265 research outputs found
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
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
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
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
Imaging appearance of treated hepatocellular carcinoma.
Surgical resection and imaging guided treatments play a crucial role in the management of hepatocellular carcinoma (HCC). Although the primary end point of treatment of HCC is survival, radiological response could be a surrogate end point of survival, and has a key role in HCC decision-making process. However, radiological assessment of HCC treatment efficacy is often controversial. There are few doubts on the evaluation of surgical resection; in fact, all known tumor sites should be removed. However, an unenhancing partial linear peripheral halo, in most cases, surrounding a fluid collection reducing in size during follow-up is demonstrated in successfully resected tumor with bipolar radiofrequency electrosurgical device. Efficacy assessment of locoregional therapies is more controversial and differs between percutaneous ablation (e.g., radiofrequency ablation and percutaneous ethanol injection) and transarterial treatments (e.g., conventional transarterial chemoembolization, transarterial chemoembolization with drug eluting beads and radioembolization). Finally, a different approach should be used for new systemic agent that, though not reducing tumor mass, could have a benefit on survival by delaying tumor progression and death. The purpose of this brief article is to review HCC imaging appearance after treatment
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
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
Hippocampal and Amygdalar Volumes Changes in Drug Addicts: A Preliminary Study
Oral comunication for American Society of Neuroradiology 45th Annual Meeting. Chicago, June 9-14 200
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
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