Radionuclide bone SPECT/CT in the evaluation of knee pain: comparing two-phase bone scintigraphy, SPECT and SPECT/CT.

OBJECTIVE:: To assess the role of single photon emission computed tomography (SPECT/CT) in the evaluation of knee pain as well as comparing bone scintigraphy (BS), SPECT and SPECT/CT, and assessing the incremental value of SPECT/CT. METHODS:: BS, SPECT and SPECT/CT of patients with knee pain (39 patients, 65 knees, 105 lesions) were directly compared for lesion detection, localisation and characterisation using lesion-based, knee-based and patient-based analyses in this retrospective study. RESULTS:: Lesion detection: BS (91.4%), SPECT (100%) and SPECT/CT (100%). SPECT and SPECT/CT detected significantly more lesions than BS (p < 0.05). Lesion localisation: BS (38.5-41.7%), SPECT (74.4-83.3%) and SPECT/CT (100%). SPECT localised significantly more lesions than BS; SPECT/CT localised significantly more lesions than BS and SPECT (p < 0.01). Lesion characterisation: BS (23.0-52.1%), SPECT (30.8-56.2%) and SPECT/CT (92.3-96.9%). SPECT/CT characterised significantly more lesions than BS and SPECT (p < 0.01). Characterisation of non-arthropathy lesions: BS (6.25%), SPECT (12.5%) and SPECT/CT (93.75%). SPECT/CT characterised significantly more non-arthropathy lesions than BS and SPECT (p < 0.01). BS and SPECT detected none, while SPECT/CT detected 100% of the causative/contributing/associated conditions that co-existed with osteoarthritis. Therefore SPECT/CT detected not only just osteoarthritis but also the causative/contributing/associated conditions. CONCLUSION:: SPECT/CT added significant incremental value to BS and SPECT irrespective of whether evaluation was lesion-based, knee-based or patient-based. SPECT/CT represents a viable alternative to MRI, and addition of SPECT/CT to BS and SPECT should be considered in the evaluation of knee pain. ADVANCES IN KNOWLEDGE:: Incremental value of bone SPECT/CT in knee pain.

(68)Ga-DOTA-peptide: A novel molecular biomarker for nasopharyngeal carcinoma.

BACKGROUND: Increased somatostatin receptor (SSTR) expression in patients with undifferentiated nasopharyngeal carcinoma (NPC) has been demonstrated with receptor autoradiography, (111) In-Octreotide scintigraphy, and (68) Ga-DOTA-TOC positron emission tomography (PET)/CT imaging. We sought to compare and correlate the uptake of fluorodeoxyglucose (FDG) and DOTA-NOC in undifferentiated NPC to ascertain the possible role of (68) Ga-DOTA-NOC PET/CT as a new imaging biomarker and to assess whether targeted peptide receptor radionuclide therapy is a feasible treatment option. METHODS: After obtaining approval from our institutional review board, 4 patients with biopsy proven nonkeratinizing undifferentiated NPC who had just undergone routine staging/restaging (18) F-FDG PET/CT imaging were prospectively and consecutively recruited for (68) Ga-DOTA-NOC PET/CT imaging. Of these 4 patients, 3 were newly diagnosed with untreated NPC, whereas 1 patient was diagnosed with a case of recurrent NPC with previous treatment. These patients subsequently underwent (68) Ga-DOTA-NOC PET/CT within 10 days from the (18) F-FDG PET/CT to ensure lesion comparability. Tracer uptake in tumor lesions were assessed visually and semiquantitatively by measuring maximum standardized uptake values (SUVmax). RESULTS: There were 12 FDG-avid lesions of which 7 showed avid uptake of DOTA-NOC greater than liver uptake, whereas 5 showed low uptake of DOTA-NOC less than liver uptake. Subset analysis of the FDG-avid lesions at the primary and recurrent sites showed that all the FDG-avid primary tumors in the nasopharynx showed avid uptake of DOTA-NOC. On the contrary, the case of recurrent NPC showed avid FDG uptake but low DOTA-NOC uptake. Subset analysis of the suspicious FDG-avid cervical lymph nodes showed that 50% of them demonstrated avid DOTA-NOC uptake greater than liver uptake, whereas the remaining demonstrated low-grade DOTA-NOC uptake less than liver uptake. The 2 subcentimeter cervical lymph nodes that showed low-grade uptake of FDG lower than mediastinal blood pool activity were deemed to be reactive/inflammatory and showed low-grade uptake of DOTA-NOC. CONCLUSION: This study highlights the potential of (68) Ga-DOTA-peptide PET/CT as a new molecular biomarker for newly diagnosed undifferentiated NPC, and less so for recurrent NPC and metastatic nodes. This potentially opens up new diagnostic and therapeutic options in the management of undifferentiated NPC.

Incidental possible diagnosis by 18F-fluorocholine PET/CT of Meckel's diverticulum and potential pitfalls.

UNLABELLED: A 61 years old man with a history of prostate cancer Gleason 3+4, treated with radical prostatectomy, underwent fluorine-18-fluorocholine positron emission tomography/computed tomography ((18)F-FCH PET/CT) imaging to investigate rising serum prostate specific antigen (PSA) levels. (18)F-FCH PET/CT showed a focus of linear increased uptake by a possible Meckel's diverticulum in the right hemi-pelvis, which was an incidental finding in this asymptomatic patient. Uptake of (18)F-FCH by Meckel's diverticulum has not been reported before and thus the mechanism of uptake has not been established. Two postulations may explain this uptake. First, since Meckel's diverticulum is a true diverticulum containing all layers of the intestinal wall, the uptake may be related to physiological bowel-related uptake. Second, the uptake may be due to heterotopic pancreatic tissue in Meckel's diverticulum, especially since the intensity of uptake we have noticed was similar to that of physiological pancreatic uptake. As (18)F-FCH PET/CT scan is often used for evaluating prostate cancer, (18)F-FCH uptake by Meckel's diverticulum in the pelvis or lower abdomen may be mistaken for tumor involvement/recurrence. The identification by imaging of Meckel's diverticulum relies on the identification of a blind ending tubular structure, arising from the distal ileum. The identification of this structure may be best appreciated on the axial, coronal or sagittal plane. CONCLUSION: In this particular case, we managed to clearly demonstrate the presence of a tubular blind ending structure arising from the distal ileum on the sagittal images. The careful identification of this structure indicated that tracer uptake was in a Meckel's diverticulum and not within a pelvic lymph node or pelvic organ hence excluding recurrent disease.

Potential pitfall of FDG PET/CT in assessing residual masses postchemotherapy.

A 22-year-old man with primary mediastinal choriocarcinoma and bilateral lung metastases underwent an FDG PET/CT scan after completing chemotherapy. Serum beta-human chorionic gonadotropin had normalized. PET/CT showed increased FDG uptake in the anterior mediastinal and lung lesions, suspicious for residual disease. After resection of the mediastinal and lung lesions, histopathology revealed necrosis and fibrohistiocytic reaction with no viable tumor. There was discordance between beta-human chorionic gonadotropin (negative) and FDG PET/CT (positive) findings, with PET/CT findings being false positive. Awareness of this potential pitfall of FDG PET/CT is important, and caution should be exercised when using FDG PET/CT to assess residual masses after chemotherapy.

Value of SPECT/CT in the evaluation of knee pain.

Bone scintigraphy (BS) has a good sensitivity but limited specificity. Moreover, planar imaging limits localization of lesion especially of overlapping structures in close proximity. SPECT allows tomographic imaging, resulting in better localization and characterization of the lesion. Addition of CT to SPECT in hybrid SPECT/CT further improves the precision of localization and accuracy of characterization of the lesion. Combining functional and anatomical imaging is complementary with improved sensitivity, specificity, and diagnostic confidence. These advantages of SPECT/CT are illustrated by 3 cases where diagnostic confidence was higher with SPECT/CT compared to BS or CT alone, highlighting the incremental value of SPECT/CT in assessing knee pain.

Nephrogenic systemic fibrosis in a patient with renal failure demonstrating a "reverse superscan" on bone scintigraphy.

Nephrogenic systemic fibrosis (NSF) has been linked to utilization of gadolinium-based contrast agents in patients with renal impairment. We present a 19-year-old female patient with end-stage renal failure presenting with joint pains and subcutaneous nodules. She had a prior gadolinium-enhanced magnetic resonance angiography when she was 14 years old. Clinical findings revealed firm subcutaneous nodules in both thighs. Whole-body bone scan demonstrates tracer uptake predominantly in the soft tissues and muscles of the extremities with minimal bony uptake. Incisional biopsy of the left thigh nodule revealed features of NSF with a total pathological score of 4, highly consistent with NSF.

The scar sign: a useful finding on FDG PET/CT to distinguish sarcoidosis from other causes of lymphadenopathy.

Scar involvement is a rare but characteristic cutaneous manifestation of sarcoidosis. The concurrent presence of FDG-avid lymphadenopathy and scar involvement (the "scar sign") is a useful finding on FDG PET/CT to suggest sarcoidosis, especially when biopsy specimens are difficult to obtain. A 46-year-old woman who presented with fever, cough, and weight loss was found to have mediastinal and hilar lymphadenopathy on chest radiography and CT scan. FDG PET/CT scan showed FDG-avid lower cervical, mediastinal, hilar, and inguinal lymphadenopathy. There was also increased FDG uptake along an old hysterectomy scar. Mediastinoscopy and nodal biopsy revealed noncaseating granulomas compatible with sarcoidosis.

Single photon emission computed tomography/computed tomography in the evaluation of neuroendocrine tumours: a review of the literature.

The scintigraphic investigation of neuroendocrine tumours such as carcinoids has depended on standard techniques such as I-metaiodobenzylguanidine and In-pentetreotide imaging. More recently, the use of PET techniques such as Ga-DOTATATE has been advocated. An alternative improved modality is high-quality single photon emission computed tomography/computed tomography (SPECT/CT), which has the advantages of better sensitivity and specificity and has shown improved localization in up to 60% of cases. These advantages are especially true for pancreatic and lymph node lesions. Overall, SPECT/CT can result in a change in clinical management in 25% of patients. Although it is possible to combine SPECT and CT performed at different time points, there is better anatomical localization and improved reporter confidence when SPECT and CT are performed simultaneously.