Technical note
Imaging parameter effects in apparent diffusion coefficient determination of magnetic resonance imaging

https://doi.org/10.1016/j.ejrad.2009.06.031Get rights and content

Abstract

Purpose

Although an apparent diffusion coefficient (ADC) value is often used for differential diagnosis of tumours, it varies with scanning parameters. The present study was performed to investigate the influence of imaging parameters, i.e., b value, repetition time (TR) and echo time (TE), on ADC value.

Methods

The phantoms were scanned using diffusion weighted imaging (DWI) with changing b values (b = 0–3000 s/mm2), TR and TE to determine the influence on ADC. Moreover, ADC of the brain in normal volunteers was determined with varying b values (b = 0–1000 s/mm2).

Results

Diffusion decay curves were obtained by biexponential fitting in all phantoms. The points where fast and slow components of the biexponential decay crossed were called turning points. The b values of turning points that crossed from the biexponential curve were different in each phantom. The b values of turning points depended on ADC of fast diffusion component. When ADC is calculated using two b values of front and back for the turning point, the ADC value may be different. Therefore, it was necessary to perform calculations by b value until the turning point to obtain the ADC value of the fast component. In addition, b  100 was recommended to avoid the influence of perfusion by blood. Furthermore, the choice of long TR and short TE was effective for accurate measurement of ADC.

Conclusion

It is important to determine the turning point for measuring ADC.

Introduction

Diffusion weighted images (DWI) obtained on magnetic resonance imaging (MRI) are useful for diagnosis of acute cerebral stroke. DWI is often used for examination of the human body because an echo planar imaging sequence with parallel imaging yields excellent image quality [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13]. Body DWI may allow rough differential diagnosis of tumours and is useful in examinations to find tumours. The apparent diffusion coefficient (ADC) is used frequently in differential diagnosis. It has been reported that DWI has the potential to differentiate between benign and malignant tumours [14], [15], [16], [17], [18], [19], [20], [21], [22]. On the other hand, some investigators have reported that because ADC values of benign tumours and malignant tumours overlap, they are therefore not useful to differentiate between bulk benign and malignant tumours [23]. In these cases, it is problematic that the ADC value varies with the scanning parameters. This leads to serious problems when ADC is used to distinguish a tumour. In addition, use of ADC value with an error may lead to wrong conclusions. Therefore, we reviewed how ADC value varies with scanning parameters, how to obtain ADC with high precision and points to which attention should be paid.

The purpose of this study was to identify the scanning parameters to obtain ADC value measurement with a high degree of precision.

Section snippets

Influence of b value

The phantoms were scanned with various b values (b = 0–3000 s/mm2) to determine the influence of the b value of the motion probing gradient (MPG) on signal intensity of DWI. Five types of phantom (agarose 1 g, 3 g, 4 g and 5 g in 100 mL of hot water and 100 mL of liquid detergent in bottles) were fixed in a water tank.

T1 and T2 values of each phantom are shown in Table 1.

Scanning parameters were TR/TE with 8000/100 ms with spin-echo type single-shot echo planar imaging (EPI), matrix size, 128 × 128; field

Results

The logarithms of DWI signal intensities with b = 0–3000 s/mm2 are plotted in Fig. 2 In all phantoms, the signal intensity deteriorated as b value increased, indicated by two straight lines on the logarithmic scale. That is, diffusion decay curves were obtained from the biexponential in all phantoms. The points where fast and slow components of the biexponential decay crossed were called turning points (Fig. 3).

The positions of the turning points were different in each phantom in Fig. 2. Fig. 4

Discussion

In all phantoms, the signal intensity deteriorated with increases in b value as shown in Fig. 2. The decay curves were best fit with the biexponential function. In general, biexponential decay occurs due to intra- and extracellular diffusion [24], [25]. Other investigators reported that the fast and slow diffusion components responsible for the biexponential decay are attributable to water and lipid protons using dairy cream [26], [27]. In this study, the biexponential decay was seen in the

Conclusions

Recently, DWI and ADC have become important tools in surveying and discrimination of tumours. Many studies are now performed using ADC value to distinguish tumours. On the other hand, the ADC value varies with scanning parameters of DWI. Use of an ADC value with an error may lead to wrong conclusions.

Therefore, the present study was performed to investigate the scanning parameters to obtain high precision in ADC measurement. It is necessary to use b values smaller than the turning point so that

References (27)

  • S. Naganawa et al.

    Diffusion-weighted imaging of the liver: technical challenges and prospects for the future

    Magn Reson Med Sci

    (2005)
  • M.D. Pickles et al.

    Diffusion-weighted imaging of normal and malignant prostate tissue at 3 T

    J Magn Reson Imaging

    (2006)
  • M. Koinuma et al.

    Apparent diffusion coefficient measurements with diffusion-weighted magnetic resonance imaging for evaluation of hepatic fibrosis

    J Magn Reson Imaging

    (2005)
  • Cited by (66)

    • Simultaneous multislice diffusion-weighted imaging with short tau inversion recovery fat suppression in bone-metastasizing breast cancer

      2020, European Journal of Radiology
      Citation Excerpt :

      One possible explanation for the lower ADC values is the shorter TR used in mb-DWI compared to c-DWI. When the TR is shortened, the ADC value becomes influenced by the T1 relaxation time of the tissue with a reduction in the ADC value seen in tissues with long T1 relaxation times [30] like the liver and muscles. Indeed, reduced ADC values of mb-DWI was observed in the liver and muscle, but not in organs with short T1 like the spleen and kidney.

    • Diffusion weighted (DW) MRI role in characterization of breast lesions using absolute and normalized ADC values

      2018, Egyptian Journal of Radiology and Nuclear Medicine
      Citation Excerpt :

      In this study, we used a cut value of 1.1 × 10−3 cm2/sec achieving a sensitivity of 89.75% “with false negative results encountered in DCIS which was falsely categorized by means of ADC as benign lesion and invasive ductal carcinoma presented with non mass enhancement”, specificity of 94.4% “with false positive cases in intraductal papilloma”, PPV of 92.42% and NPV of 94.45%. The calculated ADC value is affected by the scanning parameters (TR and TE), and b value used for DWI [18]. That's why there is different cutoff values for the discrimination of the malignant from benign lesions among the different studies.

    View all citing articles on Scopus
    View full text