Measurement of Prostate Specific Antigen (PSA) in serum is a cornerstone in the monitoring of asymptomatic prostate cancer (PCa) Patients after curative treatment,
including both radical prostatectomy (RP) and radiotherapy (RT).
A rapidly increasing PSA level (i.e.,
high PSA velocity and short PSA doubling time) is usually related to the presence of distant metastases (i.e.,
skeletal or lymph nodal),
while a slow and progressive increase in serum PSA concentration is often because of local disease recurrence [1].
In Patients with biochemical recurrence,
imaging plays a key role in the identification of the site of PCa recurrence,
and imaging documentation is often required for establishing an appropriate second-line treatment [2,
3].
After both RP and RT,
advanced multimodality imaging including Fusion Imaging techniques can be successfully employed to provide detailed documentation of the PCa relapse.
In clinical practice,
in the case of biochemical relapse,
MRI is often performed in association with whole-body PET/CT.
Multiparametric MRI (mMRI) imaging is considered very useful in the study of prostatic bed and lower abdomen during follow-up in prostate cancer Patients: morphological T2-weighted (T2w) sequences are combined with functional MRI techniques,
including diffusion-weighted imaging (DWI) and dynamic contrast-enhanced (DCE) perfusion imaging.
Tracers widely used in Positron Emission Tomography (PET)/Computed Tomography (CT) with radio-labelled derivatives [4] imaging are PSMA,18F-Choline,
and,
more recently,
64CuCl2 was introduced in clinical practice.
Multimodality Fusion Imaging relies on the combination of two or more imaging techniques,
in order to obtain a single series of juxtaposed images,
which is more informative than either of the imaging techniques taken separately,
thanks to the precise overlap of single frames [5].
The process of spatial co-registration is necessary,
in order to ensure that the pixels from the various imaging data sets represent the same volume with acceptable precision [6,
7].
Registration can be rigid or elastic (deformable) [5,
6].
Only translation and rotation are possible with rigid co-registration,
whereas rotation,
translation and localized stretching are performed with elastic co-registration,
thus improving the matching of anatomical structures.
This latter modality may be particularly useful in the pelvis,
where the anatomical relationships between different structures can be affected by the degree of distension of the urinary bladder and the presence of peristaltic movement [8].
This multimodal combined approach has great potential in the assessment of biochemical recurrence after PCa treatment [8].
New combined PET/MRI scanners provide simultaneous acquisition of both imaging modalities by performing an automated co-registration process with perfect temporal correlation of dynamically acquired datasets and MRI-based attenuation correction.
However,
these expensive systems are not widely available and are mainly limited to research facilities [9].
By contrast,
multimodal fusion imaging software platforms allow the co-registration of different imaging datasets acquired at different times [8,
10].
This process is called retrospective co-registration.
Retrospective co-registration can be performed with a large variety of dedicated software platforms that employ either rigid or elastic co-registration techniques and can be installed on common radiological workstations.
Currently,
the main potential future role of combined PET/MRI scanners seems to be the integration of local,
nodal,
and whole-body staging of tumours in a single ‘‘one-stop shop’’ modality,
while avoiding the use of ionizing radiation [11].
On the other hand,
dedicated software platforms for retrospective fusion are a low cost and valid alternative that allow us to bring Multimodality Fusion Imaging out of research facilities and into routine clinical practice.
In this study we considered a population of 50 Prostate Cancer Patients treated with Radical Prostatectomy (RP) and/or External Beam Radiation Therapy (EBRT),
presenting with biochemical relapse.
We compared the diagnostic accuracy of Fused 64CuCl2 PET/MRI with Fused 18F-Choline-PET/MRI,
64CuCl2 PET/CT,
18F-Choline-PET/CT and mMRI in the detection of the site of recurrence.
The aim of this work is to evaluate the role and the reliability of Multimodality Fusion Imaging in the early detection of recurrence in PCa Patients presenting with biochemical relapse if compared to other non-fusion techniques.
Furthermore,
two Fusion Imaging techniques,
Fused 18F-Choline PET/MRI and Fused 64CuCl2 PET/MRI were compared to assess which tracer could be considered more promising and reliable.