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[Magnetic resonance imaging in management of prostate cancer.]

Authors:

Abstract

The development of multiparametric magnetic resonance imaging (MRI) offers new possibilities in management of prostate cancer due to its high-resolution and soft-tissue contrast. By combining high-resolution anatomical imaging with functional imaging techniques multiparametric MRI is now proven to be the most sensitive and specific imaging tool for detection, localization and staging of prostate cancer.
2 VIDENSKAB
Magnetisk resonans-skanning af patienter
med prostatacancer
Lars Boesen1 & Henrik S. Thomsen2
Prostatacancer er nu den hyppigste maligne sygdom
hos mænd i Danmark med over 4.000 nye tilfælde pr.
år og med fortsat stigende incidens. Dette skyldes
ikke mindst øget fokus på prostataspecifikt antigen
(PSA)-blodprøve og usystematisk screening.
Der opstår mistanke om prostatacancer ved for-
højet PSA-koncentration og/eller suspekt palpatorisk
fund ved rektaleksploration. Diagnosen stilles efter-
følgende histologisk på 10-12 transrektale ultralyd-
vejledte biopsier fra standardzoner i prostata. Da op
mod 40-50% af prostatacancerforandringerne ikke
kan ses med ultralyd [1], er der en stor risiko for fejl-
prøver ved biopsierne, så en eventuel klinisk signifi-
kant tumor enten ikke diagnosticeres, eller den mest
aggressive del af tumoren ikke biopteres. Dette resul-
terer i forkert tumorgradering eller talrige rebiopsier,
hvis cancermistanken fortsat er til stede på trods af
tidligere negativ histologi.
Når cancer i prostata er diagnosticeret, har det
afgørende betydning for behandlingsvalg og pro-
gnose at vurdere tumorudbredelsen (det kliniske
T-stadie) og specielt afgøre, om tumoren sidder lokalt
inden for prostata, eller om den vokser gennem pro-
statas omgivende kapsel. Klassifikation af T-stadiet
afgøres i Danmark udelukkende på baggrund af rek-
taleksploration og eventuelt ved transrektal ultralyd-
skanning, hvilket fører til en fejlestimering på op mod
50% [2, 3]. Der er således brug for metoder, der kan
forbedre diagnosticering og kortlægning af prostata-
cancer.
Udviklingen af magnetisk resonans (MR)-
skanning gør det i dag muligt at fremstille prostata-
vævet på en helt ny måde. Dette bidrager til at finde
og visualisere udbredelsen af eventuelle tumorer og
til at guide biopsinålen mod malignitetssuspekte om-
råder [4].
MODERNE MAGNETISK RESONANS-SKANNING AF
PROSTATA
Moderne MR-skanning af prostata, også kaldet multi-
parametrisk MR (mMR)-skanning, har i de seneste år
udviklet sig enormt pga. fremkomsten af kraftigere
og hurtigere skannere samt muligheden for MR-funk-
tionelle undersøgelser. mMR-skanning af prostata
kan ved kombination af teknikker vise både anatomi-
ske og funktionelle forandringer i prostata med høj
sensitivitet, specificitet og nøjagtighed [5, 6]. Herved
kombineres typisk højopløselige anatomiske T2-væg-
tede billeder med diffusionsvægtede og dynamisk
kontrastforstærkede MR-skanningsbilleder. Der fin-
des også mulighed for brug af proton-MR-spektrosko-
pisk undersøgelse som supplement til de øvrige MR-
skanningsteknikker. Denne undersøgelse viser de
ændringer i vævets metabolisme, der typisk sker ved
prostatacancer, men undersøgelsen kræver høj eks-
pertise og længere skanningstid og bruges derfor
mest i forskningsøjemed og i differentialdiagnostiske
tvivlstilfælde.
MULTIPARAMETRISK MAGNETISK RESONANS-
UNDERSØGELSE
MR-skanning af prostata kan udføres på enten en
1,5 tesla-MR-skanner med rektalspole eller en 3 te-
sla-MR-skanner med eller uden brug af rektalspole,
afhængig af den kliniske problemstilling. Der anven-
des en overfladespole placeret over bækkenet. Brug
af rektalspole øger billedkvaliteten og fikserer pro-
stata under skanningen, hvilket mindsker bevægel-
sesartefakter. Ulempen ved rektalspolen er forøget
skanningstid, øgede omkostninger og nedsat pa-
tientkomplians pga. placeringen af spolen i endetar-
men. Ved brug af 3 tesla-MR-skanner øges den spa-
tiale opløsning (evnen til at adskille to tætte
strukturer fra hinanden) og signal-støj-forholdet,
hvilket gør det muligt at foretage de fleste prostata-
undersøgelser med acceptabel billedkvalitet uden
brug af en rektalspole.
Ved indledning af undersøgelsen anlægges et pe-
rifert venekateter til injektion af kontrast og spasmo-
lytikum for at reducere tarmperistaltikken og undgå
bevægelsesartefakter. Herefter optages typisk føl-
gende billesekvenser i henhold til de internationale
kliniske retningslinjer for MR-skanning af prostata fra
European Society of Urogenital Radiology 2012 [7]:
1) T2-vægtede billeder i tre planer.
2) T1-vægtede anatomiske oversigtsbilleder.
3) Diffusionsvægtede aksiale billeder med multiple
b-værdier og udregning af apparent diffusionsko-
efficient (ADC)-map.
STATUSARTIKEL
1) Urologisk Afdeling H,
Herlev Hospital
2) Radiologisk Afdeling
X, Herlev Hospital
VIDENSKAB 3
4) T1-vægtede aksiale billeder før, under og efter
kontrastindgivelse.
MULTIPARAMETRISKE MAGNETISK RESONANS-
SKANNINGSTEKNIKKER
T2-vægtede billeder
Højopløselige T2-vægtede (T2W)-billeder i tre planer
har vist sig at være yderst velegnede til cancerdiagno-
stik, da man ved tynde snit kan opnå et godt overblik
over prostatas zonale anatomi. Den normale periferi-
zone ses som en lysere homogen zone med øget sig-
nalintensitet, mens transitionszonen har en mere he-
terogen intermediær signalintensitet, der typisk er
præget af hyperplastiske runde benigne noduli
(BPH). Cancerforandringer på T2W-billeder viser sig
typisk som hypodense mørke homogene foci (Figur
1). Kapslen ses som en mørk, tynd bræmme med lavt
signal rundt om periferizonen, og det er derfor nød-
vendigt med så høj spatialopløsning som muligt, hvis
man skal vurdere eventuelle tegn på ekstrakapsulær
tumorvækst. Såfremt tegn på minimal ekstrakapsulær
vækst er afgørende for behandlingsvalget, anbefales
det at bruge rektalspole for at opnå så høj spatialop-
løsning som muligt.
Udelukkende brug af T2W-billeder til cancer-
diagnostik anbefales ikke, da prostatacancer kan
fremstå isointens på T2W-billeder og derved overses,
og flere benigne lidelser, såsom blødning, hypertrofi
(BPH), atrofi og prostatitis kan fremstå med hypoin-
tensitet og ligne en tumor. Derfor bør T2W-billeder
altid kombineres med MR-funktionelle teknikker i
differentialdiagnostisk øjemed.
T1-vægtede billeder
T1-vægtede (T1W)-billeder analyseres i sammenhæng
med T2W-billeder for at vurdere differentialdiagnosti-
ske tilstande, såsom blødning i prostata [8]. T1W-bille-
der kan desuden med fordel bruges med udvidet felt til
at se efter patologiske lymfeknuder i det lille bækken,
identificere det neurovaskulære bundt og se efter me-
tastaser i de medskannede knogler.
DIFFUSIONSVÆGTEDE BILLEDER
Diffusionsvægtet (DWI)-skanning er en noninvasiv
funktionel MR-teknik, der reagerer på ændringer i
vandmolekylers diffusion gennem væv pga. mikro-
skopiske strukturelle forandringer. Prostatacancer-
væv har generelt større celletæthed og mere hæmmet
diffusion end det normale glandulære væv, hvilket
ses som lyse områder på DWI-billeder (Figur 2). Ned-
sat diffusion giver tilsvarende lavere udregnede ADC-
værdier, der afspejler sig som mørke områder på
ADC-map’et. DWI-billeder og ADC-map kan således
være til hjælp i differentieringen mellem malignt og
benignt prostatavæv. Helt nye studier tyder desuden
på, at den relative ændring i vævets diffusion, der er
angivet på ADC-map’et, er korreleret til den histologi-
ske Gleasonscore [9]. Da Gleasonscoren er et mål for
tumorens aggressivitet, kan ADC-map’et således po-
tentielt bruges som et noninvasivt mål herfor. Brug af
DWI sammen med T2W øger især MR-undersøgel-
sens specificitet [10].
DYNAMISK CONTRAST-ENHANCED
MAGNETISK RESONANS-SKANNING
Ved dynamisk contrast-enhanced (DCE)-MR-skanning
udnytter man, at malignt og benignt prostatavæv udvi-
ser forskellige opladningsprofiler efter injektion af
kontraststof. Med DCE-MR-skanning kan man analy-
sere ændringer i vævets farmakokinetiske egenskaber
ved cancer pga. øget vaskularisering og karpermeabili-
tet. Tumorer udviser typisk en hurtigere og kraftigere
kontrastopladning (øget enhancement) efterfulgt af en
hurtigere udvaskning af kontrasten (Figur 3). DCE-
MR-skanning kræver både høj spatial og høj temporal
opløsning, da andre benigne tilstande i prostata, så-
som BPH og prostatitis, også kan give patologisk op-
ladning på DCE-MR-billeder [11]. Derfor analyseres
DCE-MR-billeder bedst i sammenhæng med de øvrige
mMR–teknikker, for at man kan opnå bedst mulig sen-
sitivitet og specificitet. Brugen af DCE-MR-skanning
øger især mMR-undersøgelsens sensitivitet [10].
FIGUR 
A B
T2-vægtet magnetisk
resonans-skanning af
prostata med cancer i
periferizonen på venstre
side (hvide pile).
A. Aksialt snit.
B. Koronalt snit.
FIGUR 
Diffusionsvægtet magnetisk resonans (DWI-MR)-skanning med korre-
sponderende apparent diffusionskoefficient (ADC)-map af den
samme prostatacancer, som i Figur 1. A. Tumoren ses lys på DWI-MR-
skanningen og B. mørk på ADC-map’et.
A B
4 VIDENSKAB
Der er international konsensus om, at mMR-
skanning er det mest sensitive og specifikke billed-
diagnostiske værktøj til diagnostik af primær prosta-
tacancer [5, 12-20] (Tabel 1).
DISKUSSION
Internationalt publicerede data [7, 14, 21] underbyg-
ger den stærkt voksende brug af mMR-skanning som
værende det mest sensitive og specifikke billeddiag-
nostiske værktøj til brug hos prostatacancerpatienter.
mMR-skanning kan give information om morfologi-
ske, metaboliske og cellulære forandringer samt ka-
rakterisere vævs- og tumorvaskularitet og korrelere
det til tumoraggressivitet.
mMR-skanning kan som minimum hjælpe klini-
keren på tre afgørende punkter:
1) Detektion af klinisk signifikant prostatacancer
ved rebiopsi med et reduceret antal indstik [22].
2) Karakterisering af den præterapeutiske vurde-
ring af tumorens udbredelse og bedre planlæg-
ning og målretning af relevant individuel be-
handling [22].
3) Tidlig identifikation af lokalrecidiv hos patienter
med biokemisk recidiv efter primærbehandling
[23].
MR-target-biopsier af suspekte forandringer set med
mMR-skanning har vist en høj sensitivitet og specifici-
tet ved rebiopsi [22]. Brugen af mMR-skanning har
ikke til formål at øge detektionsraten af prostatacan-
cer generelt, men at øge detektionsraten af klinisk
signifikante cancere og reducere detektionsraten af
klinisk insignifikante cancere, der typisk ikke ses på
mMR-skanninger. Antallet af biopsiindstik pr. patient
ved rebiopsi kan reduceres ved at gøre biopsierne
mere målrettede, hvorved komplikationsraten poten-
tielt også reduceres tilsvarende. Brugen af mMR-
skanning kan desuden støtte klinikeren i at udvælge
de patienter, hvis mMRI-skanningsbilleder ikke viser
suspekte forandringer, således at de ikke behøver
yderligere unødige rebiopsier [22].
Brug af mMR-skanning i den præterapeutiske
vurdering af T-stadiet hos patienter med nydiagnosti-
ceret prostatacancer kan forbedre planlægningen af
relevant individuel behandling pga. bedre kortlæg-
ning af tumoren og dennes relation til det omgivende
væv.
Moderne mMR-skanning af prostata i Danmark
skal ses som et nyt og forbedret noninvasivt diagno-
stisk supplement til de konventionelle metoder, så-
som rektaleksploration, transrektal ultralydskanning
og statistikker (nomogrammer) i udredningen af ud-
valgte patienter med prostatacancer. I skrivende
stund anbefales mMR-skanning i internationale klini-
ske retningslinjer før rebiopsi og indgang i active sur-
veillance-protokol samt ved stadieinddeling før kura-
tiv behandling [7]. Brugen af mMR-skanning hertil
vil efter vor mening føre til forbedret behandlingsef-
fekt og ikke bidrage til øget overdiagnostik, overbe-
handling og stage-migration.
Udførelsen af mMR-skanning af prostata er en
specialistopgave, der kræver avanceret udstyr samt
erfarne dedikerede radiologer og urologer samlet på
centraliserede centre, hvor man er trænet i at læse
mMR-skanningsbillederne. Der findes talrige diffe-
rentialdiagnostiske tilstande i prostata, der vanskelig-
gør tolkningen af billederne. Manglende erfaring og
teknisk uegnet udstyr har tidligere været delvist årsag
til vekslende resultater med for stor interobservatør-
variation ved brug af mMR-skanning til prostatacan-
TABEL 
Diagnostik af primær prostatacancer.
Billedmodalitet, reference Accuracya, %
TRUS, [] 
TW-MR, [, ] -
TW + DWI-MR, [, ] 
TW + DCE-MR, [, ] 
TW + DWI + DCE-MR, [] 
DCE = dynamisk contrast-enhanced; DWI = diffusionsvægtet; MR =
magnetisk resonans-skanning; TW = T-vægtet; TRUS = transrektal
ultralydskanning. a) Accuracy: Mål for hvor godt man med en test
identificerer eller udelukker en tilstand.
FIGUR 
Dynamisk contrast-enhanced (DCE)-magnetisk resonans-skanning af
den samme prostatacancer som i Figur 1 og Figur 2. A. DCE-farvekor-
tet viser maksimal kontrastoptagelse i tumoren (rødt område).
B. Den tilsvarende blå kurve L3 er en typisk suspekt malignitetskurve
med hurtig og kraftig kontrastopladning (øget enhancement) efter-
fulgt af en hurtigere udvaskning. Den gule kurve L4 er fra et område i
den kontralaterale prostatahalvdel og viser tilsvarende en oplad-
ningskurve fra normalt prostatavæv.
AB
VIDENSKAB 5
cerdiagnostik. Udviklingen af moderne 3 tesla-MR-
udstyr med øget spatial opløsning og muligheden for
funktionelle undersøgelser med diffusion og kontrast
øger den diagnostiske værdi af mMR-skanning mar-
kant og muliggør bedre differentiering imellem de
mange differentialdiagnostiske tilstande.
Der foreligger endnu ingen eksakte data fra eva-
luering af cost-benefit for mMR-skanning af prostata,
men internationale erfaringer fra de førende uroradi-
ologiske prostatacentre angiver, at mMR-skanning af
prostata giver forbedret initial diagnose, hvilket med-
fører en mere effektiv og individuelt målrettet be-
handlingsstrategi, der reducerer de samlede udgifter.
KONKLUSION
Brug af moderne mMR-skanning i klinikken kan for-
bedre udredningen og behandlingsplanlægningen
hos danske mænd med prostatacancer og er klar til
implementering i klinikken.
KORRESPONDANCE: Lars Boesen, Urologisk Afdeling H, Herlev Hospital,
Herlev Ringvej ,  Herlev E-mail: lboe@heh.regionh.dk
ANTAGET: . oktober 
FØRST PÅ NETTET: . februar 
INTERESSEKONFLIKTER: Forfatternes ICMJE-formularer er tilgængelige sammen
med artiklen på Ugeskriftet.dk
FAKTABOKS
Magnetisk resonans (MR)-skanning er den bedst egnede billedmoda-
litet til detektion, lokalisation og T-stadieinddeling af prostatacancer.
Med MR-skanning kan man bedre end med ultralydskanning vise
cancere i hele prostata, inklusive den anteriore del og transitionszo-
nen.
Multiparametrisk MR-skanning kombinerer anatomiske billeder med
funktionelle MR-undersøgelser.
Det typiske cancerfokus er hypointenst på anatomiske billeder med
en lav apparent diffusionskoefficient (ADC)-værdi og en hurtig ind- og
udvaskning af kontrast.
ADC-værdien er fundet at være moderat korreleret til canceraggressi-
vitet.
Med MR-skanning kan man identificere patienter med risiko for kli-
nisk sygdom, målrette biopsier mod suspekte områder og reducere
antallet af rebiopsier.
MR-skanning til stadieinddeling på 1,5 tesla skal udføres med rek-
talspole. Rektalspole på 3 tesla er kun nødvendig, hvis viden om mi-
nimal ekstraprostatisk vækst er afgørende for behandlingsvalget.
MR-skanning forbedrer den præterapeutiske vurdering af det kliniske
T-stadie.
MR-skanning er den mest sensitive billedmodalitet til diagnostik af
lokalrecidiv i prostata.
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whom, why and how? Diagn Interv Imaging ;:-.
SUMMARY
Lars Boesen & Henrik S. Thomsen:
Magnetic resonance imaging in management of prostate cancer
Ugeskr Laeger  Feb  [Epub ahead of print]
The development of multiparametric magnetic resonance
imaging (MRI) offers new possibilities in management of
prostate cancer due to its high-resolution and soft-tissue
contrast. By combining high-resolution anatomical imaging with
functional imaging techniques multiparametric MRI is now
proven to be the most sensitive and specific imaging tool for
detection, localization and staging of prostate cancer.
... Recently published data [62][63][64][65][66][67] indicates the rapidly growing use of mpMRI as the most specific and sensitive diagnostic imaging modality for PCa management. MpMRI provides detailed information about the morphological, metabolic, and cellular changes in the prostate as well as characterize tissue vascularity and correlate it to tumor aggressiveness [68,69]. MP MRI sequences include high-resolution anatomical T2-weighted (T2W) and T1-weighted (T1W) images in combination with one or more functional MRI techniques such as diffusion-weighted imaging (DWI) and dynamic contrastenhanced (DCE) imaging [63]. ...
... The value of mp-MRI is not only in the radiological diagnosis and risk stratification of prostate cancer. It allows the urologist to target radiologically significant disease during TRUS biopsy, a feature that is not possible using conventional ultrasound guidance alone [9,10]. From the urologist's perspective, radiologically significant disease is that highest risk lesion in the prostate that determines the Gleason grade and stage, and hence aids in deciding on the appropriate course of treatment. ...
Chapter
Throughout history, physicians believed that the perception of pain could be explained by a single, simplified physiologic pathway (Loeser et al. 2001a). Their theories described pain as its own sensory apparatus, independent of touch and other senses, or as a result of excessive stimulation from the touch sensation. While the exact mechanisms were unknown, most physicians agreed that pain required a triggering stimulus and that removal of the stimulus should relieve pain. More recently, practitioners focus on pain that occurs during the absence of tissue damage or other organic pathology. While most pain experienced may have an initial inciting event, continuation of pain after removal of the stimulus indicates that many factors and biological pathways interact to cause the sensation of pain. Hence, the initial assessment of an individual’s pain is important in determining the underlying cause and the possible treatments available for that individual (Loeser et al. 2001b, c; Garratt et al. 1993).
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Figure 1. (A) Axial BAC image shows the cancer focus (arrow), no capsular irregularity seen. (B) Axial ERC image reveals extraprostatic extension (arrow). (C) Histopathology confirmed the extension (EPE, red arrow) and staged the patient as stage pT3a. Introduction In 2005, approximately 232,000 men will have been diagnosed with prostate cancer in the United States (1). Magnetic resonance (MR) imaging can play a role in the diagnostic process of prostate cancer. At standard clinical field strengths of 1.5 tesla (T) the endorectal coil (ERC) is necessary to obtain a sufficiently high spatial resolution with an adequate signal-to-noise ratio for cancer localization and staging. MR imaging at higher field strengths (e.g. 3T) increases the signal-to-noise ratio, and the need for an ERC to localize or stage prostate cancer at this field strength has yet to be determined. Imaging without an ERC could increase the clinical applicability of MR imaging in prostate cancer. Therefore, the goal of this study was to compare the image quality and prostate cancer localization and staging performance between body array coil (BAC) and ERC MR imaging with whole-mount section histopathology as standard of reference. Materials and methods After written informed consent, 25 consecutive patients with biopsy-proven prostate cancer underwent an MR imaging examination on a 3T whole-body system (Magnetom TRIO, Siemens Medical Solutions, Erlangen, Germany) prior to radical prostatectomy. First, T2-weighted images in three planes were obtained with an eight-element BAC. Sequence parameters were: TR/TE 3700/124 msec; FOV: 220x100 mm; slice thickness: 4 mm; matrix: 512x512; variable flip angle to reduce SAR; voxel size: 0.43x0.43x4.00 mm 3 ; two averages; acquisition time: 4.57 minutes. Subsequently, the BAC was removed and a prototype 3T ERC (Medrad, Pittsburgh, PA) inserted. Prior to ERC imaging patients received a 1 mg intramuscular injection of glucagon (Glucagen ® , Novo Nordisk A/S, Denmark) to suppress bowel motion. The T2-weighted imaging was then repeated. Sequence parameters were: TR/TE 5000/153 msec; FOV: 200x100 mm; slice thickness: 2.5 mm; matrix: 768x384; variable flip angle; voxel size: 0.26x0.26x2.50 mm 3 ; one average; acquisition time: 2.58 minutes. Three radiologists, A, B and C, with 4 years, 2 years and no prior experience, respectively, read all imaging sets. For each imaging set ten image quality characteristics taken from literature (2,3) that were related to localization and staging (see Table 1) were scored on a five-point scale. The radiologists also scored the presence of cancer in a 14-segment model of the whole prostate on a five point probability scale. Lastly, for each imaging set the readers determined the disease stage on a five point probability scale. Whole-mount section histopathology was used as standard of reference. A single experienced pathologist who was blinded to the MR imaging results outlined the presence and extent of cancer on all radical prostatectomy specimens and staged each patient. For each reader the areas under the receiver operating characteristic curve (AUC) were determined for both BAC and ERC imaging. Diagnostic performance parameters were calculated by dichotomizing the results. P<0.05 was considered statistically significant. Results Significantly more motion artifacts were present at ERC MR imaging (p<0.01). All other image quality characteristics improved significantly with ERC MR imaging (p<0.05). For localizing prostate cancer with BAC imaging the AUCs for radiologists A, B and C were 0.71, 0.55 and 0.64, respectively, while with ERC imaging the AUCs were 0.69, 0.66 and 0.55, respectively. Six patients had stage pT3 disease at histopathology. The AUCs for staging for radiologists A, B and C were 0.71, 0.54 and 0.68, respectively for BAC imaging and 0.92, 0.97 and 0.68 for ERC imaging. The single case of seminal vesicle invasion was not detected by any reader. The sensitivity for detecting stage pT3a (extracapsular extension) increased to 80% (4/5) for all readers with ERC imaging (Table 2). An example of the increased sensitivity with ERC imaging compared with BAC imaging is shown in Figure 1.
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The aim was to develop clinical guidelines for multi-parametric MRI of the prostate by a group of prostate MRI experts from the European Society of Urogenital Radiology (ESUR), based on literature evidence and consensus expert opinion. True evidence-based guidelines could not be formulated, but a compromise, reflected by “minimal” and “optimal” requirements has been made. The scope of these ESUR guidelines is to promulgate high quality MRI in acquisition and evaluation with the correct indications for prostate cancer across the whole of Europe and eventually outside Europe. The guidelines for the optimal technique and three protocols for “detection”, “staging” and “node and bone” are presented. The use of endorectal coil vs. pelvic phased array coil and 1.5 vs. 3 T is discussed. Clinical indications and a PI-RADS classification for structured reporting are presented. Key Points • This report provides guidelines for magnetic resonance imaging (MRI) in prostate cancer. • Clinical indications, and minimal and optimal imaging acquisition protocols are provided. • A structured reporting system (PI-RADS) is described.
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In the diagnostic process of prostate cancer, several radiologic imaging modalities significantly contribute to the detection and localization of the disease. These range from transrectal ultrasound (TRUS) and magnetic resonance imaging (MRI) to positron emission tomography (PET). Within this review, after evaluation of the literature, we will discuss the advantages and disadvantages of these imaging modalities in clarifying the patient's clinical status as to whether he has prostate cancer or not and if so, where it is located, so that therapy appropriate to the patient's disease may be administered. TRUS, specifically with the usage of intravenous contrast agents, provides an excellent way of directing biopsy towards suspicious areas within the prostate in the general (screening) population. MRI using functional imaging techniques allows for highly accurate detection and localization, particularly in patients with prior negative ultrasound guided biopsies. A promising new development is the performance of biopsy within the magnetic resonance scanner. Subsequently, a proposal for optimal use of radiologic imaging is presented and compared with the European and American urological guidelines on prostate cancer.
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Since there are salvage solutions, it is important to detect local recurrence of prostate cancer as early as possible. The first sign is "biochemical failure" in that the prostate specific antigen (PSA) concentration rises again. The definition of biochemical failure varies depending on the initial treatment: PSA greater than 0.2ng/mL after prostatectomy, nadir+2ng/mL after radiotherapy. There is no standardised definition of biochemical failure after cryotherapy, focused ultrasound, or brachytherapy. Magnetic resonance imaging (MRI) (particularly dynamic MRI) can detect local recurrence with good sensitivity. The role of spectroscopy is still under discussion. For the moment, ultrasound techniques are less effective than MRI.
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Accurate pretreatment assessment of prostate cancer (PCa) aggressiveness is important in decision making. Gleason grade is a critical predictor of the aggressiveness of PCa. Transrectal ultrasound-guided biopsies (TRUSBxs) show substantial undergrading of Gleason grades found after radical prostatectomy (RP). Diffusion-weighted magnetic resonance imaging (MRI) has been shown to be a biomarker of tumour aggressiveness. To improve pretreatment assessment of PCa aggressiveness, this study prospectively evaluated MRI-guided prostate biopsies (MR-GBs) of abnormalities determined on diffusion-weighted imaging (DWI) apparent diffusion coefficient (ADC) maps. The results were compared with a 10-core TRUSBx cohort. RP findings served as the gold standard. A 10-core TRUSBx (n=64) or MR-GB (n=34) was used for PCa diagnosis before RP in 98 patients. Using multiparametric 3-T MRI: T2-weighted, dynamic contrast-enhanced imaging, and DWI were performed to identify tumour-suspicious regions in patients with a negative TRUSBx. The regions with the highest restriction on ADC maps within the suspicions regions were used to direct MR-GB. A 10-core TRUSBx was used in a matched cohort. Following RP, the highest Gleason grades (HGGs) in biopsies and RP specimens were identified. Biopsy and RP Gleason grade results were evaluated using chi-square analysis. No significant differences on RP were observed for proportions of patients having a HGG of 3 (35% vs 28%; p=0.50), 4 (32% vs 41%; p=0.51), and 5 (32% vs 31%; p=0.61) for the MR-GB and TRUSBx cohort, respectively. MR-GB showed an exact performance with RP for overall HGG: 88% (30 of 34); for TRUS-GB it was 55% (35 of 64; p=0.001). In the MR-GB cohort, an exact performance with HGG 3 was 100% (12 of 12); for HGG 4, 91% (10 of 11); and for HGG 5, 73% (8 of 11). The corresponding performance rates for TRUSBx were 94% (17 of 18; p=0.41), 46% (12 of 26; p=0.02), and 30% (6 of 20; p=0.01), respectively. This study shows prospectively that DWI-directed MR-GBs significantly improve pretreatment risk stratification by obtaining biopsies that are representative of true Gleason grade.
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Although magnetic resonance imaging (MRI) is emerging as the most commonly used imaging modality for prostate cancer (PCa) detection, treatment planning, and follow-up, its acceptance has not been uniform. Recently, great interest has been shown in multiparametric MRI, which combines anatomic T2-weighted (T2W) imaging with MR spectroscopic imaging (MRSI), dynamic contrast-enhanced MRI (DCE-MRI), and diffusion-weighted imaging (DWI). The aim of this article is to review the current roles of these MR techniques in different aspects of PCa management: initial diagnosis, biopsy strategies, planning of radical prostatectomy (RP) and external radiation therapy (RT), and implementation of alternative focal therapies. The authors searched the Medline and Cochrane Library databases (primary fields: prostatic neoplasm, magnetic resonance). The search was performed without language restriction from January 2008 to November 2010. Initial diagnosis: The data suggest that the combination of T2W MRI and DWI or MRSI with DCE-MRI has the potential to guide biopsy to the most aggressive cancer foci in patients with previously negative biopsies, increasing the accuracy of the procedure. Transrectal MR-guided prostate biopsy can improve PCa detection, but its availability is still limited and the examination time is rather long. Planning of RP: It appears that adding MRSI, DWI, and/or DCE-MRI to T2W MRI can facilitate better preoperative characterization of cancer with regard to location, size, and relationship to prostatic and extraprostatic structures, and it may also facilitate early detection of local recurrence. Thus, use of these MR techniques may improve surgical, oncologic, and functional management. Planning of external RT and focal therapies: MR techniques have similar potential in these areas, but the published data remain very limited. MRI technology is continuously evolving, and more extensive use of MRI technology in clinical trials and practice will help to improve PCa diagnosis and treatment planning.
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To review the current status of MRI techniques in identification of organ-confined prostate cancer with a focus on their implication for focal therapy and active surveillance. MRI is currently focusing on intraprostatic prostate cancer identification and at 1.5T, it provides excellent imaging of the whole gland including the challenging anterior part. Improvements in accuracy for cancer detection and volume estimation result from dynamic contrast-enhanced and diffusion-weighted MRI sequences. 3T MRI might improve cancer identification. Histological correlations showed high sensitivity and specificity for significant volume cancers larger than 0.5 cm3. Important knowledge on modelling of cancer morphology such as zone of origin and intraprostatic patterns of spread at histopathology was made available for imaging interpretation and treatment planning decision. MRI results allow focused use of biopsy which led to better cancer characterization such as extent and grade. Ongoing focal therapy protocols and active surveillance treatments should benefit from these imaging advances. At present, high-resolution MRI with pelvic coil appears to offer the most readily available and useful imaging. Future studies should work towards helping define standard, reproducible approaches to imaging and image reporting for research and clinical practice.
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To review the current status of advanced imaging techniques in identification of organ-confined prostate cancer with a focus on their impact on patient management. Transrectal ultrasound suffers from poor accuracy despite significant technical improvements. Generally used to distinguish cancers with extraprostatic spread, MRI is now focusing on intraprostatic prostate cancer identification. At 1.5T, the most recent high-resolution pelvic phased-array coils provide excellent imaging of the whole gland, including this challenging anterior part. Improvements in accuracy for cancer detection and volume estimation result from dynamic contrast-enhanced and diffusion-weighted imaging sequences. Histological correlations showed high sensitivity/specificity for significant volume cancers. 3T MRI scanners will improve these results. Most of the recent PET/computed tomography imaging studies use choline derivatives ((11)C-choline and (18)F-fluorocholine). Their results are promising but insufficient to be currently recommended in routine practice. Considerable advances have been made in the identification of organ-confined prostate cancer with multiparametric MRI. Only prebiopsy MRI can provide best quality of cancer assessment and allows for targeting biopsies. It is hoped that advances in 3T MRI as well as in radiotracers for PET/computed tomography will further improve diagnosis, treatment selection, planning and outcomes.