the incidence of hbv or hcv - associated viral hepatitis is increasing , along with the incidence of hepatocellular carcinoma ( hcc ) .
however , advances in diagnostic imaging techniques such as ultrasonography , computed tomography ( ct ) , and magnetic resonance imaging ( mri ) now enable early detection and diagnosis of hcc . in recent years
, hcc detected by these diagnostic imaging techniques has been treated locally by radiofrequency ablation ( rfa ) and other techniques , with favorable therapeutic outcomes comparable to hepatectomy [ 3 , 4 ] .
however , abdominal ultrasonography does not always provide precise guidance in identifying isoechoic tumors , tumors recurring locally in areas treated with lipiodol following transarterial chemoembolization ( tace ) , or tumors recurring in areas treated by rfa or percutaneous ethanol injection ( pei ) procedures .
we have recently utilized the approaches which involved preparing multiplanar reconstruction ( mpr ) images that matched ultrasonography images of lesions and expected puncture routes on a workstation .
mpr images were reconstructed by matching ultrasonography images and ct data ( digital imaging and communications in medicine ( dicom ) data ) obtained by prior ct during arterial portography ( ctap ) and ct during hepatic arteriography ( ctha ) , followed by more accurate coagulation based on scans of target areas while referring to the relative positions of surrounding vessels and organs shown of the images .
one problem with this technique is that mpr images are prepared in advance , and critical discrepancies can arise in scans of intercostal spaces due to axial rotation of a probe between the mpr and ultrasound images . seeking to resolve this problem
, we investigated the feasibility of hitachi medical real - time virtual sonography ( rvs ) , a system that generates mpr images in real - time , as a probe scans over target areas .
among consecutive subjects who admitted to saga medical school with diagnosed hcc from january 2004 to january 2005 , candidates for unresectable invasive therapy were eligible for enrollment after informed consent was obtained .
diagnosis was confirmed by needle biopsy or by plural imaging techniques including ultrasonography , dynamic ct , dynamic mri , and super paramagnetic iron oxide mri .
subjects with up to 3 nodules less than 3  cm in diameter were excluded from this study and received transarterial chemo - embolization .
ctap / ctha was performed for all enrolled subjects ; 1 ) to confirm hcc which showed low density tumor with ctap , high density tumor with early phase ctha , and low density tumor with corona enhancement with delayed phase ctha , 2 ) to survey multi - centric occurrence of hcc , and 3 ) to confirm intrahepatic tumor staging .
the therapeutic system used comprised the hitachi medico digital ultrasound eub-8500 and hitachi medico workstation rvs ( hitachi medico .
the rvs , a revolutionary real - time mpr imaging machine that supports ultrasonography diagnosis developed by hitachi medico , consists of a small magnetic sensor attached to a convex - shaped eub-8500 probe .
this magnetic sensor precisely and consistently captures changes in magnetic fields generated by the generator placed on the left flank of a patient and detects the changes in the location , direction , and rotation of the probe scanning of the patient .
the rvs instantaneously processes changes in positional information detected by the magnetic sensor and generates real - time mpr images matching cross - sectional images of the abdomen captured by the probe ( fig .  1 ) .
the actual procedure is as follows : 1 ) ctap / ctha was performed , followed by transfer of volume data ( dicom data ) to the rvs .
ctap data was used because ctap detects portal and hepatic veins , which was captured by ultrasonography .
the positional relationship of a tumor to these vessels is critical for identifying lesions which ultrasonography can not detect .
2 ) a magnetic field generator is placed on the left flank of a patient .
3 ) the sagittal section of the left hepatic lobe is first captured using a probe equipped with a magnetic sensor .
when a ct image with the tip of the xiphoid process captured before mpr processing matches the tip of the xiphoid process on the actual abdominal ultrasound image , the rvs begins continuous generation of mpr images in real - time , displaying the images on the workstation monitor .
4 ) a cross - sectional image showing the tumor is displayed with the mpr image , and both images are corrected based on neighboring portal and hepatic veins ; and 5 ) the tumor is then punctured and coagulated under rvs - guidance in the conventional technique .
the rfa device used in the methods were cool - tip electrode with a 2- or 3-cm exposed tip and a radiofrequency generator ( radionics , burlington , ma ) .
the procedures were each performed by one of three experienced rfa physicians ( y.e , t.y , and t.m ) .
abdominal dynamic ct was performed on all patients approximately 3 days and 1 month after the treatment for evaluation after rfa .
complete response was confirmed by dynamic ct showed widely low density area with sufficient safety margin .
among consecutive subjects who admitted to saga medical school with diagnosed hcc from january 2004 to january 2005 , candidates for unresectable invasive therapy were eligible for enrollment after informed consent was obtained .
diagnosis was confirmed by needle biopsy or by plural imaging techniques including ultrasonography , dynamic ct , dynamic mri , and super paramagnetic iron oxide mri .
subjects with up to 3 nodules less than 3  cm in diameter were excluded from this study and received transarterial chemo - embolization .
ctap / ctha was performed for all enrolled subjects ; 1 ) to confirm hcc which showed low density tumor with ctap , high density tumor with early phase ctha , and low density tumor with corona enhancement with delayed phase ctha , 2 ) to survey multi - centric occurrence of hcc , and 3 ) to confirm intrahepatic tumor staging .
the therapeutic system used comprised the hitachi medico digital ultrasound eub-8500 and hitachi medico workstation rvs ( hitachi medico .
the rvs , a revolutionary real - time mpr imaging machine that supports ultrasonography diagnosis developed by hitachi medico , consists of a small magnetic sensor attached to a convex - shaped eub-8500 probe .
this magnetic sensor precisely and consistently captures changes in magnetic fields generated by the generator placed on the left flank of a patient and detects the changes in the location , direction , and rotation of the probe scanning of the patient .
the rvs instantaneously processes changes in positional information detected by the magnetic sensor and generates real - time mpr images matching cross - sectional images of the abdomen captured by the probe ( fig .  1 ) .
the actual procedure is as follows : 1 ) ctap / ctha was performed , followed by transfer of volume data ( dicom data ) to the rvs .
ctap data was used because ctap detects portal and hepatic veins , which was captured by ultrasonography .
the positional relationship of a tumor to these vessels is critical for identifying lesions which ultrasonography can not detect .
2 ) a magnetic field generator is placed on the left flank of a patient .
3 ) the sagittal section of the left hepatic lobe is first captured using a probe equipped with a magnetic sensor .
when a ct image with the tip of the xiphoid process captured before mpr processing matches the tip of the xiphoid process on the actual abdominal ultrasound image , the rvs begins continuous generation of mpr images in real - time , displaying the images on the workstation monitor .
4 ) a cross - sectional image showing the tumor is displayed with the mpr image , and both images are corrected based on neighboring portal and hepatic veins ; and 5 ) the tumor is then punctured and coagulated under rvs - guidance in the conventional technique .
the rfa device used in the methods were cool - tip electrode with a 2- or 3-cm exposed tip and a radiofrequency generator ( radionics , burlington , ma ) .
the procedures were each performed by one of three experienced rfa physicians ( y.e , t.y , and t.m ) .
abdominal dynamic ct was performed on all patients approximately 3 days and 1 month after the treatment for evaluation after rfa .
complete response was confirmed by dynamic ct showed widely low density area with sufficient safety margin .
in this study , 21 patients included seven men and fourteen women were enrolled ( fig .  2 ) .
twenty five nodules in 21 patients were diagnosed hcc ( 23 nodules were diagnosed by ctap / ctha , 2 nodules were diagnosed with needle biopsy as well differentiated hcc .
rfa was performed using the present system to treat all 25 nodules in 21 patients .
of the 25 nodules , 11 nodules were tumors with unclear margins , as seen in representative ultrasonography images shown in fig .  3 ,
5 were tumors arising in the vicinity of areas coagulated following radiofrequency ablation ; 4 were tumors that could not be fully identified due to their position beneath the diaphragm ; 4 were viable tumors emerging following tace in areas affected by posterior acoustic enhancement of lipiodol deposition ; and 1 was a recurrent tumor located at a resection stump following hepatectomy ( table  1 ) . in all cases , conventional ultrasonography failed to detect the entire lesion accurately .
in contrast , the current rvs made it possible to accurately and conveniently ascertain the extent of nodules .
rfa was performed using the present system to treat all 25 nodules in 21 patients .
the average tumor diameter was 2.4    1.6  cm , and punctures and coagulation were performed an average of 2.2 and 3 times per session .
dynamic ct for evaluation after rfa showed widely low density area with sufficient safety margin and confirmed that each tumor had been effectively coagulated .
hcc is seen in the area with a reduced portal flow in segment 4 ( arrow head ) on ctap ( fig . 
4a ) , the area with high hepatic arterial flow on early - phase ctha ( fig . 
in recent years , hcc has been treated effectively by combining various therapeutic techniques . among these techniques ,
use of percutaneous rfa in particular has grown , with therapeutic outcomes for hcc of less than 3  cm in diameter comparable to pei therapy or hepatectomy [ 3 , 79 ] .
a recent study shown rfa for hcc is a definitive treatment as a bridge to liver transplantation .
but in recent years , treatment has increasingly tackled lesions recurring in the vicinity of areas treated by rfa or tace .
such recurrent lesions and isoechoic tumors are often difficult to identify by conventional b - mode ultrasonography , and imaging success depends heavily on operator s skill .
techniques used to improve the effectiveness of this approach include use of coded - harmonic images and ultrasonographic contrast media ; deliberate injection of pleural or peritoneal fluid to aid imaging ; and ct - guided punctures .
we have recently utilized the approaches which involved preparing mpr images that matched ultrasonography images of lesions and expected puncture routes on a workstation .
discrepancies can arise between mpr and ultrasound images due to axial rotation of a probe for scans of intercostal spaces .
rvs could solve this problem by real - time adjustment based on neighboring portal and hepatic veins , and shapes of the liver bed .
while reports have referenced therapeutic systems that generate mpr images like the rvs items   are unable to reconstruct accurate and real - time mpr imaging capable of keeping pace with probe - scanning , the current rvs we employed makes it possible to accurately and conveniently ascertain the extent of nodules which were difficult to identify by conventional ultrasonography .
rvs also clearly indicates the location of the lungs , intestines , or mesentery , minimizing the risk of inducing pneumothorax , puncturing the intestinal canal , or burning other organs , even when tumors are located beneath the diaphragm or in the liver bed .
these qualities make it an extremely effective approach for treating liver tumors , including cases of hcc , which are not readily identifiable by conventional ultrasonography .
several previous reports indicated that the hcc nodule , which was not detected by conventional b - mode and was detected only by ctap / ctha , was detected during surgical operation [ 1719 ] . as indicated in this study , rvs might be one of modalities which recovered defect of conventional b - mode and rvs enabled accurate detection for a target , which supported appropriate therapeutic approach to the hcc nodule .
first , rvs requires close synchronization of mpr and ultrasound images , making it essential to obtain ct data on portal and hepatic veins , which makes it necessary to investigate rvs systems in patients in whom dynamic ct or dynamic mri is contraindicated due to issues such as contrast medium allergies or renal dysfunction .
second , the synchronized image on rvs is not perfectly the same slice but the discrepancy in most cases can be adjusted with neighboring portal and hepatic veins , and shapes of the liver bed . in one case in this study
third , it is difficult to lead accurately rfa needles to nodules in some cases , even when rvs can reveal the position of tumor .
because of distortion of the liver , we experienced three nodules those were needed to re - insert for a sufficient puncture . as a result , effective ablations were performed in all cases in this study . in our current study , the outcome obtained from these patients using rvs systems showed favorable clinical course in spite of these limitations in relatively small sample size . further study with control group in larger number
, our study demonstrates that the rvs system is capable of effectively and accurately percutaneous coagulation for hcc which is difficult to detect by conventional ultrasonography .
 radiofrequency ablation has been applied to treat hepatocellular carcinoma , with favorable therapeutic outcomes . 
 nevertheless , practitioners have approached radiofrequency ablation with some reluctance due to the difficulty of identifying isoechoic tumors and recurrent tumors . 
 the aim of the present study is to investigate the efficacy of real - time virtual sonography to treat hepatocellular carcinoma difficult to detect by conventional ultrasonography . 
 real - time virtual sonography is a system generating multiplanar reconstruction images in real - time using the hitachi medico eub-8500 equipped with a probe . 
 the system included following components : 1 ) digital imaging and communications in medicine ( dicom ) data from dynamic ct , 2 ) a magnetic field generator to match the multiplanar reconstruction image on the monitor and the actual ultrasonography image , 3 ) the cross section with the tumor displayed as a multiplanar reconstruction image . 
 total twenty - five nodules of twenty - one patients underwent radiofrequency ablation monitored by real - time virtual sonography . 
 all nodules difficult to detect via conventional ultrasonography were clearly visualized in real - time . 
 the average nodule diameter was 2.4    1.6  cm , and punctures and coagulation were performed an average of 2.2 and 3 times per session . 
 dynamic ct after session confirmed effective coagulation of each nodule . in conclusion 
 , this study demonstrates that the present system is capable of effectively and accurately treating tumors difficult to detect by conventional ultrasonography . 
Introduction
Materials and Methods
Subjects
Therapeutic system and procedures
Efficacy assessment
Results
Discussion