Optimization of prostatic magnetic resonance imaging technique.

With a 1.5-T magnetic resonance imager the authors systematically varied a large number of technical factors to obtain an optimum balance between high image quality and reasonable imaging time for the prostate gland. Each parameter was adjusted relative to benchmark images of very high quality to achieve a reasonable acquisition time with as little loss of the signal-to-noise ratio (SNR) as possible. Image quality was judged subjectively by magnetic resonance radiologists and objectively by measurements of SNR for the prostate. The authors recommend multislice, multiecho spin-echo pulse sequences with dual surface coils, fat suppression, reduced bandwidth, a repetition time of 1500 ms, echo times of 30 and 60 ms, a flip angle of 60 degrees, two excitations, a slice thickness of 5 mm with a 1.5-mm gap and 192 phase-encoding steps. The acquisition time for one such series was 9.6 minutes.     

磁共振功能成像在肝细胞癌中的应用

近年来,肝细胞癌的发病率与死亡率在全球范围内逐年上升.随着分子影像学的发展,磁共振功能成像技术在各系统疾病中的应用越来越广泛,其在肝细胞癌诊断、鉴别诊断、术后疗效评估等方面发挥越来越重要的作用.作者就目前常用的几种功能磁共振成像技术在肝细胞癌中的应用现状进行综述.     

Quantitative magnetic resonance imaging in rectal carcinoma

T1 and T2 relaxation times have been calculated in 30 patients with rectal carcinoma and seven patients with a fibrotic pelvic mass. The relaxation times were calculated using a multipoint iterative method with data from seven total saturation recovery and six spin-echo sequences. The results show that the calculated T1 relaxation value is a useful discriminant between carcinoma and pelvic fibrosis and should improve the detection of early tumour recurrence.     

Staging of prostatic carcinoma. Accuracy of magnetic resonance

Twenty-nine prostatic cancer patients were evaluated for staging purpose by Magnetic Resonance (MR). MR findings were correlated with the pathologic examination in 18/29 patients who underwent radical prostatectomy. Four MR staging parameters were evaluated individually: periprostatic fat; periprostatic venous plexus; seminal vesicles and pelvic adenopathy. MR correctly staged 16/18 patients, with one case of overstaging and one case of understaging. The diagnostic accuracy of MR in differentiating intracapsular stage B from extracapsular stage C was 87%, with a sensitivity of 90% and a specificity of 87%. MR and CT results agreed in 4 of the 7 operated patients who were examined with both techniques; in 3 cases there was disagreement, and MR was correct.     

Clinical and experimental sodium magnetic resonance imaging

In conclusion, sodium MR imaging has potential for providing physiologic information relevant to cell mitosis, cell energy state, rCBV, and seizures. Considerable technical and experimental development is necessary, however, before sodium MRI becomes a routine examination in the clinical setting.     

Evaluation of gall bladder carcinoma with dynamic magnetic resonance imaging and magnetic resonance cholangiopancreatography

The objective of this study is to evaluate the efficacy of dynamic MRI with magnetic resonance cholangiopancreatography (MRCP) in the preoperative assessment of gall bladder carcinoma. Magnetic resonance imaging and MRCP were carried out in 15 patients with gall bladder carcinoma before surgery and the imaging findings correlated with surgical and pathological findings. Gall bladder carcinoma manifested as focal or diffuse wall thickening in 73% (11/15) and as a mass replacing the gall bladder in 27% (4/15). All tumours showed enhancement in the early phase, which persisted into the delayed phase. The sensitivity and specificity of MRI with MRCP in detecting hepatic invasion, lymph node metastasis and bile duct invasion was 87.5 and 86%, 60 and 90%, and 80 and 100%, respectively. Magnetic resonance imaging correctly diagnosed duodenal invasion in only 50% and in none of the two patients with peritoneal metastasis. In conclusion, dynamic MRI with MRCP is an accurate and a reliable method of showing gall bladder carcinoma and in assessing its local and regional extent as part of preoperative assessment.     

Clinical impact of shoulder magnetic resonance imaging

The clinical impact of magnetic resonance imaging (MRI) of the shoulder is dependent upon the clinical diagnosisand clinical indications for surgical management. MRI of the shoulder is very useful in defining the anatomic pathology associated with shoulder pain and disability. The clinical impact of MRI is improved when it is obtained under well defined criteria which should be based upon clinical treatment algorithms. Shoulder MRI is best used to define the anatomic pathology associated with rotator cuff tears and traumatic glenohumeral instability.     

Clinical applications of functional magnetic resonance imaging

Despite its immediate success as a tool for basic research, the clinical application of functional MRI(fMRI) is still limited. FMRI has proven useful for presurgical functional mapping of the eloquent cortices. Localization of the sensorimotor cortex by fMRI may be of relatively limited value because the sensorimotor cortex can often be readily localized by means of anatomical methods. In contrast, the language cortices may not be localized anatomically and the language dominant hemisphere has been determined by invasive Wada test. Previous reports have shown that fMRI can be a promising alternative to the Wada test. A recent clinical trial has suggested that fMRI can be used to diagnose Alzheimer's disease in its earliest stage, detecting subclinical deterioration of the memory function. FMRI may be useful to predict the future decline of memory in people with genetic risks. Monitoring of the functional recovery of post-stroke brains may be another promising clinical application of fMRI. FMRI has demonstrated functional reorganization of the brain that may be related to the restoration of motor and language functions.     

Clinical impact of elbow magnetic resonance imaging

The elbow and its articulations are subject to tremendous forces during overhead sports. The elbow joint is vulnerable to a variety of injuries as a result of either acute traumatic events or chronic repetitive overuse. Elbow pathology in throwing athletes has been classified according to the mechanism of injury: medial tension overload, lateral compression, extension overload, and posterolateral rotatory instability. Given the complexity of these injuries, complete diagnosis and treatment requires a thorough evaluation of the elbow. This evaluation begins with a history and physical examination, an understanding of pathomechanics, and an assessment of normal and pathological anatomy. Imaging studies may be of assistance in defining this anatomy. The correlation of these imaging studies with clinical information is essential in the proper diagnosis and management of these complex injuries. This article presents the impact of elbow magnetic resonance imaging (MRI) for the clinical diagnosis of the three most common elbow disorders for which MRI has diagnostic efficacy in the athlete.     

Nuclear magnetic resonance imaging characteristics of gallstones in vitro

The nuclear magnetic resonance (NMR) imaging characteristics of gallstones of various composition from 36 patients were studied in vitro using a spin-echo imaging technique. The majority of gallstones (83%) produced no measurable NMR signal despite having a mean water content of 12% and a mean cholesterol content of 61%. Six (17%) of the stones had a weak but measurable signal in the center of the stone, which was thought to represent signal from water in clefts or pores within the stones. The mean water and cholesterol content of the stones with measurable signal did not differ significantly from that of stones with no signal. A possible explanation for these findings, based on the known NMR characteristics of solid materials, is offered.     

Characteristics of ductal carcinoma in situ in magnetic resonance imaging

PURPOSE: The aim of this study was to evaluate typical dynamic and morphological characteristics of ductal carcinoma in situ (DCIS) in magnetic resonance imaging (MRI). An optimized diagnosis of DCIS is considered to be valuable for radiologists and clinicians, especially for early and successful treatment planning. MATERIALS AND METHODS: Magnetic resonance examinations of 74 patients with pure DCIS were evaluated. Categories were established for signal increase (C1=the same enhancement as glandular tissue; C2=slow and continuous; C3=strong initial and slow further increase; C4=strong initial increase and plateau phenomenon; and C5=strong initial increase followed by a washout phenomenon) and morphological findings (M0=no pattern observed; M1=linear or linear-branched; M2=segmental dotted or granular; M3=segmental homogenous; and M4=focal spotlike). All cases were associated with histopathological results. RESULTS: Regarding the 74 DCIS lesions, 37 (50%) showed a signal increase typical of malignancy (C4 and C5). Among all cases, 33.3% of G1 lesions, 68.4% of G2 lesions, and 55.5% of G3 lesions presented a C4 or C5 enhancement. Furthermore, 55.4% (n=41) showed a segmental dotted enhancement (M2), whereas 17.6% showed a focal spotlike enhancement (M4). The morphological features of the other lesions were as follows: 12.2% homogeneous (M3) and 4.0% linear (M1). In 8 cases (10.8%), no significant pattern was observed (M0). Combining dynamic and morphological characteristics, 68.9% presented an appearance comparable with the appearance of invasive breast cancer in MRI. CONCLUSIONS: Ductal CIS lesions show typical morphological and kinetic, but heterogeneous, characteristics in MRI, comparable with the histopathological variety of the disease. For detecting pure DCIS cases early and precisely, a combination of dynamic and morphological criteria seems to be important.     

High-resolution magnetic resonance imaging of squamous cell carcinoma of the tongue: an in vitro study

OBJECTIVES: To determine in vitro the potential of high-resolution MRI for evaluating the depth of tumor invasion of the tongue. METHODS: Twenty-one resected specimens of squamous cell carcinoma of the tongue were examined on a 1.5T MRI system with a 4 cm surface coil using four different sequences; T1W SE, T2W SE, 3D-FISP and 3D-CISS. The thickness of normal epithelium, tumor depth and width were measured on both MR images and histopathological sections. RESULTS: The mucosal epithelium, lamina propria and muscles of the tongue were clearly identifiable on MRI. All 21 carcinomas, including three early invasive carcinomas, were clearly demonstrated. A high correlation was found between the values measured by MRI and histopathology for thickness of mucosal epithelium and both depth and width of tumors. There was a good agreement between the T2W SE and the other imaging sequences for measurements of both depth and width of tumors. CONCLUSION: High-resolution MR imaging appears reliable for the in vitro evaluation of depth of tumor invasion in carcinoma of the tongue.     

MR对声门上型喉癌分期的价值

目的：探讨MR对声门上型喉癌术前T分期的准确性，为治疗方案选择提供影像学依据。方法：对手术切除的48例声门上型喉癌的MR资料进行分析，观察肿瘤侵犯范围及有无颈淋巴结转移，按双盲法根据MR表现进行T分期并与手术病理结果进行对比。结果：NR术前肿瘤T分期的准确性为89．5％(43／48)，判断肿瘤侵犯周围结构的准确性在85％～100％之间，诊断颈部淋巴结的准确性为89％(24／27)。结论：MR能准确判断肿瘤的侵犯范围，准确判断有无淋巴结的转移，对临床治疗方案的选择具有重要意义。     

Clinical implementation of spin-tag perfusion magnetic resonance imaging

Arterial spin-labeled magnetic resonance imaging is a powerful method for generating quantitative cerebral perfusion data. Clinical adoption of this technique is hampered by the lack of availability of the final postprocessed images. This is predominantly due to the need for research personnel to handle image transfer, postprocessing, and image display/review. Here, we describe a fully automated pipeline for clinical implementation of a magnetic resonance spin-tag perfusion sequence that can be extended to any studies requiring off-line processing.     

Clinical nuclear magnetic resonance imaging of the body

NMR promises great advances in diagnosis and has delivered so much already that it is expected that in the future it will replace many applications of the currently used imaging modalities. Although x-ray computed tomography is continuing to advance in speed of scanning and resolving power, NMR will most likely soon eliminate its use in many studies of the central nervous system and also in many other areas of the body. The promise of combining topical spectroscopy with imaging is also exciting and should provide further information about metabolic processes of various organs. Progress in NMR is so rapid and the future is so bright that one of the great problems will be to develop a new breed of radiologists who are versatile in biochemistry, mathematics, and computers, as well as competent in morphologic anatomy and pathologic physiology. As time goes on, advances in NMR will be achieved only by teams of clinical and basic scientists encompassing multiple disciplines.     

Clinical applications of high-resolution ocular magnetic resonance imaging

Magnetic resonance imaging (MRI) using fast sequences with subjects staring at a target can provide motion-free ocular images, and small receiver surface coils make it possible to produce ocular images with high spatial resolution. MRI using half-Fourier single-shot rapid acquisition with a relaxation enhancement sequence as a fast T2-weighted imaging yields useful images for the morphologic diagnosis of ocular diseases, and MRI using a fast spoiled gradient-recalled-echo sequence as a T1-weighted imaging yields additional information by the administration of gadolinium-based contrast material for assessing the vascularity of intraocular tumors. These ocular imaging techniques are useful for the evaluation of patients with angle closure glaucoma, congenital abnormality of ocular globes, intraocular tumors and several types of detachments, as well as patients after ocular surgery. In this pictorial essay, we demonstrate the clinical applications of fast high-resolution ocular MRI with fixation of the subjects?? visual foci.     

Clinical use of urinary tract magnetic resonance imaging

MR imaging should not be used to evaluate the majority of the lesions described herein but should be reserved for specific clinical situations. The detection and differential diagnosis of adrenal masses is a legitimate application of this technique. The staging of renal tumors in patients in whom CT fails to do so may be accomplished by MR imaging. Establishment of patency of the renal veins and of surgical shunts involving these veins may be performed by MR imaging if Doppler ultrasonography proves unsatisfactory. MR imaging may differentiate between stable retroperitoneal fibrosis and malignant disease in patients in whom this differential is a problem. Hematomas may be distinguished from nonhemorrhagic fluid collections anywhere in the abdomen or pelvis. In selected patients, the local extent of certain bladder tumors may be evaluated by MR imaging when CT and biopsy fail to do so. In testicular disease, MR imaging may aid in the differential diagnosis of abnormalities that are not sufficiently characterized by ultrasonography, and MR imaging may detect undescended testes in some patients in whom ultrasonography fails to do so. In the future, wider application of fast scanning with bolus administration of soluble paramagnetic contrast agents may refine the differential diagnosis of adrenal masses and aid in the detection of renal masses. MR angiographic techniques ultimately may constitute a screening procedure for renal arteriostenosis. A subset of patients with prostate carcinoma may prove to benefit from local staging of the disease by MR imaging.     

Accuracy of nasopharyngeal carcinoma staging by magnetic resonance imaging

To audit the accuracy of magnetic resonance (MR) staging of nasopharyngeal carcinoma (NPC) in daily reporting, the MR images of 101 adult patients with newly diagnosed NPC reported between December 1996 and February 2002 were reviewed retrospectively. Based on the American Joint Committee on Cancer/International Union Against Cancer (AJCC/UICC) TNM staging criteria (1997), the tumour staging obtained from the MR reports and the MR films was compared by two experienced head and neck radiologists. The number of patients being upstaged, downstaged or unchanged was noted. In all stages, the NPC staging obtained from the MR reports revealed 18 (17.8%) understaged, eight (7.9%) overstaged and 75 (74.2%) the same stage when compared to the staging obtained from the MR films based on the AJCC/UICC criteria. The percentage of patients being understaged or overstaged, in decreasing order of frequency, were stages II, III, IV and I. Magnetic resonance of NPC should be reported by radiologists who are not only familiar with the pathology of this condition and its pattern of spread but who should also base their reports on the AICC/UICC staging criteria. The necessity to improve our MR staging accuracy is largely because it determines the type of therapy to be given and this has to be appropriate and adequate for a successful treatment.