High-field MRI and US evaluation of the pelvis in women with leiomyomas

Magnetic resonance imaging (MRI) and real-time transabdominal ultrasonography (US) were performed on 23 women with uterine leiomyomas. The uterus, ovaries, and cul de sac were evaluated. Accurate determination of uterine volume was possible in all cases by MRI, but was limited on US in uteri larger than 140 cc. Marked enlargement also prevented visualization of contour abnormalities in eight patients on US, but none on MRI. The endometrial stripe and junctional zone could not be adequately visualized in 21/23 US examinations, whereas they were identified in all 23 MRI (8 normal and 15 distorted). Individual leiomyomas were clearly depicted on 4 US and 19 MR scans, the smallest being 1.1 cm and 0.8 cm, respectively. Of the 31 fibroids present on MRI: 13 were intramural, 4 subserosal, and 14 submucosal. MRI successfully identified 44/46 ovaries as compared to 21/46 on US. Cul de sac fluid was noted in seven women by MRI alone. This data suggests that MRI is superior to US in examination of the entire pelvis in women with leiomyomas.     

MRI appearance of the pelvis in the post cesarean-section patient

Fever in the post-cesarean section patient may indicate the presence of a potentially life-threatening complication, including abscess, ovarian vein thrombosis, and uterine dehiscence. Imaging findings are often utilized to ascertain the presence or absence of such complications. Familiarity with the normal findings in the post-operative period is essential in making this determination. The purpose of this investigation is to describe the MRI appearance of the post-cesarean section pelvis. Over a 67-month period, 50 patients with persistent low-grade fevers following c-section were referred for MR imaging. Imaging was performed 3-10 days post-operatively. Axial T1-weighted and T2-weighted images were acquired in addition to sagittal T2-weighted images. Coronal images were obtained in some cases. Clinical correlation was obtained through the patients charts, confirming discharge of the patients in stable condition. The uterine incision site usually demonstrated findings consistent with subacute hematoma. The anterior uterine myometrium demonstrated enlargement relative to the posterior uterine wall. Bladder flap hematomas were seen in 64% of cases. Three cases (6%) demonstrated parametrial edema and none of these patients demonstrated ovarian vein thrombosis. Two cases of pelvic hematoma were noted. The normal post-c-section incision site may demonstrate increased or decreased signal intensity on T2-weighted images and intact endometrial and serosal layers mitigate against the diagnosis of incisional dehiscence. Bladder flap hematomas occurred in slightly more than half the cases. Parametrial edema and pelvic hematoma can be seen as post-surgical changes.     

Observer reliability in CT and MRI of the abdomen/pelvis

The purpose of this research was to evaluate two sources of error in the performance of computerized tomography (CT) and magnetic resonance imaging (MRI) of the abdomen/pelvis. The sources of error assessed were inter- and intra-observer reliability. Thirty abdomen/pelvis CT scans were randomly selected from each of three hospitals (university, VA, military) with different CT scanners. Two radiologists were recruited from each site to be CT observers. Forty-five abdomen/pelvis MRI scans were randomly selected from two institutions with different MRI scanners. Four observers were recruited to read the MRI scans. All scans were read blind without clinical information or patient identification. Overall inter-observer and intra-observer diagnostic agreement was significantly higher for MRI compared to CT. Inter-observer diagnostic agreement rates were also significantly higher for MRI when the etiologies of neoplastic vascular and metabolic/toxic were assigned. Observer experience in CT (range: 5-9 yr) or MRI (range: 2-4 yr) was not statistically associated with improved diagnostic agreement. This research addresses many of the criticisms of the MRI literature and compares MRI favorably to CT.     

Plexiform neurofibroma of the pelvis: CT and MRI findings

We present a case of plexiform neurofibroma of the pelvis in a patient with neurofibromatosis using magnetic resonance imaging (MRI) with computed tomography (CT) correlation. We discovered an extensive pelvic mass with a slightly greater signal intensity than muscle in T1-weighted images and a marked increased signal intensity in T2-weighted images. Multiple hypointense septations were identified throughout the tumor, particularly in the T2-weighted images. The MR appearance of pelvic plexiform neurofibroma is identical to those found in spinal and paraspinal locations. In the presence of an extensive pelvic mass in a patient with neurofibromatosis, MRI is recommended in evaluating and diagnosing plexiform neurofibroma. Since the MRI appearance of this tumor is characteristic, other lesions can possibly be ruled out. In addition, MRI's multiplanar capability is ideally suited to demonstrate the extension of these large tumors.     

Magnetic resonance imaging of postpartum pelvic hematomas: early experience in diagnosis and treatment planning.

The purpose of this study was to determine the utility of magnetic resonance imaging (MRI) in detecting and localizing clinically non-apparent postpartum pelvic hematomas, and to describe the therapeutic implications of MRI in these patients. MRI examinations were performed on seven women with pelvic pain and/or fullness following difficult vaginal deliveries. None had clinically evident hematomas, and none were scheduled for surgery. Hematomas in the pelvis were identified with conventional T1-weighted, and conventional and fast spin echo T2-weighted sequences. Intravenous contrast was not used. Pelvic hematomas were identified in contiguity with the vagina, cervix, and bladder, within the broad ligament, and in the presacral space. In two patients, hematomas were confined to the perivaginal and pericervical regions. In three patients, perivaginal hematomas extended between the double layers of the broad ligaments. In one patient, a perivaginal hematoma extended into the perivesical space. In one patient, a hematoma was identified only within the presacral space. Based on MRI as the only contributory imaging study, five patients were treated successfully with invasive means and two patients were managed successfully with conservative means. MRI successfully detects and localizes postpartum hematomas, information that often is unavailable from the clinical examination. This information facilitates decisions regarding the need for intervention and the appropriate type of procedure when intervention is necessary for this potentially life-threatening problem. We advocate the use of MRI to evaluate patients at risk for postpartum hemorrhage following difficult vaginal deliveries.     

Spin echo MRI in the evaluation of hearts with a double outlet right ventricle: usefulness and limitations

The surgical approach to a double outlet right ventricle (DORV) is dependent on the spatial relationship of the semilunar valves, outflow tracts and ventricular septal defect (VSD). The purpose of the study was to assess the value of MRI for the evaluation of cardiovascular anatomy in patients before and after surgery for DORV. Spin echo MRI was performed in 12 patients with DORV (eight preoperative and four postoperative patients). Thin-section MRI was performed in three orthogonal planes and selected angulated views were obtained. Conventional imaging by color Doppler echocardiography and cine-angiocardiography and surgical findings, when present, served as the reference standards. The results found that the spatial relationship between semilunar valves and VSD was accurately assessed by MRI in eight out of eight preoperative patients. In the four postoperative cases MRI depicted the morphology of both outflow tracts and provided adequate information on their patency. Of the eight preoperative patients, five have undergone corrective surgery and the MRI findings were confirmed. MRI provided additional information to conventional imaging preoperatively in three cases in which the VSD opened into the outlet portion of the DORV, without there being a direct relation to a semilunar valve. In two preoperative cases in which the VSD was directly committed to the aorta, conventional imaging was conclusive. MRI was unable to depict aberrant chordae tendineae in four out of four cases. We conclude that MRI provides accurate additional anatomic information in patients with DORV, which is helpful in presurgical planning as well as during follow-up. Spin echo MRI does not visualize aberrant chordae tendineae.     

MRI of female uterine and juxta-uterine masses: clinical application in 25 patients.

The clinical utility of magnetic resonance imaging (MRI) in the diagnosis of gynecologic masses was evaluated in 25 patients. In each patient the final pathologic diagnosis was semiquantitatively correlated with the diagnostic impressions from pelvic examination, ultrasound and MRI. There were 9 uterine, 11 ovarian and 5 nonovarian pelvic masses. Pelvic examination correlation with final diagnosis was 26%, consistent with the literature. Ultrasound fared surprisingly poorly, with only 44% correlation. MRI showed an 87% correlation with the final diagnosis. MRI was able to accurately identify masses, discriminate adnexal masses from fluid-filled bowel, identify dermoids, and in one case obviated surgery in a pregnant patient. MRI provided significant clinical management information with greater accuracy than did ultrasound or pelvic examination.     

Ultrafast MRI of the fetus: an increasingly important tool in prenatal diagnosis of congenital anomalies

Objective

To demonstrate the additional utility of ultrafast magnetic resonance imaging (MRI) of the fetus in the evaluation of sonographically detected or equivocal fetal congenital anomalies.

Material and Methods

Twenty five pregnant women with ultrasound detected fetal congenital anomalies underwent ultrafast fetal MRI.

Results

MRI findings altered the diagnosis of two cases of giant arachnoid cyst and sizable interhemispheric cyst associated with agenesis of the corpus callosum. MRI added additional findings of occult spinal diastematomyelia in two out of four cases of Chiari/meningocele malformation. MRI revealed impaired sulcation and unilateral cleft palate in suspected case of Walker-Warburg syndrome. In the remaining 18 cases MRI confirmed the diagnosis of Meckel–Gruber syndrome in three cases, hydronephrosis in six cases, cerebral ventriculomegaly in five cases, isolated omphalocele in three cases and findings suggestive of aneuploidy in the last case.

Conclusion

Ultrasound is the screening method of choice for evaluation of the fetus. Ultrafast MRI is a complementary adjunctive modality with excellent tissue contrast that can image the fetus in multiple planes and add information in sonographically detected or equivocal congenital anomalies that may be significant to establish definitive accurate diagnosis and hence adequate management and counseling.     

Pelvic phased array coil: image quality assessment for spin-echo MR imaging.

The NMR phased array coil (PA) provides improved signal-to-noise ratio (SNR) over that available with the body coil. We evaluated image quality obtained with a pelvic PA compared to that obtained with the body coil for spin-echo imaging. Thirty-three women undergoing clinical pelvic MRI were imaged with the body coil followed by imaging with the PA with the same field-of-view (FOV) in 11 patients, and with a small FOV in 23 patients. Image quality was assessed independently by two radiologists. In individual cases there was significant improvement in image quality with the PA, however the expected marked improvement in image quality was not consistently found. Two factors which may limit image quality are increased motion artifact and nonuniformity of signal with distance from the coils. Significant improvements in image quality may occur with improved techniques to decrease motion artifact.     

Simultaneous PET–MRI in oncology: a solution looking for a problem?

With the recent development of integrated positron emission tomography–magnetic resonance imaging (PET–MRI) scanners, new possibilities for quantitative molecular imaging of cancer are realized. However, the practical advantages and potential clinical benefits of the ability to record PET and MRI data simultaneously must be balanced against the substantial costs and other requirements of such devices. In this review, we highlight several of the key areas where integrated PET–MRI measurements, obtained simultaneously, are anticipated to have a significant impact on clinical and/or research studies. These areas include the use of MR-based motion corrections and/or a priori anatomical information for improved reconstruction of PET data, improved arterial input function characterization for PET kinetic modeling, the use of dual-modality contrast agents, and patient comfort and practical convenience. For widespread acceptance, a compelling case could be made if the combination of quantitative MRI and specific PET biomarkers significantly improves our ability to assess tumor status and response to therapy, and some likely candidates are now emerging. We consider the relative advantages and disadvantages afforded by PET–MRI and summarize current opinions and evidence as to the likely value of PET–MRI in the management of cancer.     

Imaging treatment effects in Alzheimer's disease

Alzheimer's disease (AD) is the commonest form of degenerative dementia and is characterised by progressive cognitive decline. Despite extensive research, the cause of AD is unknown and there is no cure at present. Of the deficits found in AD, that affecting the cholinergic neurotransmitter system is the best established and the only one translated into symptomatic treatment. Cholinergic enhancement with cholinesterase inhibitor (ChEI) drugs has been achieved and their efficacy and safety ascertained by conventional clinical trials. The mechanism of action of these drugs, however, is not well understood. Imaging with SPECT, PET, MRI and fMRI after treatment has clarified what happens in the brains of those AD patients treated with ChEI drugs. Studies with these techniques have identified increases in brain blood flow and glucose metabolism, restoration of nicotinic receptor function and re-establishment of task-related regional brain activation in response to cognitive stimulation after treatment. Structural MRI studies have explained, to some degree, why only a proportion of patients benefits from ChEI treatment and there is some evidence that some ChEI drugs might be neuroprotective. There are, however, many unsolved problems. Timing of treatment intervention to obtain maximum response and the determinants of treatment response are mostly unknown. It is also unclear whether administration of treatment in those patients who have no potential for response accelerates disease progression. These issues cannot be solved by conventional clinical trials. Pharmacoimaging studies could assist the development and refinement of drugs to treat those diseases, such as AD, which affect the central nervous system.     

The short TI inversion recovery sequence--an approach to MR imaging of the abdomen

Initial clinical experience with magnetic resonance imaging (MRI) of the abdomen using short TI inversion-recovery (STIR) pulse sequences is described and compared with X-ray CT in a variety of abdominal disease. The extent of abnormality shown with MRI was greater than that with CT in 21 of 30 cases and equal in 9 cases. Lesion contrast was greater with MRI in 15 cases, equal in 14 and less in 1. The level of artefact was equal in 27 cases and greater with MRI in 3 cases. The STIR pulse sequence has significant advantages in producing high soft-tissue contrast, controlling respiratory artefact, avoiding confusion with intra-abdominal fat and identifying bowel loops.     

On the down-sampling of diffusion MRI data along the angular dimension

BackgroundIt has been established that the diffusion gradient directions in diffusion MRI should be uniformly distributed in 3D spherical space, so that orientation-dependent diffusion properties (e.g., fractional anisotropy or FA) can be properly quantified. Sometimes the acquired data need to be down-sampled along the angular dimension before computing diffusion properties (e.g., to exclude data points corrupted by motion artifact; to harmonize data obtained with different protocols). It is important to quantitatively assess the impact of data down-sampling on measurement of diffusion properties.Materials and methodsHere we report 1) a numerical procedure for down-sampling diffusion MRI (e.g., for data harmonization), and 2) a spatial uniformity index of diffusion directions, aiming to predict the quality of the chosen down-sampling schemes (e.g., from data harmonization; or rejection of motion corrupted data points). We quantitatively evaluated human diffusion MRI data, which were down-sampled from 64 or 60 diffusion gradient directions to 30 directions, in terms of their 1) FA value accuracy (using fully-sampled data as the ground truth), 2) FA fitting residuals, and 3) spatial uniformity indices.ResultsOur experimental data show that the proposed spatial uniformity index is correlated with errors in FA obtained from down-sampled diffusion MRI data. The FA fitting residuals that are typically used to assess diffusion MRI quality are not correlated with either FA errors or spatial uniformity index.ConclusionsThese results suggest that the spatial uniformity index could be more valuable in assessing quality of down-sampled diffusion MRI data, as compared with FA fitting residual measures. We expect that our implemented software procedure should prove valuable for 1) guiding data harmonization for multi-site diffusion MRI studies, and 2) assessing the impact of rejecting motion corrupted data points on the accuracy of diffusion measures.     

Assessing functional connectivity in the human brain by fMRI

Functional magnetic resonance imaging (fMRI) is widely used to detect and delineate regions of the brain that change their level of activation in response to specific stimuli and tasks. Simple activation maps depict only the average level of engagement of different regions within distributed systems. FMRI potentially can reveal additional information about the degree to which components of large-scale neural systems are functionally coupled together to achieve specific tasks. In order to better understand how brain regions contribute to functionally connected circuits, it is necessary to record activation maps either as a function of different conditions, at different times or in different subjects. Data obtained under different conditions may then be analyzed by a variety of techniques to infer correlations and couplings between nodes in networks. Several multivariate statistical methods have been adapted and applied to analyze variations within such data. An approach of particular interest that is suited to studies of connectivity within single subjects makes use of acquisitions of runs of MRI images obtained while the brain is in a so-called steady state, either at rest (i.e., without any specific stimulus or task) or in a condition of continuous activation. Interregional correlations between fluctuations of MRI signal potentially reveal functional connectivity. Recent studies have established that interregional correlations between different components of circuits in each of the visual, language, motor and working memory systems can be detected in the resting state. Correlations at baseline are changed during the performance of a continuous task. In this review, various methods available for assessing connectivity are described and evaluated.     

Composite and classified color display in MR imaging of the female pelvis.

Because of its superior soft-tissue-imaging capabilities, MRI has proved to be an excellent modality for visualizing the contents of the female pelvis. In an effort to potentially improve gynecological MRI studies, we have applied color composite techniques to sets of spin-echo and gradient-echo gray-tone MR images obtained from various individuals. For composite generation, based on tissue region of interest calculated mean pixel intensity values, various colors were applied to spatially aligned images using a DEC MicroVAX II computer with interactive digital language (IDL) so that tissue contrast patterns could be optimized in the final image. The IDL procedures, which are similar to those used in NASA's LANDSAT image processing system, allowed the generation of single composite images displaying the combined information present in a series of spatially aligned images acquired using different pulse sequences. With our composite generation techniques, it was possible to generate seminatural-appearing color images of the female pelvis that possessed enhanced conspicuity of specific tissues and fluids. For comparison with color composites, classified images were also generated based on computer recognition and statistical separation of distinct tissue intensity patterns in an image set using the maximum likelihood processing algorithm.     

The diagnostic role of gadolinium enhanced MRI in distinguishing between acute medullary bone infarct and osteomyelitis

The objective of the study was to evaluate the diagnostic utility of contrast enhanced magnetic resonance imaging (MRI) for distinguishing between acute medullary bone infarct and osteomyelitis. There were 11 patients (age 6-34 years) presented to our institution between December 1994 and February 1998 with a clinical differential diagnosis of acute bone infarct versus osteomyelitis and inconclusive radiographs were imaged using MRI. All but one received i.v. gadolinium. Nine of the patients had homozygous Sickle Cell disease (SCD) and two had Systemic Lupus Erythematosus (SLE), the latter requiring chronic methylprednisolone. Osteomyelitis was confirmed either by biopsy alone or by the combination of Gallium(67) scan in conjunction with positive blood cultures and clinical resolution following antibiotics. Infarcts without osteomyelitis were confirmed either by biopsy or resolution of symptoms without antibiotic therapy. All patients had at least six months clinical follow-up. The results found that seven of nine patients with SCD had acute infarct only. One patient with SCD had osteomyelitis only. Three patients (two SLE and one SCD) had both acute-on-chronic infarcts and superimposed osteomyelitis, one with an adjacent soft tissue abscess. Accurate distinction between infarct and osteomyelitis was impossible for one patient with SLE who did not receive contrast. All other cases were correctly diagnosed prospectively based on distinct patterns of MRI contrast enhancement. In all adult patients, acute infarcts demonstrated thin, linear rim enhancement on MRI while osteomyelitis revealed more geographic and irregular marrow enhancement. Two of four cases of osteomyelitis also demonstrated subtle cortical defects with abnormal signal traversing marrow and soft tissue. The single pediatric patient demonstrated elongated, serpiginous central medullary enhancement with periostitis. We concluded that the pattern of MR contrast enhancement may allow accurate distinction between acute infarct and osteomyelitis, or recognition of osteomyelitis superimposed on bone infarction.     

Pure uterine lipoma

Lipomatous tumors of the uterus are unusual, benign neoplasms seen in postmenopausal women. Although many of the mixed-type cases such as lipoleiomyoma and fibrolipoma have been reported, pure uterine lipomas are extremely rare. In the literature, a few cases with pure uterine lipoma have been reported. We first present the advanced magnetic resonance findings of pure uterine lipoma, followed by those of ultrasonography (US) and computed tomography (CT). We markedly detected lipid peaks on the magnetic resonance spectroscopy (MRS) and the apparent diffusion coefficient value to be 0.00 due to chemical-shift effects with diffusion-weighted imaging (DWI). Although pelvic lipomatous tumors can be diagnosed with US and CT, in some cases, further workup may be required to localize the lesion. MRI may yield more valuable data for differential diagnosis. MRS and DWI findings provide additional clues on the nature of the lesion.     

Profile analysis and background noise

Spectral shape discrimination, or profile analysis, of complex waveforms (21 components) in the presence of broadband noise and special sinusoidal maskers of random amplitude was studied. The first experiment involved the discrimination between a standard flat spectrum and a "rippled" spectrum in broadband noise of different spectrum levels. Thresholds obtained under control conditions, without noise or without a standard, were used to estimate constants of an equation that predict thresholds where standard and noise are both present. The model assumes an external variance, produced by the noise, is added linearly to an internal variance caused by the flat standard. The mean squared error is less than 2 dB. The second experiment involved the detection of an increment on the center component of the 21-component standard. Added to the standard was an additional masking sinusoid of random amplitude. Both the frequency and the range of the random amplitude were varied and both showed a systematic influence on the detectability of the 1000-Hz increment.     

Bacterial pyomyositis: MRI and clinical correlation

OBJECTIVE: To characterize the findings of magnetic resonance imaging (MRI) of bacterial pyomyositis (PM) and correlate these data with the clinical information. MATERIALS AND METHODS: Eighty-one patients were diagnosed with PM in our institute between 1997 and 2003. Of these, 40 patients (21 male, 19 female; mean age, 53 years) also underwent MRI examination. The clinical manifestation underlying medical problems and the characteristics of MRI were analyzed. Thirty of the patients received surgical intervention or image-guided drainage/aspiration of the abscess along with administration of antibiotics, while the remaining 10 patients were promptly treated solely with antibiotics. RESULTS: Thirty-one of 40 patients had underlying medical problems. These involved diabetes mellitus (DM, n = 16), malignancies including cervical cancer, prostate cancer, non-Hodgkin's lymphoma and acute lymphocytic leukemia (n = 10, one case also had DM), autoimmune disease or asthma with long-term steroid usage (n = 4, one case also had DM), liver cirrhosis (n = 2) and chronic renal insufficiency (n = 1). Four patients had no abscess formation at presentation (invasive or early purulent stage), while the remaining 36 cases presented with at least one abscess (purulent stage). Patients older than 40 years or DM patients tended to have larger abscess(s) (P < .05). Gadolinium-enhanced images demonstrated either thick (n = 12) or thin rim enhancement (n = 24) of the abscess wall. For those 10 patients promptly treated solely with antibiotics, nine demonstrated thin rim enhancement of the abscess (P < .05). CONCLUSION: Magnetic resonance imaging plays an important role in the early recognition of bacterial PM. By precisely demarcating the extent of the disease, MRI can allow planning prompt antibiotic treatment combined with or without interventional procedures.     

基于AI+MRI的影像诊断的样本增广与批量标注方法

训练样本是所有领域人工智能（AI）研发的关键因素.目前，基于人工智能+磁共振成像（AI+MRI）的影像诊断存在着训练样本的有效标注数量和类型无法满足研发需求的瓶颈问题.本文利用临床MRI设备对志愿者或阳性病例进行正常或重点病灶区的定量扫描，获取高分辨率各向同性的纵向弛豫时间（T₁）、横向弛豫时间（T₂）、质子密度（Pd）和表观扩散系数（ADC）等物理信息的多维数据矩阵，作为原始数据.开发虚拟MRI技术平台，对原始数据（相当于数字人体样本）进行虚拟扫描，实现不同序列不同参数下的多种类磁共振图像输出.选择感兴趣组织具有最好边界区分度的图像种类，经有经验的影像医生对其进行手动勾画并轨迹跟踪形成三维MASK标注矩阵，作为其他种类图像的图像勾画标注模板，从而实现低成本、高效率的MRI样本增广和批量标注.该平台以临床少量阳性病例作为输入，进行样本增广和标注，极大地减少AI对实际扫描样本的要求，降低了影像医生的精力和时间投入，极大地节省了成本，并输出了数量足够的磁共振图像，为基于AI+MRI的影像诊断研发提供低成本的训练数据解决方案.