Evaluation of incidentally discovered adrenal masses with PET and PET/CT

Usefulness of 68 Ga-Pentixafor PET/CT on Diagnosis and Management of Cushing Syndrome

PURPOSE

This pilot study investigated the performance of C-X-C motif chemokine receptor 4 (CXCR4) molecular imaging ( 68 Ga-pentixafor PET/CT) in Cushing syndrome (CS) and the correlation between CXCR4 signaling interactions and glucose metabolism in adrenocorticotropin-cortisol pathway.

METHODS

We retrospectively evaluated 31 patients (16 patients with CS and 15 patients with nonfunctioning pituitary or adrenal adenomas). All patients underwent 68 Ga-pentixafor PET/CT, and 11 with pituitary adenoma also underwent 18 F-FDG PET/CT. The diagnosis accuracy of 68 Ga-pentixafor PET/CT was calculated. The correlation between radiouptake along the pituitary-adrenal axis and hormone levels was calculated.

RESULTS

Patients with Cushing disease characterized a focal uptake in adrenocorticotropic hormone-producing pituitary adenoma (ACTH-PA). In ACTH-independent CS, there was increased uptake of 68 Ga-pentixafor in adrenal lesions but not in the pituitary fossa. The nonfunctioning pituitary or adrenal adenomas showed negative 68 Ga-pentixafor signal. The one patient with metastatic ectopic ACTH syndrome had multiple 68 Ga-pentixafor-avid lesions. Using the threshold of SUV max >8.5 in the adrenal lesions, the sensitivity and specificity of 68 Ga-pentixafor PET/CT to diagnose cortisol-producing adenoma were 100% and 84.9%. A cutoff SUV max value of 3.0 on 68 Ga-pentixafor PET/CT had 100% sensitivity and specificity for differentiating ACTH-PA. The corresponding hormone level was significantly correlated with uptake of 68 Ga-pentixafor in pituitary adenoma and adrenal tissue but not with glucose metabolism.

CONCLUSION

We have characterized the performance of 68 Ga-pentixafor in different subtypes of CS. 68 Ga-pentixafor PET/CT is promising in the differential diagnosis of both ACTH-independent and ACTH-dependent CS. Activated CXCR4 molecular signaling along the pituitary-adrenal axis was found in patients with Cushing disease.

An assessment of medical students' proficiency regarding the hazards of radiological examinations on the health of workers and patients: a cross-sectional study from Palestine

BACKGROUND

The use of radiological examination is increasing worldwide. Since radiation exposure can result in many health hazards, medical professionals, as well as medical students, should possess adequate knowledge regarding radiation and its related hazards to protect themselves and the patients. Many studies have assessed medical students' knowledge on this topic, but never in Palestine. In this study, we aimed to examine Palestinian medical students' awareness and knowledge regarding radiological examination modalities and their risks on themselves and their patients.

METHODS

This was an observational, cross-sectional, population-based study, conducted to assess the awareness of radiation exposure and its risks among Palestinian medical students. An online questionnaire was implemented on medical students at An-Najah National University. A total knowledge score that ranged from 0 to 22 was calculated for each participant, with higher scores indicating better knowledge regarding radiation doses and the related hazards.

RESULTS

Two hundred eighty and seven students participated in our study, with a response rate of 71%. The average knowledge score of the participants was 10.97 ± 4.31 out of a maximum of 22 points. Male participants and participants in advanced study years achieved better knowledge scores (p-values were 0.034 and < 0.001, respectively). Perceived radiology knowledge was significantly associated with the actual knowledge score among the participants (p-value< 0.001). Receiving radiology lectures in fourth and fifth years significantly affected the participants' knowledge score (p-values were < 0.001).

CONCLUSIONS

We found a severe lack of knowledge regarding radiation doses and related risks among medical students. Therefore, we recommend that medical schools update and supplement their curriculum regarding knowledge on radiation.

Medical doctors' awareness of radiation exposure in diagnostic radiology investigations in a South African academic institution

Background

Diagnostic investigations using radiation have become a critical feature of medical practice in recent times. However, the possibility of doctors’ underestimation of risks of over-exposure of patients to diagnostic radiation still warrants further evaluation.

Objectives

To investigate doctors’ awareness of diagnostic radiation exposure at Dr George Mukhari Academic Hospital, South Africa.

Methods

This was a cross-sectional, analytical investigation of the awareness of doctors about radiation exposure in diagnostic radiology investigations. A cluster sampling technique was employed to recruit 217 participants. Consent and approval of the participants were sought and obtained before questionnaire administration during departmental meetings between October 2017 and March 2018.

Results

Of the participants, 80% had no formal training on radiation exposure and 33.8% of them correctly estimated natural background radiation. Correct estimates of the effective dose from a single-view abdominal X-ray (AXR) were expressed by 7.5%, quantity of radiation of a single-phase computed tomography (CT) abdomen by 30.3% and dosage from a two-view unilateral mammogram by 29.1% of the participants. More than 75% of participants agreed that children are more sensitive to radiation, but only 10.5% suggested medical termination of pregnancy for a woman who had CT abdomen and pelvis with contrast. Dosage and risk of inducing fatal cancer from common but more complex imaging procedures were poorly understood. Only the doctors of the radiology department showed a statistically significant (p < 0.0001) association with regards to their radiation awareness.

Conclusion

Because of the high rate of poor awareness of radiation risks observed in this study, it is important to initiate, early in the medical curriculum for medical students, the need for a rotation in the Department of Radiology, similar to such rotations in other medical specialties.

Diagnostic efficacy of 18F-FDG PET/CT in patients with adrenal incidentaloma

BACKGROUND

The management of adrenal incidentaloma is still a challenge with respect to determining its functionality (hormone secretion) and malignancy. In this light, we performed 18F-FDG PET/CT scan to assess the SUVmax values in different adrenal masses including Cushing syndrome, pheochromocytoma, primary hyperaldosteronism and non-functional adrenal adenomas.

METHODS

Total 109 (73 F, 36 M) patients with adrenal mass (incidentaloma), mean age of 53.3 ± 10.2 years (range, 24-70) were screened by 18F-FDG PET/CT. Data of 18F-FDG PET/CT imaging of the patients were assessed by the same specialist. Adrenal masses were identified according to the calculated standardized uptake values (SUVs). Clinical examination, 24-h urine cortisol, catecholamine metabolites, 1-mg dexamethasone suppression test, aldosterone/renin ratio and serum electrolytes were analyzed.

RESULTS

Based on the clinical and hormonal evaluations, there were 100 patients with non-functional adrenal mass, four with cortisol-secreting, four with pheochromocytomas and one with aldosterone-secreting adenoma. Mean adrenal mass diameter of 109 patients was 2.1 ± 4.3 (range, 1-6.5 cm). The 18F-FDG PET/CT imaging of the patients revealed that lower SUVmax values were found in non-functional adrenal masses (SUVmax 3.2) when compared to the functional adrenal masses including four with cortisol-secreting adenoma (SUVmax 10.1); four with pheochromcytoma (SUVmax 8.7) and one with aldosterone-secreting adenomas (SUVmax 3.30). Cortisol-secreting (Cushing syndrome) adrenal masses showed the highest SUVmax value (10.1), and a cut-off SUVmax of 4.135 was found with an 84.6% sensitivity and 75.6% specificity cortisol-secreting adrenal adenoma.

CONCLUSIONS

Consistent with the similar studies, non-functional adrenal adenomas typically do not show increased FDG uptake and a certain form of functional adenoma could present various FDG uptake in FDG PET/CT. Especially functional adrenal adenomas (cortisol secreting was the highest) showed increased FDG uptake in comparison to the non-functional adrenal masses. Therefore, setting a specific SUVmax value in the differentiation of malignant adrenal lesion from the benign one is risky and further studies, including a high number of functional adrenal mass are needed.

Practical Approach to Adrenal Imaging

Various pathologies can affect the adrenal gland. Noninvasive cross-sectional imaging is used for evaluating adrenal masses. Accurate diagnosis of adrenal lesions is critical, especially in cancer patients; the presence of adrenal metastasis changes prognosis and treatment. Characterization of adrenal lesions predominantly relies on morphologic and physiologic features to enable correct diagnosis and management. Key diagnostic features to differentiate benign and malignant adrenal lesions include presence/absence of intracytoplasmic lipid, fat cells, hemorrhage, calcification, or necrosis and locoregional and distant disease; enhancement pattern and washout values; and lesion size and stability. This article reviews a spectrum of adrenal pathologies.

The Frequency of Focal Thyroid Incidental Findings and Risk of Malignancy Detected by 18F-Fluorodeoxyglucose Positron Emission Tomography in an Iodine Deficient Population

Incidental focal uptake of 18F-fluorodeoxyglucose (FDG) in the thyroid on positron emission tomography (PET/CT) is rare but often associated with malignancy. The epidemiology of thyroid incidentalomas has only to some extent been described in countries with iodine deficiency. Here we report data from Denmark, a country with known iodine deficiency and wide access to PET/CT. All FDG PET/CT comprising the head and neck region, during 2014, were retrospectively reviewed, and patients with focal FDG uptake in the thyroid gland were identified. A total of 2451 patients had an FDG PET/CT of which 59 (2.4%) patients presented with FDG-avid focal lesions in the thyroid gland. Among the 59 patients with FDG-avid lesions, 33 patients (56%) received work up with ultrasound, thyroid technetium scintigraphy, fine needle aspiration, and/or histology of which 20 patients had a conclusive pathology report. Ten patients with FDG-avid lesions were identified with thyroid malignancy. The risk of thyroid malignancy was 16.9% among patient with incidental FDG-avid thyroid lesions. Our findings indicated a similar frequency of FDG thyroid incidentalomas and malignancy rates in an iodine deficient population compared to summary data from prior studies, studies mostly performed in geographical areas of normal or excess iodine supplementation.

Practical Approach to Adrenal Imaging

Various pathologies can affect the adrenal gland. Noninvasive cross-sectional imaging is used for evaluating adrenal masses. Accurate diagnosis of adrenal lesions is critical, especially in cancer patients; the presence of adrenal metastasis changes prognosis and treatment. Characterization of adrenal lesions predominantly relies on morphologic and physiologic features to enable correct diagnosis and management. Key diagnostic features to differentiate benign and malignant adrenal lesions include presence/absence of intracytoplasmic lipid, fat cells, hemorrhage, calcification, or necrosis and locoregional and distant disease; enhancement pattern and washout values; and lesion size and stability. This article reviews a spectrum of adrenal pathologies.

Diffusion-weighted and PET/MR Imaging after Radiation Therapy for Malignant Head and Neck Tumors

Interpreting imaging studies of the irradiated neck constitutes a challenge because of radiation therapy-induced tissue alterations, the variable appearances of recurrent tumors, and functional and metabolic phenomena that mimic disease. Therefore, morphologic magnetic resonance (MR) imaging, diffusion-weighted (DW) imaging, positron emission tomography with computed tomography (PET/CT), and software fusion of PET and MR imaging data sets are increasingly used to facilitate diagnosis in clinical practice. Because MR imaging and PET often yield complementary information, PET/MR imaging holds promise to facilitate differentiation of tumor recurrence from radiation therapy-induced changes and complications. This review focuses on clinical applications of DW and PET/MR imaging in the irradiated neck and discusses the added value of multiparametric imaging to solve diagnostic dilemmas. Radiologists should understand key features of radiation therapy-induced tissue alterations and potential complications seen at DW and PET/MR imaging, including edema, fibrosis, scar tissue, soft-tissue necrosis, bone and cartilage necrosis, cranial nerve palsy, and radiation therapy-induced arteriosclerosis, brain necrosis, and thyroid disorders. DW and PET/MR imaging also play a complementary role in detection of residual and recurrent disease. Interpretation pitfalls due to technical, functional, and metabolic phenomena should be recognized and avoided. Familiarity with DW and PET/MR imaging features of expected findings, potential complications, and treatment failure after radiation therapy increases diagnostic confidence when interpreting images of the irradiated neck. Online supplemental material is available for this article.

Patient perspectives and preferences for communication of medical imaging risks in a cancer care setting

PURPOSE

To identify opportunities for improving patient-centered communication about diagnostic imaging tests that involve the use of radiation in a cancer care setting.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained for this HIPAA-compliant study. Patient knowledge, information sources, and communication preferences were assessed in six focus groups during 2012. The groups consisted of patients undergoing treatment for metastatic colorectal carcinoma, women treated within the past 6 months for early-stage breast carcinoma, men undergoing surveillance after testicular cancer treatment, parents of patients treated for stage I-III neuroblastoma, patients in a thoracic oncology survivorship program, and participants in a lung cancer screening program. A multidisciplinary research team performed thematic content analysis of focus group transcripts. High-level findings were summarized during consensus conferences.

RESULTS

Although they were aware of the long-term risk of cancer from exposure to ionizing radiation, most participants reported that their health care provider did not initiate discussion about benefits and risks of radiation from imaging tests. Most patients obtained information by means of self-directed internet searches. Participants expressed gratitude for tests ("That CT saved my daughter's life," "I'd rather have the radiation dosage than being opened up"), yet they expressed concern about having to initiate discussions ("If you don't ask, nobody is going to tell you anything") and the desire to be offered information concerning the rationale for ordering specific imaging examinations, intervals for follow-up imaging, and testing alternatives. Participants believed that such information should be available routinely and that conversation with their personal physician or endorsed, readily available reference materials were ideal methods for information exchange. Understanding imaging radiation risks and active participation in decision making about imaging were especially important to cancer survivors.

CONCLUSION

A substantial gap exists between patient expectations and current practices for providing information about medical imaging tests that involve the use of radiation.

What parameters from 18F-FDG PET/CT are useful in evaluation of adrenal lesions?

PURPOSE

Prior studies have suggested that (18)F-FDG PET/CT can help characterize adrenal lesions and differentiate adrenal metastases from benign lesions. The aim of this study was to assess the value of (18)F-FDG PET/CT for the differentiation of malignant from benign adrenal lesions.

METHODS

This retrospective study included 85 patients (47 men and 38 women, age 63.8 ± 10.8 years) who had undergone (18)F-FDG PET/CT (60 min after injection 300 - 370 MBq (18)F-FDG; Biograph 64 scanner) for evaluation of 102 nonsecreting adrenal masses. For semiquantitative analysis, the maximum standardized uptake value (SUVmax), adrenal to liver (T/L) SUVmax ratio, mean CT attenuation value and tumour diameter were measured in all lesions and compared with the pathological findings.

RESULTS

Malignant adrenal tumours (68% of evaluated tumours) had a significantly higher mean SUVmax (13.0 ± 7.1 vs. 3.7 ± 3.0), a higher T/L SUVmax ratio (4.2 ± 2.6 vs. 1.0 ± 0.9), a higher CT attenuation value (31.9 ± 16. 7 HU vs. 0.2 ± 25.8 HU) and a greater diameter (43.6 ± 23.7 mm vs. 25.6 ± 13.3 mm) than benign lesions. The false-positive findings were tuberculosis and benign phaeochromocytoma. Based on ROC analysis, a T/L SUVmax ratio >1.53, an adrenal SUVmax >5.2, an attenuation value >24 HU and a tumour diameter >30 mm were chosen as the optimal cut-off values for differentiating malignant from benign tumours. The areas under the ROC curves for the selected cut-off values were 0.96, 0.96, 0.88 and 0.77, respectively. A multivariate logistic regression model revealed that the T/L SUVmax ratio was an independent prognostic factor for malignancy (p < 0.001); a CT attenuation value of >25 HU and a tumour diameter >30 mm had no additional individual importance in the diagnosis of malignancy.

CONCLUSION

Using a T/L SUVmax ratio >1.53 and an adrenal SUVmax >5.2 in (18)F-FDG PET/CT led to high diagnostic sensitivity, specificity and negative predictive value for characterizing adrenal tumours. The diagnostic accuracies of the two parameters were comparable, but T/L SUVmax ratio was an independent predictor of malignancy.

Nuclear medicine imaging of endocrine neoplasms

Endocrine tumors are hormonally active benign or malignant neoplasms arising within endocrine organs or from specialized cells of the amine precursor uptake and decarboxylation system. The detection rate of these tumors is increasing as a result of sensitive biochemical tests and high-resolution diagnostic imaging. Medical imaging has become a key component in the diagnosis and staging of endocrine malignancies; however, despite the impressive advances in computed tomography (CT) and MRI, detection of small primary tumors and metastases continues to be a challenge. Functional imaging techniques use radiopharmaceuticals targeted at unique tumor cellular processes in order to provide sensitive and highly specific whole-body imaging. Functional imaging allows prediction of the efficacy of radionuclide or receptor-based therapies and surveillance after therapy. Advances in imaging have not been limited to radiopharmaceuticals. Hybrid scanner technology in the form of PET/CT and single photon emission computed tomography (SPECT)/CT, designed to combine functional images with anatomic maps, has further improved the diagnostic accuracy. High-resolution hybrid imaging when deployed with novel PET and SPECT radiopharmaceuticals has the potential to dramatically change, individualize, and optimize imaging plans based on the histological grade, degree of differentiation, and genetic profile of each patient's endocrine neoplasm.

18F-fluorocholine uptake in a case of adrenal incidentaloma: possible diagnostic pitfall or potential tool for adrenocortical tumors characterization?

The understanding of radiotracer's physiological biodistribution as well as the potential source of false-positive results is crucial for an accurate diagnostic interpretation of (18)F-fluorocholine PET/CT examination in patients with prostate cancer. We illustrate the results of whole-body (18)F-fluorocholine PET/CT in a 79-year-old man with biochemical suspicion of prostate adenocarcinoma relapse. PET/CT study showed a focally increased (18)F-fluorocholine uptake, characterizing an incidentally found adrenocortical adenoma. Finally, we draw oncologists' attention to the possible false-positive results of (18)F-fluorocholine PET related to benign and unsuspected adrenocortical lesions in patients with a history of prostate malignancy.

Cross-sectional imaging work-up of adrenal masses

Advances in medical imaging with current cross-section modalities enable non-invasive characterization of adrenal lesions. Computed tomography (CT) provides characterization with its non-contrast and wash-out features. Magnetic resonance imaging (MRI) is helpful in further characterization using chemical shift imaging (CSI) and MR spectroscopy. For differentiating between benign and malignant masses, positron emission tomography (PET) imaging is useful with its qualitative analysis, as well as its ability to detect the presence of extra-adrenal metastases in cancer patients. The work-up for an indeterminate adrenal mass includes evaluation with a non-contrast CT. If a lesion is less than 10 Hounsfield Units on a non-contrast CT, it is a benign lipid-rich adenoma and no further work-up is required. For the indeterminate adrenal masses, a lipid-poor adenoma can be differentiated from a metastasis utilizing CT wash-out features. Also, MRI is beneficial with CSI and MR spectroscopy. If a mass remains indeterminate, PET imaging may be of use, in which benign lesions demonstrate low or no fluorodeoxyglucose activity. In the few cases in which adrenal lesions remain indeterminate, surgical sampling such as percutaneous biopsy can be performed.