National guidelines recommend prostate multiparametric (mp) MRI in men with suspected prostate cancer before biopsy. In this study, we explore prostate mpMRI protocols across 14 London hospitals and determine whether standardisation improves diagnostic quality.
An MRI physicist facilitated mpMRI set-up across several regional hospitals, working together with experienced uroradiologists who judged diagnostic quality. Radiologists from the 14 hospitals participated in the assessment and optimisation of prostate mpMRI image quality, assessed according to both PiRADSv2 recommendations and on the ability to “rule in” and/or “rule out” prostate cancer. Image quality and sequence parameters of representative mpMRI scans were evaluated across 23 MR scanners. Optimisation visits were performed to improve image quality, and 2 radiologists scored the image quality pre- and post-optimisation.
20/23 mpMRI protocols, consisting of 111 sequences, were optimised by modifying their sequence parameters. Pre-optimisation, only 15% of T2W images were non-diagnostic, whereas 40% of ADC maps, 50% of high b-value DWI and 41% of DCE-MRI were considered non-diagnostic. Post-optimisation, the scores were increased with 80% of ADC maps, 74% of high b-value DWI and 88% of DCE-MRI to be partially or fully diagnostic. T2W sequences were not optimised, due to their higher baseline quality scores.
Targeted intervention at a regional level can improve the diagnostic quality of prostate mpMRI protocols, with implications for improving prostate cancer detection rates and targeted biopsies.
Standardisation of diagnostic image quality of prostate multiparametric MRI is crucial to optimise clinically significant prostate cancer detection. Pre-optimisation, the majority (85%) of the T2 -weighted images were partially or fully diagnostic, whereas 40% of ADC maps, 50% of high b-value diffusion-weighted images and 41% of dynamic contrast-enhanced MRI were non-diagnostic. After applying the standardisation process across the several prostate multiparametric MRI protocols, the majority of the scores were increased resulting in 80% of ADC maps, 74% of high b-value diffusion-weighted images and 88% of dynamic contrast-enhanced MRI to be partially or fully diagnostic.
Worldwide, there were an estimated 359,000 prostate cancer (PCa) deaths in 2018 [
A range of challenges are evident in implementing prostate mpMRI nationally, many of which were discussed in the 2018 United Kingdom (UK) Prostate Cancer Consensus Meeting [
Prostate mpMRI consists of 3 components: T2-weighted (T2W) anatomical imaging, diffusion-weighted MRI (DW-MRI) assessment of tissue cellularity, and dynamic contrast-enhanced MRI (DCE-MRI) evaluation of tissue vascularity. Prostate Imaging and Reporting and Data System [
This study explores regional prostate mpMRI protocols across 23 MR scanners situated across 14 London hospitals by assessing their diagnostic quality and determining whether standardisation can improve their diagnostic quality.
An MRI physicist (M.-V.P.) experienced with prostate mpMRI (2 years) was employed by North Central and East London Cancer Alliance in a dedicated role to facilitate mpMRI set-up across the regional network hospitals. The physicist led the optimisation of mpMRI protocols over a year (from May 2018 to April 2019, based on the availability of time for optimisation at each hospital), working closely with 2 uroradiologists from the region leading hospital (C.A., L.D., each with > 5 years prostate mpMRI and reporting > 500 studies per year). In Fig. Flow chart presenting the outline of the optimisation procedure of the prostate multiparametric (mp) MRI protocols
In June 2018, radiologists specialised in reporting prostate mpMRI across different hospitals in North Central and East London Cancer Alliance network were invited to participate in a prostate imaging meeting. The aim of the meeting was to identify the need of acquiring acceptable diagnostic quality prostate mpMRI, to define an image quality system for prostate mpMRI and to invite them to participate in the set-up and use of a standardised and diagnostic quality protocol for prostate mpMRI. Subsequently, 20 radiologists from 14 hospitals (totally 23 MR scanners) participated (7 hospitals had 2 MR scanners and one had 3 scanners). These hospitals work independently in terms of prostate mpMRI, but their relationship with the leading hospital is that all the prostate cancer surgery is performed at the leading hospital. Hence, it would be important all of them to adopt the same imaging set-up ensuring high diagnostic quality of the prostate mpMRI. Therefore, a quality assurance framework for prostate mpMRI was proposed and accepted by the participants, aiming to establish a reliable imaging set-up and protocol across the region. The imaging set-up and protocol were determined following PiRADSv2 recommendations which was current at the time the work commenced [
Scanner characteristics, patient set-up and acquired sequences were recorded for each one of the protocols. A representative prostate mpMRI from each MR scanner was assessed for sequence parameters by the physicist compared to PiRADSv2 standards and for diagnostic quality by the two uroradiologists using the above 5-point scoring system.
Following the review of MRI scans, visits for protocol optimisation were organised. The optimisation involved the modification of sequence parameters according to PiRADSv2 recommended sequence parameters and radiologists’ scores. During the optimisation, images from the pre-optimised (original) protocol were acquired on real-life patients of each hospital list undergoing prostate mpMRI, followed by optimised sequences (patients were consented for longer protocol duration). At the end of the optimisation session, an initial informal review of quality assessment was performed by at least two radiologists, one from the leading and one or more from the visiting hospital, on the optimised sequences. Further visits were performed if the images were considered not yet fully optimised. Once completed, the new optimised protocol was integrated by the hospital. Due to the high baseline quality scores of T2W images, the DW-MRI and DCE-MRI protocols were prioritised for the optimisation process. For the DCE-MRI protocol optimisation, it was not possible to inject the patient twice. We acquired the pre-optimised sequence during contrast injection and the new sequence at time points just before and just after this in order to compare images with similar amounts of injected contrast in the tissue. When an improvement in the image quality was observed for the optimised sequence, that protocol was examined during the contrast agent injection and chosen as the final optimised.
The prostate MR images of PiRADSv2 required sequences were qualitatively assessed by two radiologists in consensus from the leading hospital, one with 20 years (C.A.) and another with 7 years (F.G.) reading experience. Five image acquisitions were reviewed: (1) axial T2W, (2) coronal T2W, (3) sagittal T2W, (4) ADC map, (5) high b-value DWI and (6) DCE-MRI. For the majority of the scanners, DW-MRI and DCE-MRI sequences were acquired twice on the same patient, with the pre- and post-optimised sequences. The radiologists were unaware of which sequence was pre- and which was post-optimisation. For each anonymised sequence, a qualitative assessment was performed (Table Diagnostic quality assessment questionnaire T2-Weighted Diffusion-weighted imaging (DWI) Dynamic contrast-enhanced MRI Axial Coronal Sagittal DWI High b-value DWI Angulation Yes/no Yes/no Yes/no Yes/no Yes/no Yes/no Does the current angulation match with the T2W axial? Yes/no Yes/no Yes/no Image resolution Poor/adequate/good Poor/adequate/good Poor/adequate/good Poor/adequate/good Poor/adequate/good Poor/adequate/good FOV Small/sufficient/large Small/sufficient/large Small/sufficient/large Small/sufficient/large Small/sufficient/large Small/sufficient/large SNR Low/adequate/high Low/adequate/high Low/adequate/high Low/adequate/high Low/adequate/high Low/adequate/high b-values (s/mm2) 0, 150, 500, 1000 1400 @ 1.5 T 2000 @ 3.0 T Artifacts Yes/no Yes/no Yes/no Yes/no Yes/no Yes/no Image blurring due to motion Yes/no Yes/no Yes/no Yes/no Yes/no Yes/no Is it possible to rule in tumours? Yes/no Yes/no Yes/no Yes/no Yes/no Yes/no Is it possible to rule out tumours? Yes/no Yes/no Yes/no Yes/no Yes/no Yes/no Is it possible to clearly visualise the periprostatic and cavernosal vessels? Yes/no Number of dynamic measurements Few/adequate/many Temporal resolution of each dynamic measure
From 23 prostate mpMRI protocols, one presented high diagnostic image quality and was used as an exemplar (Fig. Flow chart presenting the initial number of assessed prostate multiparametric (mp) MRI protocols and the final number completely optimised acquiring all the recommended sequences. (DWI: diffusion-weighted imaging, DCE: dynamic contrast enhanced)
Patient set-up was evaluated in terms of patient position, coil and administration of antispasmodic agent. Only in 1/20 (5%) protocol, patient’s position was headfirst. 15/20 (75%) protocols utilised surface phased array coils and 5/20 (25%) used body array coils. For 6/20 (30%), an antispasmodic agent was administered prior to imaging.
2/20 (10%) protocols acquired only axial and coronal T2W images, which was compliant with the newer PiRADSv2.1 recommendations, but not with the PiRADSv2. The other protocols acquired T2W across the 3 orthogonal orientations. 14/20 (70%) protocols acquired a high b-value DWI acquisition, where 2/14 (14.3%) utilised the calculated high b-value DWI. 3/20 (15%) protocols did not include DCE-MRI. The mean protocol duration was 33 min (range 18–45 min). For all protocols, the sequence parameters of the reviewed sequences were evaluated against PiRADSv2 and PiRADSv2.1 standards (Table Summary of acquisition parameters range prior the optimisation related to Prostate Imaging Reporting and Data System (PiRADSv2 and v2.1) Sequence parameter PiRADSv2 standard (PiRADSv2.1 standard) Mean Range Field of view (mm) 120–200 200 170–240 Slice thickness (mm) 3 3.2 3–4 Slice gap (mm) 0 0.3 0.-0.75 Acquired pixel size (mm) × (mm) ≤ 0.4 (frequency) 0.7 (frequency) 0.5–1.0 ≤ 0.7 (phase) 0.9 (phase) 0.6–1.3 Field of view (mm) 120–200 204 180–240 Slice thickness (mm) 3 3.1 3–4 Slice gap (mm) 0 0.3 0–0.7 Acquired pixel size (mm) × (mm) ≤ 0.4 (frequency) 0.7 (frequency) 0.5–1.0 ≤ 0.7 (phase) 0.9 (phase) 0.6–1.1 Field of view (mm) 120–200 212 180–250 Slice thickness (mm) 3 3.5 3–6 Slice gap (mm) 0 0.4 0–2 Acquired pixel size (mm) × (mm) ≤ 0.4 (frequency) 0.8 (frequency) 0.6–1.1 ≤ 0.7 (phase) 1.0 (phase) 0.6–1.5 Repetition time (ms) ≥ 3000 4921 1320 -23,651 Echo time (ms) ≤ 90 80 48–117 Field of view (mm) 160–220 275 220–380 Slice thickness (mm) ≤ 4 4.45 2.5–6 Slice gap (mm) 0 0.5 0–1 Acquired pixel size (mm) × (mm) ≤ 2.5 (frequency) 2.23 1.3–4.8 ≤ 2.5 (phase) 2.64 1.5–4.8 Number of b-values for ADC map At least 2 b-values 3.35 2–4 Proposed b-values (s/mm2) (0), 50, 150, 500, 1000 High b-value (s/mm2) 1400 at 1.5 T 1333 1200–1500 2000 at 3 T 1400 1200–1600 Repetition time (ms) < 100 5.4 3.2–8.2 Echo time (ms) < 5 2.25 1.6–3.2 Field of view (mm) Encompass the entire prostate gland and the seminal vesicles 274 205–400 Slice thickness (mm) 3 3 2–6 Slice gap (mm) 0 0.8 0–3 Acquired pixel size (mm) × (mm) ≤ 2.0 (frequency) 1.4 0.75–1.65 ≤ 2.0 (phase) 1.5 0.75–2.07 Temporal resolution (s) 14.7 6–32 Total duration ≥ 2 min 5 min 2 min–10 min 46 sec
Only 1 sequence was optimised in 2/20 mpMRI protocols, 2 sequences in 6/20, whereas 3 sequences in 12/20. In total, 50/57 (88%) sequences were either optimised or implemented including 18/20 (90%) sequences for ADC map production, 19/20 (95%) for high b-value DWI, and 13/18 (72%) for DCE-MRI. The PiRADSv2 patient set-up was recommended, included feet first for patient’s comfort, surface coil and administration of an antispasmodic agent. 2/5 protocols adopted the cardiac coil and 5/14 protocols the administration of an antispasmodic agent. 3/20 (15%) hospitals did not have a cardiac or surface coil. 3/20 (15%) protocols included the high b-value DWI with a 5 min increase in protocol duration and 1/3 protocol included DCE-MRI. The mean protocol duration following optimisation was 33 min (range 21–43 min).
All DW-MRI sequences used the same b-values for the ADC map, the spatial resolution and FOV all complied with PiRADSv2 but with a 5 mm slice thickness. For the high b-value DWI, all the 1.5 T sequences encompassed the b-value of 1400 s/mm2 and all the 3.0 T protocols a b-value of 2000 s/mm2 and thus were compliant with PiRADSv2. In DCE, the slice thickness, the spatial resolution adhered to PiRADSv2, the temporal resolution was longer but then adhered to PiRADSv2.1.
In 13/20 mpMRI protocols, both DW-MRI and DCE-MRI sequences were completely optimised and complied with PiRADSv2, whereas in 7/20 protocols it was not possible for all sequences to be fully optimised (Fig. Scores of the image quality assessment of the T2-weighted (T2W) (axial, coronal and sagittal) images. The numbers denote the MR scanners Pre- and post-optimisation scores of the completely optimised multiparametric MRI protocols of ( Pre- and post-optimisation scores of the incompletely optimised multiparametric MRI protocols of (
After the optimisation, the number of fully and partially diagnostic sequences was increased. Post-optimisation, 9/39 (23%) DW-MRI sequences were scored as non-diagnostic. In all of these cases, the age (> 8 years old) of the MR scanners restricted the optimisation process and necessitated longer protocol durations for full implementation of PiRADSv2 recommendations. The corresponding hospitals were unable to accommodate any further increase in protocol duration due to scheduling constraints.
For the majority of the protocols, the T2W sequences were partially or fully diagnostic (Fig.
Pre-optimisation, the scores of the ADC maps (Figs. Images (
Post-optimisation, 18/20 (90%) sequences were modified, resulting in improvement from 4/18 (22.2%) to 7/18 (38.9%) fully diagnostic, from 6/18 (33.3%) to 7/18 (38.9%) partially diagnostic and a reduction from 8/18 (44.4%) to 4/18 (22.2%) non-diagnostic ADC maps. For some MR scanners, longer protocol duration was required for improved diagnostic quality. For example: for the SNR increase, the number of signal averages (NSA) had to be increased resulting in a longer protocol duration; for image resolution improvement, the voxel size had to be reduced by increasing the number of phase encoding lines in the acquisition matrix, which increased further the protocol duration. However, these hospitals were unable to increase their protocol duration despite the suggestions; subsequently, some ADC maps remained non-diagnostic after the optimisation. Figure
Pre-optimisation, 16/20 protocols included the acquisition or the calculation of the separate high b-value DWI (Figs.
Post-optimisation, 16/20 (75%) high b-value DW sequences were optimised and another 3 were implemented, resulting in improvement from 1/16 (6.2%) to 9/19 (47.7%) fully diagnostic, a reduction from 7/16 (43.8) to 5/19 (26.3%) partially diagnostic and from 8/16 (50%) to 5/19 (26.3%) non-diagnostic high b-value DWI. An example of an optimised high b-value DW image is presented in Fig.
17/20 (85%) prostate mpMRI protocols included DCE-MRI (Figs.
12/20 (60%) DCE sequences were optimised and one new sequence was implemented. Post-optimisation, the scores were improved from 3/12 (25%) to 6/13 (46.1%) fully diagnostic, from 3/12 (25%) to 6/13 (46.1%) partially diagnostic and a reduction from 6/12 (50%) to 1/13 (7.7%) non-diagnostic DCE-MRI. Figure
In the current study, prostate mpMRI protocols across 23 MR scanners situated across 14 London hospitals were explored, and after standardisation, the overall diagnostic quality was improved in the majority. The initial protocol heterogeneity, in terms of patient set-up, sequence type and parameters, was reduced after the optimisation resulting in a common and standardised procedure. Post-optimisation, the diagnostic acceptability of mpMRI was improved, increasing radiologists’ confidence in “ruling in” and “ruling out” PCa. Other multicentre studies highlighted the need for prostate mpMRI optimisation not only to comply with PiRADSv2 [
PiRADSv2 standards were used for study design and optimisation. These standards were updated to PiRADSv2.1 during the course of the study. For example, although 3 orthogonal planes were required for PIRADSv2 for the T2W images, PiRADSv2.1 only requires axial and one additional plane. In general, PiRADSv2.1 criteria were less restrictive than PiRADSv2. However, it should be mentioned that compliance with PiRADS guidelines does not necessarily equate to good image quality [
This study aimed at improving image quality using the existing scanner resources at each of the 14 hospitals. Post-optimisation, the practice at 5/14 (36%) hospitals was changed to include the use of antispasmodics and 1/3 hospital added a DCE protocol. The diagnostic acceptability was improved. 14% sequences for the ADC map production became fully diagnostic (totally 40%), 40% were partially diagnostic and 20% non-diagnostic. Regarding the high b-value DWI, 41.2% became fully diagnostic (totally 47.4%) and 26.3% remained partially and 26.3% non-diagnostic. 17% DCE-MRI became fully diagnostic (totally 47%), 41% were partially and 12% non-diagnostic. These results depict the various challenges during the optimisation.
The major challenge was to perform the optimisation in men undergoing prostate mpMRI within the routine schedule of each hospital. This was achieved by adding 10 min to each prostate mpMRI scan, enabling the acquisition of pre- and post-optimised sequences for each patient. Several iterations of post-optimised sequences were required in order to achieve best quality images, best achieved over several different scans in order that the length of scan for each patient was not excessive. This approach required the booking of at least 4 prostate mpMRI scans during each optimisation session, although this was difficult to schedule for the majority of the hospitals. For at least one of the booked scans, either the patient did not attend the session or had MR contraindications or was unable to tolerate the scan any longer. In some cases, the anatomical factors (e.g. after radical prostatectomy) did not allow the optimisation to be carried out. Other "real-life" limitations included the presence of rectal air, deteriorating the optimisation in DW-MRI sequences, especially where no antispasmodic agent was administered [
Another limiting factor was in the different capabilities of the MR scanners, which varied in field strength, manufacturer, age, hardware and software. For old (age > 8 years) 3.0 T scanners, the optimisation of the DW-MRI sequences was more challenging, as compared to the new (1 year) 3.0 T scanners. In patients’ scans where no antispasmodic agent was administered and the rectum was full of air, distortions and signal voids were more prominent at 3.0 T due to the magnetic field inhomogeneities, as compared to the 1.5 T scanners. At high b-value DW-MRI at 3.0 T, the suggested b-value (b = 2000 s/mm2) required higher NSA to increase SNR and image quality [
Our study has some limitations. The optimised sequences could only be acquired and scored only in one patient; subsequently, we recognised that the image quality assessment was also dependant on patient’s body habitat. Ideally scans should be acquired on many more patients and scored both pre- and post-optimisation. Moreover, the pre- and post-optimised DCE-MRI sequences were acquired and compared either pre- or post-injection, because it was not feasible to inject the same patient twice. For few protocols, the DCE-MRI was not optimised, and this was due to limited time for optimisation at the particular hospitals. Lastly, the overall impact of the optimisation on diagnosis and management was not assessed, due to the fact that it was beyond the study scope and duration.
This study explored regional prostate mpMRI protocols across 23 MR scanners situated across 14 London hospitals, demonstrated heterogeneity in diagnostic quality and showed how targeted intervention could help standardise and improve diagnostic quality. We show a methodology for engagement of non-specialist hospitals, show which scans typically are problematic and quantify how much of a change this type of intervention can achieve. Although populations and the management of healthcare differs by region, the information presented should be informative for many settings. This work presents as an example the prostate mpMRI standardisation across a hospital network in London. Other hospitals or countries might adopt a different approach depending on their regulations and their clinical schedule.
This work has been supported by the North East London Cancer Alliance funding, KCL/UCL Comprehensive Cancer Imaging Centre funding and the UCLH Biomedical Research Centre funding. The majority of this work was undertaken at University College London Hospital (UCLH) and University College London (UCL), which receive a proportion of funding from the NIHR Biomedical Research Centre funding scheme
S.P. is the scientific guarantor. All authors read and approved the final manuscript.
This study has received funding by the North East London Cancer Alliance funding, the KCL-UCL Comprehensive Cancer Imaging Centre funding [Cancer Research UK (CR-UK) & Engineering and Physical Sciences Research Council (EPSRC)] and the Royal College of Radiologists funding. The majority of this work was undertaken at University College London Hospital (UCLH) and University College London (UCL), which receive a proportion of funding from the NIHR Biomedical Research Centre funding scheme [Department of Health UK].
The data are included in this manuscript.
Institutional review board approval was not required because this work was classified as service development.
This work was classified as service development aiming to improve the delivery of prostate multiparametric MRI service, which does not need a written consent in UK. However, verbal consent for longer protocol duration was obtained from all subjects (patients) in this study.
The authors declare that they have no competing interests.
Apparent diffusion coefficient
Dynamic contrast-enhanced magnetic resonance imaging
Diffusion-weighted magnetic resonance imaging
Frequency encoding
Field of view
Multiparametric magnetic resonance imaging
National Institute of Health and Care Excellence
Number of signal averages
Prostate cancer
Phase encoding
Prostate Imaging and Reporting and Data System
Signal-to-noise ratio
T2-weighted
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