扩散张量成像在视辐射成像中的应用

MR检查中扩散张量成像为研究脑白质纤维束(包括视辐射)的走行提供了可能,介绍各向异性扩散加权磁共振成像与扩散张量成像的原理、白质纤维束成像与功能磁共振成像的结合,探讨其在视辐射中的应用价值.     

磁共振新技术在阿尔茨海默病研究中的应用

阿尔茨海默病(AD),又称老年性痴呆,随着年龄的增长和人口的老龄化,发病率呈增高趋势。近年来,随着磁共振在临床的广泛应用,扩散加权成像、扩散张量成像、质子磁共振波谱成像、β-淀粉样蛋白的MR检测等在早期诊断AD上的优势逐步体现。就MR新技术在AD诊断中的价值予以综述。     

移植肾磁共振成像研究进展

近年来随着成像技术的进步,磁共振在移植肾中的应用逐渐增多,本文旨在介绍磁共振血管成像、扩散加权成像、磁共振灌注成像、血氧水平依赖成像、磁共振弹性成像在移植肾功能评估及并发症诊断中的应用和价值.     

磁共振弥散成像、非增强磁共振和多排CT对结直肠癌术后肝转移灶检出的对比分析

目的 比较磁共振扩散加权成像、非增强磁共振和多排CT对结直肠癌肝转移的诊断价值.方法 27例结直肠癌患者行肝脏磁共振扩散加权成像、非增强磁共振和多排CT检查.阅片前告知阅片者患者为结直肠癌术后,但不提供临床病史和既往影像学资料.结果 多排CT、非增强磁共振和扩散加权成像对肝转移灶的敏感性分别为72%(45/63)、76%(48/63)和93%(58/63),扩散加权成像对肝转移灶具有更高的敏感性且与多排CT或非增强MRI具有显著差异.结论 磁共振扩散加权成像对结直肠癌肝转移灶的检出率高于多排CT和非增强MRI.     

一种新的淋巴结成像方法的探讨--采用STIR-EPI扩散加权磁共振成像

目的:评价一种新的成像方法的可行性。即使用短TI反转恢复平面回波成像(STIR-EPI)序列进行磁共振弥散加权成像(DWI),评价其在鉴别转移性和非转移性淋巴结中的价值。方法:对11例头颈部鳞状细胞癌患者进行DWI(STIR-EPI)和T2加权成像。使用1.5T MR扫描仪(Gyroscan intera Master飞     

MR脑功能成像

脑部MR功能成像包括弥散加权成像、弥散张量成像、灌注加权成像、血氧水依赖性成像、脑磁共振波谱分析和磁共振波谱成像等，论述上述各脑功能成像的简单原理以及在临床上的应用。     

子宫内膜癌的功能磁共振研究进展

子宫内膜癌又称子宫体癌,是女性第4位常见的恶性肿瘤.MRI因其良好的软组织分辨力及高质量的三维成像,在子宫内膜癌的探测、定级及分期等许多方面都优于CT及超声(US),成为评价子宫内膜癌最为可靠的影像方法[1,2].随着现代影像学技术的发展,MR已从单纯的形态解剖学成像发展为功能成像,弥补了常规磁共振扫描的不足[3],在子宫内膜癌的诊断方面有着巨大的潜能.目前用于子宫内膜癌的磁共振功能成像方法主要包括:扩散加权成像(diffusion weighted imaging,DWI)、动态增强磁共振成像(dynamic contrast-enhanced MRI,DCE-MRI)及磁共振波谱(magnetic resonance spectroscopy,MRS).     

高分辨率MRI在颅内动脉斑块的应用研究

目的 探讨高分辨率磁共振成像(HR-MRI)在颅内动脉斑块的临床应用价值,比较多种MR扫描技术对有临床症状脑卒中患者的动脉斑块及其供血区域脑卒中的辨别分析.方法 回顾性分析21例有缺血性脑卒中症状的颅内动脉粥样硬化患者的影像资料及临床指标,所有患者均行HR-MRI、磁共振血管成像(MRA)、扩散加权成像(DWI)及常规...     

进一步推动MRCP的临床应用研究

磁共振成像自问世以来,因它的多序列、多参数及多平面成像而受到普遍关注.随着MR硬件及软件的不断改进、发展和开发,成像时间越来越短、图像越来越清晰,使得MR的功能越来越多,应用范围越来越广泛,磁共振水成像(MR fluid imaging, MR water imaging, MR hydrography)就是MR成功应用的一个方面,倍受临床重视,其中磁共振胰胆管成像(MR cholangiopancreatography, MRCP)最早应用于临床,也最受临床的欢迎.     

MR多参数联合成像在前列腺癌诊断中的研究进展

前列腺癌近年来在我国男性中的发病率逐步上升,已成为威胁中老年男性健康的重要疾病.MR有着良好的软组织分辨力和多方位成像优势,其多参数联合成像无创性诊断前列腺癌具有较大价值.随着MR技术的进展,扩散加权成像(diffusion weighted imaging,DWI)、扩散张量成像(diffusion tensor imaging,DTI)、扩散峰度成像(diffusion kurtosis imaging,DKI)、基于体素内不相干运动(intravoxel incoherent motion imaging,IVIM)的多b值DWI联合动态增强磁共振成像(dynamic contrast enhanced MRI,DCE-MRI)已经逐步应用于前列腺癌的研究及诊断.     

Influence of renal angiography in living potential kidney donors

The angiograms of 258 potential kidney donors were retrospectively reviewed to assess the influence of angiography for deciding whether or not to accept the potential donor for nephrectomy and which kidney to use for transplantation. Twenty-five potential donors were rejected. In only 8 of these was angiography necessary to reveal the pathology. Angiography was found to be important in deciding which kidney to donate. In 81 donors the right kidney was used for donation and in 50 this decision was based on findings at angiography.     

Multicystic dysplasia and crossed renal ectopia

Multicystic renal dysplasia in a crossed fused or nonfused ectopic kidney is a rare occurrence that produces unusual imaging findings. In four such cases in neonates, three presented with a palpable abdominal mass and one was discovered in utero with maternal sonography. In three cases, sonography showed a multicystic mass, contiguous with the lower pole of the orthotopic kidney. In the fourth infant, a crossed, tiny dysplastic kidney was not visualized, but its markedly dilated ectopic ureter was seen traversing the spine on CT. Ureteropelvic junction obstruction was present in the three fused orthotopic kidneys. The characteristic imaging findings of multicystic dysplasia and crossed renal ectopia include a multicystic mass of variable size that is contiguous with the lower pole of a hydronephrotic, malrotated kidney; ureteral displacement and/or dilatation; and contralateral absence of the kidney and its renal artery.     

Sodium-23 MR imaging of the kidney in guinea pig at 2.1 T, following arterial, venous, and ureteral ligation

In vivo 23Na magnetic resonance images of guinea pig kidney were obtained at 2.1 T using a spin-echo sequence with an echo time of 19 ms. The intact kidney showed a very strong signal intensity in the sodium image. The signal intensity of the kidney decreased to 55% after ligation of the renal artery together with the vein and the ureter. The total sodium content in the excised kidney after arterial occlusion, measured by flame photometry, was 24% higher than that in the intact kidney. The transverse relaxation time (T2) of the extracellular sodium in the isolated kidney decreased to one-third of that in the intact kidney. This shortening of T2 may be partly responsible for the decrease in the 23Na signal intensity from the kidney after arterial occlusion.     

B-mode ultrasound and the nonvisualizing kidney in pediatrics.

Ultrasonic definition of the kidney is independent of renal function and therefore capable of imaging impaired or dysplastic renal tissue, In 28 cases, B-mode scanning delineated one or both kidneys which failed to visualize during intravenous pyelography. Similar imaging of both kidneys was obtained in 10 cases of renal failure in which intravenous pyelography was not attempted. The presence and relative severity of hydronephrosis was established. In three cases of multicystic kidney, a diagnostic appearance was elicited. In these instances, in one additional case of renal dysplasia, and in three cases of severe obstructive uropathy, sonography provided the only presurgical definition of the abnormal kidney. Suspected kidney enlargement was rapidly confirmed in a case of renal vein thrombosis and excluded in a case of chronic renal failure. In both instances hydronephrosis was excluded. In 12 of the 38 cases, ultrasonic guidance was utilized for percutaneous renal biopsy.     

Dynamic CT of the urogenital tract

The theoretical basis for and the technique of intravenous contrast enhancement by bolus injection for dynamic CT examination of the kidney are described. The clinical applications of this method include the study of normal vascular anatomy of the kidney, congenital kidney abnormalities and form variants, space-occupying lesions, and kidney trauma. In tumoral lesions of the kidney, dynamic CT aids in detecting the lesion as well as in the tumor staging and evaluating operability. CT time density curves can be used to study disturbances in renal perfusion, but the clinical value of this method needs further confirmation.     

Radiation dose distribution in human kidneys by octreotides in peptide receptor radionuclide therapy.

Ex vivo autoradiographs of healthy kidney tissue from patients who received (111)In-DTPA-octreotide (DTPA is diethylenetriaminepentaacetic acid) before nephrectomy showed very heterogeneous radioactivity patterns in the kidneys. The consequences of the reported inhomogeneities have been evaluated for radionuclide therapy with (90)Y- DOTA-Tyr(3)-octreotide (DOTA is 1,4,7,10-tetraazacyclododecane-N,N',N',N'-tetraacetic acid), (177)Lu-DOTA-Tyr(3)-octreotate, and (111)In-DTPA-octreotide by calculating dose distributions and dose-volume histograms (DVHs) for the kidneys. METHODS: Monte Carlo radiation transport calculations were performed by using the MCNP code version 5. The autoradiography data were used in a 2-dimensional model of the kidney tissue sections. A voxel structure inside the MIRD Pamphlet 19 multiregion kidney model was developed to generate a 3-dimensional representation of the autoradiographs. Dose distributions were calculated for the beta-emitter (90)Y, the low-energy electron and gamma-emitter (111)In, and the beta- and gamma-emitter (177)Lu. Isodose curves were generated for the 2-dimensional kidney sections and DVHs for the 3-dimensional kidney model. RESULTS: The isodose curves for the high-energy beta-emitter (90)Y did not show a sign of the inhomogeneous activity distribution, apart from the cortex-medulla boundaries. Both (111)In and (177)Lu isodose curves follow the autoradiographic activity distribution exactly. The 2 gamma-rays from (111)In give higher doses to the low-radioactivity regions in the kidney sections. The DVHs show that the inhomogeneous activity distribution creates considerable volumes within the kidney and within the cortex with lower doses than the average kidney dose, together with volumes receiving much higher doses. This effect is most profound for (177)Lu, but also (111)In shows this heterogeneity in the dose distribution. CONCLUSION: Kidney dosimetry for radionuclide therapy can be based on average MIRD-based dose models for high-energy beta-emitters (such as (90)Y). In contrast, low-energy beta-emitters (such as (177)Lu) and Auger-electron-emitting radionuclides (such as (111)In) produce dose distributions in the kidneys that are very dependent on the activity distribution pattern in the kidney or renal cortex. Complication probability models for renal tissue damage after radionuclide therapy with these latter nuclides need to be developed, as the existing models based on average dose to the kidney or cortex from external beam therapy experience are most probably not valid.     

Relay kidney transplantation in Korea--legal, ethical and medical aspects

Living kidney transplantations constitute the majority of kidney transplantations in Korea. Recently, relay kidney transplantation, which is a modified form of both 'exchange transplantation' and 'living anonymous donation', has become at issue. After a living anonymous donor makes the initial donation, the next donor, who is related to the first recipient, makes the second donation; the third donor, who is related to the second recipient, makes the third donation; and so on. In relay kidney transplantation, organ trafficking, coercion of donation, assessment order, breach of agreement, and recipient burden should be evaluated with respect to ethical, legal and medical considerations. Despite these problems, a non-governmental body, the Korean Organ and Tissue Donor Program, has been promoting relay kidney transplantations to address the shortage of cadaveric kidney donations. Acceptance of the method of relay kidney transplantation requires the institution of supplementary measures to minimize the related problems.     

Individual kidney glomerular filtration rate in the interpretation of non-diagnostic curves on captopril renography

Captopril renography is known to have low sensitivity in the detection of renovascular disease in patients with bilateral renovascular disease and in patients with unilateral renovascular disease with a small kidney. In these groups of patients, we have tried to make the standard captopril renogram more objective by simultaneously estimating the individual kidney glomerular filtration rate (IKGFR). Twenty-five patients (10 bilateral, 15 unilateral) with angiographically proven renal artery stenosis (RAS) were studied. Ten renal units in five hypertensive patients with normal renal arteries were used as controls. A fall of more than 10% in IKGFR post-captopril was considered a positive result. The sensitivities of renogram and IKGFR in patients with bilateral RAS were 52.9% and 88.2% respectively. In patients with unilateral RAS, the sensitivities of renogram and IKGFR were 30% and 80% respectively. A significant fall in IKGFR was noted in eight of the 15 'normal' renal units of the unilateral RAS group. In conclusion, individual kidney GFR estimation in combination with captopril renography improved significantly the sensitivity in patients with symmetrical bilateral RAS and unilateral RAS with a small, poorly functioning kidney. A fall in GFR in the normal counterpart of a unilateral RAS kidney may be indicative of ongoing damage in the non-involved kidney.     

Differences of renal parenchymal attenuation for acutely obstructed and unobstructed kidneys on unenhanced helical CT: a useful secondary sign?

OBJECTIVE: The purpose of this study was to ascertain whether the difference in attenuation frequently noted on unenhanced helical CT scans between a patient's acutely obstructed kidney and the unobstructed kidney is a reliable secondary sign of acute renal obstruction. CONCLUSION: In 95% of patients with acute renal obstruction, the affected kidney was less dense than the unobstructed kidney. When visually detected by radiologists using CT, this difference in density was at least two standard deviations above normal, making it a reliable secondary sign for acute obstruction.     

Multiple foci of increased accumulation of Ga-67 citrate in a horseshoe kidney. Differentiation of infection from nephroblastomatosis.

In the proper clinical setting, Ga-67 citrate appears to be a highly valuable radionuclide which may be used to differentiate an infectious process in the kidney from nephroblastomatosis. The authors present the case of a 7-year-old boy with multiple well-circumscribed foci of intense Ga-67 citrate accumulation in a horseshoe kidney. After a 2-week course of antibiotic therapy, the kidney showed significant improvement.