OBJECTIVE: To evaluate the pulsatility index of umbilical artery (UAPI) and middle cerebral artery (MCAPI), as well as the umbilical-cerebral pulsatility (UAPI/MCAPI) ratio in fetuses of hypertensive pregnant women and associated adverse perinatal outcomes. MATERIALS AND METHODS: The authors have analyzed UAPI, MCAPI and UAPI/MCAPI ratio in 289 fetuses of hypertensive women, correlating the results with the presence of adverse perinatal outcomes. Results were compared with and without adjustment for gestational age. RESULTS: Apgar score < 7 at the 5th minute was associated with altered outcomes after adjustment for gestational age. The risk for small-for-gestational-age infant increased three times after such adjustment, with statistical significance for all the Doppler parameters. The increase in risk for neonatal hypoxia after adjustment for gestational age was statistically significant for UAPI and UAPI/MCAPI ratio. No increase was observed in the risk for respiratory distress syndrome in the adjusted analysis. A three-time higher risk for perinatal mortality and altered UAPI with statistical significance was observed after adjustment. CONCLUSION: In fetuses of hypertensive pregnant women, UAPI demonstrated better correlations with perinatal outcomes than MCAPI and UAPI/MCAPI ratio. The risk for adverse gestational outcome should be evaluated taking the gestational age into consideration.

Keywords: Doppler velocimetry, Hypertension, Perinatal outcome

OBJECTIVE: To calculate spectra of cobalt-60 beam at water depth and correction factors for absorbed dose measurements obtained with lithium fluoride thermoluminescent dosimeters using Monte Carlo simulation. MATERIALS AND METHODS: The simulations of secondary spectra of clinical cobalt-60 sources were performed with the PENELOPE Monte Carlo code at different water depths. Experimental measurements of deep doses were obtained with thermoluminescent dosimeters and ionization chamber under reference conditions for radiotherapy. Correction factors for the thermoluminescent dosimeters detectors were obtained through the ratio between the relative energy absorption for the low energy spectrum and the total spectrum. RESULTS: Deep spectral analysis has demonstrated the presence of secondary low-energy spectra responsible for a significant portion of the dose deposition. Discrepancies of 3.2% were observed among the doses measured with ionization chamber and thermoluminescent dosimeters. The adoption of correction factors has allowed a reduction in the discrepancy among absorbed doses to a maximum of 0.3%. CONCLUSION: Simulated spectra allow the calculation of correction factors for reading of thermoluminescent dosimeters utilized in the measurement of deep doses, contributing for the reduction of uncertainties associated with quality control of clinical beams in radiotherapy.

Keywords: Monte Carlo simulation, Radiotherapy, Spectrometry, Quality control, Thermoluminescent dosimetry, TLD

OBJECTIVE: The PENELOPE code was utilized to simulate irradiation geometries where heterogeneities are present and to simulate a photon beam behavior under these conditions. MATERIALS AND METHODS: For the homogeneous case, the ionizing radiation behavior was simulated only with water, and different materials were introduced to simulate heterogeneous conditions. Cubic geometries were utilized for the homogeneous phantoms, and parallelepiped-shaped geometries for the heterogeneities with the following composition: bone and lung tissue simulators, as recommended by the International Commission on Radiological Protection, and titanium, aluminum and silver. Input parameters were defined as follows: energy and type of source, 6 MV photons; source-surface distance=100 cm; and radiation field of 10x 10 cm². RESULTS: Percentage depth-dose curves were obtained for all the cases. As result, it was observed that for high electronic density materials, such as silver, the absorbed dose is higher than the absorbed dose in the homogeneous phantom, and for the lung tissue simulator, it is lower. CONCLUSION: Results clearly demonstrate the relevant role of heterogeneities in the treatment planning system algorithms utilized in the calculation of dose distribution in patients, increasing the accuracy of the dose delivered to the tumor and avoiding unnecessary irradiation of healthy tissues.

Keywords: Radiotherapy, Monte Carlo, PENELOPE, Heterogeneities, Depth-dose distribution

Necrotizing enterocolitis is one of the most frequent and severe gastrointestinal emergencies occurring in the neonatal period. Once necrotizing enterocolitis is suspected a simple abdominal x-ray is a routine examination and this film will play an essential role in the diagnosis of the disease and the follow-up care of the patient, as well as in the detection of complications. In the present study we reviewed the pertinent literature and described the radiological findings, illustrated with cases from our institution. We concluded that the radiological diagnosis of necrotizing enterocolitis done at all stages contributes for an immediate therapeutic management, reducing the complications and improving the patient's survival.

Keywords: Necrotizing enterocolitis, Newborn, Radiological diagnosis

OBJECTIVE: To evaluate the prognostic value of bowel loops dilatation as a finding on radiographs in the development and mortality of neonates with necrotizing enterocolitis. MATERIALS AND METHODS: On abdominal radiographs of 53 patients for diagnostic suspicion of necrotizing enterocolitis, the major diameters of dilated bowel loops (AD) were measured, as well as the distance between the upper border of the first lumbar vertebra and the lower border of the second one (L1-L2), and the distance between the lateral borders of the first lumbar vertebra (L1) pedicles, and the subsequent association between AD/L1-L2, AD/L1. This measure was considered as a possible determining factor for potential complications, surgical intervention and mortality. RESULTS: The patients who needed surgical management and who had complications during progression and died of the disease had showed increased AD and AD/L1-L2 (p < 0.05). AD/L1 values and site of the most dilated bowel loop were not different in the groups with unfavorable progression. CONCLUSION: Bowel loop dilatation detected on initial supine abdominal radiographs suggests a worst prognosis in necrotizing enterocolitis. Furthermore, measurement of the most dilated bowel loop on these radiographs is a simple and reproducible method that adds diagnostic and prognostic information.

Keywords: Necrotizing enterocolitis, Radiography, Progression

OBJECTIVE: The present study was aimed at analyzing the value of the early diagnosis of hemodynamic changes in hemorrhages and hypoxic-ischemic events in premature, very-low-birth-weight neonates through the evaluation of images and resistance index measurement by means of transcranial Doppler ultrasonography. MATERIALS AND METHODS: Fifty premature, very-low-birth-weight neonates were submitted to transcranial Doppler ultrasonography with sequential transfontanellar and transtemporal techniques. RESULTS: Cerebral abnormalities were detected in 32% of the neonates (22% with intracranial hemorrhage, 8% with periventricular leukomalacia, and 2% with toxoplasmosis). Among the 34 cases (68%) of neonates in whom no brain lesion was detected at transcranial Doppler ultrasonography, 18 (53%) presented changes in the resistance index. Such resistance index varied according to the time of the examination. CONCLUSION: There is a correlation between the presence of cerebral hemodynamic changes demonstrated by resistance index measurements and the subsequent development of hemorrhages and hypoxic-ischemic lesions. Although not being a death predictor, changes in the resistance index are associated with the severity of the clinical conditions in preterm, very-low-birth-weight neonates.

Keywords: Transcranial Doppler ultrasonography; Premature, very-low-birth-weight neonates; Ultrasonography; Resistance index.

Objective: To compare data regarding dosimetry and photons fluence in different breast phantoms, discussing constancy tests and dosimetry applied to mammography. Materials and methods: Different homogeneous breast phantoms and one anthropomorphic voxel phantom were developed for collection of data regarding total absorbed dose in the phantom, absorbed dose in the glandular tissue material-equivalent, absorbed dose and photons fluence at different depths in the phantoms. A simulated ionization chamber collected the entrance skin kerma. Target-filter combinations (Mo-30Mo and Mo-25Rh) were studied for different accelerating potentials of 26 kVp to 34 kVp. Results: As compared with the voxel phantom, the normalized glandular dose resulted in differences from –15% to –21% for RMI, –10% for PhantomMama, and 10% for the Barts and Keithley models. The half-value layer variation was generally < 10% for all the sensitive volumes. Conclusion: The phantom proposed by Dance is recommended for evaluating the glandular dose and normalized glandular dose in a standard breast. Homogeneous phantoms should be utilized for constancy tests in dosimetry, but they are not appropriate for estimating dosimetry in actual patients.

Keywords: Mammography; Dosimetry; Monte Carlo simulation; Geant4.

The authors report a case of umbilical venous catheter malposition with air in the portal venous system in a preterm neonate. Initially, the hypothesis of necrotizing enterocolitis was considered, but the newborn progressed with no finding of disease and the air disappeared at follow-up radiography. The differential diagnosis of such a finding can avoid unnecessary clinical treatments.

Keywords: Umbilical venous catheter; Newborn; Portal air; Necrotizing enterocolitis; Radiological study.

OBJECTIVE: Derive filtered tungsten X-ray spectra used in digital mammography systems by means of Monte Carlo simulations. MATERIALS AND METHODS: Filtered spectra for rhodium filter were obtained for tube potentials between 26 and 32 kV. The half-value layer (HVL) of simulated filtered spectra were compared with those obtained experimentally with a solid state detector Unfors model 8202031-H Xi R/F & MAM Detector Platinum and 8201023-C Xi Base unit Platinum Plus w mAs in a Hologic Selenia Dimensions system using a direct radiography mode. RESULTS: Calculated HVL values showed good agreement as compared with those obtained experimentally. The greatest relative difference between the Monte Carlo calculated HVL values and experimental HVL values was 4%. CONCLUSION: The results show that the filtered tungsten anode X-ray spectra and the EGSnrc Monte Carlo code can be used for mean glandular dose determination in mammography.

Keywords: Mammography; X-ray spectra; HVL; Monte Carlo.

OBJECTIVE: To perform a comparative dosimetric analysis, based on computer simulations, of temporary balloon implants with ^99mTc and balloon brachytherapy with high-dose-rate (HDR) ¹⁹²Ir, as boosts to radiotherapy. We hypothesized that the two techniques would produce equivalent doses under pre-established conditions of activity and exposure time. MATERIALS AND METHODS: Simulations of implants with ^99mTc-filled and HDR ¹⁹²Ir-filled balloons were performed with the Siscodes/MCNP5, modeling in voxels a magnetic resonance imaging set related to a young female. Spatial dose rate distributions were determined. In the dosimetric analysis of the protocols, the exposure time and the level of activity required were specified. RESULTS: The ^99mTc balloon presented a weighted dose rate in the tumor bed of 0.428 cGy.h^-1.mCi^-1 and 0.190 cGyh^-1.mCi^-1 at the balloon surface and at 8-10 mm from the surface, respectively, compared with 0.499 and 0.150 cGyh^-1.mCi^-1, respectively, for the HDR ¹⁹²Ir balloon. An exposure time of 24 hours was required for the ^99mTc balloon to produce a boost of 10.14 Gy with 1.0 Ci, whereas only 24 minutes with 10.0 Ci segments were required for the HDR ¹⁹²Ir balloon to produce a boost of 5.14 Gy at the same reference point, or 10.28 Gy in two 24-minutes fractions. CONCLUSION: Temporary ^99mTc balloon implantation is an attractive option for adjuvant radiotherapy in breast cancer, because of its availability, economic viability, and similar dosimetry in comparison with the use of HDR ¹⁹²Ir balloon implantation, which is the current standard in clinical practice.

Keywords: Breast brachytherapy; Balloon; Radiotherapy dosage; Radiotherapy, adjuvant; ^99mTc; ¹⁹²Ir; Monte Carlo method.

OBJECTIVE: To determine whether preterm infants diagnosed with intracranial hemorrhage (by transfontanellar ultrasound) at birth have cerebral lesions that are detectable by magnetic resonance imaging (MRI) upon reaching school age. MATERIALS AND METHODS: MRI scans of the brain were obtained in 22 school-age children. Fifteen had presented intracranial hemorrhage at birth, and seven had not. We calculated the odds ratio (OR) for the occurrence of brain alterations detectable by MRI and the kappa index for discrepancies among the radiological reports. RESULTS: The children without previous intracranial hemorrhage presented normal MRI findings. Of the 15 children with previous intracranial hemorrhage, 6 (40%) presented brain alterations on MRI: isolated ventricular alteration (dilation and asymmetry), in 2 (13.3%); and ventricular asymmetry accompanied by parenchymal lesion, in 4 (26.7%). The nine remaining children with previous intracranial hemorrhage (60%) presented normal MRI findings. The children with previous intracranial hemorrhage were more likely to present ventricular alteration (OR = 7.8) and parenchymal lesions (OR = 5.4). CONCLUSION: Ventricular and parenchymal brain alterations detected by MRI suggest isolated morphologic alterations that do not result in neurological impairment detectable on physical examination in school-age children.

Keywords: Newborn; Premature; Intra]cranial hemorrhage; Magnetic resonance imaging; Child.

OBJECTIVE: To analyze the radiological aspects of pulmonary atelectasis in newborns on mechanical ventilation and treated in an intensive care unit, associating the characteristics of atelectasis with the positioning of the head and endotracheal tube seen on the chest X-ray, as well as with the clinical variables. MATERIALS AND METHODS: This was a retrospective cross-sectional study of 60 newborns treated between 1985 and 2015. Data were collected from medical records and radiology reports. To identify associations between variables, we used Fisher’s exact test. The level of significance was set at p < 0.05. RESULTS: The clinical characteristics associated with improper positioning of the endotracheal tube were prematurity and a birth weight of less than 1000 g. Among the newborns evaluated, the most common comorbidity was hyaline membrane disease. Atelectasis was seen most frequently in the right upper lobe, although cases of total atelectasis were more common in the left lung. Malpositioning of the head showed a trend toward an association with atelectasis in the left upper lobe. CONCLUSION: Pulmonary atelectasis is a common complication in newborns on mechanical ventilation. Radiological evaluation of the endotracheal tube placement provides relevant information for the early correction of this condition.

Keywords: Pulmonary atelectasis/diagnostic imaging; Respiration, artificial; Infant, newborn; Premature birth; Infant, low birth weight.