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Biomedical subjects

Diane M Twickler

Publications and source records attributed to Diane M Twickler.

At least 19 recordsLinked to original sources
PubMed2006

Alpha-fetoprotein detection of neural tube defects and the impact of standard ultrasound.

OBJECTIVE: The purpose of this study was to evaluate neural tube defect (NTD) detection according to whether serum alpha-fetoprotein (AFP) screening or standard ultrasound are performed. STUDY DESIGN: Prenatal and neonatal datasets were reviewed to identify pregnancies with NTDs from 1 institution between January 2000 and December 2003. AFP screening was offered < 21 weeks and considered elevated if > or = 2.50 multiples of the median. Standard ultrasound was performed for specific indications in low-risk pregnancies. RESULTS: There were 66 NTDs, 1 per 950 deliveries. AFP sensitivity was 65%. If the gestational age used for AFP calculation was confirmed with ultrasound, sensitivity improved to 86%. The sensitivity of standard ultrasound was 100%, P < .001 compared with AFP screening. NTDs detected with standard ultrasound were identified later in gestation, as examinations were performed for other indications. CONCLUSION: Standard ultrasound improved NTD detection over AFP screening alone, by improving AFP test sensitivity and identifying NTDs in low-risk pregnancies.

Adult↗
PubMed2005

MR findings of complicated multifetal gestations.

This paper presents a review of various complications of multifetal gestations identified on MR imaging and highlights findings of those complications unique to monochorionic twinning. The goal is to illustrate the potential of MR as a useful application in these clinical circumstances. A total of 32 women with multifetal gestations and suspected complication detected initially by US underwent T2-weighted MR imaging. Additional T1-weighted images were obtained when intracranial hemorrhage was suspected. MR and US findings were compared in all cases. Of 32 cases, six demonstrated fetal complications specific to monochorionic twinning; the findings consisted of conjoined twins (n=2), twin-twin transfusion syndrome (n=1), co-twin demise with embolic disease (n=2), and twin-reversed arterial perfusion. (TRAP) syndrome (n=1). MR imaging confirmed US findings in all cases and was particularly helpful in delineating the extent of intracranial complications of monochorionic twins. The technique also showed improved anatomical detail in cases of conjoined twins. MR imaging provided additional information in cases of complicated monochorionic twinning, making it a useful complementary technique when combined with initial sonographic assessment.

Adult↗
PubMed2005

Appearance of the levator ani muscle in pregnancy as assessed by 3-D MRI.

OBJECTIVE: The purpose of this study was to describe levator ani (LA) anatomy in postterm nulliparas using 3-dimensional (3-D) magnetic resonance (MR). STUDY DESIGN: Nulliparas (n = 84) with uncomplicated, postterm pregnancies underwent an MR (4 mm slices, 0 gap) of the uterus and pelvis. LA volume and morphometry were assessed using 3-D post-processing software. RESULTS: LA insertion into the symphysis was visible in 93%, and the iliococcygeus muscle assumed a convex shape (arch) in the 92% of the 84 women. The LA shape was characterized as "U" in 53% and "V" in 47%. Mean LA volume was 13.5 (3.7) cm3. There was a positive association between LA volume and higher fetal station (P = .02) and increasing BMI (P < .001). However, no relationship between LA volume and station was found after adjusting for BMI. CONCLUSION: BMI was correlated with LA volume in postterm nulliparas. LA insertion into the symphysis and the iliococcygeus arch were well-preserved overall and morphometry was variable.

Adolescent↗
PubMed2005

The effect of magnesium sulfate on large cerebral artery blood flow in preeclampsia.

OBJECTIVES: To determine the effect of a 6 gram intravenous bolus of magnesium sulfate on maternal cerebral blood flow in women with preeclampsia. STUDY DESIGN: Velocity-encoded phase-contrast magnetic resonance imaging studies were performed on twelve preeclamptic women prior to and immediately after infusion of a 6 gram magnesium sulfate loading dose. Cerebral blood flow was determined at the bilateral proximal middle and posterior cerebral arteries. Study participants returned 6 weeks postpartum for a non-pregnant measurement of cerebral blood flow. The Wilcoxon paired-sample test was used with statistical significance defined as p<0.05. RESULTS: There was no significant difference in cerebral vessel diameter nor blood flow for any of the examined arteries between the pre- and post magnesium sulfate therapy states. CONCLUSIONS: The absence of a significant difference in cerebral blood flow of the middle and posterior cerebral arteries before and after infusion of a 6 gram loading dose of magnesium sulfate in women with preeclampsia could suggest the absence of vasoconstriction of the large cerebral arteries in preeclampsia and question the role of magnesium sulfate as a vasodilator of these arteries.

Adult↗
PubMed2005

Magnetic resonance imaging pelvimetry and the prediction of labor dystocia.

OBJECTIVE: To study whether magnetic resonance imaging (MRI) pelvimetry has the ability to identify those women who require cesarean delivery for labor dystocia. METHODS: From July 2003 to April 2004, nulliparous women scheduled for a labor induction for prolonged pregnancy (42 weeks) were asked to participate in a pelvimetry study. Those who consented underwent fast-acquisition MRI that included two 90-second acquisitions to evaluate fetal biometry and volumetry and maternal pelvimetry, including novel measurements of pelvic bony and soft tissue volumes as determined by MRI. Information about each patient's pregnancy, labor course, and neonatal outcome was prospectively collected. Pelvimetry results for those women undergoing operative delivery for labor dystocia were compared with those who did not. Single fetal and maternal pelvic measurements, as well as ratios of both, were analyzed. In addition, previously described radiographic pelvimetry techniques and formulas to predict dystocia were used. RESULTS: One hundred one women underwent MRI, and 22 of these underwent cesarean delivery for dystocia. No single fetal measurement was statistically associated with dystocia. Several maternal pelvic measures, fetal-to-maternal ratios, and previously reported pelvimetric techniques were significantly associated with dystocia. The ratio of magnetic resonance (MR) fetal head volume to pelvic soft tissue volume had statistical significance (P = .04). Receiver operator characteristic curves were developed for the different measurements, ratios, and formulas studied to assess whether any of the techniques could accurately predict labor dystocia requiring operative delivery. The area under the curve values ranged from 0.6 to 0.8, with the ratio of MR head volume to pelvic soft tissue being 0.7. These values suggest that MRI can identify those women at greatest risk for dystocia, but it cannot with accuracy predict which ones will require a cesarean. CONCLUSION: We found significant associations with MRI pelvimetry and labor dystocia, but MRI was not a significant improvement over previously described pelvimetric techniques. LEVEL OF EVIDENCE: II-3.

Adult↗
PubMed2005

MRI calculation of lung volumes to predict outcome in fetuses with genitourinary abnormalities.

OBJECTIVE: The purpose of our study was to evaluate MRI total lung volumes (TLV) for predicting outcome in fetuses with genitourinary abnormalities and to compare lung volumes with the presence or absence of oligohydramnios. MATERIALS AND METHODS: Fetuses with genitourinary abnormalities underwent blinded retrospective calculation of TLV. Distribution of the TLV-gestational age ratios for survivors and nonsurvivors were compared using the Wilcoxon's rank sum test. Lung volume calculation was compared with the presence or absence of oligohydramnios. RESULTS: There were 21 survivor and 24 nonsurvivor outcomes based on neonatal discharge. TLV-gestational age ratios were significantly different between the survivor and nonsurvivor groups (p = 0.0001). No apparent difference was seen until after 26 weeks of gestation. TLV-gestational age ratios were equal to the presence or absence of oligohydramnios in predicting outcome after 26 weeks of gestation. CONCLUSION: After 26 weeks' gestation, the prediction of outcome in fetal genitourinary abnormalities using the MRI TLV-gestational age ratio is comparable to the presence or absence of oligohydramnios.

Adult↗
PubMed2005

Fetal MRI of urine and meconium by gestational age for the diagnosis of genitourinary and gastrointestinal abnormalities.

OBJECTIVE: The purpose of our study was to assess the appearance of the colon and genitourinary tract in fetuses with respect to gestational age with T1- and T2-weighted MRI acquisitions and their applications to abnormalities in these systems. MATERIALS AND METHODS: Retrospective review of the fetal MRI database was performed to select studies in which both T1- and T2-weighted acquisitions were obtained. The signal characteristics of fluid in the fetal colon and urine in the fetal bladder were evaluated, and gestational age and fetal MRI diagnosis were recorded. A Mantel-Haenszel chi-square analysis was performed to evaluate the relationship of gestational age to MRI signal intensity. In fetuses with suspected colonic and genitourinary abnormalities, an assessment was made about whether the T1-weighted findings added information to the T2-weighted findings. RESULTS: Eighty fetal MRI studies were reviewed. Forty-three studies showed normal findings, and 37 depicted genitourinary or gastrointestinal abnormalities. The mean gestational age was 27 weeks 6 days. The MRI signal characteristics of urine and meconium became significantly more conspicuous with increasing gestational age (urine bright on T2, p < 0.001; urine dark on T1, p < 0.001; meconium bright on T1, p < 0.001; meconium dark on T2, p < 0.001). Of the 37 cases with suspected problems of the gastrointestinal or genitourinary systems, the T1-weighted images added additional information in 23 cases. CONCLUSION: The appearance of urine and meconium on T1- and T2-weighted images is significantly more apparent with increasing gestational age. T1-weighted images identified meconium in the colon beyond 24 weeks' gestation and aided in the diagnosis of complex abnormalities.

Colon↗
PubMed2004

Cerebral infarction in eclampsia.

OBJECTIVE: This study was undertaken to characterize the neuroimaging findings of cerebral edema associated with eclamptic seizures by use of diffusion-weighted magnetic resonance imaging (MRI). STUDY DESIGN: During the 3-year period ending March 2002, 27 nulliparous women with eclampsia were evaluated with diffusion-weighted MRI and apparent diffusion coefficient mapping. Those with findings of restricted diffusion suggestive of cytotoxic edema underwent neuroimaging again 6 weeks post partum. RESULTS: All but 2 of these 27 women (93%) had reversible vasogenic edema. Six were also found to have areas of cytotoxic edema consistent with cerebral infarction. Five of these 6 women had persistent imaging findings of infarction when studied post partum, however, without clinical neurologic deficits. CONCLUSION: The spectrum of cerebral lesions in eclampsia as seen with MRI varies from initially reversible areas of vasogenic edema that may progress to cytotoxic edema and infarction in up to a fourth of women.

Adult↗
PubMed2004

Correlation of measured amnionic fluid volume to sonographic and magnetic resonance predictions.

OBJECTIVE: The purpose of this study was to compare the relationship between the actual amnionic fluid volume that was measured at delivery and magnetic resonance amnionic fluid volume determination, largest vertical pocket, and amnionic fluid index. STUDY DESIGN: Three hours before cesarean delivery, 80 women had sonographic measurement of the amnionic fluid index and the largest vertical pocket. Magnetic resonance imaging was then completed, and the magnetic resonance amnionic fluid volume was determined. At surgery, the amnionic fluid was collected. Pearson correlations were determined. Receiver operating characteristic curves were developed for each method as a measure of predictability for oligohydramnios. RESULTS: The correlations for the magnetic resonance amnionic fluid volume, amnionic fluid index, and largest vertical pocket to amnionic fluid volume was 0.84, 0.77, and 0.71, respectively. Magnetic resonance amnionic fluid volume has a statistically higher correlation than the largest vertical pocket ( P = .046). The 3 methods, however, are statistically comparable for identifying oligohydramnios. CONCLUSION: Magnetic resonance imaging is comparable with ultrasound evaluation for the prediction of oligohydramnios. Correlations to actual amnionic fluid volume are also comparable.

Adult↗
PubMed2004

Increased cerebral blood flow in preeclampsia with magnetic resonance imaging.

OBJECTIVE: The purpose of this study was to compare third trimester and nonpregnant cerebral blood flow of women with preeclampsia to normotensive control subjects with the use of magnetic resonance imaging techniques. STUDY DESIGN: Nine normotensive pregnant women and 12 untreated women with preeclampsia underwent velocity-encoded phase contrast magnetic resonance imaging of the bilateral middle and posterior cerebral arteries in the third trimester and at 6 to 8 weeks after delivery. The Student t test was used for comparison, with a probability value of <.05 considered significant. RESULTS: Third-trimester large cerebral artery blood flow was significantly higher in preeclampsia. Mean vessel diameter was unchanged, except for the left posterior cerebral artery. There was no difference in mean vessel diameter or cerebral blood flow between the 2 groups while the women were not pregnant. CONCLUSION: Cerebral blood flow is increased significantly in preeclampsia. We hypothesize that increased cerebral blood flow ultimately could lead to eclampsia through hyperperfusion and the development of vasogenic edema.

Adult↗
PubMed2004

Optimization of fetal weight estimates using MRI: comparison of acquisitions.

OBJECTIVE: The purpose of this study was to determine whether differences are seen in calculation of fetal weight using 5-mm sagittal, 3-mm coronal, and 8-mm axial MRI acquisitions compared with term birth weight and contemporaneous sonography. MATERIALS AND METHODS: Fetal volume measurements were obtained from MRI acquisitions as follows: 5-mm sagittal (2 acquisitions), 3-mm coronal (2 acquisitions), and 8-mm axial (1 acquisition). A 90-sec single-shot fast spin-echo sequence was used. MRI and sonographic studies for fetal weight estimates were performed within 3 hr of term delivery. MRI calculation was based on the equation 0.12 + 1.031 x fetal volume (fetal area x slice thickness) (mL) = MRI fetal weight (kg). The sonographic fetal weight estimate was calculated using the Hadlock formula. MRI and sonographic calculations were compared with birth weight. Concordance coefficient analysis was performed. RESULTS: Thirty-five retrospective fetal calculations were performed. Concordance coefficients, gram weight means and standard deviations (mean +/- SD) between birth weight and MRI acquisitions were as follows: 8-mm axial, 0.91 (3,554 +/- 431 g); 3-mm coronal, 0.84 (3,752 +/- 578 g); and 5-mm sagittal, 0.83 (3,685 +/- 567 g), compared with 0.78 (3,518 +/- 332 g) for sonography. The MRI axial concordance coefficient was significantly different from that of the sonographic estimates (p = 0.05). MRI axial concordance coefficient was not statistically different from that of the MRI coronal concordance coefficient (p = 0.22) or the MRI sagittal concordance coefficient (p = 0.19). CONCLUSION: Calculated weights from a 90-sec single-shot fast spin-echo sequence MR acquisition with 8-mm-thick slices in the axial plane at term are better than sonographic estimates.

Adult↗
PubMed2003

Prenatal diagnosis of a prolapsed ureterocele with magnetic resonance imaging.

Ectopic ureterocele with ureteral duplication is the most common type of ureterocele found in children. Early accurate diagnosis is desirable to decrease the risk of urosepsis and renal damage. Prenatal imaging with ultrasonography detects the vast majority of ureteroceles; however, in some cases, the diagnosis may remain in doubt. We report on the use of magnetic resonance imaging to clarify the prenatal diagnosis of a prolapsed ureterocele.

Adult↗
PubMed2003

Megacystis microcolon intestinal hypoperistalsis syndrome with bilateral duplicated systems.

A 29-year-old multigravida woman presented for her second prenatal ultrasound evaluation at 30 weeks of gestation. The study showed a female fetus, bilateral duplicated systems with severe hydronephrosis in the upper pole moieties and a massively distended bladder. Initial interpretation suggested ectopic/obstructing bilateral ureteroceles. To evaluate these findings further, a prenatal magnetic resonance imaging scan was obtained, documenting the absence of ureteroceles. The presumptive diagnosis of megacystis microcolon intestinal hypoperistalsis syndrome was made. After birth, contrast enema confirmed the presence of microcolon. This appears to be the first reported case of megacystis microcolon intestinal hypoperistalsis syndrome with bilateral duplex systems evaluated with prenatal magnetic resonance imaging.

Abnormalities, Multiple↗
PubMed2003

Second-opinion magnetic resonance imaging for suspected fetal central nervous system abnormalities.

OBJECTIVE: The purpose of this study was to evaluate the relationship of magnetic resonance imaging and gestational age in the setting of fetuses with suspected abnormalities of the central nervous system that were detected by ultrasound scanning. STUDY DESIGN: Multiplanar magnetic resonance studies were performed in fetuses with suspected central nervous system abnormalities on ultrasound scanning. Magnetic resonance imaging was evaluated for its ability to provide additional information, change the diagnosis, or impact obstetric treatment. Patients were grouped by gestational age at the time of magnetic resonance imaging. RESULTS: Magnetic resonance imaging provided additional information in 46 of 72 pregnancies (64%), changed the diagnosis in 20 of 72 pregnancies (28%), and potentially altered the timing or mode of delivery in 8 of 72 pregnancies (11%). Additional information increased with increasing gestational age groups (P =.03). CONCLUSION: Magnetic resonance imaging provided additional information in two thirds of the fetuses with central nervous system abnormalities, which was significantly increased with increasing gestation. Antenatal treatment was influenced by magnetic resonance imaging in 11% of the cases.

Central Nervous System↗
PubMed2003

Maternal cerebral blood flow changes in pregnancy.

OBJECTIVE: This study was undertaken to determine blood flow changes in the large cerebral arteries during normal pregnancy. STUDY DESIGN: Ten healthy pregnant volunteers underwent velocity-encoded phase contrast magnetic resonance imaging at 4 time intervals: 14 to 16, 28 to 32, and 36 to 38 weeks' gestation, and at 6 to 8 weeks' postpartum. Analysis consisted of serial paired Student t tests, with P<.05 considered significant. RESULTS: By using postpartum values for comparison, cerebral blood flow decreased by 14 to 16 weeks in the middle cerebral artery (P<.001), but was not significantly changed in the posterior cerebral artery. Significant decreases occurred in both the middle (P<.0001) and posterior (P=.002) cerebral arteries in late pregnancy. CONCLUSION: An approximately 20% reduction in large artery cerebral blood flow occurs during normal pregnancy, secondary to changes in velocity, whereas the area of these vessels remains unchanged. These findings may represent generalized vasodilatation of downstream resistance arterioles, assuming constant blood flow at the tissue level.

Adult↗
PubMed2003

Feasibility of the fetal anatomic and maternal pelvic survey by magnetic resonance imaging at term.

OBJECTIVE: This study was undertaken to determine which nonbiometric components of the American College of Obstetricians and Gynecologists recommended ultrasound fetal anatomic and maternal pelvic survey can be evaluated by fast acquisition magnetic resonance (MR) imaging in the term fetus. STUDY DESIGN: Nonbiometric components of the fetal survey were retrospectively evaluated by fast acquisition MR images. Thirteen components were assessed, including fetal number, presentation, placental location, qualitative assessment of amniotic fluid, and the maternal pelvis (n=5). The fetal anatomy included bilateral cerebral ventricles, spine, bilateral kidneys, stomach, bladder, cord insertion, sex, and four-chamber view of the heart (n=8). Studies were performed before delivery and neonatal outcomes were reviewed. RESULTS: All 50 neonates were normal at follow-up. A total of 94% (702 of 750) of the components were assessed by MR imaging. CONCLUSION: Fetal MR imaging can assess 94% of the American College of Obstetricians and Gynecologists recommended ultrasound fetal and pelvic anatomic survey. If the heart is excluded, this increases to 99%.

Feasibility Studies↗
PubMed2003

Comparison of magnetic resonance imaging to ultrasound in the estimation of birth weight at term.

OBJECTIVE: This study was undertaken to compare magnetic resonance (MR) and ultrasound (US) fetal weight estimates obtained immediately before delivery with birth weight. STUDY DESIGN: Eighty women scheduled for a cesarean delivery underwent a fast acquisition MR and US for fetal weight estimation within 3 hours of delivery. Prospective MR calculation was based on the equation 0.12+1.031 g/mLxfetal volume (mL)=MR weight (g). US fetal weight estimation was calculated by the formula by Hadlock et al. Estimations were compared with birth weight. RESULTS: Correlation (95% CI) between birth weight and MR weight is 0.95 with a mean absolute error of 129 g (105-155) compared with the correlation between birth weight and US of 0.85 with a mean absolute error of 225 g (186-264). The correlation for birth weight and MR imaging is significantly greater than that of birth weight and US, P<.001. CONCLUSION: Birth weight estimation is more accurate by MR imaging than by US in term infants.

Birth Weight↗