Johnathan Chen MD, Abstract Co-Author: Nothing to Disclose

Louise Marie Truong MD, Presenter: Nothing to Disclose

Peter Lew MD, Abstract Co-Author: Nothing to Disclose

Irwin Walot MD, Abstract Co-Author: Nothing to Disclose

Certain metallic projectiles such as steel #2 birdshot in a calorimeter can produce heat when scanned in a 3T MRI.

Patients who have sustained gunshot woundsoften have imbedded ballistic projectiles such as bullets or bullet fragments within their bodies. This may present a potential clinical decision making problem when deciding whether or not to scan a patient in a MRI. A few studies involving both human subjects and phantoms  describe a possibility of motion of metallic retained bullet fragments or shrapnel as well as the remote potential of heating of the foreign body during MRI scanning using a 0.5-1.5T MRI.  In vitro experiments have been performed in the past using viscous substances such as ballistics gelatin. In order to calculate the energy produced by induction in various substances we sought to use a simple calorimetry experiment often encountered in a grade school physics class. The specific heat of a substance is defined as the amount of energy required to raise the temperature of a mass of substance by a certain temperature. It is defined by the equation: C=Q/(m•∆T), where C is the specific heat, Q is the amount of heat transferred to an object and ΔT is the change in temperature of the object; specific heat is often described in units of Joules/(kilogram∙Kelvin) (J/(kg•K). The specific heat of water is 4.1855 J/(g•K).  

The phantom that caused a detectable increase in temperature was the steel shotgun #2 birdshot. There was approximately 31.9g of steel contained per shell. The temperature of the water was increased by 1ºC making the total energy delivered approximately 126J.

Taking advantage of the specific heat of water, our experiment involved scanning phantoms of multiple different bullet and shot projectiles which were removed from the cartridge case and placed into a "coffee cup calorimeter." This calorimeter consisted of a 16 oz cup with a lid and alcohol thermometer with the bulb placed below the surface of 30mL of distilled water. Each projectile was then placed in the calorimeter and scanned in a 3T MRI using several standard pulse sequences including T1, T2 and GRE. The change in temperature of the water was recorded after the scan.

Chen, J, Truong, L, Lew, P, Walot, I, Detecting Energy Induction by Magnetic Resonance Imaging in Ballistic Projectiles Using Calorimetry in Vitro.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12027685.html