Transcranial Magnetic Resonance Imaging-Guided Focused Ultrasound Treatment at 1.5 T: A Retrospective Study on Treatment- and Patient-Related Parameters Obtained From 52 Procedures

Objective: To present a retrospective analysis of patient- and sonication-related parameters of a group of patients treated with a transcranial magnetic resonance imaging (MRI)-guided focused ultrasound (tcMRgFUS) system integrated with a 1.5-T MRI unit. Methods: The data obtained from 59 patients, who underwent the tcMRgFUS procedure from January 2015 to April 2019, were retrospectively reviewed for this study. The following data, among others, were mainly collected: skull density ratio (SDR), skull area (SA), number of available transducer elements (Tx), and estimated focal power at target (FP). For each of the four different treatment stages, we calculated the number of sonication processes (S-n), user-defined sonication power (S-p), effective measured power (S-mp), sonication duration (S-d), user-defined energy (E), effective measured energy (E-m), maximum temperature (T-max), and MR thermometry plane orientation. Furthermore, the time delay between each sonication (S-t) and the total treatment time (T-t) were recorded. Results: Fifty-two patients (40 males and 12 females; age 64.51 +/- SD 11.90 years; range 26-86 years), who underwent unilateral Vim thalamotomy (left = 50, 96.15%; right = 2, 3.85%) for medication-refractory essential tremor (n = 39; 78%) or Parkinson tremor (n = 13; 22%) were considered. A total of 1,068 (95.10%) sonication processes were included in our final analysis (average S-n per treatment: 20.65 +/- 6.18; range 13-41). The energy released onto the planned target was found to decrease with the SDR for all temperature ranges. A positive correlation was observed between the slope of T-max vs. E-m plot and the SDR (R-2 = 0.765; p < 0.001). In addition, the T-max was positively correlated with SDR (R-2 = 0.398; p < 0.005). On the contrary, no significant correlation was found between SDR and SA or Tx. An analysis of the MR thermometry scanning plane indicated that, at our site, the axial and the coronal planes were used (on average) 10.4 (SD +/- 3.8) and 7.7 (SD +/- 3.0) times, respectively, whereas the sagittal plane was used only 2.5 (SD +/- 3.0) times per treatment. Conclusion: Our results confirm the factors that significantly influence the course of a tcMRgFUS procedure even when a 1.5-T MRI scanner is used for procedure guidance. The experience we gained in this study indicates that the SDR remains one of the most significant technical parameters to be considered in a tcMRgFUS procedure. The possibility of prospectively setting the sonication energy according to the presented curves of energy delivery as a function of SDR for each treatment stage could provide a further understanding and a greater awareness of this emerging technology

Detection of liver metastases in cancer patients with geographic fatty infiltration of the liver: the added value of contrast-enhanced sonography

The aim of this study is to assess the role of contrast-enhanced ultrasonography (CEUS) in the detection of liver metastases in cancer patients with geographic liver fatty deposition on greyscale ultrasonography (US)

MR Imaging of Perianal Crohn Disease: The Role of Contrast-enhanced Sequences

The MR imaging protocol described by the authors includes contrast-enhanced T1-weighted imaging with fat saturation in all patients except those with poor renal function. Horsthuis et al demonstrated in 2009 the usefulness of contrast-enhanced MR imaging for determining disease activity. Contrast agent administration is also required in case of suspicion of neoplastic tissue complicating fistulas. The joint European Crohn\u2019s and Colitis Organisation\u2013European Society of Gastointestinal and Abdominal Radiology guidelines report that T2-weighted images and contrast-enhanced T1-weighted images are included in the MR imaging protocol for the evaluation of perianal CD. However, as we have demonstrated, an axial T2-weighted fast spinecho sequence with fat saturation, in particular the short inversion time inversion-recovery (STIR) sequence, is a valid alternative to postcontrast T1- weighted fat-saturated imaging, allowing the identification of the primary fistula and any secondary ramification

Utility of post mortem computed tomography in clivus fracture diagnosis. Case illustration and literature review

Clivus fractures are usually associated with head blunt trauma due to traffic accident and falls. A 23–year-old man died immediately after a smash-up while he was stopping on his motorcycle. Post-mortem Computed tomography (PMCT), performed before autopsy, revealed a complex basilar skull base fractures associated with brainstem and cranio-vertebral junction injuries, improving the diagnostic performance of conventional autopsy. Imaging data were re-assessable and PMCT offers the possibility to perform multiplanar and volume rendered reconstructions, increasing forensic medicine knowledge related to traumatic injuries

Imaging findings of hepatic focal nodular hyperplasia in men and women: are they really different?

Purpose This study was undertaken to compare the imaging findings of focal nodular hyperplasia (FNH) in men and women, as seen on multidetector computed tomography (MDCT), magnetic resonance imaging (MRI) and contrast-enhanced ultrasound (CEUS). Materials and methods Two radiologists reviewed 195 imaging studies (17 MDCT, 81 MRI and 97 CEUS examinations) pertaining to 111 FNHs (mean size 3 cm) in 91 patients (mean age 39 years). For each lesion, the readers assessed size, location, echogenicity, attenuation, or signal intensity in comparison with adjacent liver parenchyma on both unenhanced and postcontrast images. Results Eighty-nine FNHs (mean size 3.1 cm) were observed in 73 women (mean age 37.9 years) and 22 FNHs (mean size 2.7 cm) in 18 men (mean age 41.2 years). No statistically significant differences were found between men and women in terms of age, FNH lesions per patient (1.22 and 1.21, respectively), size, baseline and enhancement pattern on MRI, CEUS and MDCT (p < 0.05). A central scar in FNHs was depicted in 4/18 (22.2 %) men and 16/63 (25.4 %) women on MRI (p < 0.05), and in 1/2 (50 %) men and 7/15 (46.7 %) women on MDCT (p < 0.05), whereas a spoke-wheel pattern, central scar, and/or feeding vessel were seen in 5/17 (29.4 %) men and 22/80 (27.5 %) women on CEUS (p < 0.05). Conclusions Our results did not show any differences in imaging features, age of occurrence and size of FNH between men and women

Incidence of new foci of hepatocellular carcinoma after radiofrequency ablation: role of multidetector CT

Purpose. The authors sought to assess the incidence of new foci of hepatocellular carcinoma (HCC) using multidetector computed tomography (MDCT) in patients treated with radiofrequency ablation (RFA). Materials and methods. Two readers retrospectively reviewed by consensus the follow-up MDCT studies of 125 patients (88 men and 37 women; mean age 68 years) with 141 HCCs (size 1\u20135.2 cm; mean 2.2 cm) treated with RFA. MDCT follow-up was performed at 1 and 3 months and every 6\u201312 months thereafter. Reviewers assessed: (1) the presence of new HCC foci in the same liver segment or in a different segment; (2) complete or incomplete tumor ablation; (3) tumour progression. Results. A total of 113 new HCCs (size 0.7\u20134.8 cm; mean 1.7 cm) were detected in 69/125 (55.2%) patients (mean follow-up 30.38\ub119.14 months). Of these, 86 (76.1%) new HCCs were multiple (p<0.0001), and 92 (81.4%) occurred in a different segment from that of the treated HCC (p<0.0001). New HCCs were observed in the first 12 months, between 12 and 24 months and after 24 months in 31/69 (44.9%), 24/69 (34.8%) and 14/69 (20.3%) patients, respectively (p=0.175). Mean diseasefree interval was 16.1\ub116.31 (range 1\u201352) months. Complete tumour ablation was achieved in 132/141 (93.6%) treated HCCs, and tumour progression occurred in 29/141 (20.6%) cases. Conclusions. In patients with RFA-treated HCCs, MDCT follow-up revealed a high incidence of new HCCs, even after 1 year of follow-up. The new foci tended to be multiple and located in a liver segment different from that of the previously treated nodules

Intravenous contrast agent in abdominal CT: Is it really needed to identify the cause of bowel obstruction? Proof of concept

Background. To compare sensitivity of unenhanced computed tomography (CT) and contrast-enhanced CT for the identification of the etiology of bowel obstruction. Materials and Methods. We retrospectively evaluated abdominal CT scans of patients operated for bowel obstruction from March 2013 to October 2017. Two radiologists evaluated CT scans before and after contrast agent in two reading sessions. Then, we calculated sensitivity of CT in the diagnosis of bowel obstruction and determined in which cases the etiology of bowel obstruction was detected on both unenhanced and enhanced CT or on enhanced CT only. The reference standard was defined as the final diagnosis obtained after surgery. Results. Eighteen patients (mean age 72±15 years, age range 37-88 years) were included in the study. Sensitivity of unenhanced CT and enhanced CT was not significantly different in either small bowel obstruction (64%, 7/11 patients vs. 73%, 8/11 patients; P=0.6547) or large bowel obstruction (71%, 5/7 patients vs. 100%, 7/7 patients; P=0.1410). Adhesions were identified on unenhanced CT as the etiology of small bowel obstruction in 80% (4/5) of patients. Tumors were identified on unenhanced CT as the etiology of large bowel obstruction in 67% (4/6) of patients. Conclusion. In the diagnosis of small bowel obstruction due to adhesions with normal bowel wall thickening and when a neoplasm is identified as the etiology of large bowel obstruction on unenhanced CT, an intravenous contrast agent may be avoided for the identification of the etiology. In remaining cases, contrast agent is still recommended

Perfusion MR Imaging in Differentiating High-Grade from Low-Grade Gliomas

To correlate perfusion MR imaging with histologic grade of cerebral gliomas. Materials & Methods Relative cerebral blood volume (rCBV) maps were determined in 22 patients with pathologically proved gliomas (11 glioblastomas, 8 anaplastic gliomas and 2 low-grade gliomas) by dynamic contrast-enhanced T2*-weighted MR imaging. MR examination was completed with conventional T1- and T2-weighted imaging. The rCBV maps were calculated with an independent workstation by fitting a gamma-variate function to the contrast material concentration versus time curve. Relative CBV ratios obtained between tumor and normal white matter were compared between glioblastomas, anaplastic gliomas and low-grade gliomas by means of receiver operating characteristic (ROC) analysis. Results Mean rCBV ratios were 4.85 (\ub1 1) for glioblastomas, 3.87 (\ub1 0.7) for anaplastic gliomas and 1.65 (\ub1 1.6) for low-grade gliomas. Receiver operating characteristic analysis demonstrates significant differences between glioblastomas and anaplastic gliomas (p<.05), between anaplastic gliomas and low-grade gliomas (p<.05) and between glioblastomas and low-grade gliomas (p<.01). The rCBV ratio cutoff value between highgrade gliomas and low-grade gliomas was 2.52 with a sensitivity and specificity of 100% and 75% respectively. Conclusion Perfusion MR imaging is a reliable technique for differentiating high-grade from low-grade glioma

Magnetic resonance imaging of the cirrhotic liver in the era of gadoxetic acid

Gadoxetic acid improves detection and characterization of focal liver lesions in cirrhotic patients and can estimate liver function in patients undergoing liver resection. The purpose of this article is to describe the optimal gadoxetic acid study protocol for the liver, the unique characteristics of gadoxetic acid, the differences between gadoxetic acid and extra-cellular gadolium chelates, and the differences in phases of enhancement between cirrhotic and normal liver using gadoxetic acid. We also discuss how to obtain and recognize an adequate hepatobiliary phase