Single-shot Fast Spin-echo Magnetic Resonance Imaging Research Articles

The role of ultrasound and antenatal single-shot fast spin-echo MRI in the evaluation of herniated bowel in case of first trimester ultrasound diagnosis of fetal gastroschisis

To report on a clinical antenatal management strategy based on integrating ultrasound (US) and magnetic resonance imaging (MRI) in the evaluation of herniated bowel following early prenatal diagnosis of gastroschisis. Antenatal US and ultrafast single-shot spin-echo (SSSE) MRI. Fetal gastroschisis was documented at 12 weeks at the time of first trimester screening for Down syndrome. Fetal karyotype was performed at 16 weeks and showed a 46,XY karyotype. Ultrasound scan at 20 weeks diagnosed gastroschisis as isolated finding. Follow-up scans were planned monthly, and antenatal ultrafast SSSE MRI was arranged at 35 weeks and demonstrated a right fetal abdominal wall defect measuring 2.4 mm on transverse diameter with an integrity of the intra-abdominal and extra-abdominal loops of small bowel. The colon was in situ as were the stomach, the liver, and the spleen. The choice of integrating both the diagnostic procedures has shown to be clinically useful in planning the timing of delivery (Cesarean section) and in turn has been associated with an easy surgical repair and to a favorable postnatal outcome. The result of amniocentesis was crucial for the parent's decision-making process whether to continuing with the pregnancy. Moreover, amniotic fluid α-fetoprotein levels may be used as an index of small bowel damage when loops of small bowel lied uncovered within the amniotic cavity.

The Appendix in Pregnancy

To estimate the position of the appendix in term pregnancy using magnetic resonance imaging (MRI) technique. Appendiceal distance from the iliac crest and axis rotation were determined in women between 39 and 40 weeks of gestation who were undergoing scheduled repeat cesarean delivery. A single-shot fast spin-echo MRI sequence of the maternal pelvis was performed without gadolinium contrast. A board-certified radiologist interpreted the MRIs and measured the distance from the base of appendix (or cecum) to the iliac crest in centimeters as well as the axis of the appendix using clock position annotation. Seventy-two women had optimal imaging for interpretation. The mean displacement of the appendix above the iliac crest was 45 mm and was significantly higher than previously described in the term pregnant woman (P<.001). Despite recent studies supporting the contrary view, the upward displacement of the appendix in term pregnancy is confirmed in this study. II.

Localization of the Appendix at MR Imaging during Pregnancy: Utility of the Cecal Tilt Angle

To determine whether the cecal tilt angle on sagittal magnetic resonance (MR) images in pregnant patients correlates with the location of the appendix and gestational age and whether the cecal tilt angle can help predict the location of the appendix. This HIPAA-compliant retrospective study was approved by the institutional review board. Informed consent was waived. Of 146 consecutive pregnant patients suspected of having appendicitis (mean age, 29 years) who underwent MR imaging, 143 had MR images in which the appendix and cecum were identifiable in the sagittal plane. Two observers reviewed the MR images; findings were agreed upon by consensus. With use of sagittal single-shot fast spin-echo MR images, the cecal tilt angle was calculated as the angle between the imaging table and a line drawn between the cecal tip and the luminal center of the most proximal inflection point in the ascending colon. The location of the appendiceal base relative to the lumbosacral spine was recorded. Statistical analyses were performed by using Spearman and Pearson correlation coefficients to evaluate the relationship among gestational age, appendiceal base location, and cecal tilt angle. Receiver operating characteristic curve analysis was performed to assess the ability of the cecal tilt angle to help differentiate between a high and low appendiceal base level. Cecal tilt angles showed moderate correlation with appendiceal base levels (Spearman correlation coefficient, 0.44; P < .001) and poor correlation with gestational age (Pearson correlation coefficient, 0.25; P = .002). Regardless of gestational age, cecal tilt angles of at least 90 degrees were predictive of a high appendiceal base level with a specificity of 98% (95% confidence interval: 92%, 100%). The cecal tilt angle is useful for localizing the appendix in pregnant patients at MR imaging and helps predict the location of the appendix within the right upper quadrant of the abdomen with high specificity, irrespective of gestational age.

Prenatal diagnosis of hemifacial microsomia by magnetic resonance imaging

We present a case of hemifacial microsomia, first detected by prenatal sonography and confirmed by ultrafast magnetic resonance (MR) imaging. A 26-year-old patient was referred to our hospital at 20 weeks of gestation because of unilateral right-sided ventriculomegaly and of a possible ventriculoseptal defect (VSD). Our sonographic examination suggested a right orbital hypoplasia and a hemiatrophy of the nose. The ultrafast T2-weighted single-shot fast-spin echo MR imaging, demonstrated a right ear hypoplasia (microtia), a right orbital hypoplasia, and a right renal hypoplasia. Epibulbar dermoid or conjunctival lipodermoid were not recognized. The fetus was prenatally diagnosed as hemifacial microsomia. Termination of pregnancy was performed at 21 weeks gestation, and a male baby weighing 342g was stillborn. The baby showed facial asymmetry, including hemiatrophy of the right nose, and right ear hypoplasia. Autopsy revealed a 2mm area of VSD, agenesis of the right kidney and ureter, pancreatic and renal aberration into right adrenal gland, thymus hypoplasia and an unfixed ascending colon without intestinal malrotation. To the best of our knowledge, this is the first report of prenatal diagnosis for hemifacial microsomia using fetal MR imaging. In our case, fetal MR imaging has evolved into a powerful diagnostic tool, for the accurate prenatal diagnosis.

The use of quick-brain magnetic resonance imaging in the evaluation of shunt-treated hydrocephalus

Children with shunt-treated hydrocephalus are exposed to serious amounts of radiation when undergoing computerized tomography (CT) scanning. The authors report their clinical experience with single-shot fast-spin echo (SSFSE) (quick-brain) magnetic resonance (MR) imaging as the modality of choice for the workup and follow up of patients in whom a shunt has been placed to treat hydrocephalus. A retrospective chart review was performed to obtain data on all cases in which a quick-brain MR image was acquired for either symptomatic workup or asymptomatic follow-up examination of shunt-treated hydrocephalus. Data regarding demographics, origin of hydrocephalus, MR imaging indications and findings, use of sedation, imaging-related complications, use of adjunctive CT scanning, details of shunt revision, and cause of shunt malfunction were collected. The authors found that SSFSE MR imaging is a sufficient, radiation-free diagnostic alternative to CT scanning that minimizes movement artifact and duration of scanning and eliminates the need for sedation. In light of these findings, the authors propose that quick-brain MR imaging replace CT scanning as the diagnostic modality of choice in examining and following shunt-treated patients because it offers significant advantages.

Pseudolesions related to uterine contraction: characterization with multiphase-multisection T2-weighted MR imaging.

To evaluate whether multiphase-multisection T2-weighted magnetic resonance (MR) images help exclude pseudolesions mimicking leiomyoma and adenomyosis on static T2-weighted fast spin-echo (FSE) MR images and to characterize temporal changes in uterine signal intensity related to uterine contraction. T2-weighted FSE and multiphase-multisection single-shot FSE (SSFSE) MR imaging were performed in 43 patients who underwent hysterectomy. Each imaging set was evaluated separately by two independent readers, and receiver operating characteristic analysis was performed. In the 43 patients and in 49 other patients suspected of having pelvic abnormality, a combination of signal intensity changes on FSE and SSFSE MR images was classified into five patterns, and temporal low-signal-intensity changes on SSFSE MR images were characterized. For detection of leiomyoma on FSE and SSFSE MR images, the respective values of the area under the receiver operating characteristic curve were 0.98 and 0.97 for reader 1 and 0.96 and 0.96 for reader 2; for detection of adenomyosis on FSE and SSFSE MR images, the respective values were 0.82 and 0.84 for reader 1 and 0.80 and 0.89 for reader 2 (P >.05). SSFSE MR images helped exclude pseudolesions in 1%-3% cases of leiomyoma and in 3%-4% cases of adenomyosis. Temporal signal intensity changes were observed in 53% of 368 segments. The most frequent shape of temporal low signal intensity was diffuse followed by ill-defined focal type. Characteristic shape of temporal low signal intensities was band- or sticklike, which was observed in as many as 19% of 368 segments. Multiphase-multisection T2-weighted SSFSE MR images do not improve accuracy in detection of leiomyoma and adenomyosis compared with FSE MR images; however, they helped characterize features of temporal low signal intensities in the uterus, which are related to uterine contractions.

Pancreatic cysts: depiction on single-shot fast spin-echo MR images.

To evaluate single-shot fast spin-echo (SE) magnetic resonance (MR) imaging for depiction of pancreatic cysts in a large number of patients and to analyze cyst prevalence with respect to patient age and sex and other clinical information. Single-shot fast SE images of the pancreas were obtained in 1,444 patients. The images were reviewed for presence of pancreatic cysts, which were classified as simple and nonsimple types, and cyst diameters were measured. kappa statistic, Fisher exact, McNemar Q, and Pearson product moment correlation tests were performed. Two hundred eighty-three (19.6%) patients had at least one pancreatic cyst. The prevalence of pancreatic cysts increased with age (r = 0.96). The percentages of male and female patients with pancreatic cysts (20.4% vs 18.8%) were not significantly different. Two hundred seventy-one (18.8%) patients had simple cysts, and 147 (10.2%) had nonsimple cysts. Of 283 patients with pancreatic cysts, 158 (55.8%) had only one pancreatic cyst. The number of patients with multiple cysts increased with age after 70 years. Four hundred fifteen (83.8%) cysts were 10 mm in diameter or smaller; 56 (11.3%), 11-20 mm in diameter; and 24 (4.9%), 21 mm in diameter or larger. Sixteen (5.7%) patients with pancreatic cysts had malignant pancreatic tumors, and 75 (26.5%) patients had pancreatitis. The prevalence of pancreatic cysts at single-shot fast SE MR imaging-especially cysts with a diameter smaller than 10 mm-is similar to that of pancreatic cysts at autopsy and higher than that of pancreatic cysts at transabdominal ultrasonography. Prevalence is especially high in patients with pancreatitis.

Changes in myometrial and junctional zone thickness and signal intensity: demonstration with kinematic T2-weighted MR imaging.

To demonstrate uterine contractions by evaluating changes during time in the thickness of the myometrium and junctional zone and in signal intensity of the uterus with T2-weighted fast magnetic resonance (MR) images in a kinematic fashion. Sagittal MR imaging was performed with T2-weighted fast spin-echo (FSE) and multiphase-multisection single-shot FSE (SSFSE) in 60 premenopausal patients during free breathing. SSFSE MR images were evaluated with cine display. The pattern of uterine contractions and changes in signal intensities of the uterine structures were evaluated. Thickness of both myometrium and junctional zone, and their signal intensities, were measured during 15 phases of SSFSE and FSE MR imaging. Slow-massive (mean, 55%), middle-cycle (mean, 80%), and fine (mean, 93%) contractions were observed. Shape of junctional zones dynamically changed during time, showing focal (mean, 58%) and diffuse (mean, 82%) thickening and wavelike motions (mean, 88%). Ratio of thickness of the myometrium to junctional zone with FSE MR imaging was not significantly different from the mean ratio during 15 phases of SSFSE MR imaging, although maximum percentage of change of the ratio during 15 phases was 42.5%-56.8%. The signal intensities of the myometrium (97%) and junctional zone (75%) changed during time. Kinematic T2-weighted SSFSE MR images demonstrate uterine contractions related to dynamic changes in thickness and signal intensities of the myometrium and junctional zone, and these findings might affect the diagnosis of uterine disease.

Colonic masses: detection with MR colonography.

To assess magnetic resonance (MR) colonography as a method for detection of colorectal masses, with conventional colonoscopy as the reference standard. MR colonography was performed in 132 patients referred for colonoscopy because of the possible presence of a mass. After rectal filling with a gadopentetate dimeglumine and water enema, T1-weighted three-dimensional gradient-echo MR studies were acquired with the patient in the prone and supine positions. Water-sensitive single-shot fast spin-echo MR images were also obtained. Surface-rendered virtual endoscopic endoluminal views, orthogonal sections in three planes, and water-sensitive MR images were interactively assessed for presence of colorectal masses by two radiologists. MR colonography was well tolerated without sedation or analgesia. MR image quality was sufficient for diagnosis in 127 (96%) patients. Most small (</=5-mm-diameter) masses were overlooked at MR colonography, but 19 of 31 6-10-mm lesions and 26 of 27 large (>10-mm) lesions were correctly identified. For these large masses, MR colonography had a sensitivity of 93%, specificity of 99%, positive predictive value of 92%, and negative predictive value of 98% for detection of masses. MR colonography is a promising modality for help in detecting colorectal mass lesions larger than 10 mm in diameter.

Single-shot fast spin-echo MR imaging of the fetus: a pictorial essay.

Ultrasonography (US) is the modality of choice for prenatal screening, but occasionally additional imaging information is needed. Magnetic resonance (MR) imaging is an attractive alternative but until recently has been limited by motion artifact. Single-shot fast spin-echo MR imaging was used to depict normal and abnormal anatomy in 26 fetuses. Thirteen studies were performed for maternal indications and 13 were performed to evaluate fetal abnormalities identified or suspected at US. Three of the fetal abnormalities involved the central nervous system (CNS) and 10 involved other anatomic sites. Results were correlated with findings at postnatal clinical examination, imaging, and pathologic analysis. MR imaging demonstrated normal fetal anatomy without substantial motion artifact. CNS structures were well visualized as early as 18-20 weeks gestation, as were most other normal anatomic structures except the heart. MR imaging also allowed characterization of a variety of abnormalities of the CNS (Arnold-Chiari malformation, Walker-Warburg syndrome, amniotic band syndrome) as well as of other structures (renal agenesis, multicystic dysplastic kidney, abdominal masses, severe limb-body wall defect, clubfoot with arthrogryposis, diaphragmatic hernia). US findings were confirmed in most cases, and additional information about the precise diagnosis or the severity or location of the anomaly often helped guide clinical management. Single-shot fast spin-echo MR imaging of the fetus is a useful adjunct to US in difficult diagnostic situations.