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Kidney Stone Structural Analysis By Helical Computed Tomography (CT)

Kidney Stone Structural Analysis By Helical Computed Tomography (CT)
Posted 2006-11-30 13:30:44
Vik S posted: Earlier, the diagnosis of kidney stones did not involve information regarding the fragility of the stones. This made it impossible to determine the intensity and number of shock waves required during Lithotripsy to disintegrate the stone. Many patients would end up receiving more shock waves than was necessary to break up their stones. To regulate the use of SWL, investigators have found that computed tomography (CT) images of kidney stones can reveal significant internal structure in stones--structure that is likely to be useful in predicting stone fragility.
The Indiana Kidney Stone Institute in collaboration with Indiana University School of Medicine and National Kidney Foundation of Indiana sponsored a study to determine whether available clinical helical CT is able to reveal internal structure of kidney stones. Forty candidates, above 18 years of age, men as well as women, were enrolled in the study in July 2002, to be followed up till February 2006.
Eligibility was based on the ability to suspend respiration for at least 20 seconds, and those needing a computed tomography scan prior to their stone surgical treatment. Pregnant women and candidates with a history of abdominal malignancy were excluded.
Although, Helical computed tomography was commonly used in the assessment and treatment of kidney stone patients, its full potential to differentiate among stone types by structure or radiodensity was yet to be realized. CT scans were usually conducted only to identify the existence of the stone and to indicate its size and location. The use of soft tissue windows failed to reveal the structure within the kidney stone.
Treatment of Kidney stones is dependant on three factors- the type, size and location of the kidney stone. Shock wave Lithotripsy is used to break down stones into gravel that may be naturally removed from the body. However, shock waves may not be ideal to break down certain stones, or due to the complicated location of a stone it may have to be removed through more invasive surgical means. In addition, SWL is not without complications with long-term risks of hypertension and renal insufficiency.
Also, kidney stones vary in their SWL fragility. With the continuous advancement of technology for clinical CT, the latest generation of multidetector helical CT machines has considerably improved image resolution over single-detector CT technology. These quad-slice scanners have 4 contiguous, parallel rows of x-ray detectors combined with a higher gantry rotation speed which increase the speed of data collection by a factor as high as 8 over the conventional single-slice spiral CT scanners.
The latest technology makes for higher spatial resolution along the longitudinal axis of the patient. The scans can also be performed much faster, which means improved temporal resolution and less motion artifacts. Thus, CT scan has the ability to both predict stone composition and delineate structural features necessary to predict stone fragility to lithotripter shock waves.
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