CTU is the primary test of choice for the evaluation of the UUT. The performance of MRU will be compared to that of CTU in the same patient population

MR Urography; CT Urography

Ritva Vanninen, MD; PhD

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.

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.

MR Urography vs CT Urography

Opacification of the Upper Urinary Tract With MR Urography Compared to CT Urography

Data will be shared after manuscript submission

The UUT will be devided into 6 regions: Upper calyces, lower calyces, pelvis, and upper, middle and lower ureter, and the percentage opacification of each segment will be scored visually using 6 percentage-categories. Results of the opacification scores will be compared between MRU and CTU.

Pathological findings from CTU will be compared to MRU; i.e. for the presence of tumors, Stones, obstruction and its causes.

Kuopio University Hospital

Senior Radiology Consultant

Neoplasms

All Conditions

Urinary Tract, Sexual Organs, and Pregnancy Conditions

Rare Diseases

Carcinoma

Urinary Bladder Neoplasms

Carcinoma, Transitional Cell

Urologic Neoplasms

Urogenital Neoplasms

Urogenital Diseases

Female Urogenital Diseases

Pregnancy Complications

Female Urogenital Diseases and Pregnancy Complications

Urinary Bladder Diseases

Urologic Diseases

Male Urogenital Diseases

Transitional Cell Carcinoma

CTU = Computed Tomography Urography + IVU = Intravenous Urography

CTU performed at least a day before or after the IVU procedure.

Computed Tomography Urography (CTU)

A routine IVU procedure performed prior to or after CTU.

Intravenous Urography (IVU)

Chaan Ng, MD

The goal of this clinical research study is to use computed tomography urography (CTU) scans and intravenous urography (IVU) scans to check the status of urothelial cancer, in order to try to learn the level of effectiveness of possibly using CTU by itself in future patients.

Background for the Study:

Currently, IVU is used to detect urothelial tumors and then computed tomography (CT) scans are performed after that, to check the status of the disease. This is typically done every 3 months for the first 2 years after diagnosis, and then every 6 months for the next 2 years. Researchers want to learn if this current routine method of using 2 diagnostic procedures can be replaced with CTU alone, in future patients.

CTU uses the same scanner machine as CT scans do. The difference between these 2 types of scans is that in addition to collecting the same type of images and information that CT scans do, CTU may also allow the doctor to look at the lining of the tubes that carry urine from the bladder. Looking at the lining of these tubes is something that IVU is used for, and researchers want to find out if CTU can also be used for this purpose.

Study Procedures:

If you are found to be eligible to take part in this study, you will have a CTU procedure performed at least a day before or after your routine IVU. If your doctor has ordered a CT of your abdomen and pelvis and IVU, the CTU will be performed instead of a routine CT scan of the abdomen and pelvis that would normally occur. If your doctor has ordered just a CTU, you will have an IVU as well.

CTU Procedure:

The CTU procedure is very similar to the standard CT of the abdomen/pelvis that you would otherwise receive along with an ITU. To prepare for the CTU, you will be asked to drink contrast solution (a type of dye) in order to allow the tumor(s) to be more easily seen and checked. You will be given about 30 ounces (3 3/4 cups) of contrast solution to drink at 30 minutes before the CTU and another 7 ½ ounces (about a cup) of contrast solution to drink while you are on the scanning table. You will also receive Lasix (furosemide) by injection. Furosemide is given to help the tubes in your kidney dilate (expand) to improve the quality of the images.

For the CTU , you will lie flat on a CT scanner and will receive additional contrast solution by vein during the scan. While the scan is being performed, you will be asked to hold your breath several times, for about 15-20 seconds each time. The process of having the CTU performed should take about 10 minutes longer than a regular CT scan. If the images are not clear enough, all or part of the scanning process may need to be repeated (without repeating the contrast).

IVU Procedure:

Either before the CTU or after it, depending on the order in which you were assigned to receive these procedures, you will receive the IVU as part of your routine care.

Length of Study Participation:

After one set of IVU and CTU scans have been performed, your participation in this study will be over. At least 3 months after your scans are performed, your images will be reviewed a second time by 2 additional M. D. Anderson doctors (radiologists) to compare their findings with the original radiologist's findings.

This is an investigational study. The routine way to check the status of urothelial cancer is to use IVU and CT scanning. It is considered experimental, however, to use CTU instead of routine CT scanning for checking the status of urothelial cancer. At this time, using CTU for this purpose is being done in research only.

Up to 135 patients will take part in this study. All will be enrolled at MD Anderson.

Computed Tomography Urography (CTU) vs Intravenous Urography (IVU) on Patients at Risk of Urothelial Tumors

Pilot Study Assessing the Technical Efficacy of Computed Tomography Urography (CTU) vs Intravenous Urography (IVU) With Particular Focus on Patients at Risk of Urothelial Tumors

Comparison of relative technical performance of computed tomography urography (CTU) to intravenous urography (IVU) using digital tomosynthesis, in terms of visualization and diagnostic quality of segments of the upper urinary tract.

Study title	NCT ID	Conditions	Interventions	Eligibility	Organization	Link
MR Urography vs CT Urography	NCT02606513	Neoplasms	MR Urography; C...	18 Years -	Kuopio University Hospital
Computed Tomography Urography (CTU) vs Intravenous Urography (IVU) on Patients at Risk of Urothelial Tumors	NCT00567684	Bladder Cancer	Computed Tomogr... Intravenous Uro...	18 Years -	M.D. Anderson Cancer Center

Spots Global Cancer Trial Database for computed tomography urography