Added value of MRI tractography of peri-prostatic nerve plexus to conventional T2-WI in detection of extra-capsular extension of prostatic cancer.

PURPOSE: To evaluate the role of DTI (with fibretracking) and T2-weighted imaging (T2-WI) used together for predicting extra-capsular extension in patients with localized prostate cancer. METHOD AND MATERIALS: Thirty-six patients with biopsy-proven diagnosis of prostatic neoplasia performed MRI and underwent radical prostatectomy. Histopathological analysis showed ECE in 15/36 and capsule sparing in 21/36. By means of T2-WI, ECE was evaluated in a qualitative manner, according to PI-RADS v.2 (two groups with low and high risk of ECE); sensitivity and specificity were calculated for both groups. We performed a quantitative analysis on two tractographic parameters, fractional anisotropy (FA) and apparent diffusion coefficient (ADC) and computed the ratio between the lesion quadrant and its contralateral (L/H ratio). We compared L/H ratios of patients with and without ECE; ROC analyses were performed to determinate ECE cut-off values of tractographic parameters. These cut-off values were used in association with T2-WI to reassess patients and to evaluate whether specificity and sensitivity of ECE detection change. RESULTS: T2-WI showed a sensitivity of 80% and a specificity of 71% in detection of ECE. Tractography displayed a significant difference in L/H ratio for FA and ADC between patients with and without ECE. The simultaneous use of T2-WI and tractography revealed high sensitivity (100%) on patients with low suspect of ECE (on T2-WI) and high specificity (83%) on patients with high suspect of ECE (on T2-WI). CONCLUSION: The morphologic component of T2-weighted imaging and functional aspect of DTI should be interpreted together to more successfully assess the presence of ECE.

Chronic Asymptomatic Pancreatic Hyperenzymemia: A Long-term Follow-up.

OBJECTIVES: Chronic asymptomatic pancreatic hyperenzymemia (CAPH) was described as a benign disease. However, we already described clinically relevant findings requiring surgery or follow-up in half of the subjects. The aim of this study was to evaluate the long-term outcome of CAPH in terms of symptoms and evolution toward chronic pancreatitis. METHODS: Subjects previously enrolled in the first phase of the study (from 2005 to 2010) were reinvestigated from December 2013 to January 2017 with a phone call ± magnetic resonance cholangiopancreatography with secretin stimulation. RESULTS: A total of 133 subjects were eligible for the follow-up study (75 males, 58 females; age, 48.4 [standard deviation {SD}, 14] years); 24 (18%) of them dropped out. During a mean follow-up of 9.3 (SD, 5.2) years after the first diagnosis of CAPH, no episode of acute pancreatitis or abdominal pain was reported. Sixty-three subjects (58%) of 109 underwent magnetic resonance cholangiopancreatography with secretin stimulation with a mean follow-up of 5.7 [SD, 3.1] years (range, 1-11 years). Secretin stimulation-MRCP resulted unchanged in 54 (90%) of 60 subjects, worsened in 3 (5%) and improved in 3 (5%). Two subjects died from causes unrelated to pancreatic disease. CONCLUSIONS: Excluding subjects with a pancreatic disease at index magnetic resonance imaging, CAPH is a benign condition.

Effect of Endurance and Strength Training on the Slow Component of O 2 Kinetics in Elderly Humans.

We compared the effects of 8 weeks of high intensity, aerobic interval training (HIT) and isoinertial resistance training (IRT) on: (i) O 2 kinetics during heavy (HiEx) intensity exercise and; (ii) work economy during moderate (ModEx) intensity exercise in 12 healthy elderly men (69.3 ± 4.2 years). Breath-by-breath O 2 and muscle deoxygenation ([HHb] by means of NIRS) were measured in HiEx and ModEx at identical workloads before and after trainings. In HiEx, O 2 and HHb responses were modeled as tri-exponential and mono-exponential increasing functions, respectively. A two-way ANOVA for repeated measures analysis was made; Effect size (η2) was also evaluated. After HIT the amplitude and the time delay of the slow component of O2 uptake (O 2sc) during HiEx were smaller (-32%; P = 0.045) and longer (+19.5%; P = 0.001), respectively. At Post IRT: (i) during ModEx, gain was lower (-5%; P = 0.050); (ii) during HiEx, τ2 (+14.4%; P = 0.050), d3 (+8.6%; P = 0.050), and τ3 (+17.2%; P = 0.050) were longer than at Pre IRT. After HIT, the decrease of the O 2sc amplitude was likely induced by the beneficial effects of training on a more responsive O 2 delivery and consumption cascade leading to a better muscle metabolic stability. IRT training was able to increase exercise economy during ModEx and to reduce the amplitude and delay the onset of O 2sc during HiEx. These effects should be due to the reduction and the delayed recruitment of Type II muscle fibers. The better exercise economy and the delayed appearance of O 2sc induced by IRT suggests that strength training might be included in endurance training programs to improve exercise economy and resistance to fatigue in this population of old subjects.

Type 1 and Type 2 Autoimmune Pancreatitis: Distinctive Clinical and Pathological Features, But Are There Any Differences at Magnetic Resonance? Experience From a Referral Center.

OBJECTIVES: This study aimed to evaluate magnetic resonance imaging findings of autoimmune pancreatitis (AIP) and to find radiological patterns that could differentiate type 1 and type 2 AIP. METHODS: Eighty-four patients with diagnosis of AIP were enrolled. Image analysis included pancreatic signal intensity abnormalities, enhancement pattern, extrapancreatic involvement, and main pancreatic duct alterations. RESULTS: Pancreatic parenchyma resulted in hypointensity on T1-weighted images in 65 (98.5%) of 66 cases in type 1 and in 17 (94.5%) of 18 in type 2 (P > 0.05) and in hyperintensity on T2-weighted images in 41 (62%) of 66 and in 15 (83.4%) of 18, respectively (P > 0.05). Lesions were hypovascular in 64 (97%) of 66 cases in type 1 and in 16 (88.9%) of 18 in type 2 with delayed contrast retention in 56 (84.8%) of 66 and in 17 (94.5%) of 18, respectively (P > 0.05). Autoimmune cholangitis was found in 29 (43.9%) of 66 patients with type 1 and in 3 (16.7%) of 18 with type 2 (P = 0.02); renal involvement was observed in 20 (30.3%) of 66 and 1 (5.5%) of 18, respectively (P = 0.02). Both subtypes presented with multiple stenoses (P > 0.05). Dilation of upstream duct was more frequent in type 1 (P = 0.02). CONCLUSIONS: Magnetic resonance imaging is useful in detecting extrapancreatic involvement, typically seen in type 1. Dilation of the upstream duct suggests type 1 AIP.

Surgery after FOLFIRINOX treatment for locally advanced and borderline resectable pancreatic cancer: increase in tumour attenuation on CT correlates with R0 resection.

OBJECTIVES: To assess factors associated with radical resection (R0) of pancreatic ductal adenocarcinoma (PDAC) after induction treatment with FOLFIRINOX. METHODS: Patients with either locally advanced (LA) and borderline resectable (BR) PDAC undergoing surgical exploration after FOLFIRINOX were retrospectively enrolled. Two pancreatic radiologists reviewed the CT blinded to the final outcome and assessed chemotherapy response and resectability. Patients were then divided into R0 resected (group A) and not resected/R1 resected (group B), which were compared. RESULTS: Of 59 patients included, 19 were defined as unresectable (32%), 33 borderline resectable (56%) and 7 resectable (12%) during the blind radiological evaluation after FOLFIRINOX. Once in a surgical setting, 27% were non-resectable, whereas 73% received surgical resection with a 70% R0 rate. Consequent sensitivity and specificity were 86% and 29%. At imaging review, significant decreases in longest tumour dimension were observed in both groups: from 32 mm (95% CI 15-55) to 21 (10-44) in group A and from 34 (18-70) to 26 (7-60) in group B, p < 0.05. However, a significant increase in tumour attenuation in all phases was only observed for R0 resected, from 52 HU (26-75) to 65 (35-92) in arterial phase (p < 0.001) and from 62 (36-96) to 78 (40-120) in the venous (p = 0.001). CONCLUSION: After neoadjuvant FOLFIRINOX, CT predicted resectability with acceptable sensitivity but low specificity. The observation of increased tumour attenuation at CT scan after FOLFIRINOX treatment might represent a reliable predictor of R0 resection. KEY POINTS: • CT drives the assessment of PDAC resectability after FOLFIRINOX • CT predicts resectability with acceptable sensitivity but low specificity • Significant increase in tumour attenuation was only observed for R0 resected PDAC • Tumour attenuation after FOLFIRINOX represents a reliable predictor of R0 resection.

Evaluation of periprostatic neurovascular fibers before and after radical prostatectomy by means of 1.5 T MRI diffusion tensor imaging.

OBJECTIVE: To evaluate if diffusion tensor imaging (DTI) is able to detect changes of periprostatic neurovascular fibers (PNFs) before and after radical prostatectomy (RP), and if these changes are related to post-surgical urinary incontinence and erectile dysfunction. METHODS: 22 patients (mean age 62.6 years) with biopsy-proven prostate cancer underwent 1.5 T DTI before and after RP. The number, fractional anisotropy (FA) values and length of PNFs before and after RP were compared using Student's t-test. Each patient filled out two questionnaires before and after RP, one for the evaluation of urinary continence (ICIQ-SF) and one for the evaluation of erectile function (IIEF-5). The ratios of the number, FA values and length of PNFs before and after RP (DTI B-A RATIOs) and the ratios between the scores obtained before and after RP for both ICIQ-SF and IIEF-2 (ICIQ-SF B-A RATIOs and IIEF-2 B-A RATIOs) were calculated to perform the Kendall's τ-test between them. RESULTS: There was a statistically significant decrease of the number of PNFs after RP at base, midgland, and apex (p < 0.01) and of FA values at midgland (p < 0.05), with positive statistically significant correlation between the DTI B-A RATIOs of the number of PNFs and IIEF-2 B-A RATIOs (p < 0.05, ρ = 0.47). CONCLUSION: DTI was able to detect that the decrease of the number of the PNFs after RP was statistically related to the post-surgical erectile dysfunction (p < 0.05). Advances in knowledge: This work demonstrates that: (1) 1.5 T MRI DTI is able to detect the decrease of the number and of the FA of PNFs after prostatectomy; (2) the decrease of the number of PNFs after prostatectomy is related with the post-surgical erectile dysfunction; (3) 1.5 T MRI DTI has demonstrated to be a reproducible technique in detecting the changes of the PNFs induced by RP, with high interobserver agreement.

Major pancreatic resections: normal postoperative findings and complications.

OBJECTIVES: (1) To illustrate and describe the main types of pancreatic surgery; (2) to discuss the normal findings after pancreatic surgery; (3) to review the main complications and their radiological findings. BACKGROUND: Despite the decreased postoperative mortality, morbidity still remains high resulting in longer hospitalisations and greater costs. Imaging findings following major pancreatic resections can be broadly divided into "normal postoperative alterations" and real complications. The former should regress within a few months whereas complications may be life-threatening and should be promptly identified and treated. IMAGING FINDINGS: CT is the most effective postoperative imaging technique. MRI and fluoroscopy are used less often and only in specific cases such as assessing the gastro-intestinal function or the biliary tree. The most common normal postoperative findings are pneumobilia, perivascular cuffing, fluid collections, lymphadenopathy, acute anastomotic oedema and stranding of the peri-pancreatic/mesenteric fat. Imaging depicts the anastomoses and the new postoperative anatomy. It can also demonstrate early and late complications: pancreatic fistula, haemorrhage, delayed gastric emptying, hepatic infarction, acute pancreatitis of the remnant, porto-mesenteric thrombosis, abscess, biliary anastomotic leaks, anastomotic stenosis and local recurrence. CONCLUSIONS: Radiologists should be aware of surgical procedures, postoperative anatomy and normal postoperative imaging findings to better detect complications and recurrent disease. TEACHING POINTS: • Morbidity after pancreatic resections is high. • CT is the most effective postoperative imaging technique. • Imaging depicts the anastomoses and the new postoperative anatomy. • Pancreatic fistula is the most common complication after partial pancreatic resection.

CT imaging of primary pancreatic lymphoma: experience from three referral centres for pancreatic diseases.

PURPOSE: To describe CT characteristics of primary pancreatic lymphoma (PPL), a rare disease with features in common with adenocarcinoma. MATERIALS AND METHODS: Fourteen patients were enrolled. CT: unenhanced scan, contrast-enhanced pancreatic and venous phases. Image analysis: tumour location; peri-pancreatic vessel encasement; necrosis; enlarged lymph nodes; fat stranding; enlarged bile duct and pancreatic duct; neoplasm longest dimension, volume and density. RESULTS: Histopathological diagnoses: follicular non-Hodgkin lymphoma (5/14), diffuse large B-cell lymphoma (6/14) and high-grade B-cell lymphoma not otherwise specified (3/14). Six of 14 PPLs were located in the pancreatic head and 7/14 in the body-tail; 1/14 involved the whole gland. In 5/14 cases the superior mesenteric artery and vein were encased; splenic vein and artery encasement was depicted in 2 PPLs. Necrosis was present in 2/14. Enlarged retroperitoneal lymph nodes were found in 11 cases and fat stranding in all patients. The bile duct was dilated in six cases and the pancreatic duct in five. Mean neoplasm longest diameter and volume were 8.05 cm and 210.8 cm3. Mean tumour attenuation values were 39.1 HU at baseline, 60.6 HU in the pancreatic phase and 71.4 HU in the venous phase. CONCLUSIONS: PPL presents as a large mass lesion with delayed homogeneous enhancement; peri-pancreatic fat stranding and vessel encasement are present, without vascular infiltration. Pancreatic duct dilatation is rare. KEY POINTS: • Primary pancreatic lymphoma (PPL) is a rare haematological disease • PPL presents imaging features in common with pancreatic carcinoma but also some distinctive findings • The majority of PPLs are large lesions with delayed homogeneous enhancement • Peri-pancreatic fat stranding and vessel encasement are common in PPL • Vascular infiltration and pancreatic duct dilatation are rare in PPL.

Prevent Pancreatic Fistula after Pancreatoduodenectomy: Possible Role of Ultrasound Elastography.

BACKGROUND: The purpose of the study is to evaluate the utility of acoustic radiation force impulse (ARFI) on pancreatic tissue as a preoperative predictor of postoperative pancreatic fistula (POPF). Studied patients underwent exclusively to pancreaticoduodenectomy (PD) surgery. METHODS: Shear wave velocity of pancreas was measured using ARFI in 71 patients scheduled for PD. An intraoperative pancreas palpation was made by surgeons. A postoperative clinical evaluation to detect occurrence of POPF was performed. Sensitivity, specificity, positive and negative predictive values together with the accuracy of the method were investigated. RESULTS: Incidence of fistula observed in 17 patients with soft pancreas was approximately 53% vs. 47% without fistula. Percentage of patients without fistula was higher (66%) among 24 patients with medium parenchymal texture values, and was even higher (69%) in 26 patients with hard pancreas. Comparing ARFI and intraoperative pancreatic palpation, low wave velocity values (≤1.40 m/s) match 60% with soft parenchyma assessed by palpation and high values (>2 m/s) match 59% with hard pancreas on palpation. CONCLUSIONS: This study shows that ARFI elastography may be clinically useful as a preoperative predictor of pancreatic fistula following PD.

Paraduodenal pancreatitis as a mimicker of pancreatic adenocarcinoma: MRI evaluation.

PURPOSE: To evaluate the MRI features of paraduodenal pancreatitis (PDP) and to define useful signs to differentiate PDP from pancreatic ductal adenocarcinoma (PDAC). MATERIAL AND METHODS: We reviewed the MRI scans of 56 patients, 28 affected by PDP and 28 by PDAC, all pathologically proven. The following parameters were evaluated: signal intensity of the lesion on T1-, T2-WI, DWI (b800) and after contrast medium administration; presence of cysts; dilation of common hepatic duct and main pancreatic duct; focal thickening of the second portion of the duodenum; maximum diameter and volume of the lesion. RESULTS: Both PDPs and PDACs were more frequently hypointense on T1-WI, iso-hyperintense on T2-WI, hypointense in the pancreatic phase and iso-hypointense in the venous phase (p>0.05); in the delayed phase most PDP were hyperintense (p=0.0031); on DWI 71.4% PDPs were isointense and all PDACs were hyperintense (p=0.0041). Cystic components were present in 85.7% PDPs (p=0.0011); double duct sign was present in 50% PDACs (p=0.0048); focal thickening of the duodenum was depicted in 89.3 PDPs (p=0.0012). PDPs were larger than PDACs (p=0.0003). CONCLUSION: The most suggestive signs of PDP are: signal hyperintensity in the delayed phase, isointensity on DWI, presence of cysts, focal thickening of the duodenum and large size of the lesion.

Solid non-functioning endocrine tumors of the pancreas: correlating computed tomography and pathology.

BACKGROUND: Since prognosis and treatment of pancreatic endocrine tumors (pNET) are based on tumor grade, contrast-enhanced multidetector computed tomography (MDCT) features of solid non-functioning pNETs were studied and correlated with pathology tumor grading. METHODS: MDCTs of diagnosed pNETs were reviewed retrospectively. Each tumor was analyzed for location, size, homogeneity, margins, arterial and venous phase enhancement, main pancreatic duct diameter, calcifications, vascular invasion, lymph-nodes enlargement, and liver metastases. RESULTS: Of 154 pNETs presenting between January 2000 and May 2016 with available histology from resected specimen or biopsy, there were 65 G1, 72 G2 and 17 G3 pNETs. Tumor diameter varied significantly between the three groups. Tumors >20 mm were more frequently malignant and non-homogeneous than smaller tumors. G1 tumors were more commonly hypervascular and G3 tumors more often non-hypervascular in the arterial phase. Arterial phase non-hyperdensity and tumor non-homogeneity had a higher rate of metastatic lesions. Vascular invasion correlated with presence of metastases and histological grade. G3 tumors were all >20 mm (p = 0.007), more often non-hypervascular in the arterial phase (p = 0.0025), and non-hyperdense in the venous phase (p = 0.009), and showed more often vascular invasion (p = 0.0198). CONCLUSION: CT correlated with tumor grade; differentiating low-grade and high-grade pNETs through routine CT imaging might improve patient management.

Classification of first-episode psychosis in a large cohort of patients using support vector machine and multiple kernel learning techniques.

First episode psychosis (FEP) patients are of particular interest for neuroimaging investigations because of the absence of confounding effects due to medications and chronicity. Nonetheless, imaging data are prone to heterogeneity because for example of age, gender or parameter setting differences. With this work, we wanted to take into account possible nuisance effects of age and gender differences across dataset, not correcting the data as a pre-processing step, but including the effect of nuisance covariates in the classification phase. To this aim, we developed a method which, based on multiple kernel learning (MKL), exploits the effect of these confounding variables with a subject-depending kernel weighting procedure. We applied this method to a dataset of cortical thickness obtained from structural magnetic resonance images (MRI) of 127 FEP patients and 127 healthy controls, who underwent either a 3Tesla (T) or a 1.5T MRI acquisition. We obtained good accuracies, notably better than those obtained with standard SVM or MKL methods, up to more than 80% for frontal and temporal areas. To our best knowledge, this is the largest classification study in FEP population, showing that fronto-temporal cortical thickness can be used as a potential marker to classify patients with psychosis.

Pancreatic duct stenosis: Differential diagnosis between malignant and benign conditions at secretin-enhanced MRCP.

PURPOSE: To define imaging criteria of benign and malignant nature in patients with main pancreatic duct (MPD) stenosis. MATERIALS-METHODS: S-MRCPs of 35 patients with pancreatitis and 14 with adenocarcinoma were evaluated. RESULTS: Adenocarcinoma caused higher prevalence of complete stenosis (14/14-100% vs 17/35-49%), dilated side-branches (14/14-100% vs 18/35-51%) and lower prevalence of duct-penetrating sign (0/14-0% vs 31/35-89%). The number of stenoses was higher in benign conditions (mean 1.4 Vs 1). Upstream MPD diameter was higher in cancer-induced stenoses (4.5 vs 2.9mm). CONCLUSIONS: Single complete stenosis with dilated side branches, increased MPD caliber and absent duct-penetrating sign are suggestive of malignancy.

Dual-energy CT of the brain: Comparison between DECT angiography-derived virtual unenhanced images and true unenhanced images in the detection of intracranial haemorrhage.

OBJECTIVE: To evaluate the diagnostic performance of virtual non-contrast (VNC) images in detecting intracranial haemorrhages (ICHs). METHODS: Sixty-seven consecutive patients with and 67 without ICH who underwent unenhanced brain CT and DECT angiography were included. Two radiologists independently evaluated VNC and true non-contrast (TNC) images for ICH presence and type. Inter-observer agreement for VNC and TNC image evaluation was calculated. Sensitivity and specificity of VNC images for ICH detection were calculated using Fisher's exact test. VNC and TNC images were compared for ICH extent (qualitatively and quantitatively) and conspicuity assessment. RESULTS: On TNC images 116 different haemorrhages were detected in 67 patients. Inter-observer agreement ranged from 0.98-1.00 for TNC images and from 0.86-1.00 for VNC images. VNC sensitivity ranged from 0.90-1, according to the different ICH types, and specificity from 0.97-1. Qualitatively, ICH extent was underestimated on VNC images in 11.9% of cases. Haemorrhage volume did not show statistically significant differences between VNC and TNC images. Mean haemorrhage conspicuity was significantly lower on VNC images than on TNC images for both readers (p < 0.001). CONCLUSION: VNC images are accurate for ICH detection. Haemorrhages are less conspicuous on VNC images and their extent may be underestimated. KEY POINTS: • VNC images represent a reproducible tool for detecting ICH. • ICH can be identified on VNC images with high sensitivity and specificity. • Intracranial haemorrhages are less conspicuous on VNC images than on TNC images. • Intracranial haemorrhages extent may be underestimated on VNC images.

ARFI: from basic principles to clinical applications in diffuse chronic disease-a review.

UNLABELLED: The many factors influencing the shear wave velocity (SWV) measured with Acoustic Radiation Force Impulse (ARFI) are examined in order to define the most correct examination technique. In particular, attention is given to the information achieved by experimental models, such as phantoms and animal studies. This review targets the clinical applications of ARFI in the evaluation of chronic diffuse disease, especially of liver and kidneys. The contribution of ARFI to the clinical workout of these patients and some possible perspectives are described. TEACHING POINTS: • Stiffness significantly varies among normal and abnormal biological tissues. • In clinical applications physical, geometrical, anatomical and physiological factors influence the SWV. • Elastographic techniques can quantify fibrosis, which is directly related to stiffness. • ARFI can be useful in chronic diffuse disease of liver and kidney.

Incidental optochiasmatic cavernoma: Case report of an unusual finding on 3 Tesla MRI.

Cavernoma is a vascular hamartoma, which represents 10-20% of all central nervous system vascular malformations. The majority (80%) of them are supratentorial, while involvement of the cranial nerves and the optic pathways is extremely rare. The main clinical presentation of optochiasmatic cavernomas consists of chiasmatic apoplexy, which is a neurosurgical emergency. Here, we report a case in which the finding was incidentally detected in a 49-year-old man. We describe the imaging characteristics of the lesion in such a rare location, highlighting the role of magnetic resonance imaging (MRI) (specifically 3 Tesla) in the management of asymptomatic patients.

Secretin-enhanced MR Imaging of the Pancreas.

Secretin is a hormone that stimulates the exocrine pancreatic secretion of bicarbonate-rich fluid from the acinar cells of the pancreas that accumulates within the pancreatic ductal lumen. The exogenous administration of secretin improves the visualization of pancreatic ducts at magnetic resonance (MR) cholangiopancreatography (MRCP), because of an enlargement of the pancreatic duct system and an increase of the fluid content within the lumen of the pancreatic ducts, responsible of an increase of MR signal. In this review, the technique of secretin-enhanced MRCP, which has the aim to depict the whole pancreatic duct system, the biliary tree, the major and minor papillae, and the duodenum, will be described. Because of the anatomic contiguity between the pancreas and the gastrointestinal tract, the presence of fluid within the stomach may overlap with the pancreatic duct system and therefore the pancreatic duct may be difficult to visualize, representing a potential source of diagnostic pitfalls. The technique to reduce the signal intensity of the static fluid present within the stomach and in the duodenal lumen is also described. The technique of secretin administration will be illustrated, with emphasis on the synchronization of secretin administration and MR image acquisition. Furthermore, the frequency and number of MRCP images necessary to achieve a temporal resolution adequate to visualize the physiologic changes in the pancreatic gland, induced by the administration of secretin, is described. The assessment of pancreatic, morphologic, and functional response to the administration of secretin, as depicted on MRCP images, will be illustrated. Finally, the indications for secretin-enhanced MRCP will be discussed to define which patients will benefit from secretin-enhanced MR imaging for their treatment planning. (©) RSNA, 2016.

Acoustic radiation force impulse with shear wave speed quantification of pancreatic masses: A prospective study.

BACKGROUND: Acoustic Radiation Force Impulse (ARFI) is a new ultrasound technique that evaluates mechanical properties of tissues. To evaluate the use of ARFI with shear waves speed quantification for pancreatic masses characterization during the ultrasound examination. METHODS: 123 pancreatic lesions were prospectively evaluated. Median shear waves speeds were compared with Mann-Whitney U test. Two reading methods were applied for the characterization of adenocarcinoma: more than one measurement above the top shear waves speed (SWS) value. Two reading methods were applied to diagnose mucinous lesion: at least 2 (method 1) or 3 (method 2) numerical measurements. Sensitivity, specificity, positive and negative predictive values and accuracy of each reading method were calculated. Forty volunteers were included for normal ARFI values. RESULTS: In the adenocarcinoma group median SWS value was 2.74 m/s. In the volunteers group the median SWS value was 1.17 m/s. Significant difference between SWS median values of adenocarcinoma and normal pancreas was found (P < 0.05). For the diagnosis of pancreatic solid masses if more than one measurement is above the top SWS value of 4.00 m/s results in the study, the diagnosis of ductal adenocarcinoma is highly specific with specificity and PPV of 100%. Good sensitivity (73.3%) and specificity (83.3%) were obtained for the characterization of mucinous cystic lesions. CONCLUSIONS: Acoustic Radiation Force Impulse imaging could help in the non-invasive characterization of solid and cystic lesions of the pancreas during a conventional US examination.