Faster acquisition of magnetic resonance imaging sequences of the knee via deep learning reconstruction: a volunteer study.

AIM: To evaluate whether deep learning reconstruction (DLR) can accelerate the acquisition of magnetic resonance imaging (MRI) sequences of the knee for clinical use. MATERIALS AND METHODS: Using a 1.5-T MRI scanner, sagittal fat-suppressed T2-weighted imaging (fs-T2WI), coronal proton density-weighted imaging (PDWI), and coronal T1-weighted imaging (T1WI) were performed. DLR was applied to images with a number of signal averages (NSA) of 1 to obtain 1DLR images. Then 1NSA, 1DLR, and 4NSA images were compared subjectively, and by noise (standard deviation of intra-articular water or medial meniscus) and contrast-to-noise ratio between two anatomical structures or between an anatomical structure and intra-articular water. RESULTS: Twenty-seven healthy volunteers (age: 40.6 ± 11.9 years) were enrolled. Three 1DLR image sequences were obtained within 200 s (approximately 12 minutes for 4NSA image). According to objective evaluations, PDWI 1DLR images showed the smallest noise and significantly higher contrast than 1NSA and 4NSA images. For fs-T2WI, smaller noise and higher contrast were observed in the order of 4NSA, 1DLR, and 1NSA images. According to the subjective analysis, structure visibility, image noise, and overall image quality were significantly better for PDWI 1DLR than 1NSA images; moreover, the visibility of the meniscus and bone, image noise, and overall image quality were significantly better for 1DLR than 4NSA images. Fs-T2WI and T1WI 1DLR images showed no difference between 1DLR and 4NSA images. CONCLUSION: Compared to PDWI 4NSA images, PDWI 1DLR images were of higher quality, while the quality of fs-T2WI and T1WI 1DLR images was similar to that of 4NSA images.

Usefulness of deep learning-based noise reduction for 1.5 T MRI brain images.

AIM: To evaluate 1.5 T magnetic resonance imaging (MRI) brain images with denoising procedures using deep learning-based reconstruction (dDLR) relative to the original 1.5 and 3 T images. MATERIALS AND METHODS: Eleven volunteers underwent MRI at 3 and 1.5 T. Two-dimensional fast spin-echo T2-weighted imaging (T2WI), fluid-attenuated inversion recovery (FLAIR) imaging and diffusion-weighted imaging (DWI) sequences were performed. The dDLR method was applied to the 1.5 T data (dDLR-1.5 T), then the image quality of the dDLR-1.5 T data relative to the original 1.5 T and 3 T data was qualitatively and quantitatively assessed based on the structure similarity (SSIM) index; the signal-to-noise ratios (SNRs) of the grey matter (GM) and white matter (WM); and the contrast-to-noise ratios (CNRs) between the GM and WM (CNRgm-wm) and between the striatum (ST) and WM (CNRst-wm). RESULTS: The perceived image quality, and SNRs and CNRs were significantly higher for the dDLR-1.5 T images versus the 1.5 T images for all sequences and almost comparable or even superior to those of the 3 T images. For DWI, the SNRs and CNRst-wm were significantly higher for the dDLR-1.5 T images versus the 3 T images. CONCLUSION: The dDLR technique improved the image quality of 1.5 T brain MRI images. With respect to qualitative and quantitative measurements, the denoised 1.5 T brain images were almost equivalent or even superior to the 3 T brain images.

Magnetic resonance diffusion-weighted imaging in the characterization of pancreatic mucinous cystic lesions.

AIM: The aim of the study was to evaluate the utility of diffusion-weighted imaging (DWI), including apparent diffusion coefficient (ADC) measurement, in order to differentiate mucinous cystic neoplasms (MCNs) from intraductal papillary mucinous neoplasms (IPMNs) of the pancreas. MATERIALS AND METHODS: Fifty cases of IPMN with a total of 62 lesions, and eight cases of MCN, were retrospectively selected for the study. The cases of IPMN were selected using multimodality clinical or histopathological criteria, while all MCN lesions were histopathologically proven. DWI was carried out using b values of 500 and 1000s/mm(2). Visual assessment was performed by two radiologists who used two categories (low-iso or high signal intensity). ADC values of the lesions were also calculated. Fisher's exact test and the Mann-Whitney U test were used for statistical analysis. RESULTS: All IPMN lesions demonstrated low-iso signal intensities compared with the pancreatic parenchyma on DWI. Two of the MCN lesions demonstrated low-iso signal intensities, and six lesions demonstrated high signal intensities. The ADC values for IPMNs (mean 2.9 ± 0.024 × 10(-3)mm(2)/s) were significantly higher than those for MCNs (mean 2.1 ± 0.30 × 10(-3)mm(2)/s). ROC analysis showed an optimal cut-off value of 2.4 × 10(-3)mm(2)/s for differentiating between the two types of lesions, providing a sensitivity of 98% and a specificity of 88%. CONCLUSION: The results of the present study suggest that ADC values in mucinous cystic lesions of the pancreas can be advantageous for their characterization into IPMN and MCN.

Predicting prognosis of resected hepatocellular carcinoma by radiomics analysis with random survival forest.

RATIONALE AND OBJECTIVES: To investigate the impact of random survival forest (RSF) classifier trained by radiomics features over the prediction of the overall survival of patients with resectable hepatocellular carcinoma (HCC). MATERIALS AND METHODS: The dynamic computed tomography data of 127 patients (97 men, 30 women; mean age, 68 years) newly diagnosed with resectable HCC were retrospectively analyzed. After manually setting the region of interest to include the tumor within the slice at its maximum diameter, texture analyses were performed with or without a Laplacian of Gaussian filter. Using the extracted 96 histogram based texture features, RSFs were trained using 5-fold cross-validation to predict the individual risk for each patient on disease free survival (DFS) and overall survival (OS). The associations between individual risk and DFS or OS were evaluated using Kaplan-Meier analysis. The effects of the predicted individual risk and clinical variables upon OS were analyzed using a multivariate Cox proportional hazards model. RESULTS: Among the 96 histogram based texture features, RSF extracted 8 of high importance for DFS and 15 for OS. The RSF trained by these features distinguished two patient groups with high and low predicted individual risk (P=1.1×10-4 for DFS, 4.8×10-7 for OS). Based on the multivariate Cox proportional hazards model, high predicted individual risk (hazard ratio=1.06 per 1% increase, P=8.4×10-8) and vascular invasion (hazard ratio=1.74, P=0.039) were the only unfavorable prognostic factors. CONCLUSIONS: The combination of radiomics analysis and RSF might be useful in predicting the prognosis of patients with resectable HCC.

Regulation of mRNA expression involved in Ras and PKA signal pathways during rat hypoglossal nerve regeneration.

Using in situ hybridization histochemistry and immunohistochemistry, the present study examines the cooperative regulation of transcription of molecules involved in the Ras-signal and the cAMP dependent protein kinase (PKA) pathways during peripheral nerve regeneration in rats. Injury to hypoglossal motor neurons resulted in an increase in extracellular regulated kinase (ERK, or MAP kinase) and ERK kinase (MEK, or MAP kinase kinase) mRNAs, but in a decrease in the expression of the catalytic subunits of PKA (C alpha and C beta) mRNAs. These results show the importance of the Ras-signal pathway in the nerve regeneration process and extend recent observation which suggested a cross-talk between the Ras and PKA pathways in vitro. The down-regulation of PKA may facilitate the activation of the Ras pathway which is located downstream of the growth factor receptor. The present study may suggest a possibility of regulatory talk between these two major signal transduction pathways.

A disintegrin and metalloprotease with thrombospondin type1 motifs (ADAMTS-1) and IL-1 receptor type 1 mRNAs are simultaneously induced in nerve injured motor neurons.

Following rat hypoglossal nerve injury, expression of mRNAs for a disintegrin and metalloprotease with thrombospondin type1 motifs (ADAMTS-1) and IL-1 receptor type 1 (IL-1RT1) are induced in the injured motor neurons. Although N1E-115 (N1E) cells, which were treated with IL-1 alpha, showed no alteration of ADAMTS-1 mRNA expression, a substantial increase of ADAMTS-1 mRNA expression was observed in the N1E cells expressing IL-1RT1. These findings suggest that nerve injury promotes IL-1RT1 expression in the injured neurons and thereby ADAMTS-1 transcription was induced in response to IL-1 released from glial cells.

Up-regulation of ferritin heavy chain mRNA expression in the rat skeletal muscle after denervation: detected by means of differential display.

The differential display method was applied to identify gene expression, which is especially up-regulated in denervated skeletal muscle. Total RNA from normal and denervated rat facial muscles (muscles zygomaticus, levator nasolabialis and caninus) was isolated, amplified by polymerase chain reaction (PCR) using certain primers and separated by electrophoresis on a polyacrylamide gel. PCR products, the amounts of which were significantly higher in the operated side than in the control side, were cut out from the gel and sequenced. One of the cDNA fragments obtained in the present study showed 100% identity in nucleotide sequence to the rat ferritin heavy chain (FHC) mRNA. Northern blot analysis and in situ hybridization histochemistry confirmed that FHC mRNA expression was up-regulated after denervation and was distributed throughout whole muscle cell bodies. The biological damage attributed to superoxide and hydrogen peroxide is dependent on the presence of intracellular free iron. Intracellularly, most of the iron that is not metabolized is sequestered in ferritin as a crystalline core of ferric irons (Fe3+). These findings suggest that alterations in the ferritin subunit composition after denervation play an important role in iron metabolism in skeletal muscle cells, resulting in restriction of the biological tissue damage caused by reactive oxygen species.

Up-regulation of ERK (MAP kinase) and MEK (MAP kinase kinase) transcription after rat facial nerve transection.

Up-regulation of ERK (extracellular signal-regulated kinase or MAP kinase) and MEK (ERK kinase or MAPK kinase) expression after rat facial nerve injury was demonstrated by in situ hybridization histochemistry and immunohistochemistry. These two enzymes play roles in one of the major intracellular signal cascade pathways involving receptor tyrosine kinase common to growth factor receptors, and transcription factors. Significant increases in ERK1 mRNA levels were observed from day 3 after facial nerve transection, with the highest level of expression from 1 to 2 weeks after the operation. This high level of mRNA expression then decreased gradually to the normal level. ERK1-like immunoreactivity showed a similar time course to that of its mRNA expression; however, the decay profile was more prolonged. The up-regulation of MEK, the ERK kinase/MAPK kinase, was also detected by immunohistochemistry. The protein expression profiles were almost equivalent, but the MEK expression was slightly advanced, suggesting that the observed up-regulation of MEK was not due to that of ERK. The receptor tyrosine kinase signal transduction pathway via MEK-ERK located downstream of growth factor receptors seems vital as a regulator of the synthesis of molecules that play important roles in the recovery process following injury or/and regeneration.

MRI findings of multiple malignant gliomas: differentiation from multiple metastatic brain tumors.

Multiple malignant gliomas are relatively uncommon, but are sometimes difficult to differentiate from multiple metastatic brain tumors. We analyzed the MR findings of four cases of multiple gliomas, comparing them with 12 cases of multiple metastatic brain tumors. All tumors were pathologically proven by surgical operation or autopsy. Gliomas were located in the deep white matter of the cerebrum, with none found in the posterior fossa. Tumors were relatively large, and irregular, thick, ring-like enhancement was noted after the administration of Gd-DTPA. Intratumoral hemorrhage was noted in only one case. High signal intensity on T2WI around the tumor suggested that edema was greater and more extensive than in metastatic tumors and was seen even in the corpus callosum. One autopsied case that showed this high intensity presented not only edema but also tumor infiltration. Metastatic tumors were located mainly in the corticomedullary junction of the brain. They were relatively small, and eight of 12 tumors showed, nodular or smooth ring-like enhancement. Intratumoral hemorrhage was noted in four cases. Edema was noted mainly around the tumor. We conclude that differential diagnosis between gliomas and metastases is possible to some extent by MRI.

Significance of informed consent and truth-telling for quality of life in terminal cancer patients.

For 12 patients with terminal stage cancer who died within the period from June 1995 to the present, we retrospectively evaluated the correlation between the "information" concerning disclosure of the "diagnosis," "pathology," and "prognosis," with the length of the last admission before the death, "sedation" near death, and the choice of "do not resuscitate (DNR)." The average length of admission before death was markedly shorter for patients who had been told either the "diagnosis," "pathology," or "prognosis" than for patients who had not. A statistically significant difference was observed between those who had been told and those who had not been told the "pathology." Similarly, "sedation" tended to be done for those who had been provided with information on cancer. It was suggested that telling patients with terminal stage cancer the truth about "diagnosis," "pathology," and "prognosis" is important for them to spend a fulfilling terminal stage.

Epstein-Barr virus-positive inflammatory pseudotumour and inflammatory pseudotumour-like follicular dendritic cell tumour.

Various splenic inflammatory pseudotumours are reported to be infected with Epstein-Barr virus (EBV), which is thought to be associated with the pathogenesis of the lesion. The term "inflammatory pseudotumour (IPT)-like follicular dendritic cell tumour", all cases of which are also EBV positive, has recently been proposed. Here, we describe the imaging findings of these splenic tumours and present the cases of an IPT-like follicular dendritic cell tumour and two EBV-positive inflammatory pseudotumours in two female patients and one male patient. These splenic lesions were found incidentally on pre-operative or post-operative screening or at medical check-up. CT performed on all three patients revealed low-density solitary masses in the spleen. MRI was performed on one patient; the solitary mass demonstrated isointensity on T(1) weighted images and low intensity on T(2) weighted images relative to the surrounding splenic parenchyma. Dynamic MRI study revealed that the mass did not enhance on the early phase but enhanced to the same degree as the surrounding splenic parenchyma on the delayed phase. The imaging findings are almost identical to those found in conventional IPT because the morphology is similar in both cases; however, attention should be paid to this new entity in the diagnosis of splenic lesions because of its neoplastic nature. Longer follow-up is also necessary for these patients compared with those with conventional IPT.

Magnetic resonance imaging and diffusion tensor analysis of lymphomatoid granulomatosis of the brain.

We present the case of a 56-year-old man suffering from acquired immune deficiency syndrome associated with lymphomatoid granulomatosis. Magnetic resonance imaging performed because of convulsions revealed an ill-defined frontal mass showing hypointense on T1WI and slightly hypointense on T2WI with surrounding edema. An elevated uptake was found on T1-201 single photo emission computed tomography consistent with a central nervous system lymphoma. However, the apparent diffusion coefficient ratio calculated from diffusion-tensor acquisitions was 1.53 and was higher than that of lymphomas in previous reports. Stereotactic brain biopsy was performed and lymphomatoid granulomatosis was confirmed.

p53-independent cyclin G expression in a group of mature neurons and its enhanced expression during nerve regeneration.

An increase in cyclin G expression after nerve injury was demonstrated by differential display PCR, carried out to compare references in expression of mRNAs between axotomized and normal hypoglossal motoneurons in the rat. The nerve injury dramatically upregulated the expression of cyclin G mRNA in the motoneurons during the early phase of the nerve regeneration process, suggesting an involvement of cyclin G in the early stage of nerve regeneration. In brain, in situ hybridization studies also demonstrated cyclin G expression in a restricted group of matured neurons, particularly in the telencephalon and the thalamus. This constitutive expression in mature neurons suggests that cyclin G may have a function different from other members of the cyclin group. In addition, although cyclin G has been shown to be a transcription target of p53, the upregulation of cyclin G in injured motoneurons, as well as the expression in the adult rat brain, was not affected in the p53-deficient mouse. These data suggest that the expression of cyclin G, at least in the nervous system, is not regulated by p53 predominantly, and that there may be alternative regulatory factors or pathways for cyclin G expression.

Breath-hold T2-weighted MRI of hepatic tumors: value of echo planar imaging with diffusion-sensitizing gradient.

PURPOSE: The purpose of our study was to evaluate the efficacy of echo planar imaging (EPI) as a breath-holding T2-weighted technique for imaging focal hepatic lesions. METHOD: Forty-eight patients with focal hepatic lesions (9 metastases, 21 hepatocellular carcinomas, 1 cholangiocarcinoma, 16 hemangiomas, and 2 cysts) underwent single shot EPI with and without a small diffusion-sensitizing gradient (DSG) (beta values = 55 s/mm2) at 1.5 T. Comparison was made with breath-holding T2-weighted fast SE (FSE) sequences. RESULTS: Lesion-to-liver signal intensity ratio of EPI was significantly better than that of T2-weighted FSE (p < 0.05) in patients with metastasis. Use of DSG suppressed bright signals from vessels or periportal tissue, resulting in better conspicuity of small lesions. EPI with DSG visualized more metastatic deposits than T2-weighted FSE (p < 0.01). CONCLUSION: EPI with a small DSG is helpful for detection of small hepatic metastases.