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PubMed1996

Fetal radiation exposure is minimal after pelvimetry by modified digital radiography.

OBJECTIVE: Our purpose was to determine the maximal fetal exposure to radiation by use of thermoluminescent dosimeters when pelvic measurements were performed by standard or modified digital radiography. STUDY DESIGN: Digital radiography of the pelvis was performed according to a standard technique. Lithium fluoride thermoluminescent dosimeters were positioned on the patient's skin to quantitate the maximal amount of radiation exposure to the fetus. The standard technique often included a portion of fetal vertex. The axial view technique was modified to use an angle of inclination of 17 to 29 degrees relative to the vertical axis. RESULTS: Digital radiography was well tolerated and interpretable images were consistently obtained. The maximal dose to the fetal vertex by use of the standard digital axial slice was 465 mrad. By modifying the standard digital technique and using an angle of inclination of 17 to 29 degrees it was possible to obtain an axial section without including any portion of the fetal vertex. This reduced the maximal total dose to the fetal vertex to 55 mrad, which is less than the background radiation exposure to the fetus over a 9-month period from natural sources. CONCLUSION: Data reported indicate that total fetal radiation exposure is minimal after pelvimetry by digital radiography. Incorporating the modification of the angle for the axial slice, as reported here, resulted in a further significant decrease in fetal radiation exposure.

Female↗

PubMed2003

[Computerized tomography pelvimetry: recent advances].

We describe a new technique of pelvimetry by computerized tomography (CT), using multislice-CT. This new technique can provide measurements of the classical diameters and is able to bring new informations on anatomical aspect of the bony pelvis, especially of the superior strait, with images easier to understand by obstetricians and midwives. It is a simple technique to perform, without increasing cost. No additional irradiation is needed, but this point has to be confirmed by multicenter evaluation.

Adult↗

PubMed1994

[Pelvimetry using various magnetic resonance tomography techniques vs. digital image enhancement radiography: accuracy, time requirement and energy exposure].

In 50 patients with suspected or proven cephalo-pelvine disproportion pelvimetry was performed with MR-tomography using a gradient-echo-sequence (FLASH 2D) before or after labour. Results were compared with measurements using digital radiography. In principle, both methods are exchangeable. The sagittal pelvic in- and outlet bispinous diameters are well reproducible. On the other hand, the transverse pelvic inlet and the distance between the ischiatic tubera are not so reliably reproduced. The accuracy of measurement does not depend on individual pelvic distances. Critical statistical analysis demonstrates, that in the worst case differences between the two methods might become unacceptable. Our results indicate two major reasons: 1. there are interobserver problems which cannot be neglected, and 2. the anatomical definition of referential landmarks for the measurements is unsafe. In 10 volunteers, a comparison was made between a T1-weighted spin-echo sequence (SE), a fast gradient echo sequence (FLASH-2D) and an ultrafast gradient echo technique (Turbo-FLASH). For the examination techniques presented here, the high-frequency exposure load or specific absorption rate (SAR loc and SAR total) is below the values permitted by the German Federal Health Bureau (Bundesgesundheitsamt). Whereas the exposure load in case of spin-echo takes (SE) is 22fold higher than with the gradient echo technique (GHE), the load values of ultra-fast GE (usGE) are only about 16% of the 2D-FLASH sequence or about 0.007% of SE. The difference in image quality does not affect the accuracy of measurement.

Adolescent↗

PubMed1988

[Pelvimetry using magnetic resonance tomography].

20 woman were examined before and after partum by means of conventional and magnetic resonance pelvimetry. Besides the usual data regarding the morphology and diameters of the pelvis, MRI gives information on the soft tissues of the birth canal without the added risk of irradiation to the mother and foetus. As shown by studies done in the USA it is also possible to determine foetal maturity by MRI; this will be done in the future.

Female↗

PubMedDate not supplied

Improving the accuracy of digital CT pelvimetry.

Digital pelvimetry is performed to assess the feasibility of vaginal breech delivery. This provides measurements of the anteroposterior inlet, transverse inlet, and interspinous distance. The transverse inlet measurement determined from an anteroposterior ScoutView can be inaccurate if its level is not at the gantry isocenter. Using a simple geometric argument, the theoretical error of this measurement is calculated and a method provided to allow for correction of this error.

Humans↗

PubMed1993

Vaginal delivery after previous caesarean section: is X-ray pelvimetry necessary?

OBJECTIVE: To determine whether antepartum X-ray pelvimetry (XRP) reliably identified women suitable for a trial labour or repeat elective caesarean section after one previous section. DESIGN: A prospective controlled trial in which women were randomly allocated to either an antepartum XRP group who had XRP at 36 weeks gestation to determine mode of delivery, or a control group who had a trial labour without antepartum XRP. Following delivery, all controls had postpartum XRP. SETTING: Department of Obstetrics and Gynaecology, King Edward VIII Hospital, Durban, South Africa. SUBJECTS: Three hundred-six women with a history of one previous caesarean section. MAIN OUTCOME MEASURES: Mode of delivery, birthweight and maternal and perinatal mortality and morbidity in the two groups. RESULTS: In the antepartum XRP group, 23 of 144 (16%) of women delivered vaginally compared with 60 of 144 (42%) controls (P < 0.0001). Of the 84 women with adequate antepartum XRP only 23 (27.7%) delivered vaginally. In the control group, 33 of 60 (55%) women who had vaginal deliveries had inadequate postpartum XRP and would have had a caesarean section if this information was known in the antepartum period; 62 of 84 (74%) caesarean sections in the control group had adequate postpartum XRP. Birthweight of the infants was similar in the two groups. There were no maternal or perinatal deaths. Maternal morbidity was similar in the two groups. Neonatal morbidity was minimal. CONCLUSION: Antepartum XRP is not necessary prior to a trial labour in women with one previous caesarean section. It increases the caesarean section rate and is a poor predictor of the outcome of labour.

Adult↗

PubMed1986

Artifacts seen during CT pelvimetry: implications for digital systems with scanning beams.

During computed tomography (CT) pelvimetry of two pregnant women, bony abnormalities of the fetuses were noted on the scout images that were not confirmed at delivery. To explore the cause of these artifacts, specimen long bones were manipulated in various ways during CT scout imaging. Artifacts like those seen during in vivo imaging were found to be caused by motion of the object. The CT scout view is an example of an image produced by a digital system that uses a scanning beam. This type of digital system is being used for several types of body imaging including screening for scoliosis and chest radiography. Attention to motion artifacts should decrease diagnostic errors and aid further development of these systems.

Adult↗

PubMed1989

Fetal dose estimates for CT pelvimetry.

Fetal and maternal dose estimates for computed tomographic pelvimetry have been obtained from phantom measurements. Use of routine abdomen imaging techniques may result in localized fetal doses in excess of 13 mGy (1.3 rad). With the use of a low-exposure (40-mAs) technique, it is possible to obtain images of acceptable quality for the necessary measurements. The resulting dose to the fetus is approximately 2.3 mGy (0.23 rad).

Female↗

PubMed1991

Improvement in CT pelvimetry.

When computed tomographic (CT) digital radiography is used for pelvimetry, measurement error may occur. Geometric distortion in the lateral direction of the CT digital radiograph can lead to an error in any measurement of the transverse pelvic inlet. The authors measured the magnitude of this error on two scanners and present a general method for correction of this potential error. The authors also showed that an additional dose reduction is possible if the patient is imaged in the posteroanterior rather than anteroposterior projection.

Female↗

PubMed1984

A low-dose CT-pelvimetry.

The suitability of CT for pelvimetry was studied. For accurate measurement of the true conjugate and interspinous diameter, a lateral topogram and an axial CT slice were taken. The radiation dose was reduced from 1 mGy (in conventional system) to 0.1-0.2 mGy.

Female↗

PubMed1985

Pelvimetry by magnetic resonance imaging.

Sagittal and transverse multisection magnetic resonance imaging (MRI) in 10 patients was used to obtain dimensions of the maternal pelvis, determine fetal position, and examine maternal and fetal soft tissues. Dimensions were measured with less than 1% instrument error, and bony landmarks were readily identified. MR pelvimetry is an accurate technique for obtaining traditional pelvimetric measurements without exposure to ionizing radiation. These techniques can be further used to investigate soft-tissue dystocia and obstructed labor.

Dystocia↗

PubMed2002

MR obstetric pelvimetry: effect of birthing position on pelvic bony dimensions.

OBJECTIVE: The aim of our study was to measure the impact of supine and upright birthing positions on MR pelvimetric dimensions. MATERIALS AND METHODS: MR pelvimetry was performed in 35 nonpregnant female volunteers in an open 0.5-T MR imaging system with patients in the supine, hand-to-knee, and squatting positions. The obstetric conjugate; sagittal outlet; and interspinous, intertuberous, and transverse diameters were compared among positions. RESULTS: With patients in the hand-to-knee and squatting positions, the sagittal outlet (11.8 +/- 1.3 cm and 11.7 +/- 1.3 cm) exceeded that in the supine position (11.5 +/- 1.3 cm; p = 0.002 and p = 0.01, respectively), as did the interspinous diameter (11.6 +/- 1.1 cm and 11.7 +/- 1.0 cm vs 11.0 +/- 0.7 cm; p < 0.0001, in both cases). Intertuberous diameter was wider with patients in the squatting position than in the supine position (12.7 +/- 0.8 cm vs 12.4 +/- 1.1 cm; p = 0.01). Only the obstetric conjugate was smaller with patients in the upright squatting position than in the supine position (12.3 +/- 0.8 cm vs 12.4 +/- 0.9 cm; p = 0.01). Transverse diameter did not change significantly in any position. CONCLUSION: An upright birthing position significantly expands female pelvic bony dimensions, suggesting facilitation of labor and delivery.

Adult↗

PubMed1975

[Pelvimetry (author's transl)].

A simple and precise technique for pelvimetry, delivering only a low dose of irradiation, is described. It includes the usual lateral view, but for the AP uses that of Fernstroëm. The technique and results are described.

Humans↗

PubMed1991

[The prognostic importance of ultrasonic pelvimetry in anatomically contracted pelvis].

The lesser pelvis parameters measured by ultrasonic pelvimetry are characterized by different prognostic value for the functional assessment of various anatomic forms of contracted pelvis. Direct dimensions of the lesser pelvis, a difference of direct size of the orifice and fetal head biparietal size, and the pelviocranial index are prognostically the most valuable for patients with generally contracted pelvis. The same parameters are valuable for cases with Deventer's pelvis, and the sacrum flattening index value is also significant here. This latter characteristic is the only one prognostically valuable for cases with mesatipellic pelvis, permitting the prediction of possible labor complications.

Adult↗

PubMed1991

Magnetic resonance imaging of the female bony pelvis: MRI pelvimetry.

Magnetic resonance imaging (MRI) was used for the evaluation of the bony pelvis in 4 pregnant and 10 non-pregnant women. The anatomical details and shape of the bony pelvis were easily examined and the main pelvic measurements were estimated on the sections and programs. The end points were easily demonstrated. There was no need to correct for magnification. The study confirmed that MRI is a very valuable technique for assessment of the pelvis. Although it is expensive, it overcomes the technical difficulty of the other methods used for pelvimetry.

Adult↗

PubMed1991

A modified method of CT pelvimetry.

The authors describe a simplified routine procedure for CT pelvimetry. The procedure was successfully performed in 122 women with a 2% false positive rate corresponding to obese women. The originality of the procedure consists in the development of a simple technique of correction of the widest transverse diameter based on the anteroposterior topogram. The values obtained are transformed into real values of the transverse inlet diameter measurements. The procedure presented is simple, accurate, and enables considerable reduction of fetal radiation exposure.

Cesarean Section↗

PubMed1991

The cephalopelvic disproportion index. Combined fetal sonography and x-ray pelvimetry for early detection of cephalopelvic disproportion.

The smallest pelvic diameter (either the anteroposterior of the inlet or the bispinal of the midpelvis) was determined with x-ray pelvimetry and compared to the biparietal diameter of the fetal head at term as determined with sonography. The difference between the two indicates how much wider the smallest diameter of the bony pelvis is than the fetal skull and was termed the cephalopelvic disproportion index. Vaginal delivery was impossible when the index was less than 9 mm and impossible or very difficult when between 9 and 12 mm. When it was greater than or equal to 13 mm, 26% needed a cesarean section, 19% had a difficult vaginal delivery, and the rest delivered vaginally with minimal or no difficulty. This technique clearly indicates when a vaginal delivery is impossible (index less than 9 mm) or very difficult (index less than 13 mm). The specificity was 100%. The index therefore can recognize, before labor, the cases of obvious cephalopelvic disproportion that contraindicate a trial of labor. It does not indicate, however, if a vaginal delivery is possible in the setting of a high index (sensitivity, 51%) because of the interference of other factors besides the cephalic and pelvic bony dimensions considered here. The index may prove most important in determining if a vaginal birth should occur after a cesarean section because it can clearly identify some patients who need a repeat cesarean section.

Delivery, Obstetric↗

PubMed1990

[Pelvimetry using computerized tomography. I. Theoretical and methodical fundamentals].

The first part of our article deals with the basic aspects of using computed tomography in obstetrical pelvimetry. A macerated osseous female pelvis was used to measure the true conjugate, the transverse plane of the pelvic inlet, the interspinous line and the distance between the ischial tuberosities. The same pelvis was then examined computed tomographically. A lateral and a posterior-anterior scan, and a single scan through the iliac spines were performed. The results of the direct measurement agreed highly with the values achieved computed tomographically if the phantom was positioned exactly on the mid-line of the examination-table, if not, the true conjugate was elongated. Measurements of the superficial and the intravaginal radiation dose in patients demonstrated a significantly lower risk in computed tomography than in conventional x-ray methods. We recommend computed tomography in obstetrics as a safe, accurate and reliable method.

Female↗