The ability of post-chemoradiotherapy DWI ADCmean and 18F-FDG SUVmax to predict treatment outcomes in head and neck cancer: impact of human papilloma virus oropharyngeal cancer status.

OBJECTIVES: To evaluate the ability of post-chemo-radiotherapy (CRT) diffusion-weighted-MRI apparent diffusion coefficient (ADCmean) and 18F-FDG PET maximum standardized uptake value (SUVmax) to predict disease-free survival (DFS) in head and neck squamous cell carcinoma (HNSCC), and to determine whether this ability is influenced by human papillomavirus oropharyngeal cancer (HPV-OPC) status. METHODS: This prospective cohort observational study included 65 participants (53 male, mean ± SD age 59.9 ± 7.9 years, 46 HPV-OPC) with stage III or IV HNSCC. Primary tumour and nodal ADCmean (pre-treatment, 6- and 12-weeks post-CRT) and SUVmax (12-weeks post-CRT) were measured. Variables were compared with 2-year DFS (independent t-test/Mann-Whitney test) and overall DFS (Cox regression), before and after accounting for HPV-OPC status. Variables were also compared between HPV-OPC and other HNSCC subgroups after stratifying for DFS. RESULTS: Absolute post-CRT ADCmean values predicted 2-year DFS and overall DFS for all participants (p = 0.03/0.03, 6-week node; p = 0.02/0.03 12-week primary tumour) but not in the HPV-OPC subgroup. In participants with DFS, percentage interval changes in primary tumour ADCmean at 6- and 12-weeks were higher in HPV-OPC than other HNSCC (p = 0.01, 6 weeks; p = 0.005, 12 weeks). The 12-week post-CRT SUVmax did not predict DFS. CONCLUSION: Absolute post-CRT ADCmean values predicted DFS in HNSCC but not in the HPV-OPC subgroup. Amongst participants with DFS, post-CRT percentage interval changes in primary tumour ADCmean were significantly higher in HPV-OPC than in other HNSCC. Knowledge of HPV-OPC status is crucial to the clinical utilisation of post-CRT DWI-MRI for the prediction of outcomes.

Unilateral axillary adenopathy following COVID-19 vaccination: a multimodality pictorial illustration and review of current guidelines.

We present a multimodality pictorial review of axillary lymphadenopathy in patients recently vaccinated against COVID-19. As the mass vaccination programme continues to be rolled out worldwide in an effort to combat the pandemic, it is important that radiologists consider recent COVID-19 vaccination in the differential diagnosis of unilateral axillary lymphadenopathy and are aware of typical appearances across all imaging methods. We review current guidelines on the management of unilateral axillary lymphadenopathy in the context of recent COVID-19 vaccination.

Palatine tonsil SUVmax on FDG PET-CT as a discriminator between benign and malignant tonsils in patients with and without head and neck squamous cell carcinoma of unknown primary.

AIM: To analyse the maximum standardised uptake value (SUVmax) ratio between tonsils in patients with and without tonsillar carcinoma to determine useful diagnostic thresholds. MATERIALS AND METHODS: Positron-emission tomography (PET)/computed tomography (CT) examinations of patients with suspected head and neck squamous cell carcinoma (SCC) and controls from April 2013 to September 2016 were reviewed retrospectively. Tonsillar SUVmax ratios (ipsilateral/contralateral for malignant tonsils, maximum/minimum for patients without [controls]) were calculated and used to construct a receiver operating characteristic (ROC) curve. RESULTS: Twenty-five patients had tonsillar carcinoma (mean SUVmax ratio of 2, range 0.89-5.4) and 86 patients acted as controls (mean SUVmax ratio of 1.1, range 1-1.5). Using the ROC, the most accurate SUVmax ratio for identifying malignancy was >1.2 (77% sensitivity, 86% specificity). A potentially more clinically useful SUVmax ratio is ≥1.6 with 62% sensitivity and 100% specificity. CONCLUSION: An SUVmax ratio between tonsils of ≥1.6 is highly suspicious for SCC and could be used to direct site of biopsy. Some malignant tonsils had normal FDG uptake; therefore, PET/CT should not be used to exclude tonsillar cancer. Minor asymmetrical uptake is frequently seen in non-malignant tonsils and does not necessarily require further investigation. Due to the single centre nature of this study and the recognised variation in SUV measurements between PET scans, other centres may need to develop their own cut-offs.

PET/CT and PET/MRI in head and neck malignancy.

Combined 2-[18F]-fluoro-2-deoxy-d-glucose (FDG) positron-emission tomography (PET)/computed tomography (CT) has an established role in the staging of difficult cases of head and neck (HN) squamous cell carcinoma (SCC), looking for an unknown primary, assessing response post-chemotherapy at 3-6 months, and differentiating relapse from treatment effects in patients suspected to have tumour recurrence. The PET NECK trial, comparing PET/CT surveillance versus neck dissection in advanced head and neck cancer showed survival was similar among patients who underwent PET/CT-guided surveillance and those who underwent planned neck dissection, but surveillance was more cost-effective. There is growing interest in the use of hypoxia PET tracers, especially in targeting radiotherapy, where the radiotherapy dose can be boosted in regions of hypoxia; the use of 68Ga peptide tracers in neuroendocrine malignancy and also in the growing field of combined PET/magnetic resonance imaging (MRI). PET/MRI has the advantage of increased anatomical detail and radiation dose reduction combined with the molecular and metabolic data from PET, although PET/CT has the advantage in better sensitivity for imaging lung metastases. Thus far, there is good agreement between PET/CT and PET/MRI with high correlation between semi-quantitative measurements in primary, nodal, osseous, and soft-tissue lesions imaging. PET/MRI may indeed provide greater accuracy than the currently available imaging procedures in the staging and later treatment response evaluation in HNSCC.

PET imaging in endocrine tumours.

The role of PET in the assessment of endocrine tumours has been, until recently, restricted to the use of (18)F-fluoro-deoxy-D-glucose ((18)F-FDG). Being a marker of metabolically active lesions that show high grading and low differentiation, FDG is not ideal for this purpose since the majority of endocrine tumours are slow growing and highly differentiated. It is however useful when dedifferentiation takes place and provides excellent prognostic information. A number of hormone precursors and amino acids are labelled with (11)C and used successfully in the management of parathyroid, adrenal and pituitary tumours. However, the short half-life of (11)C radiopharmaceuticals restricts their use to centres with access to an on-site cyclotron, while the high cost of production may limit their use to research purposes. A promising new positron-emission tomography (PET) tracer is Gallium-68 obtained by elution from a long shelf-life generator that makes it economic and cyclotron-independent. Its short half-life and flexible labelling ability to a wide range of peptides and antibodies makes it ideal for PET imaging. In addition to imaging GEP-NETs and phaeochromocytoma, it has the potential to be used in a wider range of endocrine tumours.

Evaluation of hepatic angiography procedures and bremsstrahlung imaging in selective internal radiation therapy: a two-year single-center experience.

The imaging of Bremsstrahlung radiation is performed after hepatic radioembolization to assess the distribution of the injected radioactive material. This review assesses the role of Bremsstrahlung imaging and its relation to the angiographic procedure and technique in hepatic selective internal radiation therapy on 21 patients undergoing this procedure at a single center.

Clinical and imaging experience with yttrium-90 microspheres in the management of unresectable liver tumours.

INTRODUCTION: Selective internal radiation therapy (SIRT) is emerging as a new therapeutic modality in recent years for management of non-resectable hepatic malignancies. Our experience in clinical application of this treatment is reported here. MATERIAL AND METHODS: From June 2004, patients whose liver tumours were no longer amenable for any conventional treatment with either chemotherapy or surgery were considered for yttrium-90 microspheres treatment after discussion at our multidisciplinary meeting. A pre-treatment planning was carried out with visceral angiography and technetium-99m macroaggregated albumin (MAA) for assessment of both tumour volume and extrahepatic shunting in addition to a baseline PET and CT scans, respectively. Two weeks later, a second visceral angiogram was performed to deliver the calculated dosage of microspheres into the arterial system supplying the tumour. Patients were then followed up with tumour markers, repeat PET and CT scans of abdomen at 6 weeks and 3 monthly thereafter. RESULT: Twenty-one patients (F=11, M=10; age range 40-75 years, mean=58 years) received yttrium-90 microspheres consisting of liver metastases from colorectal primary (n=10) and non-colorectal primaries (n=8), and primary liver tumours (n=3). One patient received 2 treatments. The mean administered activity of microspheres delivered was 1.9 GBq (range 1.2-2.5 GBq). Injection of microspheres had no immediate effect on either clinical haematology or liver function tests. At follow-up, 86% of patients showed decreased activity on PET scan at 6 weeks (p=0.01). The mean pre-treatment SUV was 12.2+/-3.7 and the mean post-treatment SUV was 9.3+/-3.7, indicating a significant improvement measured with PET activity. Only 13% showed a reduction in the size of tumour on CT scan. For patients with colorectal liver metastases, there was no significant reduction in CEA level (127+/-115 vs 75+/-72 micro/l, p=0.39). Complications were seen in 4 patients (19%) including radiation hepatitis (n=2), cholecystitis (n=1) and duodenal ulceration (n=1). All resolved without surgical intervention. Seven patients died at follow-up from progressive extrahepatic disease (33%). CONCLUSION: SIRT should be considered for patients with advanced liver cancer. It has a significant effect on liver disease in the absence of extrahepatic disease. PET imaging has an integral role in the assessment of patients treated with yttrium-90 SIR-Spheres.

Treatment of primary and secondary liver tumours with selective internal radiation therapy.

When HCC is diagnosed at an early stage or liver is affected by a solitary metastasis they can be curable by surgical resection, but this may not be feasible when an extensive tumoural involvement is present. In these cases, possible non-surgical therapies include systemic chemotherapy, chemical ablation (ethanol or acetic acid), radiofrequency ablation, microwave ablation, cryotherapy and transarterial chemoembolisation. All the above mentioned treatments have advantages and disadvantages. In the present paper we reported our experience with selective internal radiation therapy (SIRT) of non-operable HCC and metastatic liver using 99Yttrium (99Y) radioactive microspheres, and our data are compared and discussed with those reported in the literature. A MEDLINE-based review of the literature has been made in the period between 1990 and April 2007. Detailed information on patients selection criteria, SIRT procedure, dose calculation, safety and adverse reactions, follow-up schedule, and clinical efficacy are provided. On the basis of our data, in agreement with those of the literature, SIRT has added another effective method for treatment of primary and secondary liver tumours, being successful in a large number of patients in different experiences. Moreover, SIRT is well tolerated and has minimal adverse effects. Despite being regarded as non-curative, it has been associated with improved survival, reduction in tumour marker, and regression in the number and size of lesions. Follow-up with imaging is essential to assess the response to therapy, and in this respect FDG PET has been shown to be more sensitive than CT, particularly in the early stages.

Gallium-68 PET: a new frontier in receptor cancer imaging.

Neuroendocrine tumours (NET) are rare tumours that occur most commonly in the GI tract. Various labelled somatostatin analogues are used to image NET expressing somatostatin receptors (SSTR). In traditional nuclear medicine, most peptides used in imaging NET have been labelled with indium-111, the commonest being indium-111-octreotide (111In-octreotide). Unfortunately, the unfavourable physical qualities of In-111 make it unsuitable for detecting small tumour deposits. The recent introduction of gallium-68-1,4, 7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (gallium-68-DOTA) compounds for positron emission tomography (PET) imaging has significantly improved the quality of imaging NET through improved resolution of PET and higher affinity of the new generation of peptides to SSTR. In the present paper, we discuss the clinical and research applications of PET radio-tracers for evaluating NET, in particular gallium-68-DOTA compounds. The recent introduction of PET imaging with gallium-68 has major bearings in current and future clinical practice. Its labelling with DOTA compounds has cleared the way for somatostatin receptor imaging with a viable PET agent, with all its inherent imaging advantages compared to single photon imaging. The pre-clinical and clinical applications of this technique has been successful in a variety of tumours, particularly NET and its labelling with other ligands and molecules will improve the management of other tumours and the assessment of infection.

Endoanal magnetic resonance imaging of fistula-in-ano: a comparison of STIR with gadolinium-enhanced techniques.

PURPOSE: To compare a STIR sequence with gadolinium-enhanced techniques on endoanal magnetic resonance (MR) imaging of fistulas-in-ano by correlating the findings with those at surgery. MATERIAL AND METHODS: Twenty-two consecutive patients with clinical suspicion of perianal sepsis were studied using an endoanal coil followed immediately by a phased array coil. T1-weighted precontrast and postcontrast and STIR images in transverse and coronal planes were produced with each coil and analysed by noting the presence and site of a collection, primary track, the position of any internal opening, and subcutaneous or supralevator extension. An "expert" and also a "trainee" radiologist assessed the images. Operative findings were similarly recorded. The Fisher exact test was used to compare imaging with surgery. Interobserver variation was calculated using a kappa statistic. RESULTS: Of 22 patients with suspected fistulas, 8 were simple, 4 were complex, and 3 were superficial sinuses. Five had no anal pathology, 1 had anal excoriation, and 1 had a polyp. At surgery, 6 intersphincteric, 1 transsphincteric, 8 extrasphincteric, no supralevator collections, and 9 internal openings were noted. The overall sensitivity and specificity for detecting these were 75% and 64%, respectively, for STIR imaging, and 58.3% and 62.8% for gadolinium-enhanced imaging. There was good agreement between the "trainee" and the "expert" in the interpretation of images (kappa=0.7). CONCLUSION: A STIR sequence is more sensitive overall than gadolinium-enhanced techniques on endoanal magnetic resonance imaging of fistulas-in-ano because of increased sensitivity in detecting the internal opening. A combination of endoanal and phased array techniques using STIR imaging sequences is valuable preoperative assessment in both simple and complex cases.

Imaging of periosteal reactions associated with focal lesions of bone.

Periosteal reaction (PR) is the response of cortical bone to an underlying insult. It is manifest in a limited number of histological and radiological patterns. Although not specific for a particular diagnosis, the appearance of PR aids the radiological characterization of bone lesions. Once ossified, PR is demonstrated well on plain radiography but can also be visualized on ultrasound, CT, MRI and bone scintigraphy, particularly in the early stage. This article provides a pictorial review of the patterns of PR with particular reference to bone tumours.