CT urography: Definition, indications and techniques. A guideline for clinical practice

Article (PDF Available)inEuropean Radiology 18(1):4-17 · February 2008with1,067 Reads
DOI: 10.1007/s00330-007-0792-x · Source: PubMed
Abstract
The aim was to develop clinical guidelines for multidetector computed tomography urography (CTU) by a group of experts from the European Society of Urogenital Radiology (ESUR). Peer-reviewed papers and reviews were systematically scrutinized. A summary document was produced and discussed at the ESUR 2006 and ECR 2007 meetings with the goal to reach consensus. True evidence-based guidelines could not be formulated, but expert guidelines on indications and CTU examination technique were produced. CTU is justified as a first-line test for patients with macroscopic haematuria, at high-risk for urothelial cancer. Otherwise, CTU may be used as a problem-solving examination. A differential approach using a one-, two- or three-phase protocol is proposed, whereby the clinical indication and the patient population will determine which CTU protocol is employed. Either a combined nephrographic-excretory phase following a split-bolus intravenous injection of contrast medium, or separate nephrographic and excretory phases following a single-bolus injection can be used. Lower dose (CTDIvol 5-6 mGy) is used for benign conditions and normal dose (CTDIvol 9-12 mGy) for potential malignant disease. A low-dose (CTDIvol 2-3 mGy) unenhanced series can be added on indication. The expert-based CTU guidelines provide recommendations to optimize techniques and to unify the radiologist's approach to CTU.
Eur Radiol
DOI 10.1007/s00330-007-0792-x
UROGENITAL
Aart J. Van Der Molen
Nigel C. Cowan
Ullrich G. Mueller-Lisse
Claus C. A. Nolte-Ernsting
Satoru Takahashi
Richard H. Cohan
CT Urography Working Group of
the European Society of Urogenital
Radiology (ESUR)
Received: 13 July 2007
Revised: 8 September 2007
Accepted: 14 September 2007
# European Society of Radiology 2007
CT urography: definition, indications
and techniques. A guideline for clinical practice
Abstract The aim was to develop
clinical guidelines for multidetector
computed tomography urography
(CTU) by a group of experts from the
European Society of Urogenital
Radiology (ESUR). Peer-reviewed
papers and reviews were systemati-
cally scrutinized. A summary docu-
ment was produced and discussed at
the ESUR 2006 and ECR 2007 meet-
ings with the goal to reach consensus.
True evidence-based guidelines could
not be formulated, but expert guide-
lines on indications and CTU exami-
nation technique were produced. CTU
is justified as a first-line test for
patients with macroscopic haematuria,
at high-risk for urothelial cancer.
Otherwise, CTU may be used as a
problem-solving examination. A dif-
ferential approach using a one-,
two- or three-phase protocol is pro-
posed, whereby the clinical indication
and the patient population will
determine which CTU protocol is
employed. Either a combined nephro-
graphic-excretory phase following a
split-bolus intravenous injection of
contrast medium, or separate nephro-
graphic and excretory phases follow-
ing a single-bolus injection can be
used. Lower dose (CTDIvol 56
mGy) is used for benign conditions
and normal dose (CTDIvol 912
mGy) for potential malignant disease.
A low-dose (CTDIvol 23 mGy)
unenhanced series can be added on
indication. The expert-based CTU
guidelines provide recommendations
to optimize techniques and to unify
the radiologist s approach to CTU.
Keywords Tomography
X-ray computed
.
Urography
.
Radiation dosage
.
Practice guidelines
Introduction
Computed tomography urography (CTU) is a relatively new
diagnostic imaging examination providing comprehensive
evaluation of the upper and lower urinary tract. Multidetector
CT (MDCT) enables isotropic or near-isotropic high-quality
multiplanar image reconstruction. As MDCT has become
more widely available, CTU has begun to replace other
imaging techniques, especially intravenous urography (IVU).
CTU is currently performed for a variety of indications using
different protocols [1, 2] for which purely CT-based
techniques as well as hybrid CT-radiography techniques
[3, 4] have been utilised.
The purpose of the CTU Working Group of the European
Society of Urogenital Radiology (ESUR) was to review the
literature and draw up guidelines for clarification of CTU
indications and CTU imaging techniques. As hybrid CT-
radiography techniques may require non-standard equipment
that is only available in specialized centres, this guideline will
focus on CT-only techniques using multidetector CT systems.
Electronic Supplementary Material The
online version of this article (doi:10.1007/
s00330-007-0792-x) contains supplemen-
tary material, which is available to autho-
rized users.
ESUR: www.esur.org
A. J. Van Der Molen (*)
Department of Radiology C-2S,
Leiden University Medical Center,
Albinusdreef 2,
2333 ZA Leiden, The Netherlands
e-mail: molen@lumc.nl
Tel.: +31-71-5262052
Fax: +31-71-5248256
N. C. Cowan
Department of Radiology,
The Churchill Hospital,
Oxford, OX3 7LJ, UK
U. G. Mueller-Lisse
Department of Clinical Radiology,
University of Munich Hospitals -
Innenstadt,
Ziemssenstraße 1,
80336 Munich, Germany
C. C. A. Nolte-Ernsting
Department of Diagnostic and
Interventional Radiology, University
Hospital Hamburg-Eppendorf,
Martinistrasse 52,
20246 Hamburg, Germany
S. Takahashi
Department of Radiology HP 212,
Radboud University Medical Center,
Geert Grooteplein 10,
6525 GA Nijmegen, The Netherlands
R. H. Cohan
Department of Radiology,
University of Michigan Health System,
B1-132 Taubman Center 0302,
1500 E Medical Center Dr.,
Ann Arbor, MI, 48109-0302, USA
Materials and methods
The members of the CTU Working Group systematically
reviewed the CTU literature using multiple database
searches (PubMed, Cochrane, EMBASE, Web of Science)
from papers published from 1995 to 2007. Search terms
included variable combinations of tomography/X-ray
computed, tomography/spiral computed, urography, hae-
maturia, urologic diseases/radiography, radiation dosage,
indications, clinical trials, etc. Results were limited to
manuscripts in the English and German languages.
Randomised clinical trials comparing different diagnos-
tic modalities or strategies prospectively and outcome
studies are not yet available. Therefore this guideline can
only be based on an extensive literature review and expert
opinion rather than on evidence-based data.
Successive draft proposals were extensively discussed
among the members by e-mail and at several meetings
during major conferences. Preliminary versions were
presented to European radiologists for discussion at the
2006 Annual Meeting of the ESUR in Cairo, Egypt and the
2007 European Congress of Radiology in Vienna, Austria.
Definition
The term CTU is often used in clinical practice for a
multitude of MDCT techniques for evaluation of the
urinary tract. Such terminology leads to confusion and
ambiguity regarding the exact nature of studies undertaken.
The 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
multidetector CT with thin-slice imaging, intravenous
administration of a contrast medium, and imaging in the
excretory phase.
Imaging in the excretory phase, either early or delayed,
is thus a mandatory part of any CTU protocol. Careful
patient preparation and attention to technique is also
essential for optimal evaluation of the collecting system
and ureters. This definition does not imply that all phases
necessarily have to be contrast-enhanced. An unenhanced
phase may also assist in high-resolution renal parenchyma
imaging. However, use of this stricter definition means that
CT performed for evaluation of urolithiasis in acute flank
pain, renal infection, renal arteries (including evaluation for
renal donation), and staging of renal cell carcinoma should
not routinely be labelled as CTU.
Indications
Most frequent present-day indications for CTU include
the investigation of haematuria, patients at increased risk
for having upper or lower tract urothelial neoplasms,
urinary diversion procedures following cystectomy, hy-
dronephrosis, chronic symptomatic urolithiasis including
planning of percutaneous nephrolithotomy (PCNL), trau-
matic and iatrogenic ureteral injury, and complex urinary
tract infections [1].
The role of CTU has been studied most extensively in
patients with haematuria. Current haematuria guidelines do
not yet give details on how to specifically use CTU. The
American Urological Association 2001 guideline for
microscopic haematuria only suggests that upper tract
imaging (by IVU or CT) be performed in all patients
irrespective of risk [5]. Others have suggested performing
CT after urinalysis for any non-glomerular microscopic
haematuria, before cytology or cystoscopy is performed
[6]. The European Urology Association 2004 guideline for
upper urinary tract transitional cell cancer (TCC) states that
IVU is still the first-choice examination for investigating
haematuria. Retrograde urography may be useful in cases
where IVU is equivocal with a sensitivity of over 75%.
With CT, it can still be difficult to accurately diagnose
small volume tumours of the renal pelvis and ureter [7].
Studies focusing on CTU in patients with microscopic
haematuria show that causes for haematuria are identified
in 33.042.6% with overall CTU sensitivity for identifica-
tion of the cause of haematuria of 92.4100% and
specificity of 89.097.4% [8 13]. In studies on micro-
scopic or unselected haematuria upper tract TCC was
present in 0.97.3% [8, 11, 14]. In these populations, CTU
detection of upper tract TCC is high [1315] and
significantly better than IVU [8]. When applied to selected
highrisk groups of macroscopic haematuria, TCC tumour
prevalence may increase to 2530% and it has been shown
that CTU of the upper tract is equivalent to RP [16]. CT
may still have problems of correctly staging advanced
tumours [15, 17].
CTU can also be powerful in the diagnosis of bladder
tumours, but results differ depending on the specific
population studied. In a population of patients with
microscopic haematuria, CTU sensitivity in comparison
with cystoscopy was only 40% [12], while in a high risk
group with macroscopic hematuria, unequivocal CTU
results were 93% sensitive and 99% specific for detection
of bladder cancer, which may obviate the need for many
flexible (diagnostic) cystoscopies [18].
The use of CTU for other indications is largely
anecdotal. CTU may be useful in guiding percutaneous
nephrolithotomy procedures [ 19], to depict abnormal
postoperative findings in patients after urinary diversions
[4], or to effectively diagnose medullary and papillary
necrosis in an early stage when treatment can reverse the
ischemic process [20]. Also, during CTU significant extra-
urinary findings may be found [8, 21]. However, additional
imaging was needed in few patients and the per-patient
incremental costs were minimal [21 ].
Given the relatively high radiation doses associated with
multiphase technique, pre-test probabilities for cancer
should be taken into consideration. CTU can be justified
as a first line test for the upper and lower urinary tract in
haematuria patients with a high pre-test probability for
TCC. Important risk factors include age >40 years, mac-
roscopic haematuria, smoking, history of GU malignancy,
and occupational exposure. The risk from the use of
radiation is relatively less important in such high-risk
groups and any comprehensive two- or three-phase CTU
protocol can be performed. Cost-effective in such patients
could be the replacement of the traditional work-up of
ultrasound + IVU + cystoscopy by a faster CTU +
cystoscopy work-up. An algorithm for the investigation of
patients with painless haematuria is outlined in Table 1 [1].
For lower risk groups, CTU can be used as a problem-
solving test if traditional work-up remains negative and
significant undiagnosed symptoms persist. In general, CTU
can be tailored towards the clinical question based on
clinical information. For benign indications where only the
excretory phase will be relevant (variant urinary tract
anatomy, ureteral pseudodiverticulosis and iatrogenic ure-
ter trauma), single-phase CTU can suffice. Patients with
more complex benign diseases and those with chronic
symptomatic urolithiasis (complex infections, PCNL plan-
ning) may benefit from adding an unenhanced phase to the
excretory phase. In chronic urolithiasis without complete
obstruction, furosemide-assisted CTU (see below) can
demonstrate most ureteral stones within the enhanced
urine. So for evaluation of hydronephrosis due to obstruc-
tion by stones, the unenhanced phase may be safely
deleted, whereas diagnosis of small non-obstructing stones
may be done by an unenhanced phase limited to the
kidneys [2].
CTU technical issues in detail
Patient preparation
The CTU study does not require any special preparation.
The use of positive contrast medium for bowel should be
avoided as it interferes with subsequent evaluation of 3D
images. Oral hydration with water is without any additional
cost. It avoids dehydration, promotes diuresis and acts as a
negative contrast medium for the gastrointestinal tract. Up
to 1,000 ml of water in 2060 min before CT has been used
[16, 22, 23]. It can improve delineation of ureteral
segments [22], and may facilitate the diagnosis of
incidental findings. If patients can not tolerate the oral
intake of water, diuresis may be promoted somewhat by a
slow intravenous drip-infusion of 0.9% saline (to a
maximum of 500 ml) before and during the CTU.
Patient positioning
Supine positioning is standard practice for CTU. Prone
imaging may be advantageous in the unenhanced phase to
discriminate uretero-vesical junction stones from stones
passed into the bladder [1]. Prone positioning for improved
depiction of the upper urinary tract during excretory phase
has shown mixed results. An early study showed better
opacification of the collecting system to mid-ureter by
prone positioning [24], but more recent studies could not
show any benefit and other factors than positioning play a
greater role [25, 26]. Given the more cumbersome position
for the patients, prone imaging is not advocated for routine
use. However, turning the patient several times before
excretory phase imaging can avoid layering effects of the
contrast medium (CM), especially when the renal collect-
ing system is dilated [2].
Intravenous injection of CM
Intravenous (i.v.) CM injection schemes are closely related
to the number and timing of CT data acquisitions. Two
major approaches have been followed: (1) a single bolus of
CM, combined with a three- to four-phase study using
unenhanced, nephrographic and excretory phase series,
versus (2) a split-bolus CM injection, combined with a two-
to three-phase study using unenhanced and a combined
nephrographic-excretory phase series. The most frequently
Table 1 Differentiated work-up
of painless haematuria and role
of CTU [1](CYS cystoscopy,
IVU intravenous urography, US
ultrasound)
Evaluation of painless microscopic or macroscopic haematuria
Probability TCC Lowest Low Medium High
Haematuria Micro Macro Micro Macro
Patient age <40 years <40 years >40 years >40 years
First line tests CYS CYS CYS CYS
US US US CTU
↓↓
Follow-up Watch & wait
if negative
IVU if US & CYS
negative and
symptoms persist
IVU or CTU if US
& CYS negative and
symptoms persist
Specialist
referral
used CM concentrations contain 300350 milligrams of
iodine per millilitre (mgI/ml).
Most groups still inject standardized volumes (e.g. 125
150 ml of 300 mgI/ml CM) at set injection rates (23 ml/s)
in all adult patients. However, ideally the volume of CM
should be adapted to the CM concentration and the
patients weight (e.g. 1.72.0 ml/kg of 300 mgI/ml CM or
1.41.6 ml/kg of 370 mgI/ml CM), while adaptation of the
injection rate to the patients weight (e.g. 0.04 ml/s/kg)
ensures a constant injection duration which is optimal for
MDCT [27].
Single-bolus CM injections use 100 150 ml of nonionic
CM (300370 mgI/ml) injected at a rate of 23 ml/s [9, 22 ,
23, 2837]. If a corticomedullary phase is employed, data
acquisition is usually started 2535 s after start of CM
injection [9, 22]. The nephrographic phase starts after a
delay of 90110 s after start of the CM injection [9, 23, 28,
30, 32, 33, 37], while for the final excretory phase a fixed
delay of 240480 s after the start of CM injection has been
used [9, 2830, 32]. In more recent times, excretory phase
data acquisition has been further delayed to 720 s for
improved depiction of the lower ureter [38]. As excretory
phase imaging may be done with CM volumes as low as
50 ml, the volume and injection rate of CM may be tailored
to the number of phases planned. If a corticomedullary or
nephrographic phase will not be performed, a high CM
volume (125150 ml) and injection rate (34 ml/s) will
often be unnecessary [2].
Different protocols have been published for split-bolus
CM injection. Either a smaller first injection of 3050 ml at
a rate of 2 ml/s, followed 215 min later by a larger second
injection of 80100 ml at 22.5 ml/s is used [
26, 3941], or
a larger first injection of 75100 ml injection at a rate of 2
3 ml/s, followed 310 min later by a smaller second
injection of 4550 ml at a rate of 23 ml/s [16, 18, 42]. The
significance of the variability in published sequences,
volumes, flow rates and injection durations remains
unclear. In general, the imaging delays for the combined
nephrographic-excretory phase with respect to the first CM
injection will vary per CM injection protocol, depending
on the interval between injections. Variable delays of 480
1,000 s from the start of the first injection with a constant
delay of 90120 s from the start of the second injection
have been published [16, 18, 3941]. Most recent practice
use delay times in the order of 600660 s from the start of
the first injection [16, 18].
In 2006, a dose-efficient CTU protocol was introduced
which is a hybrid between CTU, renal donor and renal
carcinoma evaluation protocols. The protocol employs a
triple bolus CM injection, after which one combined
corticomedullary-nephrographic-excretory phase data ac-
quisition is obtained some 510 s after start of the first bolus
(triple bolus single CTU). A small first bolus (30 ml at
2 ml/s) is used for opacification of the excretory system,
followed 7 min later by a small second bolus (50 ml at
1.5 ml/s) for the renal parenchyma and veins, and finally
followed 20 s later by a larger third bolus (65 ml at 3 ml/s)
for arterial information (M. Kekelidze, presented at ECR
2006). Most recently, a furosemide-assisted version with
50 ml for the first bolus was added (M. Kekelidze,
presented at SUR 2007).
Longer delays after single-bolus injection were bene-
ficial for both distension of the collecting system and
proximal ureter and improvement of the proportion of
opacified ureteral segments [28, 30]. With respect to
opacification of the distal ureter, the excretory phase should
be performed between 600 and 960 s (1016 min) when
single-bolus CM injection is followed by an intravenous
saline bolus. The opacification of other segments of the
upper urinary tract were not sensitive to delay time [37].
When low-dose furosemide is administered, excretory
phase delay may be reduced to an average of 450 s [36].
Number of CTU phases
The number of CTU phases generally varied between two
and four. The most frequently used phases used in a single
CM-bolus CTU are: (1) an unenhanced phase of the
abdomen and pelvis, (2) a nephrographic phase of the
abdomen, and (3) an excretory phase of the abdomen and
pelvis [9, 23, 28, 30, 32, 33]. Only a few groups employ the
use of a corticomedullary phase [9, 22]. Some extend the
nephrographic phase to the pelvis [37], especially when
the patient is at increased risk of malignancy. Such a
nephrographic phase facilitates complete tumour staging or
evaluation of associated findings. Portal venous phase CT
may already have a high detection rate for bladder tumours
[43].
When a compression device is used, the excretory phase is
split in two: (1) an earlier excretory phase of the kidneys and
proximal ureters with compression, and (2) a later excretory
phase of the mid-distal ureters and bladder after compression
release [39, 42
]. Obviously, these two excretory phase series
are acquired at different delays from the start of the injection
and will lead to a higher radiation dose.
Because of the high radiation dose of CTU, the number
of phases should be kept to a minimum. This is one of the
reasons that the split-bolus CM injection protocols have
been gaining popularity. With split-bolus injection, after
unenhanced imaging of the abdomen and pelvis a single
contrast-enhanced combined nephrographic-excretory phase
series is obtained [16, 18, 39, 40]. Single-phase CTU
techniques with use of furosemide have been suggested,
either using a single excretory phase [2]orasingle
combined nephrographic-excretory phase (F. Cornud, pre-
sented at ESUR 2005). There is also the possibility of
deleting the unenhanced phase from the CTU protocol when
using furosemide. Single-phase furosemide-CTU is able to
detect urinary calculi because the diuretic dilutes the
contrast-enhanced urine sufficiently so that the calculi are
of higher attenuation than the urine. Sensitivity in detecting
urinary tract calculi was not decreased when excretory phase
furosemide-CTU images were compared to unenhanced CT
images (J. Kemper, presented at ECR 2004).
Individualizing the delay of excretory phase imaging:
test images
Because there are large inter-individual differences in the
CM excretion, low-dose, single-slice test images through
the mid-ureter can individualize the timing of the excretory
phase [31, 33, 35, 36]. This technique has only been
applied to single-bolus CM injections, but can theoretically
be integrated with split-bolus dosing schemes, provided
that they are made before the (second) CM injection that
generates the nephrographic phase (A.J. van der Molen,
presented at SUR 2007).
Whether or not furosemide is used will determine the
start time of the first test image. If the ureter is not opacified
or if opacification is asymmetric, two to three additional
test images are done at 2-min intervals. When long timing
periods are necessary (unilateral obstruction), the time-
interval is increased to 46 min. Once symmetric ureteral
opacification is achieved, the excretory phase is started [1].
This technique can lead to improved opacification of the
middle and distal ureteral segments with non-opacification
in less than 10% of segments. The technique works best if
renal function is (near) normal, but is of limited use in
patients with high-grade obstruction or in patients with
decreased renal function [36].
Ancillary manoeuvres
An essential part of CTU is the optimization of the
visualization of the urinary tract, and a number of ancillary
manoeuvres to improve the distension and opacification of
different parts of the urinary tract on excretory phase
images can be used.
1. Compression bands
Well known from IVU, abdominal compression bands
have been used for CTU. Compression may have some
beneficial effect on distension of the renal collecting
system and proximal ureter and opacification of the
mid to distal ureter, especially when compared with
IVU [24, 29, 44]. However, longer imaging delays of
450 s showed similar effects on distension and/or
opacification [30]. Thus, longer delays for the ureteral
part of the study are probably more relevant than the
compression release itself. Therefore, the net benefit of
a compression band is probably minimal, and routine
use of this manoeuvre can not be advocated.
2. Intravenous saline hydration
The results of forced diuresis with an intravenous bolus
of 250 ml normal saline (0.9%) before CM injection
during CTU have been mixed. There may be some
beneficial effects on the opacification of the intrarenal
collecting systems or the distal ureter compared to
prone positioning [25, 30]. However, other workers
have not detected any beneficial effect of saline
infusion for upper urinary tract opacification during
CTU [45, 46]. Moreover, i.v. saline effects are
inconsistent compared with other manoeuvres [34]
and there may be heterogeneous high attenuation
values of excreted CM in the renal collecting system
(9502,550 HU), which may limit assessment of
calyceal detail [31]. The net benefit of i.v. saline
bolus hydration is probably minimal and its routine use
is thus not advocated.
3. Low-dose furosemide injection
Low-dose furosemide (Lasix) injection successfully
improves the quality of MR urography [ 47], leading to
improved distension, contrast material dilution, and
more homogeneous contrast material distribution.
Many are advocating that furosemide (0.1 mg/kg to a
maximum of 10 mg) be used for CTU as well [2, 23,
26, 32, 33, 36]. The use of furosemide leads to
homogeneous distribution of the excreted CM with
urine attenuation values of 200400 HU, much lower
than with the use of i.v. saline. Most urinary calculi
(except some uric acid stones) [48] can be well
visualised in the enhanced urinary tract lumen. There-
fore, furosemide use may obviate the unenhanced
phase in a CTU protocol for chronic urolithiasis.
Furosemide use provided improved opacification and
distension of the middle and distal ureters compared with use
of i.v. saline alone [23, 31, 34]. W ith furosemide, ureter non-
opacification was reduced to 6.4% of middle and 7.8% of
distal ureters [36]. An additional logistic benefit is that the
delay of the excretory phase can be shortened when
furosemide is used. In patients with normal renal function
a median delay of the excretory phase of 420 s (mean 450±
120 s) was seen [35, 36]. When using furosemide, 56 min is
probably a good indicative time interval between intravenous
contrast boluses when a split-bolus CM injection is used.
Some precautions must be taken when furosemide is
used. It is contra-indicated in patients with allergies to
sulphonamide drugs, acute glomerulonephritis, acute renal
insufficiency and digoxin intoxication. Also, its use is not
recommended in patients presenting with acute obstruc-
tion, but in chronic nephrolithiasis or hydronephrosis the
low dose is usually not a problem. In dehydrated patients,
the application of low-dose furosemide has to be weighed
carefully and should be combined with oral hydration or a
slow-drip infusion of (maximum 500 ml) i.v. saline (C.C.
A. Nolte-Ernsting, personal communication). Finally, loop-
diuretics such as furosemide are not advisable in patients
with hypotension or those at increased risk for contrast-
induced nephropathy [49], unless patients are adequately
hydrated.
CTU: data acquisition parameters
The main acquisition parameters for multidetector CT are
slice collimation and pitch. In combination with tube
voltage (kV) and tube load (mAs, or effective mAs = mAs/
pitch), these parameters determine the raw-data set.
In all CT systems, the tube voltage for average-sized
patients is typically 120 kV. While low kVp settings for
dose-reduction have been recommended [50], they are still
used infrequently in clinical practice. Tube load settings
have varied significantly between groups, continents and
machine types and have ranged from 50300 mAs on 4-
slice and 65200 mAs on 16-slice CT systems.
In many centres, a lower Z-axis resolution (thicker
collimation) has been used for the unenhanced and
nephrographic phases compared with the excretory phase
series, but parameters have evolved with improvements in
multidetector CT technology. From 8-slice CT systems
onwards, near-isotropic data can easily be obtained in all
phases providing the possibility of high-quality multiplanar
reformatting (MPR) in all planes.
In 4-slice CTU 4×2.53.75 mm collimation has been
employed for the unenhanced and nephrographic phases
and either 4×1.25 mm [21 , 23, 25, 28, 30, 39], or a 4×
2.5 mm collimation for the excretory phase or combined
nephrographic-excretory phase imaging [32, 40, 41, 51].
For 16-slice CT systems collimation is smaller, usually
16×1.251.5 mm for unenhanced and nephrographic
phases [36, 52] and 16×0.50.75 mm for the excretory
phase [22, 23, 52]. Only few keep collimations constant for
all phases [36]. Given the design of 64-slice systems,
collimations for all phases have decreased to 64×0.5
0.625 mm [1, 2]. To avoid excessive noise, tube load (mAs)
may have to increase.
With a maximum cranio-caudal range of 480 mm (e.g.
abdomen-pelvis CT of 420 mm and 60 mm overrange) and
a comfortable breath-hold of 10 20 s, table speed could lie
within a range of 2448 mm/s. Using a tube rotation time
of 0.5 s/rot, this translates into a table feed of 1224 mm/
rot. On 4-slice CT systems longer breath-holds (2030 s)
are necessary. The use of thin collimation requires high
pitch values of at least 1.5, while pitch values for thicker
collimations have varied from 0.75 to 1.5 [21, 25, 30, 32,
39, 40, 51]. Pitch may be lowered to 0.81.2 on 16-slice
and to 0.50.7 on 64-slice scanners, or breath-hold times
may decrease. Nevertheless, in 16- to 64-slice scanners
relatively high pitch settings of 1.21.4 remain in use
[1, 36, 52].
Any helical CT phase is associated with extra tube
rotationsoutsidetheplannedscanrangetobeableto
reconstruct images at the extremes of the planned range as
well as to accommodate reconstructions of thin- and thick-
slice images from the same raw-data set. This over-ranging is
an issue many people overlook in designing CT protocols,
and is especially important in 16- to 64-slice CT systems.
Although over-range length is medium-specific, it increases
with collimation and table feed (pitch), and also depends on
the selection of the reconstructed slice thickness. The
exposed range is much greater than the range planned by
the user. For planned examinations of 400200 mm, the
exposed range may be larger by 1540%. Over-range
substantially increases organ and effective doses (1030%).
Avoidance of small scan ranges and use of the lowest
collimation, low pitch values (below 1.0) and reconstruction
of thin slices minimizes its effects [53].
CT: reconstruction parameters
For image reconstruction, the slice thickness, reconstruction
index and reconstruction kernel are the main parameters.
W ith the acquisition parameters, these parameters are
important determinants of image quality as they determine
contrast and spatial resolution and influence the noise level.
Isotropic resolution differs from isotropic voxels. In-
plane (XY-plane) spatial resolution is determined by the
reconstruction kernel and is around 67 lp/mm (equivalent
to 0.70.8 mm) for medium-smooth to standard kernels.
Through-plane (Z-axis) spatial resolution is determined by
the effective slice thickness, which is about 30% wider than
its nominal value if slice thickness equals slice collimation,
but approaches the nominal value for thicker slices.
Completely isotropic resolution can thus only be achieved
in 16- to 64-slice CT by 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.
The choice of reconstruction parameters strongly
depends on local workflow and PACS capabilities. For 4-
slice CT scanners, contiguous 5-mm slices are the rule for
the unenhanced and nephrographic phase series. This limits
evaluation to the axial plane. For excretory phase in 4-slice
CT, images are reconstructed with slice thicknesses of
1.253.0 mm and an overlapping reconstruction index of
1.01.5 mm for creating MPR and three-dimensional (3D)
images [21, 25, 30, 32, 39, 40, 51]. Even in 16- to 64-slice
CT slightly thinner slices of 2.55 mm are used for the
unenhanced and nephrographic phases, while for the
excretory phase 0.75- to 2.0-mm slice thicknesses and a
reconstruction index of 0.51.0 mm for better evaluation in
non-axial planes are used [1, 23, 33].
To use the full capability of multidetector CT, the
optimal approach is to reconstruct each phase with thin,
overlapping slices that can be interactively viewed in any
plane using thick MPR technique (volumetric imaging with
acquire thin, view thick approach [54]). Recent studies
have shown the benefits of MPR use in routine practice,
especially by inexperienced readers [55, 56]. This approach
also allows for dose reduction, since relatively high noise
levels in these thin-slice data-sets are tolerable, which can
be reduced by the thick-slice MPR viewing process. Such
reconstructions preferably should be created at a slice
thickness which is 2030% larger than the collimation.
This is because there is an additional increase in noise
when the slice thickness is equal to the collimation [57]. A
prerequisite is that CT reading must be done on a PACS
workstation with sufficient 3D capability (e.g. linked to a
server-based thin-client 3D workstation) or on a stand-
alone thick-client 3D workstation.
Data load in CT is directly related to reconstruction
index, and data reduction in 16- to 64-slice CT systems can
be achieved by reducing the percentage overlap to 2030%
or even less, especially when through-plane resolution is
high [ 58, 59]. The reconstruction index should never be
smaller than the in-plane spatial resolution, or about 0.7
0.8 mm. In 64-slice systems, hypertropic voxels may be
created in which the slice thickness is smaller than pixel
size. Such voxels will have increased noise but MPR image
quality will not improve significantly. As noise increases
with the fourth power of the effective voxel dimension, a
substantial dose increase is necessary to maintain equal
signal-to-noise (SNR). The resulting dose increases may be
quite significant. For example, improving resolution from
1×1×1 mm (1.0 mm
3
) to 0.5×0.5×0.5 mm (0.125 mm
3
)
requires a 16-fold (2
4
) dose increase to maintain SNR [57].
Post-processing: multiplanar and 3D parameters
Post-processing techniques are similar in most centres. A
combination of rendering techniques has been used,
including multiplanar reformat (MPR), curved planar
reformat (CPR), and thin-slab or thick-slab average
intensity projection (AIP), maximum intensity projection
(MIP) or volume rendering (VR) 3D images.
MPR images should be created using thin-slab technique
(scan thin, view thick) to manage dose and noise
requirements. Depending on workflow, either standardized
MPRs are created non-interactively by the technicians or
interactively by the reading physician, either on a PACS-
integrated or stand-alone 3D workstation. The average
non-interactive MPR thickness is 35 mm, non-over-
lapping [21 ,25, 54, 58]. While in most practices MPR use
is still limited to the excretory phase data sets, it should be
applied in all phases to help in the evaluation of urolithiasis
and masses affecting the urinary tract.
Three-dimensional images are created interactively by
radiologists or by 3D technicians on a 3D workstation.
Curved MPR along the course of the ureters and thin-slab
average intensity projections (AIP), maximum intensity
projections (MIP), or volume rendered (VR) images can be
used for interactive image evaluation. Usually these are
created in coronal or oblique coronal planes. Slab thickness
for MIP and VR images varies, depending on the clinical
indication, and ranges between 5 and 50 mm [21, 24, 25,
30]. It has been shown that coronal thin-MPR is diag-
nostically equivalent to axial imaging in CT [59]. However,
most 3D images, should not be read without the source (or
MPR) images as diagnostic performance can be signifi-
cantly impaired.
Radiation dose
The relatively high radiation dose of multiphase CTU is a
significant limitation of the widespread acceptance of this
technique. Current multiphase CTU protocols can be
associated with effective doses as high as 2535 mSv
[28], depending upon the number of phases included.
Noise is a limiting factor in the improvement in spatial
resolution. Reduced dose should, therefore, always be
weighed against diagnostic image quality. Also, the
detriment from radiation dose is different for different
clinical populations. In a population with a high suspicion
for or with known malignant disease, radiation dose plays
only a relatively small role. However, for patients with
benign diseases or for susceptible patient populations, such
as children and young or pregnant women, dose is an issue.
Strict indications for multiphase CTU and reduction of the
number of phases are important tools to manage this
relatively high-dose examination.
Many dose studies compare protocols in terms of tube
voltage (kV) and tube load (mAs) parameters instead of the
more appropriate terms, volume CT Dose Index (CTDIvol,
in mGy) and dose-length product (DLP, in mGy cm). Tube
load parameters are very scanner-specific (Table 2), and
volume CTDI and DLP are better usable entities for
protocol comparison and optimisation. Dose management
technology in CT has led to optimization of CT protocols
using angular (XY-axes), longitudinal (Z-axis), or com-
bined (XYZ-axes) modulation of the dose [60]. In some
modern systems this can also be combined with 3D
adaptive noise filtration. Data on radiation dose optimiza-
tion or optimal levels of noise indices using these 3D dose
modulation or 3D noise filtering techniques for CTU
applications is currently lacking, but these techniques may
lead to dose reductions of 2030%, compared with
currently published fixed mAs protocols, without signifi-
cant loss in diagnostic image quality.
Few data on CTU radiation doses have been presented.
Four- and 16-slice scanners employing three- to four-phase
protocols are usually associated with effective dose levels
of 2335 mSv [13, 25, 28]. One estimate of 15 mSv (1.5-
times the dose of an 11-film IVU) [61] seems somewhat off
given the similar CT parameters of this protocol to the
protocol of McTavish et al. [25]. [Recalculating this with a
current dose calculator (ImPACT 0.99X) suggests values of
8.5 mSv for the unenhanced and 11.0 mSv for the excretory
phase, which seems more realistic].
Radiation dose has been one of the most important
driving factors in optimization of CTU techniques and in
selecting justified indications. Even though low-dose CT
for urolithiasis has been performed for over 10 years, data
on low-dose CTU techniques are only just becoming
available, but efficacy has not been tested. Ongoing studies
at the authors institutions have indicated a few trends. The
increased patient dose of CTU is justified by its increased
performance, especially in populations at increased risk for
GU malignancy. A very low-dose protocol using a
CTDIvol of 2.1 mGy is unlikely to be sufficient to depict
intraluminal lower ureter lesions, but may allow biphasic
excretory imaging with improved distal ureteral opacifica-
tion for selected indications [62]. Other studies indicated
that image quality of excretory phase CTU is adequate at a
CTDIvol of 5.07.1 mGy, which is currently used in
clinical practice [1, 63]. These data were further sub-
stantiated by low-dose simulation experiments in which
image quality was negligibly degraded with a dose
reduction to a CTDIvol of 6.16.7 mGy (K.T. Bae,
presented at RSNA 2005). Furthermore, lower tube
voltages of 90100 kV have favourable effects on image
quality (contrast-to-noise ratio) in the low-dose range [ 50].
Given these preliminary data, we suggest that in
average-sized patients (6080 kg) excretory phase imaging
with thin collimation may well be performed at a CTDIvol
of 56 mGy [1]. The nephrographic phase may require a
slightly higher dose for more optimal diagnosis in the liver
(CTDIvol in the order of 78 mGy). Even lower doses for
unenhanced CT (CTDIvol in the order of 23 mGy) are
acceptable [6467], and even doses comparable with one
abdominal plain-film (CTDIvol 0.9 mGy) may suffice [68].
With such optimization even three-phase protocols with
effective doses below 7 mSv can be realized (P. Dahlmann,
presented at ESUR 2006).
On the other end, if there is a high-risk for malignancy,
dose may be safely increased to a CTDIvol of 912 mGy,
especially for the nephrographic and excretory phases.
Summary: a proposed approach
CTU is a new test which is developing continuously and
which is practiced using a variety of protocols. Rando-
mized trials have not been published yet and most of the
currently published data falls within evidence categories
IIIIV [69]. Therefore, this expert-based practice guideline
focused on indications and examination technique.
Radiation dose has been one of the most important
driving factors in optimization of CTU techniques and in
selecting justified indications. The risks (detriment) of
radiation exposure are greater in susceptible patient
populations (children and young women) and benefit-risk
ratios are lower in patients with benign diseases than in
patients with malignant diseases. Surprisingly, in many
reviews only one CTU technique is suggested to
encompass all clinical indications. Therefore, we propose
a differential (1-2-3) approach with different techniques
used in different patient populations as the next logical step
in the evolution of CTU as a powerful yet dose-efficient
test for urinary tract assessment.
It has not been shown that the combined nephrographic-
excretory phase is inferior to separated nephrographic and
excretory phases. When radiation dose is an issue we prefer
the use of the combined phase to minimize the number of
phases. For the bladder, the equivalence of CTU to cystos-
copy has only been demonstrated in high-risk populations,
and a positive CTU can obviate flexible cystoscopy [18].
For situations in which only the excretory phase is
relevant a low-dose, split-bolus, one-phase, combined
nephrographic-excretory CTU technique is recommended.
Table 2 Nominal mAs values per type of CT system at 120 kV at different levels of volume CTDI (calculated with the ImPACT 0.99X dose
calculator)
CT System Collimation Pitch CTDIvol CTDIvol CTDIvol CTDIvol
mm 3 mGy 7 mGy 9 mGy 12 mGy
GE Lightspeed 16 Pro 16×0.625 0.938 28 66 85 113
Philips Brilliance 16 16×0.75 1.0
a
38 88 114 152
Siemens Sensation 16 16×0.75 1.0
a
36 85 109 145
Toshiba Aquilion 16 16×0.5 0.938 18 42 54 72
GE Lightspeed VCT 64×0.625 0.984 31 72 93 124
Philips Brilliance 64 64×0.625 1.0
a
51 119 152 202
Siemens Sensation 64 2×32×0.6 1.0
a
42 100 128 170
Toshiba Aquilion 64 64×0.5 0.828 21 48 62 82
a
Note: in Siemens and Philips CT systems, CTDIvol values are independent of pitch
Table 3 Suggestion for a differentiated approach to CTU protocols (iMPR interactive MPR)
Protocol items Benign diseases - limited Benign diseases extensive Malignant diseases (optional)
Malignant diseases
Indications Congenital anomalies Hematuria low/medium risk TCC/RCC Hematuria - high risk TCC/RCC
Hydronephrosis - benign cause Chronic urolithiasis & PCNL planning Hydronephrosis - malignant cause
Medullary and papillary necrosis
Traumatic ureter lesions Complex urinary tract infection (TBC)
Urinary diversions post-cystectomy
Extra-urinary tumours with involvement
of the urinary tract
Preparation 1,000 ml water per os 3060 min before 1,000 ml water per os 3060 min before 1,000 ml water per os 3060 min before
Positioning Supine Supine Supine
Additional manoeuvres 0.1 mg/kg furosemide i.v. 0.1 mg/kg furosemide i.v. 0.1 mg/kg furosemide i.v.
500 ml saline i.v. drip (optional) 500 ml saline i.v. drip (optional) 500 ml saline i.v. drip (optional)
Number of
phases
12(see note 3) 3 (see note 3)
Phases Combined nephrographic-excretory Unenhanced Unenhanced
Combined nephrographic-excretory Nephrographic
Excretory
Radiation dose
(see note 1)
Unenhanced phase CTDIvol 23 mGy CTDIvol 34 mGy
DLP 90135 mGy cm DLP 135180 mGy cm
Nephrographic phase CTDIvol 56 mGy CTDIvol 56 mGy CTDIvol 912 mGy
DLP 235285 mGy cm DLP 235285 mGy cm DLP 225300 (425565) mGy cm
Excretory phase CTDIvol 912 mGy
DLP 405540 mGy cm
CT anatomical range
Unenhanced phase Top kidneys bladder base (40 cm) Top kidneys bladder base (40 cm)
Nephrographic phase Top liver bladder base (42 cm) Top liver bladder base (42 cm) Top liver lower kidney (20 cm)
[Top liver bladder base (42 cm)]
Top kidneys bladder base (40 cm)
Excretory phase
Over-range Average 5 cm per phase Average 5 cm per phase Average 5 cm per phase
(increases with increasing table feed) (increases with increasing table feed) (increases with increasing table feed)
Acquisition parameters
Unenhanced phase 4×22.5 mm P 1.21.5 4×22.5 mm P 1.21.5
16×11.5 mm P 0.71.0 16×11.5 mm P 0.71.0
Protocol items Benign diseases - limited Benign diseases extensive Malignant diseases (optional)
Malignant diseases
64×0.50.625 mm P 0.50.7 64×0.50.625 mm P 0.50.7
Nephrographic phase
4×11.25 mm P 1.51.8 4×11.25 mm P 1.51.8 4×11.25 mm P 1.51.8
16×0.751.25 mm P 0.81.2 16×0.751.25 mm P 0.81.2 16×0.751.25 mm P 0.81.2
64×0.50.625 mm P 0.50.7 64×0.50.625 mm P 0.50.7 64×0.50.625 mm P 0.50.7
Excretory phase 4×11.25 mm P 1.51.8
16×0.751.25 mm P 0.81.2
64×0.50.625 mm P 0.50.7
Reconstruction parameters
Unenhanced phase 35/3
5 mm image review/PACS 35/35 mm image review/PACS
4slice 2.53/1.52 mm iMPR/3D 4slice 2.53.0/1.52mmiMPR/3D
16slice 1.52/1.21.5 mm iMPR/3D 16slice 1.52.0/1.21.5 mm iMPR/3D
64slice 0.71.0/0.70.8 mm iMPR/3D 64slice 0.71.0/0.70.8 mm iMPR/3D
Nephrographic phase 35/35 mm image review/PACS 35/35 mm image review/PACS 35/35 mm image review/PACS
4slice 1.21.5/0.71.2 mm
iMPR/3D
4slice 1.21.5/0.71.2 mm iMPR/3D 4slice 1.21.5/0.71.2 mm iMPR/3D
16slice 0.8
1.5/0.71.2 mm iMPR/3D 16slice 0.81.5/0.71.2 mm iMPR/3D 16slice 0.81.5/0.71.2 mm iMPR/3D
64slice 0.71.0/0.70.8 mm iMPR/3D 64slice 0.71.0/0.70.8 mm iMPR/3D 64slice 0.71.0/0.70.8 mm iMPR/3D
Excretory phase 35/35 mm image review/PACS
4slice 1.21.5/0.71.2 mm iMPR/3D
16slice 0.81.5/0.71.2 mm iMPR/3D
64slice 0.71.0/0.70.8 mm iMPR/3D
Postprocessing Curved MPR along ureters Curved MPR along ureters Curved MPR along ureters
Parameters Thin-slab (550 mm) AIP Thin-slab (550 mm) AIP Thin-slab (550 mm) AIP
Thin-slab (550 mm) MIP or VR Thin-slab (550 mm) MIP or VR Thin-slab (550 mm) MIP or VR
Injection of contrast medium Split bolus Split bolus Single bolus
Injection duration Injection 1=2533 s Injection 1=25
33 s Injection 1=50 s
Wait 5 min=300 s Wait 5 min=300 s
Injection 2=2538 s Injection 2=2538 s
Injection 1 (see note 2) 75100 ml CM300 @ 3 ml/s, or 75100 ml CM300 @ 3 ml/s, or 150 ml CM300 @ 3 ml/s, or
5575 ml CM400 @ 2.3 ml/s 5575 ml CM400 @ 2.3 ml/s 115 ml CM400 @ 2.3 ml/s
Injection 2 (see note 2) 5075 ml CM300 @ 2 ml/s, or 5075 ml CM300 @ 2 ml/s, or
4060 ml CM400 @ 1.5 ml/s 4060 ml CM400 @ 1.5 ml/s
Injection delays
Nephrographic phase 100120 s after start injection 2 100120 s after start injection 2 100120 s after start injection
Table 3 (continued)
Protocol items Benign diseases - limited Benign diseases extensive Malignant diseases (optional)
Malignant diseases
Excretory phase 450490 s after start injection 1 450490 s after start injection 1 450490 s after start injection
Test images (optional) 360 s after start injection
Repeat at 2-min intervals if needed
Notes
Note 1 CTDIvol and DLP levels refer to
patient weight between 6080 kg
CTDIvol and DLP levels refer to patient
weight between 6080 kg
CTDIvol and DLP levels refer to
patient weight between 6080 kg
For <60 kg multiply by 0.80.85 For <60 kg multiply by 0.80.85 For <60 kg multiply by 0.80.85
For 80100 kg multiply by 1.41.5 For 80100 kg multiply by 1.41.5 For 80100 kg multiply by 1.41.5
For >100 kg multiply by 1.82.0 For >100 kg multiply by 1.82.0 For >100 kg multiply by 1.82.0
Note 2 Contrast injection adapted to weight: Contrast injection adapted to weight: Contrast injection adapted to weight:
Injection 1: 1.01.4 ml/kg CM300 Injection 1: 1.01.4 ml/kg CM300 Injection: 2.0 ml/kg CM300
- injected with 0.043 ml/kg/s flow - injected with 0.043 ml/kg/s flow - injected with 0.043 ml/kg/s flow
Injection 2: 0.71.0 ml/kg CM300 Injection 2: 0.71.0 ml/kg CM300
- injected with 0.03 ml/kg/s flow - injected with 0.03 ml/kg/s flow
Note 3 Malignant diseases can be done with this
protocol at higher dose levels
Malignant diseases may optionally
be done with this protocol
Probable indications include the depiction of anatomical
variants of the urinary system, iatrogenic ureter trauma,
CTU as add-on to evaluation of acute flank pain.
For more comprehensive patient evaluation when CTU
is used as a problem-solving test, a low-dose, split-bolus,
two-phase CTU examination can be performed by adding
an unenhanced phase. Probable indications include chronic
symptomatic stone disease, PCNL planning, complex
infections, urinary diversions, and clinical settings with
low pre-test probability of malignant disease, such as the
evaluation of haematuria in younger patients or assessment
of the urinary tract in patients with other abdominal
tumours or tumour-like conditions.
In the evaluation of patients with a high pre-test
probability of malignant disease, radiation dose should
not be a limiting factor as long as the ALARA-principle is
kept in mind. Consequently, a similar split-bolus two-phase
CTU at an increased radiation dose level or a single-bolus,
three-phase CTU is justified in these patients. Probable
indications include evaluation of macroscopic haematuria
in older patients and TCC staging. Test-images can
potentially save dose by reducing the number of excretory
phase data acquisitions with incomplete ureteral filling. To
optimize staging or the evaluation of the lower urinary
tract, the nephrographic phase may be extended to include
the pelvis.
For the above CTU protocols, several options remain
available:
1. The unenhanced phase can be limited to the kidneys [2].
2. Three-phase protocols may be reduced to two-phase
protocols for benign indications by selectively deleting
the nephrographic phase [1, 33].
3. Information on the arterial vasculature can be inte-
grated by using a modified triple-bolus CM injection
protocol.
4. If technique is well optimized to low-dose, protocols
with separated nephrographic and excretory phases
instead of a nephrographic-excretory combination
phase may be feasible at similar radiation dose.
Problematic cases will still remain, especially when
excretion of the CM is highly asymmetric such as in
uretero-pelvic junction stenosis or high grade obstructions.
If such conditions are known in advance, availability of a
dedicated CTU protocol with a much longer and
individualized delay of the excretory phase or biphasic
excretory imaging is beneficial.
Detailed CTU protocol suggestions can be found in Table 3.
Appendix
Report summaries
Summary boxes of the different paragraphs of the report
are provided in the Electronic Supplementary Material.
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    • "Ultrasonography can display the nonfunctioning upper pole and would be useful to differentiate renal cyst from renal pelvic diverticulum. CTU and MRU can delineate essentially all abnormalities of the collecting systems , ectopic ureter, and ureterocele that benefit the Bladder-ureter malformation 5 diagnosis of duplicated and ectopic ureter [6][7][8]. However, these protocols are mainly useful in evaluating duplex kidney with approximately normal function and simple anomaly [5] . "
    [Show abstract] [Hide abstract] ABSTRACT: Background: Duplex kidney is a common anomaly that is frequently associated with multiple complications. Typical computed tomography urography (CTU) includes four phases (unenhanced, arterial, parenchymal and excretory) and has been suggested to considerably aid in the duplex kidney diagnosi. Unfortunately, regarding duplex kidney with prolonged dilatation, the affected parenchyma and tortuous ureters demonstrate a lack of or delayed excretory opacification. We used prolonged-delay CTU, which consists of another prolonged-delay phase (1- to 72-h delay; mean delay: 24 h) to opacify the duplicated ureters and affected parenchyma. Methods: Seventeen patients (9 males and 8 females; age range: 2.5-56 y; mean age: 40.4 y) with duplex kidney were included in this study. Unenhanced scans did not find typical characteristics of duplex kidney, except for irregular perirenal morphology. Duplex kidney could not be confirmed on typical four-phase CTU, whereas it could be easily diagnosed in axial and CT-3D reconstruction using prolonged CTU (prolonged-delay phase). Results: Between January 2005 and October 2010, in this review board-approved study (with waived informed consent), 17 patients (9 males and 8 females; age range: 2.5 ~ 56 y; mean age: 40.4 y) with suspicious duplex kidney underwent prolonged CTU to opacify the duplicated ureters and confirm the diagnosis. Conclusion: Our results suggest the validity of prolonged CTU to aid in the evaluation of the function of the affected parenchyma and in the demonstration of urinary tract malformations.
    Full-text · Article · Dec 2016
    • "The total effective dose for our whole study was 29.1 mSv, and Chen et al. [32] reported total effective dose of 18.5 mSv; however, in their study they obtained only two phases: non enhanced scan and volumetric perfusion scan for the kidney. In addition to that, the CT urography working group of the European [37] . The radiation dose from MAG3 renography was 2.5 mSv. "
    [Show abstract] [Hide abstract] ABSTRACT: Objectives: To assess feasibility of automatically calculated CT perfusion parameters using two different methods of drawing regions of interest (ROIs) to reflect split renal function in comparison with MAG3 renography. Methods and materials: 51 potential kidney donors (24 males, 27 females) were prospectively evaluated by preoperative CT perfusion. Post processing was done twice; one with ROI around renal cortex only and the other around cortex and medulla. Perfusion parameters (perfusion, peak enhancement intensity PEI and blood volume BV) were compared between the two methods. Split values for each of these parameters were calculated and compared to split renal function measured by MAG3 renography using paired samples . t test. Results: Perfusion was significantly lower in method 2 than in method 1 while PEI and BV showed no significant difference between the two methods. Split values of CT parameters showed no significant difference from corresponding renography split function (p value. > 0.1) except BV by method 1 and perfusion by method 2 which showed significant difference (p value. <. 0.05). Conclusion: Certain CT perfusion parameters can reflect split renal function. Perfusion was more accurate in reflecting split renal function with ROI around the cortex while BV was more accurate with ROI around the whole parenchyma.
    Full-text · Article · Aug 2016
    • "Many patient undergo the high radiation dose investigations simply to rule out the rather rare possibility of UUT malignancy. The radiation dose of 9.2 mSv administered in our triplephase MDCT protocol is within reported limits [1] but nonetheless is rather substantial; for comparison it exceeds 8 years of natural background radiation exposure in our country (on average 1.1 mSv/yr.). A crude estimation for the excess relative risk of death due to cancer from receiving a 9.2 mSv dose is one excess radiation induced death per 2000 exposed individuals if Fig 5.The value of MR imaging at different time intervals. "
    [Show abstract] [Hide abstract] ABSTRACT: Objectives: To prospectively compare the diagnostic performance and the visualization of the upper urinary tract (UUT) using a comprehensive 3.0T- magnetic resonance urography (MRU) protocol versus triple-phase computed tomography urography (CTU). Methods: During the study period (January-2014 through December-2015), all consecutive patients in our tertiary university hospital scheduled by a urologist for CTU to exclude UUT malignancy were invited to participate. Diagnostic performance and visualization scores of 3.0T-MRU were compared to CTU using Wilcoxon matched-pairs test. Results: Twenty patients (39 UUT excreting units) were evaluated. 3.0T-MRU and CTU achieved equal diagnostic performances. The benign etiology of seven UUT obstructions was clarified equally with both methods. Another two urinary tract malignant tumors and one benign extraurinary tumor were detected and confirmed. Diagnostic visualization was slightly better in the intrarenal cavity areas with CTU but worsened towards distal ureter. MRU showed consistently slightly better visualization of the ureter. In the comparison, full 100% visualizations were detected in all areas in 93.6% (with 3.0T-MRU) and 87.2% (with CTU) and >75% visualization in 100% (3.0T-MRU) and 93.6% (CTU). Mean CTU effective radiation dose was 9.2 mSv. Conclusions: Comprehensive 3.0T-MRU is an accurate imaging modality achieving comparable performance with CTU; since it does not entail exposure to radiation, it has the potential to become the primary investigation technique in selected patients. Trial registration: ClinicalTrials.gov NCT02606513.
    Full-text · Article · Jul 2016
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