between april and august 1999 , 22 consecutive patients underwent ferumoxides - enhanced mr imaging to assess known or suspected focal liver lesions .
the criteria for inclusion in this study were as follows : hcc was depicted at contrast - enhanced ct , lesions were distributed in such a way that they were resectable , and the patient was considered suitable for curative hepatic resection . on this basis , five patients were excluded because hccs were absent ( metastatic adenocarcinoma was found in two , and each of cholangiocarcinoma , hepatic adenoma , and hemangioma in one ) , and one other because hccs were distributed diffusely .
the remaining 16 patients , 14 men and 2 women ranging in age from 35 to 66 ( mean , 51 ) years , with 25 hccs ( diameter , 3 - 140 [ mean , 41 ] mm ) in 24 hepatic segments comprised our final study group . ferumoxides - enhanced mr imaging was not performed where patients were pregnant , showed severe renal failure , or were allergic to dextran - based drugs .
the study was approved by the institutional review board , and written informed consent was obtained from all patients . for 19 hccs in 11 patients ,
diagnosis was based on the histopathological findings of surgery ; for two , on those of us - guided percutaneous needle biopsy ; and for the remaining four , the basis of confirmation was an elevated serum -fetoprotein level ( over 200 ng / ml ) and characteristic helical ct findings .
thirteen patients in the study had liver cirrhosis as a result of hepatitis b ( n=12 ) , or hepatitis c ( n=1 ) , while the remaining three had hepatitis b without cirrhosis . in order to evaluate hepatic segments which according to the findings of ferumoxides - enhanced mr imaging were hcc - free , follow - up radiologic examinations ( contrast - enhanced ct or gadolinium - enhanced mr imaging ) were performed no less than 12 months later .
all mr examinations were performed on a 1.5-t mr imager ( horizon , ge medical systems , milwaukee , wis .
two respiratory - triggered fse sequences ( tr3333 - 8571/te18 and 90 - 117/etl12/nex2/fat sat . ) , four breath - hold sequences ( proton density ssfse [ tr/te39/nex0.5 ] , t2-weighted ssfse [ tr/te98/nex0.5 ] , fmpgr [ tr130/te8.4 - 9.5/flip angle 30 ] , and fmpspgr [ tr130/te8.4 - 9.5/flip angle 30 ] ) , and the grass sequence ( tr216/te20/flip angle 60 ) were performed using the parameters shown in table 1 .
transverse sections were obtained with a rectangular field of view ( six - eight ) , a slice thickness of 6 - 8 mm , and an interslice gap of 2 mm . to minimize motion artifact during gradient - echo sequences ,
the patients underwent respiratory - triggered proton density and t2-weighted fse imaging , with repetition times varying between 3,333 and 8,571 , and between 3,240 and 8,620 msec , according to the period of the respiratory cycle . at t2 * -weighted fmpspgr and fmpgr , multiple sections were obtained in an interleaved fashion , and the whole liver was covered with 20 sections using two breath - holds .
cambrige , mass . , u.s.a . ) at a dose of 15 mol fe / kg was diluted in 100 ml of 5% glucose solution and administrated intravenously through an in - line 5-m specific filter over a 30-minute period .
the images obtained during each of the seven pulse sequences were quantitatively analysed using operator - defined region - of - interest ( roi ) measurements of the mean signal intensity of liver parenchyma , lesions , and background noise . for the measurement of liver signal , rois were set in areas devoid of focal changes in signal intensity , large vessels , and prominent artifact .
if more than one hcc was present , the largest representative lesion was identified and measured at all sequences . for liver lesions , circular or ovoid rois
noise was measured on each image using rois positioned just ventral to the right anterior abdominal wall ; areas with the most prominent ghost were not included .
rois were drawn electrically , and were larger than 256 mm in the liver , 45 mm in lesions , and 846 mm2 in the noise area ; they were drawn three times in each place and mean values were obtained .
the lesion - to - liver contrast - to - noise ratio ( cnr ) was calculated using the following formula : ( signal intensity lesion - signal intensity liver)/standard deviation of background noise .
lesion - to - liver cnr was compared statistically using wilcoxon 's signed ranks test .
two readers unaware of the patients ' clinical data assessed the image quality obtained during each of the seven mr sequences .
each reader graded image quality as unacceptable , poor , fair , good , or excellent ( with numerical scores of 1 , 2 , 3 , 4 , or 5 , respectively ) with regard to lesion conspicuity and image artifacts ( 5 = absent ) .
inter - reader agreement was assessed using a  statistic : a  score of more than 0.60 was taken to indicate substantial to excellent agreement ( 27 ) .
discrepancies were resolved by consensus between the readers , and the final ranking data based on consensual interpretations were compared by means of wilcoxon 's signed ranks test .
all mr images of the 16 patients were randomized and reviewed independently by three readers experienced in mr imaging of the liver .
for each pulse sequence , they recorded the number , size , and segmental location of hccs .
the name , age , identification number and imaging parameters of each patient were masked to minimize learning bias , and mr images of each pulse sequence were reviewed on a segment - by - segment basis during sessions separated by two weeks .
to prevent mislocation of the lesion by the readers , hepatic segments were drawn directly by the study coordinator according to couinaud 's numbering system .
a total of 128 hepatic segments were reviewed , including 24 segments with 25 hccs .
the readers scored each image for the presence or absence of hccs and assigned one of five confidence levels , as follows : 1 = definitely or almost definitely absent , 2 = probably absent , 3 = possibly present , 4 = probably present , 5 = definitely or almost definitely present .
when a lesion was located in two or more segments , the readers were asked to consider only the segment mainly involved and to assess the possibility of another lesion in the other segment .
a binomial roc curve was fitted to each reader 's confidence rating using a maximum - likelihood estimation .
the diagnostic accuracy of each mr sequence determined by each reader was evaluated by calculating the area under the roc curve ( az ) .
composite roc curves that combined the performance of all readers into a single curve were obtained for each mr sequence , using the maximum - likelihood curve - fitting algorithm to rate the pooled data of the three readers ( 28 , 29 ) .
the differences between mr sequences in terms of mean az were statistically analyzed using the two - tailed student t test .
the relative sensitivity of each sequence was calculated according to the percentage of segments assigned a score of 3 or greater ( ' possibly present ' to ' definitely present ' ) among a total of 24 segments with hcc .
relative specificity calculations were based on the percentage of segments assigned a score of 1 or 2 among 93 segments without hcc . using a  statistic , inter - reader agreement regarding the detection of segments with hcc
ten hepatic cysts were diagnosed by sonography and ct , and excluded from analysis after the review was complete .
between april and august 1999 , 22 consecutive patients underwent ferumoxides - enhanced mr imaging to assess known or suspected focal liver lesions .
the criteria for inclusion in this study were as follows : hcc was depicted at contrast - enhanced ct , lesions were distributed in such a way that they were resectable , and the patient was considered suitable for curative hepatic resection . on this basis , five patients were excluded because hccs were absent ( metastatic adenocarcinoma was found in two , and each of cholangiocarcinoma , hepatic adenoma , and hemangioma in one ) , and one other because hccs were distributed diffusely .
the remaining 16 patients , 14 men and 2 women ranging in age from 35 to 66 ( mean , 51 ) years , with 25 hccs ( diameter , 3 - 140 [ mean , 41 ] mm ) in 24 hepatic segments comprised our final study group . ferumoxides - enhanced mr imaging was not performed where patients were pregnant , showed severe renal failure , or were allergic to dextran - based drugs .
the study was approved by the institutional review board , and written informed consent was obtained from all patients . for 19 hccs in 11 patients ,
diagnosis was based on the histopathological findings of surgery ; for two , on those of us - guided percutaneous needle biopsy ; and for the remaining four , the basis of confirmation was an elevated serum -fetoprotein level ( over 200 ng / ml ) and characteristic helical ct findings .
thirteen patients in the study had liver cirrhosis as a result of hepatitis b ( n=12 ) , or hepatitis c ( n=1 ) , while the remaining three had hepatitis b without cirrhosis . in order to evaluate hepatic segments which according to the findings of ferumoxides - enhanced mr imaging were hcc - free , follow - up radiologic examinations ( contrast - enhanced ct or gadolinium - enhanced mr imaging ) were performed no less than 12 months later .
all mr examinations were performed on a 1.5-t mr imager ( horizon , ge medical systems , milwaukee , wis .
two respiratory - triggered fse sequences ( tr3333 - 8571/te18 and 90 - 117/etl12/nex2/fat sat . ) , four breath - hold sequences ( proton density ssfse [ tr/te39/nex0.5 ] , t2-weighted ssfse [ tr/te98/nex0.5 ] , fmpgr [ tr130/te8.4 - 9.5/flip angle 30 ] , and fmpspgr [ tr130/te8.4 - 9.5/flip angle 30 ] ) , and the grass sequence ( tr216/te20/flip angle 60 ) were performed using the parameters shown in table 1 .
transverse sections were obtained with a rectangular field of view ( six - eight ) , a slice thickness of 6 - 8 mm , and an interslice gap of 2 mm . to minimize motion artifact during gradient - echo sequences ,
the patients underwent respiratory - triggered proton density and t2-weighted fse imaging , with repetition times varying between 3,333 and 8,571 , and between 3,240 and 8,620 msec , according to the period of the respiratory cycle . at t2 * -weighted fmpspgr and fmpgr , multiple sections were obtained in an interleaved fashion , and the whole liver was covered with 20 sections using two breath - holds .
cambrige , mass . , u.s.a . ) at a dose of 15 mol fe / kg was diluted in 100 ml of 5% glucose solution and administrated intravenously through an in - line 5-m specific filter over a 30-minute period .
the images obtained during each of the seven pulse sequences were quantitatively analysed using operator - defined region - of - interest ( roi ) measurements of the mean signal intensity of liver parenchyma , lesions , and background noise . for the measurement of liver signal
, rois were set in areas devoid of focal changes in signal intensity , large vessels , and prominent artifact .
if more than one hcc was present , the largest representative lesion was identified and measured at all sequences . for liver lesions , circular or ovoid rois
noise was measured on each image using rois positioned just ventral to the right anterior abdominal wall ; areas with the most prominent ghost were not included .
rois were drawn electrically , and were larger than 256 mm in the liver , 45 mm in lesions , and 846 mm2 in the noise area ; they were drawn three times in each place and mean values were obtained .
the lesion - to - liver contrast - to - noise ratio ( cnr ) was calculated using the following formula : ( signal intensity lesion - signal intensity liver)/standard deviation of background noise .
lesion - to - liver cnr was compared statistically using wilcoxon 's signed ranks test .
two readers unaware of the patients ' clinical data assessed the image quality obtained during each of the seven mr sequences .
each reader graded image quality as unacceptable , poor , fair , good , or excellent ( with numerical scores of 1 , 2 , 3 , 4 , or 5 , respectively ) with regard to lesion conspicuity and image artifacts ( 5 = absent ) .
inter - reader agreement was assessed using a  statistic : a  score of more than 0.60 was taken to indicate substantial to excellent agreement ( 27 ) .
discrepancies were resolved by consensus between the readers , and the final ranking data based on consensual interpretations were compared by means of wilcoxon 's signed ranks test .
all mr images of the 16 patients were randomized and reviewed independently by three readers experienced in mr imaging of the liver .
for each pulse sequence , they recorded the number , size , and segmental location of hccs .
the name , age , identification number and imaging parameters of each patient were masked to minimize learning bias , and mr images of each pulse sequence were reviewed on a segment - by - segment basis during sessions separated by two weeks .
to prevent mislocation of the lesion by the readers , hepatic segments were drawn directly by the study coordinator according to couinaud 's numbering system .
a total of 128 hepatic segments were reviewed , including 24 segments with 25 hccs .
the readers scored each image for the presence or absence of hccs and assigned one of five confidence levels , as follows : 1 = definitely or almost definitely absent , 2 = probably absent , 3 = possibly present , 4 = probably present , 5 = definitely or almost definitely present .
when a lesion was located in two or more segments , the readers were asked to consider only the segment mainly involved and to assess the possibility of another lesion in the other segment .
a binomial roc curve was fitted to each reader 's confidence rating using a maximum - likelihood estimation .
the diagnostic accuracy of each mr sequence determined by each reader was evaluated by calculating the area under the roc curve ( az ) .
composite roc curves that combined the performance of all readers into a single curve were obtained for each mr sequence , using the maximum - likelihood curve - fitting algorithm to rate the pooled data of the three readers ( 28 , 29 ) .
the differences between mr sequences in terms of mean az were statistically analyzed using the two - tailed student t test .
the relative sensitivity of each sequence was calculated according to the percentage of segments assigned a score of 3 or greater ( ' possibly present ' to ' definitely present ' ) among a total of 24 segments with hcc .
relative specificity calculations were based on the percentage of segments assigned a score of 1 or 2 among 93 segments without hcc . using a  statistic , inter - reader agreement regarding the detection of segments with hcc
ten hepatic cysts were diagnosed by sonography and ct , and excluded from analysis after the review was complete .
the quantitative results of assessment of mean hcc - to - liver cnr obtained during each pulse sequence are shown in table 2 .
the highest cnr was achieved with breath - hold t2 * -weighted fmpgr sequences ( 68.9  25.0 ) ; this ratio was statistically significantly higher than those obtained during all other sequences except breath - hold t2 * -weighted fmpspgr ( p <
1 ) . the ratio obtained during this sequence was the second highest and was statistically significantly higher than those recorded during the sequences ranked 4 to 7 ( p < .05 ) .
hccs were statistically significantly clearer at proton density and t2-weighted fse , and at all three types of gradient - echo imaging than at the two ssfse sequences ( fig .
* -weighted grass imaging depicted imaging artifacts more prominently than did the other six sequences , and image interpretation was interfered with in 63% of cases ( 10/16 ) ( table 3 ) . t2
* -weighted grass imaging demonstrated pulsation artifacts due to heartbeat in all 16 patients ( fig .
3 ) , motion - related artifacts were evident at proton density and t2-weighted fse imaging in 63% ( 10/16 ) and 50% ( 8/16 ) , respectively .
all t2 * -weighted fmpgr and fmpspgr imaging showed ghost artifacts due to aortic pulsation in the phase - encoding direction , but proton density and t2-weighted ssfse imaging revealed no such artifacts .
overall , the imaging artifacts of the six sequences other than t2 * -weighted grass were comparable .
the lowest  score for interobserver agreement between readers was 0.712 , and was for proton density ssfse imaging which depicted lesion conspicuity .
hence , agreement regarding lesion conspicuity and imaging artifacts was considered substantial to excellent for all sequences .
table 4 shows the calculated areas under the roc curves and the mean area determined by the three readers for each of the seven sequences .
roc curves drawn on the basis of pooled data from the three readers for each of these sequences are shown in figure 4 . with regard to lesion detection ,
two readers performed significantly better with the t2 * -weighted fmpgr , t2 * -weighted fmpspgr , and proton density fse sequences than the other four .
one reader 's interpretation of the seven sequences demonstrated no statistically significant differences in lesion detection . in terms of integrated lesion detectability on the basis of the pooled data reviewed by all observers , t2 * -weighted fmpgr , t2 * -weighted fmpspgr , and proton density fse imaging were statistically superior to those obtained using the other sequences ( fig .
the mean areas under the composite roc curves of the three readers were 0.965  0.015 for t2 * -weighted fmpgr sequences , 0.964  0.016 for t2 * -weighted fmpspgr , and 0.958  0.017 for proton density fse .
the relative sensitivities of t2 * -weighted fmpgr , t2 * -weighted fmpspgr , and proton density fse imaging were superior to those obtained using the other sequences ( table 5 )
. expressed as a percentage , the relative specificity of all sequences was 93 or more ( table 6 ) .
the lowest  score for interobserver agreement was 0.690 , and involved t2-weighted fse imaging between reader 2 and reader 3 .
the quantitative results of assessment of mean hcc - to - liver cnr obtained during each pulse sequence are shown in table 2 .
the highest cnr was achieved with breath - hold t2 * -weighted fmpgr sequences ( 68.9  25.0 ) ; this ratio was statistically significantly higher than those obtained during all other sequences except breath - hold t2 * -weighted fmpspgr ( p <
1 ) . the ratio obtained during this sequence was the second highest and was statistically significantly higher than those recorded during the sequences ranked 4 to 7 ( p < .05 ) .
hccs were statistically significantly clearer at proton density and t2-weighted fse , and at all three types of gradient - echo imaging than at the two ssfse sequences ( fig .
* -weighted grass imaging depicted imaging artifacts more prominently than did the other six sequences , and image interpretation was interfered with in 63% of cases ( 10/16 ) ( table 3 ) . t2 * -weighted grass imaging demonstrated pulsation artifacts due to heartbeat in all 16 patients ( fig .
3 ) , motion - related artifacts were evident at proton density and t2-weighted fse imaging in 63% ( 10/16 ) and 50% ( 8/16 ) , respectively .
all t2 * -weighted fmpgr and fmpspgr imaging showed ghost artifacts due to aortic pulsation in the phase - encoding direction , but proton density and t2-weighted ssfse imaging revealed no such artifacts .
overall , the imaging artifacts of the six sequences other than t2 * -weighted grass were comparable .
the lowest  score for interobserver agreement between readers was 0.712 , and was for proton density ssfse imaging which depicted lesion conspicuity .
hence , agreement regarding lesion conspicuity and imaging artifacts was considered substantial to excellent for all sequences .
table 4 shows the calculated areas under the roc curves and the mean area determined by the three readers for each of the seven sequences .
roc curves drawn on the basis of pooled data from the three readers for each of these sequences are shown in figure 4 . with regard to lesion detection ,
two readers performed significantly better with the t2 * -weighted fmpgr , t2 * -weighted fmpspgr , and proton density fse sequences than the other four .
one reader 's interpretation of the seven sequences demonstrated no statistically significant differences in lesion detection . in terms of integrated lesion detectability on the basis of the pooled data reviewed by all observers , t2 * -weighted fmpgr , t2 * -weighted fmpspgr , and proton density fse imaging were statistically superior to those obtained using the other sequences ( fig .
the mean areas under the composite roc curves of the three readers were 0.965  0.015 for t2 * -weighted fmpgr sequences , 0.964  0.016 for t2 * -weighted fmpspgr , and 0.958  0.017 for proton density fse . the relative sensitivities of t2 * -weighted fmpgr , t2 * -weighted fmpspgr , and proton density fse imaging were superior to those obtained using the other sequences ( table 5 ) .
expressed as a percentage , the relative specificity of all sequences was 93 or more ( table 6 ) .
the lowest  score for interobserver agreement was 0.690 , and involved t2-weighted fse imaging between reader 2 and reader 3 .
the acquisition of high - quality images in the shortest possible time has been a major field of investigation in mr imaging of the liver . according to recent reports ,
ferumoxides - enhanced mr imaging is useful for the detection of hepatic tumors , including metastasis ( 5 , 12 , 15 , 22 ) and hccs ( 3 - 5 , 24 ) , and investigators have also claimed that it is as accurate as ctap for detecting hepatic metastasis ( 12 ) or hcc ( 11 ) . t2-weighted se and t2 * -weighted gre are accepted ferumoxides - enhanced mr imaging sequences ( 13 , 24 , 30 , 31 ) . at gre imaging after intravenous ferumoxides administration , signal loss of liver parenchyma is increased by the presence of iron oxide particles because of its greater susceptibility resulting from local field inhomogeneity ( intravoxel dephasing ) ( 21 , 32 ) .
( 21 ) found that gre imaging with long te and a narrow flip angle was an ideal t2 * -weighted sequence .
yamamoto et al . ( 24 ) reported that hcc detection was similar at ferumoxides - enhanced t2-weighted se and gre imaging . in a study by schwarz et al .
( 32 ) , conventional se was found to be superior to fse due to the absence of a 180 refocusing pulse .
however , because fse sequences are less sensitive to motion artifacts , and the decrease in liver signal noted at fse is comparable to that observed at conventional se , fse sequences are , according to a recent report ( 33 ) , clinically useful for ferumoxides imaging .
( 23 ) claimed that ferumoxides - enhanced gre imaging was as accurate as t2-weighted se imaging for the detection of malignant hepatic tumors and was superior for determining their segmental location .
however , the optimal imaging sequence for lesion detection with ferumoxides enhancement is still open to debate .
our results indicate that hcc - to - liver cnr was best at t2 * -weighted fmpgr sequence , for which the ratio was statistically significantly higher than for all other sequences except t2 * -weighted fmpspgr .
one possible reason for the lower cnr found with fse and ssfse imaging is that a larger matrix is used for these sequences ; this contributes to the sharpness of lesion contour , but leads to low lesion - to - liver cnr .
the predominance of t2 * -weighted imaging is , however , thought to be caused mainly by local field inhomogeneity and the lack of a refocusing pulse ( 21 , 32 ) .
low cnr at t2 * -weighted grass results from the high noise level of this sequence . because of poor soft - tissue resolution due to the t2 filtering effect , lesion conspicuity at ssfse imaging was statistically significantly less clear than at other sequences .
motion - related artifacts were significantly less severe with t2-weighted and proton density ssfse , t2 * -weighted fmpgr , and t2 * -weighted fmpspgr imaging , mainly because of their short acquisition time , which allows successful breath - holding ( 34 ) . in terms of lesion - to - liver cnr , lesion conspicuity and artifacts , t2
* -weighted imaging was the best sequence , though vascular structures and hccs were similarly demonstrated with a ( bright ) high signal . at fse , on the other hand , vascular structures were less bright than hccs ( figs . 1 , 2 , 5 ) . in roc analysis ,
the area under the composite roc curve indicates performance . with regard to integrated lesion detectability , t2 * -weighted fmpgr , t2 * -weighted fmpspgr , and proton density fse imaging were statistically superior to other sequences .
the difference in performance among mr sequences was more prominent for small hccs because these can demonstrate active uptake of ferumoxides particles , which results in slight hyperintensity , isointensity , or even hypointensity at ferumoxides - enhanced imaging ( 6 ) .
ferumoxides - enhanced mr imaging does not always facilitate differentiation between malignant tumors and benign lesions .
( 13 ) recommended t1-weighted gre ( short te ) imaging after ferumoxides enhancement in order to detect and characterize focal liver lesions .
cysts can demonstrate low signal intensity at t1-weighted imaging , and at ferumoxides - enhanced imaging , t1-weighted sequences may permit good differentiation between malignancy and cysts . due to the t2 effect , however , cysts can show high signal intensity at gradient - recalled echo sequences with long te . according to grangier et al .
, hemangiomas can be enhanced by shortening the t1 relaxation time at t1-weighted imaging after ferumoxides administration ( 35 ) .
first , while the standard of reference is the findings of histopathological analysis of 41 resected hepatic segments in 11 patients , follow - up imaging findings were used as the standard of reference for 87 unresected segments .
second , in the segments containing two hepatocelluar carcinomas or a hepatocelluar carcinoma and a benign lesion ( 13% , n=3 ) , segment - by - segment analysis meant that comparisons for these particular lesions could not be made .
third , it was only in the detection of hccs that optimal pulse sequences for ferumoxides - enhanced mr imaging were evaluated : optimal sequences for the characterization of focal hepatic lesions could not be determined .
finally , unenhanced mr imaging was reported to be necessary in order to decrease the number of false - positive findings attributed to vascular structures . however , " biphasic " unenhanced and ferumoxides - enhanced mr imaging is time consuming and such unenhanced imaging is thus not obtained ( 36 ) . without unenhanced imaging , we recorded few false - positive findings . in conclusion , our results suggest that t2 * -weighted fmpgr , t2 * -weighted fmpspgr , and proton density fse sequences after intravenous ferumoxides administration provide higher diagnostic accuracy than the other four sequences ( t2-weighted ssfse , t2 * -weighted grass , t2-weighted fse , and proton density ssfse ) , and show higher cnrs , fewer image artifacts and better lesion conspicuity . for the detection of hccs at ferumoxides
 objectiveto identify the optimal pulse sequence for ferumoxides - enhanced magnetic resonance ( mr ) imaging in the detection of hepatocelluar carcinomas ( hccs).materials and methodssixteen patients with 25 hccs underwent mr imaging following intravenous infusion of ferumoxides . 
 all mr studies were performed on a 1.5-t mr system , using a phased - array coil . 
 ferumoxides ( feridex iv ) at a dose of 15 mol / kg was slowly infused intravenously , and axial images of seven sequences were obtained 30 minutes after the end of infusion . 
 the mr protocol included fast spin - echo ( fse ) with two echo times ( tr3333 8571/te18 and 90 - 117 ) , singleshot fse ( ssfse ) with two echo times ( tr/te39 and 98 ) , t2 * -weighted gradient - recalled acquisition in the steady state ( grass ) ( tr216/te20 ) , t2 * -weighted fast multiplanar grass ( fmpgr ) ( tr130/te8.4 - 9.5 ) , and t2 * -weighted fast multiplanar spoiled grass ( fmpspgr ) ( tr130/te8.4 - 9.5 ) . 
 contrast - to - noise ratios ( cnrs ) of hccs determined during the imaging sequences formed the basis of quantitative analysis , and images were qualitatively assessed in terms of lesion conspicuity and image artifacts . 
 the diagnostic accuracy of all sequences was assessed using receiver operating characteristic ( roc ) analysis.resultsquantitative analysis revealed that the cnrs of t2 * -weighted fmpgr and t2 * -weighted fmpspgr were significantly higher than those of the other sequences , while qualitative analysis showed that image artifacts were prominent at t2 * -weighted grass imaging . 
 lesion conspicuity was statistically significantly less clear at ssfse imaging . in term of lesion detection , 
 t2 * -weighted fmpgr , t2 * -weighted fmpspgr , and proton density fse imaging were statistically superior to the others.conclusiont2*-weighted fmpgr , t2 * -weighted fmpspgr , and proton density fse appear to be the optimal pulse sequences for ferumoxides - enhanced mr imaging in the detection of hccs . 