FDG-PET/CT pitfalls in oncological head and neck imaging

Efficacy of 18FDG-PET/CT in Detecting Synchronous Malignancies in Patients With Head and Neck Cancer: A Systematic Review and Meta-analysis

OBJECTIVE

To assess the diagnostic accuracy of fluorine-18 fluorodeoxyglucose positron emission tomography and computed tomography (18FDG-PET/CT) in detecting second primary malignancies (SPMs) in patients with treatment naïve head and neck squamous cell carcinoma (HNSCC).

DATA SOURCES

Medline, Embase, Cochrane Library, and Scopus searched from 1946 to December 2022.

REVIEW METHODS

Studies reporting the performance of 18FDG-PET/CT in patients with treatment-naïve, index HNSCC for detection of SPMs were included. The reference standard was histopathology, clinical follow-up over the duration of study, and other imaging modalities. Multiple investigators completed depth full-text analysis. Preferred Reporting Items for Systematic Reviews and Meta-analysis guidelines were followed. Methodologic and diagnostic accuracy data were abstracted independently by multiple investigators. Risk of bias assessment was conducted using the Quality Assessment of Diagnostic Accuracy Studies tool independently. Bivariate random-effects model meta-analysis and multivariable meta-regression modeling were used.

RESULTS

Seventeen studies examining 4624 patients with a total of 475 SPMs were included in the final analysis. Eleven studies were found to be at low risk for bias, while the rest were in the high-risk category. 18FDG-PET/CT demonstrated pooled sensitivity and specificity of 0.73 (95% confidence interval [CI]: 0.49-0.88) and 0.99 (95% CI: 0.98-1.00) in detecting SPMs. Further subsite analysis revealed varied diagnostic performance across different anatomical regions, with sensitivity and specificity of esophageal SPMs being 0.47 (0.30-0.64) and 0.99 (0.98-1.00), and sensitivity and specificity of 0.86 (0.73-0.94) and 0.99 (0.98-1.00) for head and neck SPMs. Finally, this imaging modality showed sensitivity and specificity of 0.92 (0.84-0.96) and 0.99 (0.98-1.00) for lung SPMs.

CONCLUSION

The findings of this study suggest varied accuracy of 18FDG-PET/CT in detecting SPMs during initial workup for HNSCC, highlighting the importance of screening modalities such as esophagoscopy in high-risk patients.

Focal incidental colorectal fluorodeoxyglucose uptake: Should it be spotlighted?

Fluorine-18 fluorodeoxyglucose (F-18 FDG) positron emission tomography/computed tomography (PET/CT) has emerged as a cornerstone in cancer evaluation imaging, with a well-established history spanning several years. This imaging modality, encompassing the examination of the body from the base of the skull to the upper thighs, comprehensively covers the chest and abdominopelvic regions in a singular scan, allowing for a holistic assessment of nearly the entire body, including areas of marginal interest. The inherent advantage of this expansive scan range lies in its potential to unveil unexpected incidental abnormal hypermetabolic areas. The identification of incidental focal FDG uptake within colorectal regions during PET/CT scans is not an uncommon occurrence, albeit fraught with challenges associated with non-specific FDG uptake. The presence of benign colorectal lesions or physiological uptake poses a particular obstacle, as these may manifest with FDG uptake levels that mimic malignancy. Consequently, physicians are confronted with a diagnostic dilemma when encountering abnormal FDG uptake in unexpected colorectal areas. Existing studies have presented divergent results concerning these uptakes. Standardized uptake value and its derivatives have served as pivotal metrics in quantifying FDG uptake in PET images. In this article, we aim to succinctly explore the distinctive characteristics of FDG, delve into imaging findings, and elucidate the clinical significance of incidental focal colorectal uptake. This discussion aims to contribute valuable insights into the nuanced interpretation of such findings, fostering a comprehensive understanding.

Diagnostic value of 18F-FDG PET/CT versus diffusion-weighted MRI in detection of residual or recurrent tumors after definitive (chemo) radiotherapy for laryngeal and hypopharyngeal squamous cell carcinoma: A prospective study

BACKGROUND

Despite advances in treatment, residual or recurrent tumors after definitive (chemo) radiotherapy for laryngeal and hypopharyngeal squamous cell carcinoma (SCC) remain a challenge in clinical management and require accurate and timely detection for optimal salvage therapy. This study aimed to compare the diagnostic value of Fluorine 18 (18F) fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) and diffusion-weighted magnetic resonance imaging (DW-MRI) in detecting residual or recurrent tumors after definitive (chemo) radiotherapy for laryngeal and hypopharyngeal SCC.

METHODS

A prospective study was conducted on 30 patients who presented with new symptoms after definitive (chemo) radiotherapy for laryngeal (n = 21) and hypopharyngeal (n = 9) carcinoma. Both 18F-FDG PET/CT and DW-MRI were performed and histopathologic analysis served as the standard of reference.

RESULTS

Histopathology showed 20 patients as positive and 10 as negative for tumors. 18F-FDG PET/CT detected all tumors correctly but was falsely positive in one case. DW-MRI detected tumors in 18 out of 20 positive patients and correctly excluded tumors in all negative patients. The sensitivity and specificity of 18F-FDG PET/CT were 100% and 90%, respectively, while the values for DW-MRI were 90% and 100%, respectively.

CONCLUSIONS

The study concludes that 18F-FDG PET/CT is slightly superior to DW-MRI in detecting residual or recurrent tumors after definitive (chemo) radiotherapy for laryngeal and hypopharyngeal SCC. The combined use of 18F-FDG PET/CT and DW-MRI can potentially improve specificity in therapy response evaluation.

Transoral robotic tongue base mucosectomy for head and neck cancer of unknown primary: six-year outcome experience

BACKGROUND AND OBJECTIVE

Head and neck carcinoma of unknown primary is a diagnostic dilemma. The clinical and imaging workup remains ineffective in two-thirds of patients. Transoral robotic surgery has shown an advantage in the primary detection over the previous standard panendoscopy.

METHODS

This is an observational cohort study that took place at a large healthcare centre with robotic surgery experience in head and neck over six-years. All included carcinoma of unknown primary patients followed the standard recommendation for primary identification. Final diagnostic step of robotic tongue base mucosectomy with or without tonsillectomy was introduced. The cancer detection rate in tongue base only, the functional outcome and the effect on the cancer pathway were evaluated.

RESULTS

Carcinoma of unknown primary was reported in 44 per cent of patients. All identified specimens were human papillomavirus positive. There was no significant effect on functional outcome of swallowing and the national 62-day cancer pathway. Robotic surgery allowed optimum treatment of carcinoma of unknown primary in early nodal disease.

CONCLUSION

Robotic surgery is a useful paradigm in the management of carcinoma of unknown primary. It is safe with minimal morbidity and good functional outcome after the surgery.

Unexpected focal fluorodeoxyglucose uptake in main organs; pass through or pass by?

Since the inception of fluorine-18 fluorodeoxyglucose (F-18 FDG), positron emission tomography/computed tomography (PET/CT) utilizing F-18 FDG has become widely accepted as a valuable imaging modality in the field of oncology, with global prevalence in clinical practice. Given that a single Torso PET/CT scan encompasses the anatomical region from the skull base to the upper thigh, the detection of incidental abnormal focal hypermetabolism in areas of limited clinical interest is both feasible and not uncommon. Numerous investigations have been undertaken to delineate the distinctive features of these findings, yet the outcomes have proven inconclusive. The incongruent results of these studies present a challenge for physicians, leaving them uncertain about the appropriate course of action. This article provides a succinct overview of the characteristics of fluorodeoxyglucose, followed by a comprehensive discussion of the imaging findings and clinical significance associated with incidental focal abnormal F-18 FDG activity in several representative organs. In conclusion, while the prevalence of unrecognized malignancy varies across organs, malignancies account for a substantial proportion, ranging from approximately one-third to over half, of incidental focal uptake. In light of these rates, physicians are urged to exercise vigilance in not disregarding unexpected uptake, facilitating more assured clinical decisions, and advocating for further active evaluation.

The utility of ultrasonographic surveillance in management of a presumed branchial cleft cyst later confirmed HPV-associated oropharyngeal cancer

While branchial cleft cysts are often considered benign pathologies, the literature discusses cases of squamous cell carcinoma (SCC) arising from these cystic lesions as either a primary or metastatic tumor. We illustrate our institutional experience and review the current literature to identify recommendations for best diagnostic, surveillance, and treatment guidelines for SCC identified in a branchial cleft cyst. A 61-year-old male presented with a right sided neck mass, with suspicion of a branchial cleft cyst due to benign findings on fine needle aspiration. Following surgical excision, a focus of SCC was found on surgical pathology. Despite PET/CT and flexible laryngoscopy, no primary tumor was identified prompting routine surveillance every 3 months with cervical ultrasonography and flexible nasolaryngoscopy. Two and a half years following his initial presentation, pathologic right level II lymphadenopathy was detected on ultrasound without evidence of primary tumor. Subsequent transoral robotic surgery with right tonsillectomy and partial pharyngectomy, with right lateral neck dissection revealed a diagnosis of pT1N1 HPV-HNSCC and he was referred for adjuvant chemotherapy and radiation. To our knowledge there are less than 10 cases of confirmed HPV-associated oropharyngeal SCC arising from a branchial cleft cyst. Here we demonstrate the utility of ultrasound as a surveillance tool and emphasize a higher index of suspicion for carcinoma in adult patients with cystic neck masses.

Evaluation of peripheral nerve injury according to the severity of damage using 18F-FDG PET/MRI in a rat Model of sciatic nerve injury

OBJECTIVES

We ascertained that the PET scan may be a valuable imaging modality for the noninvasive, objective diagnosis of neuropathic pain caused by peripheral nerve injury through the previous study. This study aimed to assess peripheral nerve damage according to severity using18F-FDG PET/MRI of the rat sciatic nerve.

METHODS

Eighteen rats were divided into three groups: 30-second (G1), 2-minute (G2), and 5-minute (G3) crushing injuries. The severity of nerve damage was measured in the third week after the crushing injury using three methods: the paw withdrawal threshold test (RevWT), standardized uptake values on PET (SUVR), and intensity analysis on immunohistochemistry (IntR).

RESULTS

There were significant differences between G1 and G3 in both SUVR and IntR (p = 0.012 and 0.029, respectively), and no significant differences in RevWT among the three groups (p = 0.438). There was a significant difference in SUVR (p = 0.012), but no significant difference in IntR between G1 and G2 (p = 0.202). There was no significant difference between G2 and G3 in SUVR and IntR (p = 0.810 and 0.544, respectively).

DISCUSSION

Although PET did not show results consistent with those of immunohistochemistry in all respects, this study demonstrated that PET uptake tended to increase with severe nerve damage. If this research is supplemented by further experiments, PET/MRI can be used as an effective diagnostic modality.

Appropriate timing to perform an interim 18F-FDG PET/CT in patients with nasal-type extranodal natural killer/T cell lymphoma

Interim 18F-FDG PET/CT (I-PET) has a role in response evaluation and treatment guidance in patients with nasal-type extranodal natural killer/T cell lymphoma (ENKTL). However, there was no agreement on the timing of I-PET performed, after chemotherapy or after chemoradiotherapy. We aimed to find the appropriate timing for I-PET by assessing the prognostic value of I-PET in response evaluation in ENKTL patients. Two hundred and twenty-seven ENKTL patients who had undergone I-PET were retrospectively included. All patients were grouped based on their therapeutic strategy received, chemotherapy or chemoradiotherapy. The Deauville 5-point score (DS) was used to interpret the I-PET images. The hazard ratio (HR) and C-index were used to measure the discriminatory and prognostic capacities of I-PET performed at different times. One hundred and six patients underwent the I-PET after chemotherapy (chemotherapy group), while I-PET was performed after chemoradiotherapy in 121 patients (chemoradiotherapy group). Eighty-seven patients were classified as metabolic remission (DS score of 1-3), while the other 140 were classified as non-metabolic remission (DS score of 4-5) according to the Deauville criteria. There were no significant survival differences between patients in metabolic remission and in non-metabolic remission in either progression-free survival (PFS, p = 0.406) or overall survival (OS, p = 0.350). In the chemotherapy group, patients in metabolic remission had significantly superior PFS than patients in non-metabolic remission (p = 0.012). For OS, a discriminative trend was also found on the survival curve between patients in metabolic remission and in non-metabolic remission (p = 0.082). In the chemoradiotherapy group, there was no significant difference in PFS (P = 0.185) or OS (P = 0.627) between patients in metabolic remission and in non-metabolic remission. I-PET after chemotherapy yields higher discriminative power and has the ability for prognostic prediction in nasal-type ENKTL patients. I-PET after radiochemotherapy has no prognostic value. Thus, the appropriate timing for I-PET is after chemotherapy but before radiotherapy for response evaluation in nasal-type ENKTL patients.

Risk of malignancy in incidental oropharyngeal lesions exhibiting fluorodeoxyglucose uptake which proceed to tissue biopsy

BACKGROUND

Utilization of positron emission tomography/computed tomography (PET/CT) with fluorodeoxyglucose is increasing in use for a variety of indications, including surveillance of cancer patients. There is a paucity of evidence pertaining to the significance of incidental PET-avid oropharyngeal lesions. This study aims to examine the clinical and radiological features of these incidental oropharyngeal lesions in patients undergoing PET for indications other than head and neck cancer.

METHODS

Retrospective cohort study of three Australian tertiary hospitals, from 2015 to 2021, on adult patients undergoing biopsy of incidental PET-avid oropharyngeal lesions. Primary outcome of interest was the incidence of malignancy. Patients with a previous history of, or undergoing investigations for, head and neck cancer were excluded.

RESULTS

Thirty-one patients were included, wherein 21 patients had tonsillar uptake, and 13 patients had base of tongue uptake. Tonsillar disease was mostly asymmetrical (n = 15/21), bilateral (n = 11/21), and had median SUVmax 9.35 (n = 12, IQR 7.4-11.15). Base of tongue was mostly asymmetrical (n = 7/13, 54%), bilateral (n = 8/13, 62%), and had median SUVmax 8.2 (n = 10, IQR 6.9-12.65). Seven patients had malignancy confirmed on tissue biopsy: five biopsies confirmed the tissue diagnosis of suspected lymphoma, and two incidental findings of unexpected malignancies: one p16 positive tonsillar squamous cell carcinoma, and one metastatic breast cancer.

CONCLUSION

In 31 patients undergoing tissue biopsy for incidental PET-avid oropharyngeal lesions, there were two unexpected malignancies. Our study results indicate that although unexpected malignancies are uncommon, a malignant diagnosis cannot be excluded from clinical features alone.

PET/MR Imaging in Head and Neck Cancer

Head and neck squamous cell carcinoma (HNSCC) can either be examined with hybrid PET/MR imaging systems or sequentially, using PET/CT and MR imaging. Regardless of the acquisition technique, the superiority of MR imaging compared to CT lies in its potential to interrogate tumor and surrounding tissues with different sequences, including perfusion and diffusion. For this reason, PET/MR imaging is preferable for the detection and assessment of locoregional residual/recurrent HNSCC after therapy. In addition, MR imaging interpretation is facilitated when combined with PET. Nevertheless, distant metastases and distant second primary tumors are detected equally well with PET/MR imaging and PET/CT.

Deep Learning-Based Feature Extraction from Whole-Body PET/CT Employing Maximum Intensity Projection Images: Preliminary Results of Lung Cancer Data

Purpose

Deep learning (DL) has been widely used in various medical imaging analyses. Because of the difficulty in processing volume data, it is difficult to train a DL model as an end-to-end approach using PET volume as an input for various purposes including diagnostic classification. We suggest an approach employing two maximum intensity projection (MIP) images generated by whole-body FDG PET volume to employ pre-trained models based on 2-D images.

Methods

As a retrospective, proof-of-concept study, 562 [18F]FDG PET/CT images and clinicopathological factors of lung cancer patients were collected. MIP images of anterior and lateral views were used as inputs, and image features were extracted by a pre-trained convolutional neural network (CNN) model, ResNet-50. The relationship between the images was depicted on a parametric 2-D axes map using t-distributed stochastic neighborhood embedding (t-SNE), with clinicopathological factors.

Results

A DL-based feature map extracted by two MIP images was embedded by t-SNE. According to the visualization of the t-SNE map, PET images were clustered by clinicopathological features. The representative difference between the clusters of PET patterns according to the posture of a patient was visually identified. This map showed a pattern of clustering according to various clinicopathological factors including sex as well as tumor staging.

Conclusion

A 2-D image-based pre-trained model could extract image patterns of whole-body FDG PET volume by using anterior and lateral views of MIP images bypassing the direct use of 3-D PET volume that requires large datasets and resources. We suggest that this approach could be implemented as a backbone model for various applications for whole-body PET image analyses.

The ptotic tongue-imaging appearance and pathology localization along the course of the hypoglossal nerve

CT and MRI findings of tongue ptosis and atrophy should alert radiologists to potential pathology along the course of the hypoglossal nerve (cranial nerve XII), a purely motor cranial nerve which supplies the intrinsic and extrinsic muscles of the tongue. While relatively specific for hypoglossal nerve pathology, these findings do not accurately localize the site or cause of denervation. A detailed understanding of the anatomic extent of the nerve, which crosses multiple anatomic spaces, is essential to identify possible underlying pathology, which ranges from benign postoperative changes to life-threatening medical emergencies. This review will describe key imaging findings of tongue denervation, segmental anatomy of the hypoglossal nerve, imaging optimization, and comprehensive imaging examples of diverse pathology which may affect the hypoglossal nerve. Armed with this knowledge, radiologists will increase their sensitivity for detection of pathology and provide clinically relevant differential diagnoses when faced with findings of tongue ptosis and denervation.

The Role of Positron Emission Tomography for the Management of Sinonasal Malignancies: A Systematic Review

BACKGROUND

Positron emission tomography (PET) scan is a valuable imaging modality widely used in the management of cancers. Its usage is well defined for most head and neck malignancies. However, there is a lack of consensus regarding the utility of PET scan for sinonasal malignancies. This is highlighted by the latest international consensus statement on endoscopic skull base surgery.

OBJECTIVE

This systematic review aims to clarify the role of PET scan in the management of sinonasal malignancies.

METHODS

We conducted a comprehensive literature search using PubMed, MEDLINE, EMBASE, Web of Science, CINAHL, and Cochrane databases for research studies of interest. The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) updated statement was used to guide the review.

RESULTS

In total, 1807 articles were assessed for eligibility. Thirty-nine original papers, published between 2004 and 2021, met inclusion criteria. Seven articles focused on the role of PET scan for inverted papilloma, 23 for sinonasal carcinoma, 4 for melanoma, and 3 for lymphoma, and finally, 3 articles focused on the use of specific PET scan tracers for sinonasal malignancies. Qualitative summaries for each potential role of PET scans were provided. In general, included studies were retrospective in nature with low level of evidence.

CONCLUSIONS

In general, and across all types of sinonasal malignancies, PET scan yielded positive results regarding detection and initial staging. It was also considered as the modality of choice for detection of distant metastases, except in the case of sinonasal lymphoma. PET scan's main limit resides in its inability to detect lesions in or close to the metabolic activity of the brain.

Prognostic Utility of Neck Lymph Node-to-Primary Tumor Standardized Uptake Value Ratio in Oral Cavity Cancer

We investigated the prognostic utility of preoperative neck lymph node-to-primary tumor maximum standardized uptake value ratios (NTRs) in oral cavity squamous cell carcinoma (OSCC). We retrospectively reviewed the medical records of 141 consecutive patients who were diagnosed as having OSCC and had received fluorodeoxyglucose-positron emission tomography within 2 weeks prior to radical surgery between 2009 and 2018. To determine the optimal NTR cutoff, receiver operating characteristic analysis for overall survival (OS) was executed. The NTR's prognostic value for disease-free survival (DFS) and OS were determined through Cox proportional hazards analysis and the Kaplan-Meier method. We determined the median (range) follow-up duration to be 35.2 (2.1-122.4) months. The optimal NTR cutoff was 0.273, and patients with a higher NTR (≥0.273) exhibited significantly worse DFS and OS (p = 0.010 and 0.003, respectively). A higher NTR (≥0.273) predicted poorer DFS (hazard ratio: 2.696, p = 0.008) and OS (hazard ratio: 4.865, p = 0.003) in multivariable analysis. We created a nomogram on the basis of the NTR, and it could accurately predict OS (concordance index: 0.774). Preoperative NTRs may be a useful prognostic biomarker for DFS and OS in patients with OSCC who have undergone surgery. NTR-based nomograms may also be helpful prognostic tools in clinical trials.

FDG Localization in Acellular Dermal Matrix, a Potential Cause of Nonpernicious Uptake Following Breast Reconstruction Surgery

ABSTRACT

A 47-year-old woman with invasive lobular carcinoma of the left breast underwent prophylactic double mastectomy which also incidentally revealed follicular lymphoma of the right breast. Reconstruction was achieved with bilateral silicone implants and acellular dermal matrix (ADM), a biological scaffold material providing mechanical support. Twelve days thereafter, staging PET/CT demonstrated symmetric moderate FDG uptake corresponding to location of the ADM slings, suspected to reflect cellular engraftment onto the ADM and confirmed by near-complete resolution at 3-month follow-up study. FDG uptake related to ADM should be recognized as reflecting expected cellular incorporation into the matrix, rather than recurrent tumor or infection.

FAPI PET/CT Imaging-An Updated Review

Despite revolutionizing the field of oncological imaging, Positron Emission Tomography (PET) with [¹⁸F]Fluorodeoxyglucose (FDG) as its workhorse is limited by a lack of specificity and low sensitivity in certain tumor subtypes. Fibroblast activation protein (FAP), a type II transmembrane glycoprotein, is expressed by cancer-associated fibroblasts (CAFs) that form a major component of the tumor stroma. FAP holds the promise to be a pan-cancer target, owing to its selective over-expression in a vast majority of neoplasms, particularly epithelial cancers. Several radiolabeled FAP inhibitors (FAPI) have been developed for molecular imaging and potential theranostic applications. Preliminary data on FAPI PET/CT remains encouraging, with extensive multi-disciplinary clinical research currently underway. This review summarizes the existing literature on FAPI PET/CT imaging with an emphasis on diagnostic applications, comparison with FDG, pitfalls, and future directions.

Preoperative Determination of Depth of Invasion in Oral Cavity Squamous Cell Carcinoma by Standard Cross-Sectional Imaging With Computed Tomography and Positron Emission Tomography/Computed Tomography

Background Depth of invasion (DOI) is a known indicator of metastatic potential in oral cavity squamous cell carcinoma (SCC). Our purpose was to investigate the accuracy of preoperative determination of DOI in oral cavity SCC by computed tomography (CT) and positron emission tomography/computed tomography (PET/CT). Methodology A retrospective study was performed using consecutive patients with histologically proven oral cavity SCC presenting to our otorhinolaryngology department between January 2014 and July 2019 who underwent preoperative contrast-enhanced CT and/or PET/CT. Pathological assessment of DOI was determined by a review of pathology reports. The degree of DOI determined by radiographic studies was correlated to pathology results. Results A total of 79 patients were screened of whom appropriate radiographic studies were available for 63 patients. The mean DOI by pathological assessment was 12.3 ± 9.1 mm. CT and PET/CT determined depth both correlated with pathological DOI (r = 0.710; p < 0.001, r = 0.798; p < 0.001). No significant correlation was seen for CT-determined depth (r = 0.136; p = 0.709) or PET-determined depth (r = 0.234; p = 0.707) with pathologically confirmed superficial tumors (<5 mm). For patients with pathological tumor depth >10 mm, CT and PET determined depth both correlated with pathological depth (r = 0.577; p = 0.002, r = 0.668; p = 0.001). The sensitivity and specificity of CT and PET for the identification of deep invasion were 88.2% and 41.7% and 52.9% and 50%, respectively. Conclusions DOI measurement is feasible with routine preoperative CT and PET/CT images and is comparable to pathological measurement in patients with oral cavity SCC.

PET-CT detection of local residual laryngeal carcinoma after definitive (chemo)radiotherapy

BACKGROUND

Positron emission tomography and computed tomography (PET-CT) is currently recommended in evaluating the treatment response after (chemo)radiotherapy ([C]RT). In the larynx, post-treatment changes and physiological uptake make image interpretation more challenging compared to other head and neck sites. Previous research has not addressed imaging factors specifically in the larynx that would help in distinguishing the residual disease and explain the unique challenges of that anatomic area. The study cohorts are small and heterogenous. Our objective was to investigate the ability of PET-CT in diagnosing local residual laryngeal carcinoma, and to uncover imaging factors that could be used in differentiating the residual disease from post-treatment and physiological changes. In the same study cohort, we also aimed to uncover prognostic factors for local residual or recurrent disease.

METHODS

Our retrospective study cohort included 73 patients with T2-T4 laryngeal carcinoma undergoing (C)RT with curative intention, and post-treatment non-contrast-enhanced PET-CT at 2-6 months. Findings were compared between local residual and non-residual disease. Local residual disease was defined as a persistent tumor growth with no evidence of remission in between, confirmed by biopsy, and evident within 6 months from the end of RT. PET-CT was evaluated using a 3-step scale: negative, equivocal, and positive.

RESULTS

Nine (12%) had a local residual tumor and 11 (15%) developed local recurrence, based on the biopsy. The median follow-up of surviving patients was 64 months (range, 28-174). In univariate analysis, primary tumor diameter greater than 2.4 cm (median value), and vocal cord fixation were prognostic for local residual or recurrent disease. Sensitivity, specificity, PPV, and NPV were 100%, 75%, 36%, and 100%, respectively, when the equivocal interpretation was grouped with the positive interpretation. All local residuals, and 28% (18/64) non-residuals, had a primary tumor area SUV_max of over 4.0 (p < 0.001). CT showed a persistent mass at the primary tumor area in 56% of residuals, and in 23% of non-residuals (p > 0.05). By combining SUV_max>4.0 and mass, specificity improved to 91%.

CONCLUSIONS

NPV of post-treatment PET-CT in laryngeal carcinoma is high, but equivocal and positive results have low PPV and require further diagnostics. All local residuals had SUV_max over 4.0. The combination of SUV_max over 4.0 and mass on CT increased specificity, but the sensitivity was low.

COVID-19: Findings in nuclear medicine from head to toe

COVID-19 is a multisystemic disease, and hence its potential manifestations on nuclear medicine imaging can extend beyond the lung. Therefore, it is important for the nuclear medicine physician to recognize these manifestations in the clinic. While FDG-PET/CT is not indicated routinely in COVID-19 evaluation, its unique capability to provide a functional and anatomical assessment of the entire body means that it can be a powerful tool to monitor acute, subacute, and long-term effects of COVID-19. Single-photon scintigraphy is routinely used to assess conditions such as pulmonary embolism, cardiac ischemia, and thyroiditis, and COVID-19 may present in these studies. The most common nuclear imaging finding of COVID-19 vaccination to date is hypermetabolic axillary lymphadenopathy. This may pose important diagnostic and management dilemmas in oncologic patients, particularly those with malignancies where the axilla constitutes a lymphatic drainage area. This article aims to summarize the relevant literature published since the beginning of the pandemic on the intersection between COVID-19 and nuclear medicine.

Diagnostic Assessment (Imaging) and Staging of Laryngeal Cancer

Diagnosis of larynx cancer relies on a detailed history and physical and objective assessment with endoscopy and imaging. Endoscopy is needed to assess for vocal fold function that directly affects staging. Computed tomography and MRI can be used to assess for tumor extent in relation to intra- and extra-laryngeal structures, especially paraglottic and pre-epiglottic space involvement as well as cartilage invasion. Accurate staging is critical for subsequent treatment decision-making regarding larynx preservation.

18F-fluorodeoxyglucose positron emission tomography findings of peripheral nerve sheath tumour of the nasal cavity in a dog

An 8-year-old Miniature Poodle presented with chronic sneezing and unilateral epistaxis. A left-sided intranasal mass was identified on computed tomography. 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) was performed to evaluate the metabolic activity of the mass. The intranasal mass showed mildly increased 18F-FDG uptake. The maximal and mean standardized uptake values (SUVs) of the mass were 3.4 and 2.6, respectively. The maximal SUV of the mass/mean SUV of the normal liver was 2.5. The 7-cm soft, pink mass was easily removed through rhinoscopy, with subsequent dramatic improvement in clinical signs. Histopathological and immunohistochemical analyses determined that the mass was an intermediate-grade malignant peripheral nerve sheath tumour (PNST). This is the first report of 18F-FDG PET findings in a PNST in dogs.

F18-FDG PET/CT accuracy in nodal staging of head and neck squamous cell carcinoma and correlation of SUVmax to the likelihood of a confirmed nodal metastasis

INTRODUCTION

This study aimed to determine F18-Fluorodeoxyglucose Positron Emission Tomography/ Computerised Tomography (FDG-PET/CT) accuracy in nodal staging of head and neck squamous cell carcinoma (HNSCC) and investigate the relationship between increasing standard uptake value max (SUV_max) thresholds and the likelihood of a diagnosis of nodal malignancy on histopathological analysis.

METHODS

Histopathological diagnosis was correlated retrospectively with the reported nodal involvement on PET/CT scans. Data was analysed to determine the accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV). SUV_max was measured for the most FDG-avid node in the nodal levels noted to be malignant on histopathological analysis and for those deemed malignant in the PET/CT report. A range of SUV_max thresholds was then applied retrospectively to calculate the corresponding likelihood of a node being truly malignant.

RESULTS

The "per lymph node level" analysis (n=216) found accuracy of 81.5%, sensitivity of 68.8%, specificity of 85.1%, PPV of 59.9% and NPV of 90.5%. A strong positive correlation was found between the threshold SUV_max and the likelihood of a diagnosis of malignancy on histopathological analysis. A significant increase in likelihood from 72.2% to 83.3% was found when the SUV_max threshold was increased from 4.0 to 4.5.

CONCLUSION

This study reinforces the utility of PET/CT as a diagnostic tool for ruling out malignant nodal dissemination due to its high NPV. Secondly, it shows a strong positive correlation between SUV_max of the lymph node and its likelihood of being malignant, which may assist in determining which lymph nodes should be biopsied.

Incidental FDG-Avid Focuses in Palatine Tonsils on PET/CT

OBJECTIVES

The management of incidental findings of FDG-avid tonsils on PET/CT (IFT) is unclear. We aimed to explore the prevalence of malignancy in IFT, identify risk factors for malignancy, and calculate optimal cutoffs of maximum standardized uptake values (SUV_max ) to discriminate between benign and malignant lesions.

METHODS

All patients who were tonsillectomized at our institution because of IFT from October 2011 to December 2020 were included. Patients undergoing PET/CT due to suspected tonsillar disease or cancer of unknown primary were excluded.

RESULTS

In total, 77 patients were included, of which 11 (14%) of them had IFT malignancy. Dysphagia (p = 0.019) and alcohol abuse (p = 0.035) were associated with malignancy. Absolute SUV_max cutoff (≥9: sensitivity 100%; specificity 53%) was superior to SUV_max side-to-side ratio (≥1.5: sensitivity 64%; specificity 70%) to discriminate between benign and malignant lesions.

CONCLUSION

We recommend tonsillectomy for patients with IFT displaying SUV_max  ≥ 9.0, ratio ≥ 1.5, or symptoms or findings suggesting malignancy.

LEVEL OF EVIDENCE

3 Laryngoscope, 132:2370-2378, 2022.

Emerging Biomaterials Imaging Antitumor Immune Response

Immunotherapy is one of the most promising clinical modalities for the treatment of malignant tumors and has shown excellent therapeutic outcomes in clinical settings. However, it continues to face several challenges, including long treatment cycles, high costs, immune-related adverse events, and low response rates. Thus, it is critical to predict the response rate to immunotherapy by using imaging technology in the preoperative and intraoperative. Here, the latest advances in nanosystem-based biomaterials used for predicting responses to immunotherapy via the imaging of immune cells and signaling molecules in the immune microenvironment are comprehensively summarized. Several imaging methods, such as fluorescence imaging, magnetic resonance imaging, positron emission tomography imaging, ultrasound imaging, and photoacoustic imaging, used in immune predictive imaging, are discussed to show the potential of nanosystems for distinguishing immunotherapy responders from nonresponders. Nanosystem-based biomaterials aided by various imaging technologies are expected to enable the effective prediction and diagnosis in cases of tumors, inflammation, and other public diseases.

Imaging of human papilloma virus associated oropharyngeal squamous cell carcinoma and its impact on diagnosis, prognostication, and response assessment

The clinical behaviour and outcomes of patients with oropharyngeal cancer (OPC) may be dichotomised according to their association with human papilloma virus (HPV) infection. Patients with HPV-associated disease (HPV+OPC) have a distinct demographic profile, clinical phenotype and demonstrate considerably better responses to chemoradiotherapy. This has led to a reappraisal of staging and treatment strategies for HPV+OPC, which are underpinned by radiological data. Structural modalities, such as CT and MRI can provide accurate staging information. These can be combined with ultrasound-guided tissue sampling and functional techniques (such as diffusion-weighted MRI and 18F-fludeoxyglucose positron emission tomography-CT) to monitor response to treatment, derive prognostic information, and to identify individuals who might benefit from intensification or deintensification strategies. Furthermore, advanced MRI techniques, such as intravoxel incoherent motion and perfusion MRI as well as application of artificial intelligence and radiomic techniques, have shown promise in treatment response monitoring and prognostication. The following review will consider the contemporary role and knowledge on imaging in HPV+OPC.

Changes in Apparent Diffusion Coefficient (ADC) in Serial Weekly MRI during Radiotherapy in Patients with Head and Neck Cancer: Results from the PREDICT-HN Study

Background: The PREDICT-HN study aimed to systematically assess the kinetics of imaging MR biomarkers during head and neck radiotherapy. Methods: Patients with intact squamous cell carcinoma of the head and neck were enrolled. Pre-, during, and post-treatment MRI were obtained. Serial GTV and ADC measurements were recorded. The correlation between each feature and the GTV was calculated using Spearman’s correlation coefficient. The linear mixed model was used to evaluate the change in GTV over time. Results: A total of 41 patients completed the study. The majority (76%) had oropharyngeal cancer. A total of 36 patients had intact primary tumours that can be assessed on MRI, and 31 patients had nodal disease with 46 nodes assessed. Median primary GTV (GTVp) size was 14.1cc. The rate of GTVp shrinkage was highest between pre-treatment and week 4. Patients with T3-T4 tumours had a 3.8-fold decrease in GTVp compared to T1-T2 tumours. The ADC values correlated with residual GTVp. The median nodal volume (GTVn) was 12.4cc. No clinical features were found to correlate with GTVn reduction. The overall change in ADC for GTVn from pre-treatment was significant for 35th−95th percentiles in weeks 1−4 (p < 0.001). Conclusion: A discrepancy in the trajectory of ADC between primary and nodal sites suggested that they exhibit different treatment responses and should be analysed separately in future studies.

Prognostic Value of Urokinase-Type Plasminogen Activator Receptor PET/CT in Head and Neck Squamous Cell Carcinomas and Comparison with 18F-FDG PET/CT: A Single-Center Prospective Study

The aim of this phase II clinical trial (NCT02965001) was to evaluate the prognostic value of urokinase-type plasminogen activator receptor (uPAR) PET/CT with the novel ligand ⁶⁸Ga-NOTA-AE105 in head and neck cancer and compare it with ¹⁸F-FDG. Methods: Patients with head and neck squamous cell carcinoma referred for curatively intended radiotherapy were eligible and prospectively included in this study. ⁶⁸Ga-uPAR and ¹⁸F-FDG PET/CT were performed before initiation of curatively intended radiotherapy, and the SUV_max of the primary tumor was measured on both PET/CT studies by 2 independent readers. Relapse-free survival (RFS) and overall survival (OS) were calculated, and optimal cutoffs were established for ⁶⁸Ga-uPAR and ¹⁸F-FDG PET independently and compared using log rank and Kaplan-Meier statistics, as well as univariate and multivariate analysis in a Cox proportional-hazards model. Results: In total, 57 patients were included and followed for a median of 33.8 mo (range, 2.30-47.2, mo). The median SUV_max of the primary tumors was 2.98 (range, 1.94-5.24) for ⁶⁸Ga-uPAR and 15.7 (range, 4.24-45.5) for ¹⁸F-FDG. The optimal cutoffs for ⁶⁸Ga-NOTA-AE105 SUV_max in the primary tumor were 2.63 for RFS and 2.66 for OS. A high uptake of ⁶⁸Ga-NOTA-AE105 (SUV_max above cutoff) was significantly associated with poor RFS and OS (log-rank P = 0.012 and P = 0.022). ⁶⁸Ga-NOTA-AE105 uptake in the primary tumor was significantly associated with poor RFS in univariate analysis (hazard ratio [HR], 8.53 [95% CI, 1.12-64.7]; P = 0.038), and borderline-associated with OS (HR, 7.44 [95% CI, 0.98-56.4]; P = 0.052). For ¹⁸F-FDG PET, the optimal cutoffs were 22.7 for RFS and 22.9 for OS. An ¹⁸F-FDG SUV_max above the cutoff was significantly associated with reduced RFS (log-rank P = 0.012) and OS (log-rank P = 0.000). ¹⁸F-FDG uptake was significantly associated with reduced RFS (HR, 3.27 [95% CI, 1.237-8.66]; P = 0.017) and OS (HR, 7.10 [95% CI, 2.60-19.4]; P < 0.001) in univariate analysis. In a multivariate analysis including ⁶⁸Ga-uPAR SUV_max, ¹⁸F-FDG SUV_max, TNM stage, and p16 status, only ⁶⁸Ga-uPAR SUV_max remained significant (HR, 8.51 [95% CI, 1.08-66.9]; P = 0.042) for RFS. For OS, only TNM stage and ¹⁸F-FDG remained significant. Conclusion: The current trial showed promising results for the use of ⁶⁸Ga-uPAR PET SUV_max in the primary tumor to predict RFS in head and neck squamous cell carcinoma patients referred for curatively intended radiotherapy when compared with ¹⁸F-FDG PET, TNM stage, and p16 status. ⁶⁸Ga-uPAR PET could potentially become valuable for identification of patients suited for deescalation of treatment and risk-stratified follow-up schemes.

Response Evaluation Following Radiation Therapy With 18F-FDG PET/CT: Common Variants of Radiation-Induced Changes and Potential Pitfalls

Radiation therapy (RT) is one of the cornerstones in cancer treatment and approximately half of all patients will receive some form of RT during the course of their cancer management. Response evaluation after RT and follow-up imaging with ¹⁸F-Fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) can be complicated by RT-induced acute, chronic or consequential effects. There is a general consensus that ¹⁸F-FDG PET/CT for response evaluation should be delayed for 12 weeks after completing RT to minimize the risk of false-positive findings. Radiation-induced late side effects in normal tissue can take years to develop and eventually cause symptoms that on imaging can potentially mimic recurrent disease. Imaging findings in radiation induced injuries depend on the normal tissue included in the irradiated volume and the radiation therapy regime including the total dose delivered, dose per fraction and treatment schedule. The intent for radiation therapy should be taken in consideration when evaluating the response on imaging, that is palliative vs curative or neoadjuvant vs adjuvant RT. Imaging findings can further be distorted by altered anatomy and sequelae following surgery within the radiation field. An awareness of common PET/CT-induced changes/injuries is essential when interpreting ¹⁸F-FDG PET/CT as well as obtaining a complete medical history, as patients are occasionally scanned for an unrelated cause to previously RT treated malignancy. In addition, secondary malignancies due to carcinogenic effects of radiation exposure in long-term cancer survivors should not be overlooked. ¹⁸F-FDG PET/CT can be very useful in response evaluation and follow-up in patients treated with RT, however, variants and pitfalls are common and it is important to remember that radiation-induced injury is often a diagnosis of exclusion.

Adenoid Cystic Carcinoma of the Breast: A Case Report

Adenoid cystic carcinoma (ACC), characterized by proliferating glands and stromal and basement membrane elements, is a tumor most commonly occurring in the salivary glands; very rarely does this tumor present as a primary tumor in the breast. We present the case of a 53-year-old female who presented with a breast mass noted to be concerning on imaging and confirmed to be ACC on biopsy. The mass was amenable to surgical excision with referrals to medical and radiation oncology. Due to the rarity of the disease, there is no consensus regarding the optimal treatment strategy for the pathology, including the use of chemotherapy and radiation. Long-term follow-up is, however, recommended in order to monitor for recurrence.

Transoral robotic surgery for the identification of unknown primary head and neck squamous cell carcinomas: Its effect on the wait and the weight

BACKGROUND

Neck carcinoma of unknown primary (CUP) is a frequent scenario. Transoral robotic mucosectomies (TORM) of pharynx have increased rate of primary identification, but come with cost of treatment delay.

METHODS

We reviewed patients who underwent CUP protocol from 2014 to 2020. Patients with cervical nodes carcinoma and failure to localize a primary source were classified as CUP. We determined primary identification rate and postoperative complications.

RESULTS

We included 65 patients underwent TORM. Surgical approach consisted of lingual and/or palatine tonsillectomies. The primary detection rate was 49.2%. Average weight reduction was 2.5 ± 4.3 kg. The average number of days from consultation to definitive treatment was 52.2 ± 18.3.

CONCLUSION

A systematic approach to patients with CUP showed a promising primary identification rate compared to panendoscopy alone. TORM carries a small risk of complications. The benefits of primary identification must be weighed with the morbidity and delay to definitive treatment.

18F-FES PET/CT Improves the Detection of Intraorbital Metastases in Estrogen-Receptor-Positive Breast Cancer: Two Representative Cases and Review of the Literature

Orbital metastases are a rare but life-altering complication in cancer. Most commonly seen in breast cancer, metastases to the optic nerves or extraocular muscles can have a devastating impact on visual acuity and quality of life. Hormone receptor status plays a central role in metastatic breast cancer treatment, with endocrine therapy often representing first-line therapy in hormone-receptor-positive cancers. Staging and treatment response evaluation with positron emission tomography (PET) computed tomography (CT) imaging with 18F-fluorodeoxyglucose (18F-FDG) is limited by high physiologic uptake in the intracranial and intraorbital compartments. Thus, traditional staging scans with 18F-FDG PET/CT may under-detect intraorbital and intracranial metastatic disease and inaccurately evaluate active metastatic disease burden. In comparison, 18F-fluoroestradiol (18F-FES) is a novel estrogen-receptor-specific PET radiotracer, which more accurately assesses the intracranial and intraorbital compartments in patients with estrogen-receptor-positive (ER+) cancers than 18F-FDG, due to lack of physiologic background activity in these regions. We present two cases of breast cancer patients with orbital metastases confirmed on MR imaging who underwent PET/CT imaging with 18F-FES and 18F-FDG. Multimodality imaging with 18F-FES PET/CT offers higher detection sensitivity of orbital metastases, compared with traditional 18F-FDG PET/CT imaging, and can improve the assessment of treatment response in patients with estrogen-receptor-positive (ER+) cancers.

Secondary thyroid malignancy - a rare clinical finding?

Metastases to the thyroid gland, while rarely seen in clinical practice, can pose a diagnostic and therapeutic challenge. Most commonly, they originate from lung, renal, and breast cancer, and are generally a sign of multiorgan metastatic disease. In most cases, metastases to the thyroid gland are diagnosed incidentally on imaging studies, since they are rarely symptomatic and often do not influence thyroid function tests. Thyroid ultrasonography and fine-needle aspiration biopsy play a pivotal role in their evaluation, as both classic immunocytochemical features, and more novel molecular markers can help in the differential diagnosis. Prognosis mainly depends on the biology of the primary tumor and its extension. Communication between clinicians is essential in such patients, in order to ensure that the treatment options are carefully balanced, thus raising the need for multidisciplinary teams in their management.

18F-FDG-PET/CT interpretation pitfalls in patients with head and neck cancer

AIM

The aim of the present study is to raise awareness of ENT Surgeons on the limitations of ¹⁸F-FDG PET/CT in head and neck cancer by presenting illustrative cases from our department archives.

MATERIALS AND METHODS

A retrospective chart review was conducted for all patients with head and neck cancer treated in our ENT department from 2015 to 2020. Cases with various interpretation pitfalls due to false-positive and false-negative PET/CT results that lead to diagnostic dilemmas and treatment delays either in their pre-therapeutic work-up or in their post-therapeutic monitoring were included.

RESULTS

Five cases of various image interpretation pitfalls (3 false negative and 2 false positive cases) were identified and are presented in detail.

CONCLUSIONS

Although ¹⁸F-FDG PET/CT has gained in popularity and improved head and neck cancer management, clinicians should be aware of its limitations. The combination of ¹⁸F-FDG PET/CT with other imaging modalities can reduce the number of interpretation pitfalls but by no means will substitute sound clinical judgement.

PET/CT and PET/MR Imaging of the Post-treatment Head and Neck: Traps and Tips

PET/computed tomography and PET/MR imaging are used to evaluate the post-treatment neck. Although 18F-FDG is helpful in the staging and treatment response assessment of head and neck cancer, recently developed PET radiotracers targeting specific surface markers are promising for applications of diagnostic problem solving and improved extent delineation. Diffusion-weighted MR imaging is helpful in the differential diagnosis of head and neck neoplasms, and improves the sensitivity and specificity for the detection of certain pathologies. Following standardized imaging parameters for PET/computed tomography and diffusion-weighted imaging in PET/MR imaging improves diagnostic accuracy and allows for future research data mining.

MR Imaging of Salivary Gland Tumors

Neoplasms of the salivary glands are characterized by their marked histologic diversity giving them nonspecific imaging findings. MR imaging is the best imaging modality to evaluate salivary gland tumors. Multiparametric MR imaging combines conventional imaging features, diffusion-weighted imaging, and perfusion imaging to help distinguish benign and low-grade neoplasms from malignant tumors; however, a biopsy is often needed to establish a definitive histopathologic diagnosis. An awareness of potential imaging pitfalls is important to prevent mistakes in salivary neoplasm imaging.

Incidental uptake of fluorodeoxyglucose in the Waldeyer's ring and risk of oropharyngeal malignancy

PURPOSE

Fluorodeoxyglucose (FDG) positron emission tomography (PET) is increasingly used to diagnose and stage malignancy. The aim of this article is to investigate the significance of incidental FDG uptake in the Waldeyer's ring and to assess its value in predicting clinically occult oropharyngeal malignancy.

METHODS

All FDG-PET/CT scans performed in Imperial College NHS Foundation Trust, UK between January 2012 and November 2018 were included. Patients with known or suspected oropharyngeal malignancy or lymphoma were excluded. Minimum follow-up was 12 months.

RESULTS

A total of 724 scans revealed oropharyngeal uptake of FDG. Of these, 102 were included in the study. Most patients (62.1%) were scanned as part of staging for other malignancies. Oropharyngeal FDG uptake was asymmetrical in 57.3% of the cases. Uptake was more common in the tonsils (56.3%), followed by the tongue base (31.1%) and both sites (12.6%). In 41.7% of reports, appearance was described as likely physiological; however, 52.4% of reports advised direct visualisation, clinical correlation or ENT opinion. Only 24.3% (25/102) of patients were referred and seen by ENT, 14.6% (15/102) of which had an interval PET scan and 8.7% (9/102) proceeded to tissue diagnosis. There was one oropharyngeal cancer identified and one unexpected metastasis from esophageal cancer.

CONCLUSION

Incidental uptake on PET/CT in the oropharynx is common. However, malignancy is rare (1.9%) and, when present, is associated with high SUVmax and asymmetrical uptake. Imaging results must be correlated clinically. These patients should be seen by an ENT specialist yet most may not require further investigations.

Whole-body hybrid positron emission tomography imaging yields clinically relevant information in the staging and restaging of sinonasal tumors

Background

Whole‐body hybrid positron emission tomography (PET) imaging is increasingly used for sinonasal tumors. However, only empirical data exist on the additional, clinically relevant information derived from these techniques.

Methods

This study included 96 regionalized magnetic resonance imaging (MRI) of the sinonasal tract/neck and separate hybrid FDG‐PET/CT or FDG‐PET/MRI in 74 patients. Additional radiological information (ARI) obtained from each hybrid examination was analyzed and its clinically relevance was determined. Clinically relevant information (CRI) was categorized with regard to primary tumor site, regional lymph node metastases, distant metastases, second primary tumors, and non‐neoplastic findings.

Results

A total of 45/96 (46.9%) hybrid PET examinations revealed ARI. CRI was found in 32/96 (33.3%) examinations and concerned the primary tumor site (6.1%), regional lymph node metastases (4.1%), distant metastases (14.3%), second primary tumors (7.3%), and non‐neoplastic findings (5.1%).

Conclusions

Hybrid PET imaging yields additional radiological information translating into clinically relevant information in a substantial proportion of patients with sinonasal tumors.

18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in Postsurgical Setting in Head and Neck Cancers - A Pictorial Essay

This pictorial essay depicts normal appearances, complications, and findings of residual and/or recurrent disease on fluorodeoxyglucose positron emission tomography/computed tomography (18F- FDG PET/CT) studies in the postsurgical setting. Reading and reporting 18F- FDG PET/CT in the postoperative scenario is demanding due to the multiple false positives seen during this period. This article which contains two parts will familiarize the readers with the normal appearance and pitfalls seen in 18F- FDG PET/CT studies during the postoperative period so as to avoid misinterpretations. This pictorial will discuss 18F- FDG PET/CT in the postoperative scenario in head and neck cancers.

Oral findings during follow-up of nasopharyngeal squamous cell carcinoma treatment: A case report

A 50-year-old woman with a long history of nasopharyngeal cancer (T2N2M0, squamous cell carcinoma) underwent chemoradiotherapy and surgery. In the past, to prevent tumor recurrence or metastasis, she underwent concurrent chemoradiotherapy or neck dissection. However, during a follow-up 10 years after the surgery, intense F-18 fluorodeoxyglucose uptake was detected in the oral area (SUVmax 6.0). A biopsy of the area with F-18 fluorodeoxyglucose uptake revealed pathological inflammation. Radiography showed the presence of a wisdom tooth, located at the F-18 fluorodeoxyglucose accumulation site, and pericoronitis of this tooth was detected. Our findings indicate the importance of considering the effect of inflammatory conditions, such as periodontal disease, in using F-18 fluorodeoxyglucose positron emission tomography/computed tomography during follow-up after head and neck cancer treatment.

Limitations and Pitfalls of FDG-PET/CT in Infection and Inflammation

White blood cells activated by either a pathogen or as part of a systemic inflammatory disease are characterized by high energy consumption and are therefore taking up the glucose analogue PET tracer FDG avidly. It is therefore not surprising that a steadily growing body of research and clinical reports now supports the use of FDG PET/CT to diagnose a wide range of patients with non-oncological diseases. However, using FDG PET/CT in patients with infectious or inflammatory diseases has some limitations and potential pitfalls that are not necessarily as pronounced in oncology FDG PET/CT. Some of these limitations are of a general nature and related to the laborious acquisition of PET images in patients that are often acutely ill, whereas others are more disease-specific and related to the particular metabolism in some of the organs most commonly affected by infections or inflammatory disease. Both inflammatory and infectious diseases are characterized by a more diffuse and less pathognomonic pattern of FDG uptake than oncology FDG PET/CT and the affected organs also typically have some physiological FDG uptake. In addition, patients referred to PET/CT with suspected infection or inflammation are rarely treatment naïve and may have received varying doses of antibiotics, corticosteroids or other immune-modulating drugs at the time of their examination. Combined, this results in a higher rate of false positive FDG findings and also in some cases a lower sensitivity to detect active disease. In this review, we therefore discuss the limitations and pitfalls of FDG PET/CT to diagnose infections and inflammation taking these issues into consideration. Our review encompasses the most commonly encountered inflammatory and infectious diseases in head and neck, in the cardiovascular system, in the abdominal organs and in the musculoskeletal system. Finally, new developments in the field of PET/CT that may help overcome some of these limitations are briefly highlighted.

PET/CT limitations and pitfalls in urogenital cancers

Hybrid FDG PET/CT plays a vital role in oncologic imaging and has been widely adopted for the staging and restaging of a variety of malignancies. Its diagnostic value in urogenital malignancies is less well-known, not at least because of the variable FDG avidity of these tumor entities, the sites of these tumors, and technical challenges associated with sequential imaging of CT and PET. PET/CT interpretation thus can be especially challenging and is associated with many pitfalls, which can lead to both false-positive and false-negative diagnoses as well as incorrect assessment of metabolic change following therapy. Currently, FDG PET/CT is not the standard of care for the initial diagnosis or staging of early-stage or low-risk urogenital cancers; however, it can help evaluate distant metastatic disease, response to therapy, and disease recurrence in high-risk patients. Knowledge of imaging features of tumor metabolic avidity and pitfalls is essential for accurate interpretation.

Imaging in head and neck cancers: Update for non-radiologist

Head and neck cancer (HNC) is the fifth most frequent cancer worldwide and associated with significant morbidity. Along with clinical examination and endoscopic evaluation, imaging plays an important role in pre- and posttherapeutic evaluation of patients with HNC. Cross-sectional Imaging techniques such as computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography / computed tomography (PET/CT) are routinely used in the assessment of these patients. This review provides an overview of the various cross-sectional imaging modalities used in the evaluation of HNC and will give a short summary of the latest imaging technologies regarding head and neck cancer diagnosis.

Targeting Treatment Resistance in Head and Neck Squamous Cell Carcinoma - Proof of Concept for CT Radiomics-Based Identification of Resistant Sub-Volumes

Purpose

Radiomics has already been proposed as a prognostic biomarker in head and neck cancer (HNSCC). However, its predictive power in radiotherapy has not yet been studied. Here, we investigated a local radiomics approach to distinguish between tumor sub-volumes with different levels of radiosensitivity as a possible target for radiation dose intensification.

Materials and Methods

Of 40 patients (n=28 training and n=12 validation) with biopsy confirmed locally recurrent HNSCC, pretreatment contrast-enhanced CT images were registered with follow-up PET/CT imaging allowing identification of controlled (GTVcontrol) vs non-controlled (GTVrec) tumor sub-volumes on pretreatment imaging. A bi-regional model was built using radiomic features extracted from pretreatment CT in the GTVrec and GTVcontrol to differentiate between those regions. Additionally, concept of local radiomics was implemented to perform detection task. The original tumor volume was divided into sub-volumes with no prior information on the location of recurrence. Radiomic features from those sub-volumes were then used to detect recurrent sub-volumes using multivariable logistic regression.

Results

Radiomic features extracted from non-controlled regions differed significantly from those in controlled regions (training AUC = 0.79 CI 95% 0.66 - 0.91 and validation AUC = 0.88 CI 95% 0.72 – 1.00). Local radiomics analysis allowed efficient detection of non-controlled sub-volumes both in the training AUC = 0.66 (CI 95% 0.56 – 0.75) and validation cohort 0.70 (CI 95% 0.53 – 0.86), however performance of this model was inferior to bi-regional model. Both models indicated that sub-volumes characterized by higher heterogeneity were linked to tumor recurrence.

Conclusion

Local radiomics is able to detect sub-volumes with decreased radiosensitivity, associated with location of tumor recurrence in HNSCC in the pre-treatment CT imaging. This proof of concept study, indicates that local CT radiomics can be used as predictive biomarker in radiotherapy and potential target for dose intensification.

Radiographic Interpretation in Oral Medicine and Hospital Dental Practice

Oral medicine practice includes the diagnosis and nonsurgical treatment of oral and orofacial diseases and oral manifestations of systemic conditions. Oral medicine specialists in medical and dental settings often require imaging in assessment and treatment of these conditions. This article reviews imaging that may be used in practice, particularly as relevant for facial pain, bone conditions, and salivary gland disease. It reviews imaging that may be considered in a hospital setting for assessment of admitted patients, patient evaluation before surgical procedures, and provision of dentistry in a hospital setting for patients who cannot submit to treatment in an outpatient setting.