38.202±2.411) months,better than that with palliative resection ((24.591±2.150) months),better than that with chemotherapy ((12.833±1.033) months).There was a significant difference in the survival time among the three groups (χ2=30.155,P<0.001).Conclusion Fully understanding of high risk factor can help reduce the probability of local recurrence.For patients with local recurrence of the rectal cancer,radical resection should be performed.In case that radical surgery is not possible,positive treatments should be adopted if the patients are in good physical condition.

Risk factors of anastomotic leakage after laparoscopic assisted Dixon / 中国现代普通外科进展

Objective:To observe the incidence and risk factors of anastomotic leakage after laparoscopic assisted Dixon.Methods:120 patients accepted laparoscopic Dixon operation in our hospital from March 2013 to March 2015 were selected as the observation object.By using the method of retrospective study,the postoperative incidence the anastomotic fistula were counted,and analyzed the risk factors for anastomotic fistula.Results:Among the 120 patients with postoperative anastomosis fistula,21 patients occurred anastomotic leakage,the anastomosis fistula incidence rate was 17.5％.Univariate analysis showed that the anastomosis fistula incidence rate of patients with more than or equal to 65 years of age,body mass index ＞ 23 kg/m2,diabetes mellitus,albumin is more than or equal to 35 g/L,preoperative radiotherapy,chemotherapy and anastomosis from the anal ＜ 7 cm were higher,the difference was statistically significant (P＜0.05).Logistic regression analysis showed that more than or equal to 65 years of age,diabetes mellitus,albumin is more than or equal to 35 g/L,anastomosis from the anal ＜7 cm were risk factors of anastomosis fistula in rectal cancer patients with Dixon operation (OR=4.356,5.238,3.562,4.415,P＜0.05).Conclusion:The factors of patients with laparoscopic Dixon operation after anastomosis fistula are age,diabetes,serum albumin levels and anastomotic distance from the anus.

The value of 3D-DIXON in quantitative diagnosis of non-alcoholic fatty liver disease / 实用放射学杂志

Objective To access the value of three dimensional gradient echo two-point Dixon water-fat separation sequence (3 D-DIXON) in quantitative diagnosis of non-alcoholic fatty liver disease(NAFLD) by comparing with in-phase/opposed-phase (IN/OPP)and proton magnetic resonance spectroscopy (1 H-MRS).Methods A total of 69 patients with NAFLD diagnosed by CT were divided into two groups by the ratio of liver spleen in CT (group A,low-grade fatty liver,n=32;group B,moderate and severe fatty liver,n=37).All patients underwent MR 3D-DIXION,1H MRS and IN/OPP examination twice within 1 week after CT examination.Fat fraction(FF) was evaluated and analyzed respectively.Results Pearson linear correlation analysis showed significant positive correlation between group A and group B about FF3D-DIXON,FFMRs and FFIN/OPP.Area under ROC curve (AUC) was different:AUCsYNTHESIZE＞AUCMRs＞AUCIN/OPP＞AUC3D-DIXON.Kruskal-Wallis H revealed significant difference among the three sequences no matter in group A or group B (P＜0.05).FF values of the three sequences (FF3D-DIXON,FFMRs and FFIN/OPP) were negatively correlated with CT liver/ spleen ratio in each group.The cut-off value of 3D-DIXON,IN/OPP and 1 H-MRS to diagnose presence or absence of fatty liver was 4.9 3 9 ％,5.2 8 4 ％ and 10.4 6 0 ％.Conclusion FF values measured by MRI methods might significantly vary based on different sequences.1 H-MRS is also the main method for quantitative assessment of fatty liver,3D-DIXON showed significant advantage in quantifying moderate and severe fatty liver.

Variabilidad en la determinación de fracción grasa muscular en resonancia magnética utilizando la técnica de Dixon / Variability in magnetic resonance quantification of muscle fat fraction using Dixon's technique

Abstract. Muscle MRI has emerged as a valuable tool in the diagnosis of neuromuscular-disorders. The Dixon fat-water separation technique allows objective intra-muscular fat quantification. There are few reports concerning measurement standardisation with Dixon technique. The objective of this study was to evaluate the variability in fat quantification using Dixon's technique in a cohort of patients with congenital myopathies, by analysing intra-segment, intra-muscle, and inter-muscle variability of 60 muscles in each patient. Whole body MRI was performed on 31 patients, 23 with congenital myopathies and 8 healthy controls, aged between 10 months and 35 years old, from January 2014 to June 2016. The mean fat-fraction in healthy patients was around 5%, with less than 2% intra-muscle variability. An intra-muscle variability between 3.1-7.8% was estimated in patients with congenital myopathies. It may be concluded that there is high intra- and inter-muscle fat-fraction variability among patients with congenital myopathies, and this is an observation that should be incorporated in the analysis of fat replacement.

Resumen. La resonancia magnética muscular ha emergido como una valiosa herramienta de apoyo diagnóstico en enfermedades neuromusculares. La técnica de Dixon permite objetivar la fracción grasa muscular, pero no existe consenso sobre la estandarización de estas mediciones. El objetivo de este estudio fue evaluar la variabilidad en la determinación de fracción grasa utilizando la técnica de Dixon, estudiando la variabilidad intrasegmentaria, intramuscular e intermuscular en 60 músculos por paciente. Se realizó RM de cuerpo completo a 31 pacientes: 23 con miopatía congénita y 8 controles, entre 10 meses y 35 años de edad, desde enero del 2014 a junio del 2016. En pacientes sanos se estimó una fracción grasa promedio cercana al 5%, con una variabilidad intramuscular inferior al 2%. En pacientes con miopatías congénitas existe una variabilidad entre el 3,1-7,8%. El estudio permite concluir que existe una alta variabilidad intra e intermuscular en pacientes miopáticos, que no se observa en pacientes sanos.

Comparison of Multi-Echo Dixon Methods with Volume Interpolated Breath-Hold Gradient Echo Magnetic Resonance Imaging in Fat-Signal Fraction Quantification of Paravertebral Muscle

OBJECTIVE: To assess whether multi-echo Dixon magnetic resonance (MR) imaging with simultaneous T2* estimation and correction yields more accurate fat-signal fraction (FF) measurement of the lumbar paravertebral muscles, in comparison with non-T2*-corrected two-echo Dixon or T2*-corrected three-echo Dixon, using the FF measurements from single-voxel MR spectroscopy as the reference standard. MATERIALS AND METHODS: Sixty patients with low back pain underwent MR imaging with a 1.5T scanner. FF mapping images automatically obtained using T2*-corrected Dixon technique with two (non-T2*-corrected), three, and six echoes, were compared with images from single-voxel MR spectroscopy at the paravertebral muscles on levels L4 through L5. FFs were measured directly by two radiologists, who independently drew the region of interest on the mapping images from the three sequences. RESULTS: A total of 117 spectroscopic measurements were performed either bilaterally (57 of 60 subjects) or unilaterally (3 of 60 subjects). The mean spectroscopic FF was 14.3 +/- 11.7% (range, 1.9-63.7%). Interobserver agreement was excellent between the two radiologists. Lin's concordance correlation between the spectroscopic findings and all the imaging-based FFs were statistically significant (p < 0.001). FFs obtained from the T2*-corrected six-echo Dixon sequences showed a significantly better concordance with the spectroscopic data, with its concordance correlation coefficient being 0.99 and 0.98 (p < 0.001), as compared with two- or three-echo methods. CONCLUSION: T2*-corrected six-echo Dixon sequence would be a better option than two- or three-echo methods for noninvasive quantification of lumbar muscle fat quantification.

Whole-Body Muscle MRI in Patients with Hyperkalemic Periodic Paralysis Carrying the SCN4A Mutation T704M: Evidence for Chronic Progressive Myopathy with Selective Muscle Involvement

BACKGROUND AND PURPOSE: Hyperkalemic periodic paralysis (hyperKPP) is a muscle sodium-ion channelopathy characterized by recurrent paralytic attacks. A proportion of affected individuals develop fixed or chronic progressive weakness that results in significant disability. However, little is known about the pathology of hyperKPP-induced fixed weakness, including the pattern of muscle involvement. The aim of this study was to characterize the patterns of muscle involvement in hyperKPP by whole-body magnetic resonance imaging (MRI). METHODS: We performed whole-body muscle MRI in seven hyperKPP patients carrying the T704M mutation in the SCN4A skeletal sodium-channel gene. Muscle fat infiltration, suggestive of chronic progressive myopathy, was analyzed qualitatively using a grading system and was quantified by the two-point Dixon technique. RESULTS: Whole-body muscle MRI analysis revealed muscle atrophy and fatty infiltration in hyperKPP patients, especially in older individuals. Muscle involvement followed a selective pattern, primarily affecting the posterior compartment of the lower leg and anterior thigh muscles. The muscle fat fraction increased with patient age in the anterior thigh (r=0.669, p=0.009), in the deep posterior compartment of the lower leg (r=0.617, p=0.019), and in the superficial posterior compartment of the lower leg (r=0.777, p=0.001). CONCLUSIONS: Our whole-body muscle MRI findings provide evidence for chronic progressive myopathy in hyperKPP patients. The reported data suggest that a selective pattern of muscle involvement-affecting the posterior compartment of the lower leg and the anterior thigh-is characteristic of chronic progressive myopathy in hyperKPP.

Diagnostic value and clinical significance of MSCT in postoperative intestinal obstruction of rectal cancer patients / 中华普通外科杂志

Objective To evaluate the value of multi-slice spiral computed tomography (MSCT) in diagnosing postoperative intestinal obstruction of rectal cancer.Methods The CT imaging results and clinical manifestation of 50 patients with postoperative intestinal obstruction of rectal cancer confirmed by pathology were reviewed retrospectively.These cases including Miles (24 cases),Dixon (18 cases),Hartmann(8 cases) procedure were collected from Tianjin People's Hospital from 2011 to 2013.Conservative management was done in 10 cases and the remaining 40 patient underwent surgical intervention.Statistical difference between the three kinds of surgical causes of intestinal obstruction was analysed by x2 test.Results Most common cause after Miles and Hartmann postoperative intestinal obstruction was of adhesion,while anastomotic stenosis was the most common reason of intestinal obstruction after Dixon procedure.The difference of incidence of intestinal obstruction caused by hernia and anastomotic stenosis between the three kinds of operation method was statistically significant (x2 =5.382、20.486,P ＜ 0.05).Conclusions MSCT could identify the etiology and site of postoperative intestinal obstruction of rectal cancer,providing favorable imaging evidence for clinical treatment.