The use of fetal MRI for renal and urogenital tract anomalies

Fetal anomalies are detected in approximately 2% of all fetuses and, among these, genitourinary tract abnormalities account for 30% to 50% of all structural anomalies present at birth. Although ultrasound remains the first line diagnostic modality, fetal MRI provides important additional structural and functional information, especially with the development of faster sequences and the use of functional sequences. The added value of MRI-based imaging is three-fold: (a) improvement of diagnostic accuracy by adequate morphological examination, (b) detection of additional anomalies, and (c) in addition, MRI has the potential to provide information regarding renal function. In this review, we describe the role of fetal MRI in the anatomical evaluation of renal and urogenital tract anomalies, and we also touch upon the contribution of functional MRI to the diagnostic workup of these conditions.     

The use of image fusion in prenatal medicine

Fusion imaging (FI), the simultaneous display of the same anatomical region using two imaging modalities, has been used in other areas of medicine for both diagnosis and guiding interventions. Examples include positron emission tomography-computed tomography (PET-CT) imaging in oncology and ultrasound-magnetic resonance imaging (US-MRI) fusion in biopsies of the prostate gland. The underlying principle is to take advantage of the complementary information in each modality to improve accuracy, be it diagnostic accuracy or targeting accuracy in biopsies. For example, PET-CT overlays the metabolic activity of lesions on the superb spatial and anatomical detail of CT. While the historical mainstay of fetal imaging has been ultrasound, advances in ultrafast MR imaging together with advances in fetal MRI over the past two decades, have resulted in the opportunity to explore fusion imaging in fetal medicine. We present an overview of the principles of US-MRI fusion imaging in prenatal medicine, report our local experience, and review the literature in this emerging area. We share our perspective on how FI can improve diagnostic confidence, be used as an educational tool, and potentially enhance guidance in certain fetal procedures.     

Bioaccumulation and elimination of tetrachlorobenzyltoluene (TCBT) by the rat and by fish

A comparative study has been made of the bioaccumulation and elimination by fish and the rat of (i) tetrachlorobenzyltoluene (TCBT), a substance recently proposed as a substitute for polychlorobiphenyl (PCB), and (ii) DP5, a pentachlorobiphenyl mixture (PCB-5 C1).

The study relating to fish (Brachydanio Rerio) comprised a 30-day accumulation period followed by a 30-day elimination period. Nominal concentrations of TCBT and PCB-5 C1, respectively, in the water, were 1mg/litre in both cases.

The study relating to the rat comprised a 90-day treatment period followed by a 30-day elimination period. The animals were exposed by oral (gavage) to doses of 0, 5, 30, and 200 mg/kg/day in the case of TCBT and to the single dose of 5 mg/kg/day in the case of PCB-5 Cl.

Concentrations of TCBT and PCB-5 Cl in rat liver and fats, in whole body tissues of fish and in water were measured by gas chromatography, using an electron capture detector.

Results showed a clear difference between TCBT and PCB-5 Cl: in fish, bioaccumulation of TCBT was relatively slight and the 50% depuration time was approximately 26 days; in rat liver and fats, TCBT was also only weakly accumulated and rapidly eliminated. This contrasted sharply with the findings for PCB-5 Cl, viz: high accumulation potential and slow elimination.

Observed rates of bioaccumulation and elimination of TCBT and PCB-5 Cl by the rat were in good agreement with the toxicological findings for the same species.