A novel method for CT dosimetry with a suspended phantom setup.

PURPOSE: This work presents a method for estimating CT dosimetric indices with a prototype designed for suspending the phantom/ion chamber system fixed at the CT isocenter. The purpose of this study was to validate the proposed methodology, which can be used to provide a direct assessment of dosimetric indices in helical scans. METHODS: The method is based on a reference setup in which the measuring system for CT dosimetry is in a stationary configuration, i.e. not bound to the CT table, and on a mathematical formalism developed for the proposed reference system. The reliability of the method was demonstrated through a set of experimental measurements. Firstly, dosimetric indices were measured with the new method and compared with the indices obtained with the procedure currently used for CT dosimetry (measuring system bound to the CT table). Secondly, dosimetric indices measured with the new method were compared with those displayed on the CT console. RESULTS: There is good agreement between the dosimetric indices obtained with the standard setup and those obtained with the suspended phantom setup, within the expected range of errors. The difference between dosimetric indices estimated with the proposed method and those displayed on the CT console is below 2%. CONCLUSIONS: The method enables CT dosimetry to be performed with the dose detector in a stationary longitudinal position thanks to the newly introduced suspended phantom setup. Using this approach, CT dose can be assessed for high pitch helical scans, acquisitions without complete tube rotation and for cases where dynamic collimation is used.

Management and follow-up of pediatric asymptomatic testicular microlithiasis: are we doing it well?

PURPOSE: To define timing and methods for a balanced follow-up of testicular microlithiasis (TM) in pediatric age. MATERIALS AND METHODS: We retrospectively reviewed medical records of 21 pediatric asymptomatic patients (42 testicular units) diagnosed with TM and without associated risk factors. Microliths were found bilaterally on ultrasonography in all the patients. Distribution of microliths (focal or diffuse) inside the parenchyma was evaluated as well as its eventual variation over time. Every six months, each patient underwent clinical and ultrasonography evaluation, as well as serum chemistry markers (α-fetoprotein and ß-human chorionic gonadotropin) measurement to detect potential malignancy. In the interval between the follow-ups, parents and/or patients themselves were asked to control eventual enlargement of the gonads or scrotal swelling. Testicular biopsy was not performed in any of our subjects. RESULTS: Of 21 patients, 6 had unilateral undescended testis, 4 varicocele, and 1 patent processus vaginalis with scrotal swelling while 10 patients did not show associated anomalies. The distribution pattern of microliths on ultrasonography remained unchanged in all follow-ups in every patient, showing a predominance of diffuse pattern in the undescended testis series. Tumor markers remained within normal limits. In no subject, we observed a shift toward a malignant condition. CONCLUSION: In the pediatric population with an incidentally diagnosed TM and without any associated risk factor, a slight follow-up is suggested, consisting of clinical evaluation every 6 months, without any justifiable recommendation to perform a testis biopsy and a measurement of serum tumor markers.

Comparison of contrast and noncontrast magnetic resonance angiography for quantitative analysis of thoracic arteries in young patients with congenital heart defects.

BACKGROUND: Contrast MRA (C-MRA) is the standard for quantitative analysis of thoracic vessels. We evaluated a noncontrast MRA (NC-MRA) sequence (3-D EKG and navigator-gated SSFP) for quantitative evaluation of the thoracic aorta and branch pulmonary arteries in young patients with congenital heart disease. OBJECTIVE: To compare contrast and noncontrast magnetic resonance angiography for quantitative analysis of thoracic arteries in young patients with congenital heart defects. METHODS: Measurements of thoracic aorta and branch pulmonary arteries were obtained from C-MRA and NC-MRA images in 51 patients, ages 2-35 years. Vessel diameters were compared using correlation and Bland-Altman analysis. Interobserver variability was assessed using percent variation. RESULTS: C-MRA and NC-MRA measurements were highly correlated (r = 0.91-0.98) except for the right pulmonary artery (r = 0.74, 0.78). Agreement of measurements was excellent (mean difference -0.07 to -0.53 mm; mean % difference -1.8 to -4.9%) except for the right pulmonary artery which was less good (mean difference 0.73, -1.38 mm; -3, -10%). Interobserver variability ranged from 5% to 8% for aortic and from 10% to 16% for pulmonary artery measures. The worse agreement and greater variability of the pulmonary artery measures appears due to difficulty standardizing the measurements in patients with abnormal and irregular vessels. CONCLUSION: These data indicate that C-MRA and NC-MRA measures are comparable and could be used interchangeably, avoiding administration of contrast in selected patients.

The impact of perinatal urinoma formation on renal function: our experience and review of the literature.

INTRODUCTION: A urinoma is a fluid mass consisting of extravasated urine in the perirenal space. Its impact on renal function was analysed. METHODS: All cases of prenatal and neonatal urinoma reported in the literature were analysed as well as two cases recently observed in our department. RESULTS: A review of all prenatally diagnosed urinomas revealed 25 cases, for a total of 30 renal units. The cause of obstruction was: lower urinary tract (LUT) obstruction in 16 cases (62.5%), upper urinary tract (UUT) obstruction in seven cases (29.5%) and unknown in two cases (8%). A preserved renal function was found in only 30% of all cases. Furthermore, prognosis for renal function was better in posterior urethral valve (PUV) patients than in uretero-pelvic junction obstruction (UPJO) patients. In addition, we analysed 35 published cases of urinoma with a neonatal onset, without prenatal diagnosis, and secondary to LUT obstruction in 27 cases (77%), UUT obstruction in seven cases (20%), while the underlying cause was unknown in one cases (3%). A preserved renal function was observed in 84% of cases with UUT obstruction and in 80% of cases presenting a LUT obstruction. CONCLUSIONS: Prognosis concerning renal function seems to be mainly related to two factors: age at presentation and underlying diagnosis. Decompression of the urinary tract by urine extravasation produces the best results in terms of preservation of the renal function in LUT obstruction (75% in prenatal and 84% in postnatal cases); UUT obstruction however is associated with a good prognosis in the neonatal period (80% of preserved renal function) but with a severe impairment (only 20% of preserved renal function) in prenatally detected cases.