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Abstract A natural magnetic resonance imaging (MRI)contrast based on the pulp of a fruit Euterpe Olercea,popularly known as Aa, was investigated. T1 and T2contrasted images shown the effects of the contrast agentincreasing the ability to visualize the contour of segments ofthe gastrointestinal tract.

INTRODUCTION

sing contrast agents is a common practice in

medical imaging protocols, as is the case of

Magnetic Resonance Imaging. The evaluation of GI

tract by means of MRI has a close relation to

availability of oral contrast agents. Oral contrasts are

attractive to MRI if they have good digestive

acceptance, uniform distribution in the bowel lumen,

unchanged contrast effect when diluted throughout the

gastrointestinal tract (GI), no toxicity, no peristalsis

stimulus, and acceptable cost. Although some of them

are commercially available, they are still not used

routinely in most clinical centers nowadays, due to

many factors, such as possible side effects. Oral

contrast agents are usually classified by their increase

(positive agents) or decrease (negative agents) of the

magnetic resonance imaging signal within the bowel

[1].

GI agents change intra-luminal signal either by a

paramagnetic shortening of T1 or T2 of nearby tissues

or by having intrinsically short relaxation times [1,2,3].

Actually, many contrast solutions would be capable of

changing signal intensity, typically based on heavy

metal ions, as of Gadolinium (III), Manganese (II),Manganese (III), Iron (III), and copper (II) [4]. However,

they have generally intrinsic side effects when used

orally [0]. Ferric iron, for example, can provoke teeth

staining, gastric irritation, nausea, diarrhea, and

constipation. Mannitol may cause nausea, vomiting,

and diarrhea [2]. Gd-DTPA without Mannitol is well

Manuscript received March 10, 2005. This work was supported in part

by the CNPq and CAPES. T. Arruda-Sanchez DFM FFCLRP Av

Bandeirantes, 3900 14.040-901 Ribeirao Preto SP Brazul

tiago@biomag.usp.br.

tolerated but usually fails in opacifying the entire

bowel. It also needs to be buffered when used orally

since this chelate is not very stable at low pH found in

the stomach, what can alter the gastric function.

We herein present the preliminary implementation of a

natural oral contrast agent, Euterpe Olercea(popularly named Aa), as a possible alternative

contrast agent for MRI of the gastrointestinal (GI) tract.

The pulp of Aa, a fruit from the Amazon area, can be

widely found in tropical regions. Considering the

biphasic contrast revealed in the preliminary study [4],

this natural oral contrast agent could be clinically used,

primarily to assist for a better contrast in images from

stomach and from a rotine examination of the

biliopancreatic tract, in Magnetic Resonance

Cholangiopancreatography (MRCP).

During MRCP, difficulties in the assessment of the

gallbladder, cystic duct, common bile duct (CBD), and

pancreatic duct may be encountered because thesestructures are frequently masked by the overlap of the

signal hyper-intensity from the surrounding tissues

contend [5]. We investigate the feasibility of using this

natural solution as a gastrointestinal oral negative

contrast agent to null the bowel signal during MRCP.

METHODOLOGY

All images were acquired using a Siemens 1.5 T

Scanner (Magneton Vision). A body array coil was

used to generate T1-weighted images (TR/TE =

177.8/4.1 ms, FOV 350 mm, 256 x 256, 6 mm slice

thickness) and T2-weighted images (TR/TE = 4400/64

ms, FOV = 350 mm, 256 x 256, 6 mm slice thickness)

at a standard turbo spin-echo (TSE) sequence.

We studied 10 non-symptomatic subjects, with 12

hours of fasting. Ten axial slices centered at the

stomach region were acquired, under three distinct

experimental conditions: first in the fasting state with

an empty stomach (baseline), followed by the ingestion

of water and finally by the ingestion of Aa. As to

implement the contrast agent in the clinical

environment, these subjects more 35 patients were

Preliminary Results from Clinical Application of a Natural OralContrast Agent in Magnetic Resonance Imaging (MRI) of the

Gastrointestinal (GI) System

T. Arruda-Sanchez; L.E.A. Troncon; R. Brandt-Oliveira; J. Elias Jr., L.A. Colnago,

D.B. Arajo, D.B. and Baffa O.

University of So Paulo Ribeiro Preto SP - Brazil

U

Proceedings of the 2005 IEEEEngineering in Medicine and Biology 27th Annual ConferenceShanghai, China, September 1-4, 2005

0-7803-8740-6/05/$20.00 2005 IEEE. 1382

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submitted to the same hospital protocol for MRCP that

is based in the same T2-weighted standard TSE

sequence parameters, which was approved by the

institutional ethics committee.

RESULTS

T1 and T2 weighted images from the stomach of a

fasting healthy volunteer are presented in figure 1. In

figure 1a and figure 1d we observe an empty stomach.

Subsequently, the subject ingested 200 ml of water,

and another set of T1 (Fig. 1b) and T2 (Fig. 1e) was

acquired. The expansion of the gastric volume is

clearly observed and two phases can be identified on

the images: a small dark region corresponding to air

and a larger area of slight contrast increase

corresponding to water. Finally, 200 ml of the Aa pulp

was ingested by the subject and the last series of MR

images were obtained. Figure 1c shows one T1-

weighted image. The increase of contrast due to the

presence of Aa is conspicuous. Three well definedregions can be identified: air, water and Aa. Also, the

T2 sequence presents a high contrast in the gastric

lumen due to low signal intensity from Aai (Fig. 1f).

We looked for intrinsic properties that could be

responsible for the T1 signal enhancement and T2

opacification. Atomic Absorption spectra revealed the

presence of Fe, Mn and Cu ions in Aai. Although

there is no information yet about how these ions are

complexed with the organic matrix, their presence is

probably the main cause for the image contrast

changes.

Figure 1. T1 and T2 weighed images in an axial plane. T1

images are on the top line, while T2 are on the bottom. (a)

T1 image of an empty stomach. (b) T1 of the same volunteerwith air and 200ml of water. (c) T1 image with air, 200ml of

water and 200ml of Aai. (d) T2 image of an empty

stomach. (e) T2 image of air and 200 ml of water. (f) T2

image of air, 200ml of water and 200ml of Aai.

Figure 2 shows T2 images, in the coronal plane,

from 2 patients submitted to MRCP. The MRI signal

from bowel loops, superposed to the common bile

duct, is subtracted, allowing the complete observation

of the gall bladder after the ingestion of Aa.

We can see the image clearance (Fig. 2) due to the

reduced signal from the Aa pulp present in stomach

and bowel loops.

DISCUSSION AND CONCLUSION

The contrast enhancement due to Aa in T1-weighed

images is evident, producing a better definition of the

gastric lumen. These results open a wide perspective

for the clinical use of such contrast agent, as an

alternative oral contrast for imaging the intestinal

lumen, functional evaluation of dyspepsia and otherpathological states.

The contrast enhancement due to Aa in T1-weighted

images is evident (Fig. 1c), producing a better

definition of the gastric lumen. Thus, these results

open a wide perspective for Aa as an alternative oral

contrast agent that can be employed for imaging the

intestinal lumen, functional evaluation of dyspepsia, in

addition to the applications of the gastrointestinal

motility [6,7].

Figure 2. T2-weighed images from 2 patients (a)

and (b) during fasting (left) and after Acai

ingestion (right). Overlap is eliminated (pentagram)

which allows gallbladder and biliary ducts (large

and small arrows ) to be more visible after Aai

ingestion.

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Aa has great advantages since is a natural and

palatable food with no expected side effects or adverse

reactions. In every patient studied thus fat, only one

had nausea after ingesting the Acai pulp. As for

MRCP, the results indicate a possible application from

the signal reduction of gastric acid and intestinal loops.

The Acai pulp may improve the visualization of

pancreatic and biliary ducts.

ACKNOWLEDGMENT

The authors thanks the technical support of Loureno

Rocha, Carlos Brunello, Matheus Guerreiro, Reginaldo

Ferreira Chagas, Luciano Kazuo Akita and the MRI

service of Hospital das Clinicas, Faculdade de

Medicina de Ribeiro Preto to make available its

facilities.

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