Low-dose computed tomography to detect body-packing in an animal model

Abstract

Objective

To assess the possible extent of dose reduction for low-dose computed tomography (CT) in the detection of body-packing (ingested drug packets) as an alternative to plain radiographs in an animal model.

Materials and methods

Twelve packets containing cocaine (purity >80%) were introduced into the intestine of an experimental animal (crossbred pig), which was then repeatedly examined by abdominal CT with stepwise dose reduction (tube voltage, 80 kV; tube current, 10–350 mA). Three blinded readers independently evaluated the CT datasets starting with the lowest tube current and noted the numbers of packets detected at the different tube currents used. In addition, 1 experienced reader determined the number of packets detectable on plain abdominal radiographs and ultrasound.

Results

The threshold for correct identification of all 12 drug packets was 100 mA for reader 1 and 125 mA for readers 2 and 3. Above these thresholds all 3 readers consistently identified all 12 packets. The effective dose of a low-dose CT scan with 125 mA (including scout view) was 1.0 mSv, which was below that of 2 conventional abdominal radiographs (1.2 mSv). The reader interpreting the conventional radiographs identified a total of 9 drug packets and detected 8 packets by abdominal ultrasound.

Conclusions

Extensive dose reduction makes low-dose CT a valuable alternative imaging modality for the examination of suspected body-packers and might replace conventional abdominal radiographs as the first-line imaging modality.

Introduction

Body-packing is the concealment of illicit substances in the human body for the purpose of smuggling. A body-packer usually swallows small packets containing heroin, cocaine, amphetamine, ecstasy, or marihuana. Thereby, up to approximately 1 kg of illicit drugs in 50–100 packets, each containing 8–14 g of drugs, can be incorporated [1], [2]. Alternatively, drug packets are concealed by inserting them into the rectum or vagina [3], [4], [5], [6]. Body-packers concealing the drug packets by swallowing use constipating substances such as diphenoxylate or ioperamide during transport [4], [7] and laxatives to accelerate excretion after arrival [7]. International drug trafficking is on the rise, and more body packers are being detected, not least of all because of increasing level of security controls at airports in recent years [8], [9], [10]. Apart from the social implications of drug smuggling, swallowers put themselves at considerable risk as rupture of a single packet inside the body may be fatal, depending on the type and concentration of drug being ingested [11], [12], [13]. Conventional abdominal radiographs in one or two planes have traditionally been used to demonstrate incorporation in suspected body packers [3], [14], [15]; detection rates of 60–90% have been reported for this method [7], [16], [17]. False-positive results of radiographs may be due to bladder stones [18], scybala [19], or intra-abdominal calcifications [20]. Inexperience of the radiologist interpreting the images is another problem [21] as the numbers of cases are very few and different packaging techniques are used. Verification of the actual detection rate is difficult because legal considerations preclude obtaining evidence for false-negative results.

Another diagnostic tool that has been used in this setting, abdominal ultrasound, was also found to detect foreign bodies with high sensitivity and correlate with abdominal radiographs; however, ultrasound was reported to be inaccurate with regard to the number of packets detected [14], [22], [23]. The best imaging modality for revealing foreign bodies is computed tomography (CT), which is superior to abdominal radiographs and ultrasound in terms of sensitivity, localization, and characterization of density [24], [25], [26], [27]. A drawback is the relatively high radiation exposure, which is why CT is not generally used as the first-line imaging modality. In most European countries, it's use is restricted to confirmation of complete elimination or suspected rupture of drug packets [28]. It would be desirable to employ CT as a first-line diagnostic tool in suspected body-packers, preferably with a substantial dose reduction but maintenance of its diagnostic performance.

We performed an experimental investigation to estimate the minimal CT-dose that still allows reliable detection of ingested drug packets.