Gaël Amzalag

PET/MR in Breast Cancer

Breast cancer is an international public health concern in which an optimal treatment plan requires a precise staging. Both MRI and PET imaging techniques have made significant progress in the last decades with constant improvements that made both modalities clinically relevant in several stages of breast cancer management and follow-up. On one hand, specific breast MRI permits high diagnostic accuracy for local tumor staging, and whole-body MRI can also be of great use in distant staging, eventually accompanied by organ-specific MRI sequences. Moreover, many different MRI sequences can be performed, including functional MRI, letting us foresee important improvements in breast cancer characterization in the future. On the contrary, (18)F-FDG-PET has a high diagnostic performance for the detection of distant metastases, and several other tracers currently under development may profoundly affect breast cancer management in the future with better determination of different types of breast cancers allowing personalized treatments. As a consequence PET/MR is a promising emerging technology, and it is foreseeable that in cases where both PET and MRI data are needed, a hybrid acquisition is justified when available. However, at this stage of deployment of such hybrid scanners in a clinical setting, more data are needed to demonstrate their added value beyond just patient comfort of having to undergo a single examination instead of two, and the higher confidence of diagnostic interpretation of these co-registered images. Optimized imaging protocols are still being developed and are prone to provide more efficient hybrid protocols with a potential improvement in diagnostic accuracy. More convincing studies with larger number of patients as well as cost-effectiveness studies are needed. This article provides insights into the current state-of-the-art of PET/MR in patients with breast cancer and gives an outlook on future developments of both imaging techniques and potential applications in the future.

Target Definition in Salvage Radiotherapy for Recurrent Prostate Cancer: The Role of Advanced Molecular Imaging

Salvage radiotherapy (SRT) represents the main treatment option for relapsing prostate cancer in patients after radical prostatectomy. Several open questions remain unanswered in terms of target volumes definition and delivered doses for SRT: the effective dose necessary to achieve biochemical control in the SRT setting may be different if the tumor recurrence is micro- or macroscopic. At the same time, irradiation of only the prostatic bed or of the whole pelvis will depend on the localization of the recurrence, local or locoregional. In the “theragnostic imaging” era, molecular imaging using positron emission tomography (PET) constitutes a useful tool for clinicians to define the site of the recurrence, the extent of disease, and individualize salvage treatments. The best option currently available in clinical routine is the combination of radiolabeled choline PET imaging and multiparametric magnetic resonance imaging (MRI), associating the nodal and distant metastases identification based on PET with the local assessment by MRI. A new generation of targeted tracers, namely, prostate-specific membrane antigen, show promising results, with a contrast superior to choline imaging and a higher detection rate even for low prostate-specific antigen levels; validation studies are ongoing. Finally, imaging targeting bone remodeling, using whole-body SPECT–CT, is a relevant complement to molecular/metabolic PET imaging when bone involvement is suspected.

Hybrid PET/MRI as a tool to detect brown adipose tissue: Proof of principle

OBJECTIVE The purpose of this study was to assess the performance of (18)F-FDG hybrid PET/MRI to detect and localise the presence of metabolically active brown adipose tissue (BAT). METHODS We retrospectively analyzed 197 consecutive (18)F-flurodeoxyglucose ((18)F-FDG) positron-emission tomographic (PET) and magnetic resonance imaging (MRI) images performed with a hybrid whole-body PET-MRI tomography in 192 patients. These patients were originally investigated mainly for oncological staging, in the absence of a cooling protocol. The presence of BAT was defined as a soft tissue structure that was larger than 4mm in diameter, had the characteristics of fat tissue on MRI and had a maximal standardised uptake value (SUV) of (18)F-FDG of at least 2.0. No specific MRI sequences for BAT detection were acquired. RESULTS PET/MRI identified the presence of metabolically active BAT in 5 out of 192 patients (2.6%). BAT positive subjects were all female, significantly younger and with significantly lower body weight than BAT negative subjects. CONCLUSIONS Whole body hybrid PET/MRI allowed for the identification of BAT, with a low prevalence, comparable to previous retrospective PET/CT studies realised in the absence of a cooling protocol. The main advantages of the PET/MRI hybrid technique, as compared with PET/CT, includes a lower radiation burden, and the possibility to combine a multiparameter fat characterization by dedicated MRI sequences. Hybrid PET/MRI might represent the ideal tool for BAT evaluation.

High protracted 99mTc-HDP uptake in synthetic bone implants — A potentially misleading incidental finding on bone scintigraphy

We report the case of a 56-year-old male with bilateral total knee prostheses suffering from bilateral knee pain mainly on the right side and referred for bone scintigraphy. The medical history of the patient revealed an opening wedge high tibial osteotomy performed nine years earlier, with insertion of two blocks of ceramic made of hydroxyapatite and tricalcium phosphate in a wedge configuration as synthetic bone substitutes. The porous structure of these implants is analogous to the architecture of cancellous bone and permits fibrovascular and bone ingrowth, promoting the healing process. Planar scintigraphy and SPECT/CT showed an intense uptake within those implants in the early phase as well as in the late phase of the bone scan. It also showed bilateral patellofemoral arthritis. A (99m)Tc-labeled antigranulocyte antibody scintigraphy was negative for infection or inflammation. Bilateral patellar resurfacing led to complete symptom regression, confirmed at 10 months follow-up. To the best of our knowledge, this scintigraphic pattern with such a high tracer uptake reflecting bone substitute osteointegration has not yet been published. This should be considered in patients with such bone replacement materials that are increasingly used, in order to avoid false diagnosis of inflammation or infection.

Whole-Body SPECT/CT versus Planar Bone Scan with Targeted SPECT/CT for Metastatic Workup

Purpose The use of SPECT/CT in bone scans has been widespread in recent years, but there are no specific guidelines concerning the optimal acquisition protocol. Two strategies have been proposed: targeted SPECT/CT for equivocal lesions detected on planar images or systematic whole-body SPECT/CT. Our aim was to compare the diagnostic accuracy of the two approaches. Methods 212 consecutive patients with a history of cancer were referred for bone scans to detect bone metastases. Two experienced readers randomly evaluated for each patient either planar images with one-field SPECT/CT targeted on equivocal focal uptakes (targeted SPECT/CT) or a whole-body (two-field) SPECT/CT acquisition from the base of the skull to the proximal femurs (whole-body SPECT/CT). The exams were categorized as “nonmetastatic,” “equivocal,” or “metastatic” on both protocols. The presence or absence of any extra-axial skeletal lesions was also assessed. The sensitivity and specificity of both strategies were measured using the results of subsequent imaging follow-up as the reference standard. Results Whole-body SPECT/CT had a significantly higher sensitivity than targeted SPECT/CT to detect bone metastases (p = 0.0297) and to detect extra-axial metastases (p = 0.0266). There was no significant difference in specificity among the two approaches. Conclusion Whole-body SPECT/CT is the optimal modality of choice for metastatic workup, including detection of extra-axial lesions, with improved sensitivity and similar specificity compared to targeted SPECT/CT.

Asymptomatic Urolithiasis Complicated by Nephrocutaneous Fistula

Asymptomatic spontaneous nephrocutaneous fistula is a rare and severe complication of chronic urolithiasis. We report a case of 56-year-old woman with a nephrocutaneous fistula (NFC) which developed from a superinfected urinoma following calyceal rupture due to an obstructing calculus in the left ureter. The patient was clinically asymptomatic and came to the emergency department for a painless left flank fluctuating mass. This urinoma was superinfected, with a delayed development of renal abscesses and perirenal phlegmon found on contrast-enhanced uro-computed tomography (CT), responsible for left renal vein thrombophlebitis and left psoas abscess.. Thereafter, a 99 mTc dimercaptosuccinic acid (DMSA) scintigraphy revealed a nonfunctional left kidney, leading to the decision of left nephrectomy. Chronic urolithiasis complications are rare and only few cases are reported in medical literature. A systematic medical approach helped selecting the best imaging modality to help diagnosis and treatment. Indeed, uro-CT scan and renal scintigraphy with 99 mTc-DMSA are the most sensitive imaging modalities to investigate morphological and functional urinary tract consequences of NFC, secondary to chronic urolithiasis.

Significance of 18F-fluorocholine PET/CT positive pulmonary lesions in prostate cancer patients.

AIM To assess the frequency and the significance of incidental pulmonary lesions with 18F-fluorocholine (18F-FCH) PET/CT in prostate cancer (PCa) patients. PATIENTS, METHODS 225 consecutive PCa patients referred for 18F-FCH PET/CT (median age 68 years) were retrospectively evaluated for the presence of lesions in the lungs: 173 referred for restaging and 52 for initial staging regarding their high risk of extra prostatic extension. The final diagnosis was based on histopathological or on clinical and radiological follow-up. RESULTS 13 patients had 18F-FCH positive pulmonary and 8 patients malignant lesions: 5 patients (38%) had a primary lung cancer (2 squamous cell carcinomas, 1 papillary adenocarcinoma, 1 typical pulmonary carcinoid, 1 bronchioloalveolar carcinoma) and 3 patients (23%) PCa metastases. Benign lesions were found in 5 subjects (38%). SUVmax and maximum diameter were neither significantly different in primary and metastatic tumors nor between malignant and benign lesions. CONCLUSIONS Although our results suggest that incidental uptake in the lungs in PCa patients are nonspecific, their detection may have a significant impact on patient management knowing that more than 60% represent malignant disease.

SPECT-CT Assessment of Pseudarthrosis after Spinal Fusion: Diagnostic Pitfall due to a Broken Screw.

A 43-year-old drug addicted female was referred for a L5-S1 posterolateral in situ fixation with autologous graft because of an L5/S1 severe discopathy with listhesis. After six months, low back pain recurred. A Tc-99m HDP SPECT-CT diagnosed a pseudarthrosis with intense uptake of the L5-S1 endplates and a fracture of the right S1 screw just outside the metal-bone interface without any uptake or bone resorption around the screw. The absence of uptake around a broken screw is a pitfall that the physician should be aware of.

Incidental 18 F-FDG Uptake of the Pubic Ramus and Abdominal Muscles due to Athletic Pubalgia During Acute Prostatitis

A 23-year-old African native male patient presented with fever, lumbalgia and dysuria after returning from a trip to Togo. His physical examination revealed pain over the pubic symphysis and rectal tenderness on digital exam. The C-reactive protein (CRP) level was elevated along with positive blood and urinary cultures for methicillin-resistant Staphylococcus aureus. An magnetic resonance imaging that has been performed to rule out arthritis/osteomyelitis in the pubis revealed edema of the symphysis. An 18F-FDG positron emission tomography/computed tomography supported the diagnosis of prostate infection and showed a focal uptake of the pubic symphysis, with diffuse hyper-metabolism of the insertions of the rectus abdominis and longus adductor muscles, corresponding to athletic pubalgia. Fever and CRP responded rapidly to antibiotherapy.

Determination of 226Ra at low levels in environmental, urine, and human bone samples and 223Ra in bone biopsy using alpha-spectrometry and metrological traceability to 229Th/225Ra or 226Ra

226Ra is a natural radioelement emitting α and γ radiations. It can be highly concentrated in TENORM materials from the petroleum or fertilizer industries. In Switzerland, 226Ra is currently a radioactive inheritance problem from the watch industry. Furthermore, 223Ra is a radium isotope used in nuclear medicine to treat bone metastasis. There exist several methods to measure radium using alpha or gamma spectrometry or using 222Rn emanation technique. The limitations of these methods are due to the required detection limits and the nature of the samples. When using alpha spectrometry to reach very low detection limits, critical technical hitches often arise because of the difficulties in separating radium from barium, in removing organics eluted from the separating chromatography column, and in plating radium. Moreover, overall chemical recovery of radium is often not reproducible, depending on the studies. Here we propose a method that separates radium from other alkaline-earth cations using cation exchange chromatography and selective complex formation by EDTA and DCTA. Radium is completely free of the 229Th tracer and its daughter products, particularly 225Ac. Organics from the column are removed in a further purification step so that radium can be plated with acceptable yields in a HCl/HNO3/ethanol solution. We successfully applied the method to soil, water, urine and human bone samples and further extended it to the determination of 223Ra in a bone biopsy, using 226Ra as an internal tracer.