Role of Diffusion Weighted Imaging in Assessment of Primary Malignant Lesion in the liver
Zinah Saeed Mahmood;
Abstract
SUMMARY
D
iffusion weighted echoplanar imaging was developed as one of the recent imaging techniques aiming at improving the specificity for characterization of focal hepatic lesions.
The importance of such facility arises from the fact that focal hepatic lesions are generally a frequent disease.
In addition the liver is affected by a wide variety of focal hepatic lesions that are mainly classified into benign and malignant.
Many imaging techniques are successful in adequate assessment of different hepatic pathological entities. The most important and widely used of which include ultrasonography CT scan and MRI as well as radioisotopic scanning. Diffusion is defined as a the thermally induced behavior of molecules moving in a microscopic random pattern. Such random motion is quantified by means of a diffusion coefficient. The apparent diffusion coefficient is used for diffusion measurements in biologic systems as it only depends on the microscopic motion of molecules and not affected by the microcirculation perfusion fraction.
The development of echo planar imaging greatly influences the success of application of diffusion technique in abdominal studies as it provides very high speed imaging reducing the problem of motion artifact during image acquisition. The effect of diffusion depends on the fact that produces a reduction of the signal intensity in each pixel.
Such performed studies have concluded that malignant solid lesions had smaller ADC values than benign lesions and that in benign lesions the ADC values of haemangiomas were smaller than those of cysts.More over other performed studies suggest that diffusion weighted imaging was useful in differentiating abscesses form cystic or necrotic tumors as they found that the ADCs of hepatic abscesses were significantly smaller than necrotic or cystic tumors.
However the diffusion technique have several limitations. First because the ADC value of some cystic tumors may overlap with haemangiomas. In addition small lesions are prone to severe chemical shift artifact . Further more lesions located at the dome of the liver and those located in the lateral segment are prone to distortion artifact resulting from the single shot echplanar technique and thus could not be properly measured.
Twenty five cases were included in our study with all have underwent conventional non contrast MR imaging preliminary to the diffusion scan. Calculation of the apparent diffusion coefficient was performed by measurements of the signal intensities in the region of interest using two gradient factors low and high ( b 200 and 800 sec/ mm2 respectively).
Diagnosis of lesions as benign or malignant on diffusion basis depends upon the change in their signal intensities on application high gradient factor (b 800) as well as the relative ADC values.
Cases included in our study are classified into benign and malignant. Benign lesions include cysts, abscesses and haemangiomas while malignant lesions include primary hepatocellular carcinomas and metastatic deposits. In most of the cases pathological result are available and correlation between the diffusion weighted imaging and histopathological diagnosis were performed. In the other cases the typical radiological appearance on the conventional imaging modalities combined with the diffusion technique was the way to attain a final diagnosis.
Our study have concluded that benign lesions have generally a higher ADC values than malignant ones and that among the studied benign lesions cysts elicit the highest ADC values followed by haemangiomas and then abscesses while for malignant lesions primary hepatic carcinomas had lower ADC values compared to metastatic lesions.
From the calculated ADC values of all studied cases a threshold value of 1.5 was suggested to differentiate between benign and malignant lesions and definite benign lesions can be diagnosed with lesions having an ADC value of 2.2 or above while definite malignant lesions have an ADC value of 1.0 or less.
D
iffusion weighted echoplanar imaging was developed as one of the recent imaging techniques aiming at improving the specificity for characterization of focal hepatic lesions.
The importance of such facility arises from the fact that focal hepatic lesions are generally a frequent disease.
In addition the liver is affected by a wide variety of focal hepatic lesions that are mainly classified into benign and malignant.
Many imaging techniques are successful in adequate assessment of different hepatic pathological entities. The most important and widely used of which include ultrasonography CT scan and MRI as well as radioisotopic scanning. Diffusion is defined as a the thermally induced behavior of molecules moving in a microscopic random pattern. Such random motion is quantified by means of a diffusion coefficient. The apparent diffusion coefficient is used for diffusion measurements in biologic systems as it only depends on the microscopic motion of molecules and not affected by the microcirculation perfusion fraction.
The development of echo planar imaging greatly influences the success of application of diffusion technique in abdominal studies as it provides very high speed imaging reducing the problem of motion artifact during image acquisition. The effect of diffusion depends on the fact that produces a reduction of the signal intensity in each pixel.
Such performed studies have concluded that malignant solid lesions had smaller ADC values than benign lesions and that in benign lesions the ADC values of haemangiomas were smaller than those of cysts.More over other performed studies suggest that diffusion weighted imaging was useful in differentiating abscesses form cystic or necrotic tumors as they found that the ADCs of hepatic abscesses were significantly smaller than necrotic or cystic tumors.
However the diffusion technique have several limitations. First because the ADC value of some cystic tumors may overlap with haemangiomas. In addition small lesions are prone to severe chemical shift artifact . Further more lesions located at the dome of the liver and those located in the lateral segment are prone to distortion artifact resulting from the single shot echplanar technique and thus could not be properly measured.
Twenty five cases were included in our study with all have underwent conventional non contrast MR imaging preliminary to the diffusion scan. Calculation of the apparent diffusion coefficient was performed by measurements of the signal intensities in the region of interest using two gradient factors low and high ( b 200 and 800 sec/ mm2 respectively).
Diagnosis of lesions as benign or malignant on diffusion basis depends upon the change in their signal intensities on application high gradient factor (b 800) as well as the relative ADC values.
Cases included in our study are classified into benign and malignant. Benign lesions include cysts, abscesses and haemangiomas while malignant lesions include primary hepatocellular carcinomas and metastatic deposits. In most of the cases pathological result are available and correlation between the diffusion weighted imaging and histopathological diagnosis were performed. In the other cases the typical radiological appearance on the conventional imaging modalities combined with the diffusion technique was the way to attain a final diagnosis.
Our study have concluded that benign lesions have generally a higher ADC values than malignant ones and that among the studied benign lesions cysts elicit the highest ADC values followed by haemangiomas and then abscesses while for malignant lesions primary hepatic carcinomas had lower ADC values compared to metastatic lesions.
From the calculated ADC values of all studied cases a threshold value of 1.5 was suggested to differentiate between benign and malignant lesions and definite benign lesions can be diagnosed with lesions having an ADC value of 2.2 or above while definite malignant lesions have an ADC value of 1.0 or less.
Other data
| Title | Role of Diffusion Weighted Imaging in Assessment of Primary Malignant Lesion in the liver | Other Titles | دور الرنين المغناطيسي باستخدام طريقة الانتشار في تقييم اصابات الكبد الناتجة عن الاورام الخبيثة الاولية | Authors | Zinah Saeed Mahmood | Issue Date | 2014 |
Recommend this item
Similar Items from Core Recommender Database
Items in Ain Shams Scholar are protected by copyright, with all rights reserved, unless otherwise indicated.