The Application Value of Ultrasound Imaging in the Differential Diagnosis of Benign and Malignant Breast Nodules of BI-RADS 3 and Above

Objective:To explore the diagnostic value of ultrasound imaging for breast nodules of breast imaging-reporting and data system(BI-RADS)category 3 and above.Methods:From June 2021 to July 2022,163 patients with breast nodules of BI-RADS 3 or above were selected as the research subjects.After pathological diagnosis,24 cases were malignant breast nodules of BI-RADS 3 or above,while 139 cases were benign breast nodules of BI-RADS 3 or above.The diagnosis rate of malignant and benign breast nodules of BI-RADS 3 or above,including 95%CI,was observed and analyzed.Results:The malignant and benign detection rates of conventional ultrasound were 88.63%and 75.00%,respectively,and the malignant and benign detection rates of ultrasound imaging were 93.18%and 87.50%,respectively,with 95%CIs greater than 0.7.Conclusion:Ultrasound imaging can help improve the diagnostic accuracy of benign and malignant breast nodules of BI-RADS 3 and above and reduce the misdiagnosis rate.

A Novel Approach to Breast Tumor Detection: Enhanced Speckle Reduction and Hybrid Classification in Ultrasound Imaging

Breast cancer detection heavily relies on medical imaging, particularly ultrasound, for early diagnosis and effectivetreatment. This research addresses the challenges associated with computer-aided diagnosis (CAD) of breastcancer fromultrasound images. The primary challenge is accurately distinguishing between malignant and benigntumors, complicated by factors such as speckle noise, variable image quality, and the need for precise segmentationand classification. The main objective of the research paper is to develop an advanced methodology for breastultrasound image classification, focusing on speckle noise reduction, precise segmentation, feature extraction, andmachine learning-based classification. A unique approach is introduced that combines Enhanced Speckle ReducedAnisotropic Diffusion (SRAD) filters for speckle noise reduction, U-NET-based segmentation, Genetic Algorithm(GA)-based feature selection, and Random Forest and Bagging Tree classifiers, resulting in a novel and efficientmodel. To test and validate the hybrid model, rigorous experimentations were performed and results state thatthe proposed hybrid model achieved accuracy rate of 99.9%, outperforming other existing techniques, and alsosignificantly reducing computational time. This enhanced accuracy, along with improved sensitivity and specificity,makes the proposed hybrid model a valuable addition to CAD systems in breast cancer diagnosis, ultimatelyenhancing diagnostic accuracy in clinical applications.

Ultrasound Imaging of Pipeline Crack Based on Composite Transducer Array

Cracks, especially small cracks are di cult to be detected in oil and gas transportation pipelines buried underground or covered with layers of material by using the traditional ultrasonic inspection techniques. Therefore, a new com?posite ultrasonic transducer array with three acoustic beam incidence modes is developed. The space model of the array is also established to obtain the defect reflection point location. And the crack ultrasound image is thus formed through a series of small cubical elements expanded around the point locations by using the projection of binariza?tion values extracted from the received ultrasonic echo signals. Laboratory experiments are performed on a pipeline sample with di erent types of cracks to verify the e ectiveness and performance of the proposed technique. From the image, the presence of small cracks can be clearly observed, in addition to the sizes and orientations of the cracks. The proposed technique can not only inspect common flaws, but also detect cracks with various orientations, which is helpful for defect evaluation in pipeline testing.

Preprocedure ultrasound imaging combined with palpation technique in epidural labor analgesia

BACKGROUND For parturients with paroxysmal uterine contraction pain,rapid analgesia is needed.We used preprocedure ultrasound imaging combined with the palpation technique in epidural analgesia for labor,and evaluated the usefulness of this technique in epidural labor analgesia.AIM To evaluate the usefulness of preprocedure ultrasound imaging in epidural analgesia for labor.METHODS In this prospective randomized observational study,72 parturients were assigned to two groups(combined or palpation group).The target interspace of all parturients was first identified by the palpation technique.Then in the combined group,preprocedure ultrasound imaging was used before epidural puncture.In the palpation group,only the traditional anatomical landmarks technique(palpation technique)was performed.The primary outcome was total duration of the epidural procedure(for the ultrasound group,the duration of the preprocedure ultrasound imaging was included).The secondary outcomes were the number of skin punctures,the success rate at first needle pass,the number of needle passes,the depth from the skin to epidural space,and the complications of the procedure.RESULTS Total duration of the epidural procedure was similar between the two groups(406.5±92.15 s in the combined group and 380.03±128.2 s in the palpation group;P=0.318).A significant improvement was demonstrated for epidural puncture and catheterization in the combined group.The number of needle passes was 1.14 in the combined group and 1.72 in the palpation group(P=0.001).The number of skin puncture sites was 1.20 in the combined group and 1.25 in the palpation group(P=0.398).The success rate at first needle pass was 88.89%in the combined group and 66.67%in the palpation group(P=0.045).CONCLUSION This study demonstrated that the total duration of epidural procedures with preprocedure ultrasound imaging combined with the palpation technique was not longer than the traditional anatomical landmarks technique,which were performed by six experienced anesthesiologists in parturients with normal weights undergoing labor analgesia.

Ultrasound imaging of chitosan nerve conduits that bridge sciatic nerve defects in rats

The repair of peripheral nerve injuries with autologous nerve remains the gold standard （Wang et al., 2005; Yao et al., 2010; Deal et al., 2012; Kriebel et al., 2014; Liu et al., 2014; Tamaki et al., 2014; Yu et al., 2014; Zhu and Lou, 2014）. With advances in tissue engineering and biomaterials, tissue-engineered nerve conduits with various biomaterials and structures, such as collagen and chitosan nerve conduits, have already been used in the clinic as alternatives to autologous nerve in the repair of peripheral nerve injury （Wang et al., 2012; Svizenska et al., 2013; Eppenberger et al., 2014; Gu et al., 2014; Koudehi et al., 2014; MoyaDiaz et al., 2014; Novajra et al., 2014; Okamoto et al., 2014; Shea et al., 2014; Singh et al., 2014; Tamaki et al., 2014; Yu et al., 2014）. Therefore, new simple and effective methods

The Diagnosis of Diffuse Goitre by Ultrasound Imaging in Children

In order to find an easy and accurate procedure for diagnosis of diffuse goitre in children, we examined 50 patients with diffuse goitre using fine needle aspiration biopsy cytology, thyroid antibody detection, thyroid hormone analysis and ultrasound imaging. In the meantime, 109 healthy children (control) were examined by ultrasound imaging. The results showed that thyroid imaging in health children was a smooth echo pattern with stronger homogenous echogram than surrounding muscle tissues. The patients with diffuse goitre showed an normally enlarged thyroid volume. In 22 (84. 6 %) of 26 children With chronic lymphocytic thyroiditis, a varied patch hypoechogenicity was found, of whom 18 (81. 8 % ) had positive results of antibody testing. On the contrary, echo-pattern was normal in 17 (70. 8 %) of 24 patients with diffuse thyroid proliferation and only the remainder (7/24, 29. 1% ) had abnormal echo-pattern as well as elevated auto-antibody titers, of whom 2 were confirmed as chronic lymphocytic thyroiditis by a repeat fine needle aspiration biopsy 1 year later. By using combined ultrasound imaging and antibody determination, 92 % of the cases with chronic lymphocytic thyroiditis could be diagnosed. Our study suggests that ultrasonic imaging is an easy, non-invasive, reproducible and effective procedure in the differen,tial diagnosis of chronic lymphocytic thyroiditis in children.

Optically-excited simultaneous photoacoustic and ultrasound imaging based on aflexible gold-PDMS film

We constructed a flexible gold-polydimethylsiloxane(gold-PDMS)nanocomposites film with controllable thickness and light transmittance,to realize optically-excited simultaneous photo-acoustic(PA)and ultrasound(US)imaging under a single laser pulse irradiation.Benefiting from the excellent thermoelastic properties,the gold-PDMS film absorbs part of the incident laser energy and produces a high-intensity US,which is used to realize US imaging.Meanwhile,the partly transmitted light is used to excite samples for PA imaging.By controlling the thickness of the gold-PDMS,we can control the center frequency in the US imaging.We experimentally analyzed the frequency of the produced US signal by the gold-PDMSfilm and compared it with the finite element analysis(FEA)method,where the experiments agree with the FEA results.This method is demonstrated by the experiments on phantoms and a mouse model.Our work provides a cost-effective methodology for simultaneous PA and US imaging.

HPDA/Zn as a CREB Inhibitor for Ultrasound imaging and Stabilization of Atherosclerosis Plaque+

Thrombosis,secondary to rupture of unstable plaque,is a fatal risk factor for myocardial infarction and ischemic stroke.At present,more novel methods are needed for the diagnosis and treatment of vulnerable plaque.Here,we report a hollow polydopamine/Zn(HPDA/Zn)ultrasound contrast agent.Through western-blot,Elisa,and other experiments,we found that in addition to having a good contrast-enhancement capability in ultrasound imaging in vitro and in vivo,HPDA/Zn also has the effect of reducing the expres-sion of CREB.CREB protein and its downstream-regulated proteins and factors are closely related to the stability of plaque.HPDA/Zn has the effect of reducing the expression of CREB protein,which leads to the decrease of expression of MMP-9,the regulatory pro-tein downstream of the CREB protein.In addition,it also reduces the secretion of inflammatory factors hs-CRP and IL-17A.Thus,HPDA/Zn can stabilize plaque by inhibiting CREB and reducing plaque vulnerable markers and inflammatory factors.In a word,HPDA/Zn is a kind of ultrasound contrast agent,which can stabilize plaques by inhibiting CREB protein.

Quantitative ultrasound brain imaging with multiscale deconvolutional waveform inversion

High-resolution images of human brain are critical for monitoring the neurological conditions in a portable and safe manner.Sound speed mapping of brain tissues provides unique information for such a purpose.In addition,it is particularly important for building digital human acoustic models,which form a reference for future ultrasound research.Conventional ultrasound modalities can hardly image the human brain at high spatial resolution inside the skull due to the strong impedance contrast between hard tissue and soft tissue.We carry out numerical experiments to demonstrate that the time-domain waveform inversion technique,originating from the geophysics community,is promising to deliver quantitative images of human brains within the skull at a sub-millimeter level by using ultra-sound signals.The successful implementation of such an approach to brain imaging requires the following items:signals of sub-megahertz frequencies transmitting across the inside of skull,an accurate numerical wave equation solver simulating the wave propagation,and well-designed inversion schemes to reconstruct the physical parameters of targeted model based on the optimization theory.Here we propose an innovative modality of multiscale deconvolutional waveform inversion that improves ultrasound imaging resolution,by evaluating the similarity between synthetic data and observed data through using limited length Wiener filter.We implement the proposed approach to iteratively update the parametric models of the human brain.The quantitative imaging method paves the way for building the accurate acoustic brain model to diagnose associated diseases,in a potentially more portable,more dynamic and safer way than magnetic resonance imaging and x-ray computed tomography.

A Modified CycleGAN for Multi-Organ Ultrasound Image Enhancement via Unpaired Pre-Training

Handheld ultrasound devices are known for their portability and affordability,making them widely utilized in underdeveloped areas and community healthcare for rapid diagnosis and early screening.However,the image quality of handheld ultrasound devices is not always satisfactory due to the limited equipment size,which hinders accurate diagnoses by doctors.At the same time,paired ultrasound images are difficult to obtain from the clinic because imaging process is complicated.Therefore,we propose a modified cycle generative adversarial network(cycleGAN) for ultrasound image enhancement from multiple organs via unpaired pre-training.We introduce an ultrasound image pre-training method that does not require paired images,alleviating the requirement for large-scale paired datasets.We also propose an enhanced block with different structures in the pre-training and fine-tuning phases,which can help achieve the goals of different training phases.To improve the robustness of the model,we add Gaussian noise to the training images as data augmentation.Our approach is effective in obtaining the best quantitative evaluation results using a small number of parameters and less training costs to improve the quality of handheld ultrasound devices.

Ovarian-adnexal reporting and data system ultrasound evaluation and pathological characteristics of ovarian collision tumor

BACKGROUND Collision tumor are neoplasms,including two histologically distinct tumors that coexist in the same mass without histological admixture.The incidence of collision tumor is low and is rare clinically.AIM To investigate ultrasound images and application of ovarian-adnexal reporting and data system(O-RADS)to evaluate the risk and pathological characteristics of ovarian collision tumor.METHODS This study retrospectively analyzed 17 cases of ovarian collision tumor diagnosed pathologically from January 2020 to December 2023.All clinical features,ultrasound images and histopathological features were collected and analyzed.The O-RADS score was used for classification.The O-RADS score was determined by two senior doctors in the gynecological ultrasound group.Lesions with O-RADS score of 1-3 were classified as benign tumors,and lesions with O-RADS score of 4 or 5 were classified as malignant tumors.RESULTS There were 17 collision tumors detected in 16 of 6274 patients who underwent gynecological surgery.The average age of 17 women with ovarian collision tumor was 36.7 years(range 20-68 years),in whom,one occurred bilaterally and the rest occurred unilaterally.The average tumor diameter was 10 cm,of which three were 2-5 cm,11 were 5-10 cm,and three were>10 cm.Five(29.4%)tumors with O-RADS score 3 were endometriotic cysts with fibroma/serous cystadenoma,and unilocular or multilocular cysts contained a small number of parenchymal components.Eleven(64.7%)tumors had an O-RADS score of 4,including two in category 4A,six in category 4B,and three in category 4C;all of which were multilocular cystic tumors with solid components or multiple papillary components.One(5.9%)tumor had an O-RADS score of 5.This case was a solid mass,and a small amount of pelvic effusion was detected under ultrasound.The pathology was high-grade serous cystic cancer combined with cystic mature teratoma.There were nine(52.9%)tumors with elevated serum carbohydrate antigen(CA)125 and two(11.8%)with elevated serum CA19-9.Histological and pathological results showed that epithelial-cell-derived tumors combined with other tumors were the most common,which was different from previous results.CONCLUSION The ultrasound images of ovarian collision tumor have certain specificity,but diagnosis by preoperative ultrasound is difficult.The combination of epithelial and mesenchymal cell tumors is one of the most common types of ovarian collision tumor.The O-RADS score of ovarian collision tumor is mostly≥4,which can sensitively detect malignant tumors.

INTRAVASCULAR ULTRASOUND IMAGING OF ANGIOGRAPHICALLY "SILENT" LEFT MAIN CORONARY ARTERY ATHEROSCLEROSIS

Patients with left main coronary artery (LMCA) atherosclerosis have a poor prognosis compared with lesions in the other coronaries. Because of the methodological problems. LMCA atherosclerotic lesions are not frequently detected by coronary angiography. The purpose of the study was to reveal the existence of LMCA disease in patients with normal coronary arteries by using intravascular ultrasound imaging. Ninety-seven patients with angiographically normal coronary arteries were examined with a 3.5 F or 4.8 F. 20 MHz intravascular ultrasound catheter. The vessel, lumen and plaque areas were determined and percent area and diameter stenosis were calculated. Plaque formation with or without calcific deposits identified by ultrasound accoustic shadowing were regarded as signs of atherosclerosis.

The application of compressed sensing in synthetic transmit aperture medical ultrasound imaging

In synthetic transmit aperture medical ultrasound imaging field,a compressed sensing ultrasound imaging method based on the sparsity in frequency domain is presented in order to reduce huge amount of data and large numbers of receiving channels.First,the sparsity in frequency domain is verified.Then the echo signal is compressively sampled in time-spatial domain based on compressed sensing and the echo signal is reconstructed by solving an optimization problem.Finally the image is made by using the synthetic transmit aperture approach.The experiments based on point target and fetus target are used to verify the proposed method.The MSE,resolution and image quality of reconstructed image and those of original image are compared and analyzed.The results show that only 30%amount of data and 50%of receiving channels were used to implement ultrasound imaging without reducing the quality of image in experiment.The amount of data and the complexity of system are reduced greatly by the proposed method based on compressed sensing.

RELATIONSHIP BETWEEN CORONARY ANGIOSCOPIC AND INTRAVASCULAR ULTRASOUND IMAGING AND RESTENOSIS

In order to investigate the relationship between restenosis and the morphology detected by coronary angioscopy (CASC) and introvascular ultrasound imaging (IVUS), 17 patients were detected by CASC and IVUS immediately and 3 months after percutaneous transluminal coronary angioscopy (PTCA), The results showed that the dilation index by IVUS (DIu) was significantly lower in restenosis patients than in non-restenosis patients (0.42 +/- 0.08 versus 0.78 +/- 0.16, P < 0.01) and that the elastic recoil (ER) was higher in restenosis patients than in non-restenosis patients (4.51 +/- 1.42 mm(2) versus 1.63 +/- 1.20 mm(2), P < 0.01), and that the elastic recoil rate (ERR) was also higher in restenosis patients than in non-restenosis patients (57.3 +/- 8.07% versus 21.80 +/- 16.84% P < 0.01), and that coronary dissection, atheromatous plaque and calcification as well as the colour of inner coronary artery had no relation with chronic restenosis. In conclusion, the elastic recoil is one of the important factors of chronic restenosis after PTCA.

Recent advances in applications of multimodal ultrasound-guided photoacoustic imaging technology

Photoacoustic imaging(PAI)is often performed simultaneously with ultrasound imaging and can provide functional and cellular information regarding the tissues in the anatomical markers of the imaging.This paper describes in detail the basic principles of photoacoustic/ultrasound(PA/US)imaging and its application in recent years.It includes near-infrared-region PA,photothermal,photodynamic,and multimode imaging techniques.Particular attention is given to the relationship between PAI and ultrasonic imaging;the latest high-frequency PA/US imaging of small animals,which involves not only B-mode,but also color Doppler mode,power Doppler mode,and nonlinear imaging mode;the ultrasonic model combined with PAI,including the formation of multimodal imaging;the preclinical imaging methods;and the most effective detection methods for clinical research for the future.

Ultrasound Imaging Signal Analysis of Underwater Topography in River Model Experiment

In this paper, we analyze the feature of ultrasonic image and investigate the effect of topography material, flow velocity and sediment concentration on the imaging of underwater topography by imaging experiments of model sands. These imaging experiments are conducted in river engineering physical model.The results show that the vertical distribution of pixel values is changed hugely at the position of imaging bright band of underwater topography. The imaging of underwater topography is not affected when flow velocity is below 40 cm/s and sediment concentration is below 5.0 ‰. The main influence factors of imaging signals are flow velocity and sediment concentration near the topographical bed. The resolution of ultrasound imaging signals is high, and the topography consisted of model sands with particle size smaller than 0.1 mm can be monitored well in the river model experiment.

Artificial intelligence-based ultrasound imaging technologies for hepatic diseases

Ultrasound(US)imaging is a non-invasive,real-time,economical,and convenient imaging modality that has been widely used in diagnosing and treating hepatic diseases.Artificial intelligence(AI)technology can predict or make decisions based on the experience of clinical experts and knowledge obtained from training data.This technology can help clinicians improve the detection efficiency and evaluate hepatic diseases,promote clinical treatment of the liver,and predict the response of the liver after treatment.This review summarizes the current rapid development of US technology and related AI methods in the diagnosis and treatment of hepatic diseases.Covered topics include steatosis grading,fibrosis staging,detection of focal liver lesions,US image segmentation,multimodal image registration,and other applications.At present,the field of AI in US imaging is still in its early stages.With the future progress of AI technology,AI-based US imaging can further improve diagnosis,reduce medical costs,and optimize US-based clinical workflow.This technology has broad prospects for application to hepatic diseases.

Contrast-enhanced ultrasound Liver Imaging Reporting and Data System:Lights and shadows in hepatocellular carcinoma and cholangiocellular carcinoma diagnosis

BACKGROUND Contrast-enhanced ultrasound(CEUS)is considered a secondary examination compared to computed tomography(CT)and magnetic resonance imaging(MRI)in the diagnosis of hepatocellular carcinoma(HCC),due to the risk of misdiagnosing intrahepatic cholangiocarcinoma(ICC).The introduction of CEUS Liver Imaging Reporting and Data System(CEUS LI-RADS)might overcome this limitation.Even though data from the literature seems promising,its reliability in real-life context has not been well-established yet.AIM To test the accuracy of CEUS LI-RADS for correctly diagnosing HCC and ICC in cirrhosis.METHODS CEUS LI-RADS class was retrospectively assigned to 511 nodules identified in 269 patients suffering from liver cirrhosis.The diagnostic standard for all nodules was either biopsy(102 nodules)or CT/MRI(409 nodules).Common diagnostic accuracy indexes such as sensitivity,specificity,positive predictive value(PPV),and negative predictive value(NPV)were assessed for the following associations:CEUS LR-5 and HCC;CEUS LR-4 and 5 merged class and HCC;CEUS LR-M and ICC;and CEUS LR-3 and malignancy.The frequency of malignant lesions in CEUS LR-3 subgroups with different CEUS patterns was also determined.Inter-rater agreement for CEUS LI-RADS class assignment and for major CEUS pattern identification was evaluated.RESULTS CEUS LR-5 predicted HCC with a 67.6%sensitivity,97.7%specificity,and 99.3%PPV(P<0.001).The merging of LR-4 and 5 offered an improved 93.9%sensitivity in HCC diagnosis with a 94.3%specificity and 98.8%PPV(P<0.001).CEUS LR-M predicted ICC with a 91.3%sensitivity,96.7%specificity,and 99.6%NPV(P<0.001).CEUS LR-3 predominantly included benign lesions(only 28.8%of malignancies).In this class,the hypo-hypo pattern showed a much higher rate of malignant lesions(73.3%)than the iso-iso pattern(2.6%).Inter-rater agreement between internal raters for CEUS-LR class assignment was almost perfect(n=511,k=0.94,P<0.001),while the agreement among raters from separate centres was substantial(n=50,k=0.67,P<0.001).Agreement was stronger for arterial phase hyperenhancement(internal k=0.86,P<2.7×10-214;external k=0.8,P<0.001)than washout(internal k=0.79,P<1.6×10-202;external k=0.71,P<0.001).CONCLUSION CEUS LI-RADS is effective but can be improved by merging LR-4 and 5 to diagnose HCC and by splitting LR-3 into two subgroups to differentiate iso-iso nodules from other patterns.

Prenatal Diagnosis of Sirenomelia by Two-Dimensional and Three-Dimensional Skeletal Imaging Ultrasound

Summary： This study sought to evaluate the contribution of two-dimensional ultrasound （2D-US） and three-dimensional skeletal imaging ultrasound （3D-SUIS） in the prenatal diagnosis of sirenomelia. Be- tween September 2010 and April 2014, a prospective study was conducted in a single referral center using 3D-SU1S performed after 2D-US in 10 cases of sirenomelia. Diagnostic accuracy and detailed findings were compared with postnatal three-dimensional helical computed tomography （3D-HCT）, radiological findings and autopsy. Pregnancy was terminated in all 10 sirenomelia cases, including 9 singletons and I conjoined twin pregnancy, for a total of 5 males and 5 females. These cases of sirenomelia were deter- mined by autopsy and/or chromosomal examination. Initial 2D-US showed that there were 10 cases of oligohydranmios, bilateral renal agenesis, bladder agenesis, single umbilical artery, fusion of the lower limbs and spinal abnormalities; 8 cases of dipus or monopus; 2 cases of apus; and 8 cases of cardiac abnormalities. Subsequent 3D-SUIS showed that there were 9 cases of scoliosis, l0 cases of sacrococ- cygeal vertebra dysplasia, 3 cases of hemivertebra, 1 case of vertebral fusion, 3 cases of spina bifida, and 5 cases of rib abnormalities. 3D-SUIS identified significantly more skeletal abnormalities than did 2D-US, and its accuracy was 79.5% （70/88） compared with 3D-HCT and radiography. 3D-SUIS seems to be a useful complementary method to 2D-US and may improve the accuracy of identifying prenatal skeletal abnormalities related to sirenomelia.

Comparison of unenhanced magnetic resonance imaging and ultrasound in detecting very small hepatocellular carcinoma

BACKGROUND In hepatocellular carcinoma(HCC),detection and treatment prior to growth beyond 2 cm are important as a larger tumor size is more frequently associated with microvascular invasion and/or satellites.In the surveillance of very small HCC nodules(≤2 cm in maximum diameter,Barcelona clinical stage 0),we demonstrated that the tumor markers alpha-fetoprotein and PIVKA-Ⅱare not so useful.Therefore,we must survey with imaging modalities.The superiority of magnetic resonance imaging(MRI)over ultrasound(US)to detect HCC was confirmed in many studies.Although enhanced MRI is now performed to accurately diagnose HCC,in conventional clinical practice for HCC surveillance in liver diseases,unenhanced MRI is widely performed throughout the world.While,MRI has made marked improvements in recent years.AIM To make a comparison of unenhanced MRI and US in detecting very small HCC that was examined in the last ten years in patients in whom MRI and US examinations were performed nearly simultaneously.METHODS In 394 patients with very small HCC nodules,those who underwent MRI and US at nearly the same time(on the same day whenever possible or at least within 14 days of one another)at the first diagnosis of HCC were selected.The detection rate of HCC with unenhanced MRI was investigated and compared with that of unenhanced US.RESULTS The sensitivity of unenhanced MRI for detecting very small HCC was 95.1%(97/102,95%confidence interval:90.9-99.3)and that of unenhanced US was 69.6%(71/102,95%confidence interval:60.7-78.5).The sensitivity of unenhanced MRI for detecting very small HCC was significantly higher than that of unenhanced US(P<0.001).Regarding the location of HCC in the liver in patients in whom detection by US was unsuccessful,S7-8 was identified in 51.7%.CONCLUSION Currently,unenhanced MRI is a very useful tool for the surveillance of very small HCC in conventional clinical follow-up practice.