Patients with mutations of BRCA have higher risk of pancreatic cancer (3-10 fold for BRCA2; 2.6-3.6 fold for BRCA1¹), and thus should be considered for pancreatic screening programs². At present there is no accepted screening protocol, due to uncertainties in diagnostic performance, potential costs, and invasiveness of some diagnostic tests. Taking advantage of the fact that carriers of BRCA mutations undergo MRI screening for breast cancer, we are developing and optimizing a < 10 minutes fast MR pancreas screening protocol (MRpsp) to be performed at the conclusion of a breast MRI without patient repositioning and using the built-in-body-coil. The protocol includes: axial and coronal T2, axial T1, and reduced Field of View (rFOV) diffusion weighted images (DWI). The aims of this study are: 1) To compare the quality of different b values in rFOV DWI, and 2) to evaluate the inter-reader agreement in normal pancreas ADC measurements.

This prospective study was approved by the local IRB.

Inclusion criteria were: female patients who are BRCA1 or BRCA2 mutation carriers undergoing breast MR screening. MRpsp was performed with a 3T magnet (MR 750, GE Healthcare, United States) after a contrast enhanced breast MR (Multihance, 0.2 ml/kg, Bracco Diagnostics, United States) with patients in the prone position and using the built-in-body-coil. DWI sequence parameters are reported in table 1. DWI of the pancreatic head, body, and tail was evaluated in consensus by two radiologists with a 5 points semi-quantitative score: 1= full diagnostic information is present; 2= most of diagnostic information is present; 3= some diagnostic information is present; 4= minimal diagnostic information is present; 5= non diagnostic. Quantitative analysis was performed by two radiologists with a commercially available post-processing workstation (Advantage Workstation 4.6, GE Healthcare, United States) placing circular, 5 mm diameter Region-of-Interest (ROI) in pancreatic head, body, and tail, and in peripancreatic fat. ROIs were automatically propagated through all the evaluated series and average signal intensity (SI) and standard deviation (SD) per ROI were recorded. Signal-to-Noise Ratio (SNR) was calculated as ROI_SI,Pancreas/ROI_SD,Pancreas. Contrast-to-Noise Ratio (CNR) was calculated as (ROI_SI,Pancreas–ROI_SI,Fat)/ROI_SD,Fat. Inter-reader agreement for ADC measurements was calculated with Intraclass Correlation Coefficient. For DWI, preliminary statistical analysis was conducted separately for lower b-value images (b<100 s/mm²) and for higher b-value images (b>100 s/mm²), considering average of measures of both readers without correction for the NEX variability for different b-values. Non-parametric tests were used, and p values <0.05 were considered significant.

Fifteen patients were imaged (Figure 1).

All low b-value (<100 s/mm²) DWI were ranked as fully diagnostic with the exception of one pancreatic tail (subject 2, rank 3= some diagnostic information, due to inconsistent breathing). As expected, DWI with b-values >100 s/mm² showed higher variability in diagnostic image quality: b=250 s/mm² DWI was ranked significantly better than b=500 s/mm² and b= 800 s/mm² DWI (Wilcoxon, p<0.05). No other significant differences were recorded (Table 2). For DWI with b<100 s/mm², SNR was significantly higher in the pancreatic head, body and tail when using b=20 s/mm². For DWI with b>100 s/mm², no relevant differences were recorded in terms of SNR (Table 3). For DWI with b<100 s/mm² images CNR was significantly higher in the pancreatic head, body and tail, when using b=20 s/mm². For b>100 s/mm² images, no significant differences in CNR were demonstrated (Table 3). ADC values (x10^-3 mm²/s) in pancreatic head, body and tail were respectively for reader 1: 1.35; 1.69; and 1.65; for reader 2: 1.47; 1.55; and 1.59. Values were comparable with the ranges reported in the literature³. Intra-class correlation coefficients between the two readers measuring ADC in different pancreatic regions were 0.6860 (head), 0.8800 (body), and 0.7143 (tail) (Table 4).

All rFOV DWI obtained with built-in-body coil and patient in prone position were of diagnostic quality. At b<100 s/mm², all images were of high diagnostic quality. Among b<100 s/mm² the highest SNR and CNR were obtained when using, b=20 s/mm². Among b>100 s/mm² qualitatively better images were obtained using b=250 s/mm². Limited inter-reader agreement was demonstrated for ADC measurements of the pancreas.