Unusual Tc-99m MDP and I-123 MIBG images in focal pyelonephritis

Unusual Renal Uptake of 131 I-MIBG in a Young Hypertensive With Renal Artery Stenosis

ABSTRACT

A 10-year-old hypertensive girl underwent 131 I-MIBG scan to rule out neural crest derived tumor. The whole-body images revealed diffuse intense tracer uptake in the right kidney, which persisted in 96-hour images as well. CT renal angiography revealed 90% to 95% right renal artery stenosis. Thereafter, she underwent baseline and angiotensin receptor blockade renal dynamic imaging, which revealed hemodynamically significant renal artery stenosis. Pattern of diffuse and intense 131 I-MIBG uptake, albeit rare, still warrants further evaluation to rule out renal artery stenosis and investigate its hemodynamic significance for appropriate management.

Does the Incremental Value of 123I-Metaiodobenzylguanidine SPECT/CT over Planar Imaging Justify the Increase in Radiation Exposure?

Purpose

Planar scintigraphy with ¹²³I-radiolabeled metaiodobenzylguanidine (¹²³I-mIBG) is an important imaging modality to evaluate neuroblastoma. In recent years, Single Photon Emission Computed Tomography combined with Computed Tomography (SPECT/CT) has revolutionized nuclear medicine. Nevertheless, the addition of the CT has increased the patients' irradiation. We aimed to evaluate the incremental benefits of ¹²³I-mIBG SPECT/CT over conventional planar imaging and to estimate the relative increase of radiation dose.

Methods

We retrospectively evaluated the added value of 56 SPECT/CT performed in 40 children in terms of better characterization of the lesion and its locoregional extension, better lymph node staging, detection of new lesions, and elimination of false positives by a paired comparison between the planar images and the SPECT/CT ones. Then, we calculated the percentage contribution of the additional radiation of the CT in this hybrid imagery.

Results

In 88% (49 out of 56) of the examinations, SPECT/CT provided additional information, which was crucial in 20% of the cases. It allowed a better characterization of the lesion and its locoregional extension in 44 cases, a better lymph node staging in 28 cases, the detection of 33 new lesions, and the elimination of 9 false positives. The CT effective dose was significantly lower than the SPECT one. The average additional radiation exposure due to CT was 12% (4-23%).

Conclusion

¹²³I-mIBG SPECT/CT has an undeniable added value that improves planar imaging interpretation and impacts patient management. These potential benefits would justify the low additional radiation induced by the CT.

Renal Metastasis From Neuroblastoma Shown on MIBG Imaging

A 6-year-old girl with high-risk neuroblastoma underwent a I-MIBG scan to monitor the disease status. In addition to the known lesion in the right retroperitoneal region, there were additional foci of increased activity in the right upper quadrate of the abdomen, which were not typical bowel activity. SPECT/CT images located the activity in the cortex of the lower pole of the right kidney, which was partially calcified. Subsequent biopsy confirmed neuroblastoma metastasis to the right kidney, which is extremely rare.

Guidelines on nuclear medicine imaging in neuroblastoma

Nuclear medicine has a central role in the diagnosis, staging, response assessment and long-term follow-up of neuroblastoma, the most common solid extracranial tumour in children. These EANM guidelines include updated information on ¹²³I-mIBG, the most common study in nuclear medicine for the evaluation of neuroblastoma, and on PET/CT imaging with ¹⁸F-FDG, ¹⁸F-DOPA and ⁶⁸Ga-DOTA peptides. These PET/CT studies are increasingly employed in clinical practice. Indications, advantages and limitations are presented along with recommendations on study protocols, interpretation of findings and reporting results.

Abnormal renal parenchyma accumulation of 123I MIBG in a child with renal artery stenosis

Hypertension is rare in the pediatric population, however renal artery stenosis (RAS) is an important cause that can be difficult to diagnose. Doppler ultrasound is the first line imaging modality, with computed tomography and magnetic resonance imaging as adjunct modalities, all with variable sensitivity for RAS. The gold standard for evaluation of RAS is invasive selective catheter angiography. We present a unique multimodality case of abnormal radiotracer uptake in the renal parenchyma on 123-Iodine metaiodobenzylguanidine (¹²³I MIBG) scan in a patient with unilateral RAS. RAS is a potential cause of a false positive MIBG scan, and proper recognition may lead to accurate diagnosis.

MIBG in Neuroblastoma Diagnostic Imaging and Therapy

Neuroblastoma is a common malignancy observed in infants and young children. It has a varied prognosis, ranging from spontaneous regression to aggressive metastatic tumors with fatal outcomes despite multimodality therapy. Patients are divided into risk groups on the basis of age, stage, and biologic tumor factors. Multiple clinical and imaging tests are needed for accurate patient assessment. Iodine 123 ((123)I) metaiodobenzylguanidine (MIBG) is the first-line functional imaging agent used in neuroblastoma imaging. MIBG uptake is seen in 90% of neuroblastomas, identifying both the primary tumor and sites of metastatic disease. The addition of single photon emission computed tomography (SPECT) and SPECT/computed tomography to (123)I-MIBG planar images can improve identification and characterization of sites of uptake. During scan interpretation, use of MIBG semiquantitative scoring systems improves description of disease extent and distribution and may be helpful in defining prognosis. Therapeutic use of MIBG labeled with iodine 131 ((131)I) is being investigated as part of research trials, both as a single agent and in conjunction with other therapies. (131)I-MIBG therapy has been studied in patients with newly diagnosed neuroblastoma and those with relapsed disease. Development and implementation of an institutional (131)I-MIBG therapy research program requires extensive preparation with a focus on radiation protection.

123I MIBG appearance of severe renal artery stenosis

We describe a patient with labile hypertension and elevated metanephrines who underwent 123Iodine metaiodobenzylguanidine (MIBG) for the detection of a possible paraganglioma. The scan revealed markedly abnormal diffusely increased activity in the right renal parenchyma. A CT angiogram showed severe renal artery stenosis of an atrophic-appearing right kidney and delayed enhancement of the right kidney, consistent with renal dysfunction due to renal artery stenosis.

Abnormal MIBG uptake in a neuroblastoma patient with right upper lobe atelectasis

A 3-month-old boy with a history of an abdominopelvic neuroblastoma presented 1 week after tumor resection for a routine follow-up 123-I Meta-iodobenzylguanidine (MIBG) scan to assess for residual mass. The study demonstrated abnormal radiotracer uptake in the right upper lobe, which correlated on the SPECT/CT to an area of airspace consolidation thought to be secondary to atelectasis. To the best of our knowledge, there is one published case of MIBG radiotracer uptake in the lung correlating with pneumonia; however, there are no reported cases to date in the literature of focal pulmonary MIBG uptake corresponding to atelectasis.

123I-Metaiodobenzylguanidine accumulation in a urinoma and cortex of an obstructed kidney after surgical resection of an abdominal neuroblastoma

Surgical ureteric injury is rare and often unsuspected for a long time. We present a child in whom an abdominal neuroblastoma was completely excised, but during surgery the left ureter was transected and anastomosed. One month later, during postoperative disease staging, abnormal (123)I-MIBG accumulation was observed in the left renal cortex and the left side of the abdomen. These findings were consistent with acute total obstruction and urinoma formation and were subsequently confirmed by renography and MRI. Despite treatment efforts, a significant amount of left renal mass and function were lost over the following months. These unusual findings are new additions to the literature regarding potential false-positive interpretations of (123)I-MIBG scans.

123I-Methyljodbenzylguanidin- (MIBG-) Szintigraphie

(123)I-metaiodobenzylguanidine (MIBG), a radio-labeled catecholamine analogue, is used for the imaging of pheochromocytoma based on the selective uptake of MIBG by chromaffin tissues. MIBG scintigraphy displays high sensitivity (90%) and specificity (close to 100%). In contrast, the false-positive uptake of MIBG by adrenal cortical carcinoma is rare. Here, we report a metastatic oncocytic adrenal cortical carcinoma with MIBG uptake used for therapeutic purposes.

Soft tissue uptake on 99mTc methylene diphosphonate bone scan imaging: pictorial review

99mTechnetium methylene diphosphonate (MDP) bone isotope may accumulate in many extra-osseous sites due to a variety of both benign and malignant conditions. This finding on a bone scan can be crucial to the diagnosis and may not be apparent in other imaging or the clinical evaluation of the patient. We present a pictorial review sampling some of the many causes of extra-osseous 99mTc MDP accumulation.

False-positive diagnosis of adrenal pheochromocytoma on iodine-123-MIBG scan

1-123 metaiodobenzylguanidine (1-123 MIBG) scintigraphy is known for its high specificity in detecting pheochromocytoma and other tumors of neural crest origin. In this rare case report, we describe a definite adrenocortical adenoma that demonstrated false-positive uptake at I-123 MIBG scintigraphy and a remarkable accumulation of 75-SE-6-beta-selenomethyl-norcholesterol.