Clinical Trial Details
— Status: Completed
Administrative data
NCT number |
NCT02606513 |
Other study ID # |
MR_CT_URO |
Secondary ID |
|
Status |
Completed |
Phase |
N/A
|
First received |
November 12, 2015 |
Last updated |
March 13, 2016 |
Start date |
January 2014 |
Est. completion date |
December 2015 |
Study information
Verified date |
March 2016 |
Source |
Kuopio University Hospital |
Contact |
n/a |
Is FDA regulated |
No |
Health authority |
Finland: Ethics Committee |
Study type |
Interventional
|
Clinical Trial Summary
Tumors of the UUT are rare and usually presenting as micro- or macrohematuria either
symptomatic or asymptomatic. Rapid advances in CT technology accelerated the research into
the application of this new technology in the evaluation of the UUT and readily proved to be
superior to other imaging modalities. Nevertheless the increase in radiation dose is a major
issue of concern. Initial research into the utility of MRI in the evaluation of the UUT was
promising, yet the success of CT together with the cost, limited availability and the longer
duration of MR urography (MRU) examination, nearly halted the investigations into the
feasibility of MRU which is unfortunate as MRU is a safe alternative to CT.
Description:
Images from a MDCT scan are reconstructed into thin slices which can be viewed in any
orientation with similar image quality compared to the original axial images. Completely
isotropic resolution in 16- to 64-slice CT can be achieved using 0.5- to 0.625-mm slice
thickness. Resulting images have high noise levels unless the tube load is increased
considerably. In most clinical situations a near-isotropic resolution with 1.0- to 1.5-mm
effective slice thickness suffices for high-quality images created in any plane using MPR.
Research into the accuracy of CTU in the evaluation of possible UUT malignancy soon proved
CTU to be a very sensitive and specific method with pooled sensitivity of 96% (range
88-100%), and pooled specificity of 99% (range 93-100%). Furthermore direct comparison
confirmed the superiority of CTU over IVU in terms of sensitivity and specificity.
In order to reduce confusion in terminology, the European Society of Urogenital Radiology's
(ESUR) CTU Working Group proposes to define CTU as "a diagnostic examination optimized for
imaging the kidneys, ureters and bladder. The examination involves the use of MDCT with
thin-slice imaging, intravenous administration of a contrast medium, and imaging in the
excretory phase." ESUR guideline comprehensively addresses all aspects of CTU based on
extensive literature review and on the opinion of leading researchers in this
field. To begin with, hydrating the patient is beneficial to reduce
possible contrast induced nephropathy especially in otherwise dehydrated or not well
hydrated patient, and at the same time provides negative bowel contrast medium. Usually 1
liter of water is slowly ingested during a period of 20-60 minutes before the CTU
examination or alternatively a maximum of 500 ml slow intravenous drip-infusion of 0.9%
saline may be used in patients who cannot tolerate per oral hydration. Nevertheless the ESUR
guideline also concludes that the net benefit of intravenous saline bolus hydration is
probably minimal and its routine use is thus not advocated. Bowel preparation with positive
contrast will inevitably interfere with the interpretation especially in the demonstrative
quality of reformatted images and is not recommended. In diuretic-enhanced CT urography, the
patients are asked to empty their bladder before starting the CTU examination, nevertheless
the ESUR guidelines have no stand on this issue. The use of compression pads is a routine
practice in IVU and consequently it was thought that this maneuver can be transferred to the
CTU protocol. However after evaluating of the available evidence ESUR guideline do not
advocate the use of compression.
Patients are scanned in supine position. Prone position is not advocated to be used
routinely but can be used in special cases e.g. to reduce layering effects of the contrast
medium, especially when the renal collecting system is dilated.
After the introduction of the rapid MDCT technology it became clear that this new imaging
modality is more accurate than IVU in the initial workout of a wide range of UUT pathology.
Images from a MDCT scan are reconstructed into thin slices which can be viewed in any
orientation with similar image quality compared to the original axial images. Completely
isotropic resolution in 16- to 64-slice CT can be achieved using 0.5- to 0.625-mm slice
thickness. Resulting images have high noise levels unless the tube load is increased
considerably. In most clinical situations a near-isotropic resolution with 1.0- to 1.5-mm
effective slice thickness suffices for high-quality images created in any plane using MPR.
Research into the accuracy of CTU in the evaluation of possible UUT malignancy soon proved
CTU to be a very sensitive and specific method with pooled sensitivity of 96% (range
88-100%), and pooled specificity of 99% (range 93-100%). Furthermore direct comparison
confirmed the superiority of CTU over IVU in terms of sensitivity and specificity.
In order to reduce confusion in terminology, the European Society of Urogenital Radiology's
(ESUR) CTU Working Group proposes to define CTU as "a diagnostic examination optimized for
imaging the kidneys, ureters and bladder. The examination involves the use of MDCT with
thin-slice imaging, intravenous administration of a contrast medium, and imaging in the
excretory phase.". ESUR guideline comprehensively addresses all aspects of CTU based on
extensive literature review and on the opinion of leading researchers in this
field. To begin with, hydrating the patient is beneficial to reduce
possible contrast induced nephropathy especially in otherwise dehydrated or not well
hydrated patient, and at the same time provides negative bowel contrast medium. Usually 1
liter of water is slowly ingested during a period of 20-60 minutes before the CTU
examination or alternatively a maximum of 500 ml slow intravenous drip-infusion of 0.9%
saline may be used in patients who cannot tolerate per oral hydration. Nevertheless the ESUR
guideline also concludes that the net benefit of intravenous saline bolus hydration is
probably minimal and its routine use is thus not advocated. Bowel preparation with positive
contrast will inevitably interfere with the interpretation especially in the demonstrative
quality of reformatted images and is not recommended. In diuretic-enhanced CT urography, the
patients are asked to empty their bladder before starting the CTU examination, nevertheless
the ESUR guidelines have no stand on this issue. The use of compression pads is a routine
practice in IVU and consequently it was thought that this maneuver can be transferred to the
CTU protocol. However after evaluating of the available evidence ESUR guideline do not
advocate the use of compression.
The first popular CTU protocol is the single-bolus
3-phase technique. After hydration, a low-dose unenhanced CT is acquired from the top of
kidneys to the base of the bladder, followed first by low-dose diuretic and 1-2 minutes
later by contrast injection. Imaging strategy after the administration of contrast material
is controversial with different protocols available aimed mainly to detect or rule out
possible malignancies and no scientific evidence is available on the superiority of specific
protocols. Contrast enhanced abdominal scan can be obtained at corticomedullary phase (25-35
s delay after start of contrast injection) or at nephrographic (delay of 90-110 s) or with a
combination of nephrographic-corticomedullary (so called dose-efficient or
arterial-nephrographic-corticomedullary phase after splitting of the contrast injection into
two or three bolus in modified protocols. The third excretory phase (240-480 s delay) is the
most important scan with the purpose of achieving excellent endoluminal opacification,
preferably with some UUT dilatation. Even better results are reported if acquisition is
further delayed to 720 s for improved depiction of the lower ureter while opacification of
other UUT segments are not sensitive to delay time. When low-dose furosemide is
administered, excretory phase delay may be reduced to an average of 450 s.
The other CTU protocol is called the split-technique with considerably different protocols
of contrast bolus. The main idea is in the administration of one bolus of contrast followed
by a variable delays of 480-1,000 s (recent practices report 600-660 s delay) and then
followed by the injection of a second contrast bolus. After a constant delay of 90-120 s
from the second bolus, an abdominal scan is acquired and as the first injected contrast is
already excreted, the acquisition contains combined nephrographic and excretory phases in
one scan therefore reducing radiation dose. Further modifications of the split-bolus
technique includes triple-bolus contrast injection for the acquisition of combined
corticomedullary-nephrographic-excretory phase data some 510 s after start of the first
bolus with or without low-dose diuretics Imaging of the UUT with MRI is
challenging and, as with other imaging modalities MRU, has its strengths and weaknesses. MRI
is susceptible to various artefacts including chemical shift misregisteration, wraparound,
phase-encoded motion and susceptibility artefacts, which might be more prominent at higher
field strength. Furthermore standing wave and conductivity artifact are noticed in obese
or ascites patients at 3T imaging. Therefore good knowledge and experience of both normal
anatomy and artefacts are a prerequisite for correct image interpretation. MRI is lengthy
examination and needs patient cooperation. Breath-hold ultrafast sequences and the use of
parallel imaging reduces imaging time and are useful to obtain high quality images and hence
help reduce movement artifacts. It is also beneficial to raise the arms over the head during
coronal imaging to prevent wraparound artifact. In the investigators' experience reader
should be always familiar with the artefacts related to the enhanced excretion of urine such
as void lines and turbulence artefacts especially in the dilated pelvis. The investigators
also recommend imaging the UUT routinely in both axial and coronal planes during the
excretory phase. The
inability to visualize calcifications are considered as a limitation to the use of MRU in
the evaluation of UUT stone disease. Indeed possible stone is visualized as a partial or
complete intraluminal filling defect which is nonspecific and should be differentiated with
blood clot or tumor. Nevertheless, a clot is usually hyperintense at unenhanced sequence and
do not enhance after the administration of contrast and additionally the margins of the
soft-tissue abnormality are usually irregular compared with the well-defined margins of
calculi. Opposite to that a tumor will usually enhance. Therefore any MRU protocol should
include both T2 and T1 sequences and the latter both pre- and postcontrast sequences. The
failure to do so might result in misinterpretations, yet occasionally severe edema might be
misinterpreted as of a possible tumo. Different results from the literature should be
interpreted with caution because of the variability of used sequences and selection bias.
Not all studies evaluating the performance of MRU use both T1 and T2 sequences and as
previously mentioned, T2 sequences alone are insufficient to evaluate the cause of
obstruction.
MRU was shown to be superior to IVU in the detection of UUT stones. MRU was found to be at
least as accurate as helical CT in the evaluation of patients with acute flank pain. Also
the presence of secondary signs of obstruction such as the perirenal edema on the side of
symptoms are highly suggestive of acute obstruction and is better visualized at MRU than at
CT. Yet CT gained wider acceptance: CT is widely available, accurate and rapid imaging
modality in the evaluation of acute flank pain and stone disease. MRU is an acceptable
substitute in cases where the use of radiation is not desired in special patient populations
i.e. in children, young adults and pregnant patients.
Another limitation of MRU is in the slight underestimation of the size of ureteral stones
compared to CT and IVU. Also, according to the published results, small ureteral stones can
be occasionally missed in chronic obstructions, especially when the secondary signs of acute
obstruction are absent to raise the suspicions of a stone disease. Additionally MRU is
insensitive in the detection of small calyceal stones therefore cannot reliably evaluate the
actual stone disease-burden of the calyceal system, yet small stones are rarely of clinical
importance.
A comprehensive MRU protocol facilitates evaluation of the renal parenchyma, UUT,
surrounding structures and if needed the renal vasculature. This "one-stop evaluation"
approach is fully applicable with MRU which is additionally free from radiation.
Additionally MR is superior to CT in that it provides better tissue contrast resolution and
greater sensitivity for contrast enhancement. Therefore MRU became the secondary
investigation of choice after US in pediatric UUT imaging. The European Society of
Paediatric Radiology uroradiology task force and ESUR paediatric working group recommends to
always consider MRU, when available, as a secondary investigation after US in applicable
situations, with the main principle being to avoid CT whenever possible. The few accepted
major indications for CTU in children being severe urinary tract trauma,
complicated/equivocal urolithiasis (if high level US+KUB are not conclusive and if there is
expected therapeutic impact).
The MRU protocol includes always Both T2 and T1 breath-hold sequences in coronal orientation
as a minimum. Nevertheless there are no universally accepted consensus protocol. As a safe
method the investigators believe that MRU protocols should not duplicate CTU protocols in
comparison, but a comprehensive protocol with multiple acquisitions is most probably
beneficial.