Najeeb Ahmed

The clinical utility of combining pre-operative axillary ultrasonography and fine needle aspiration cytology with radionuclide guided sentinel lymph node biopsy in breast cancer patients with palpable axillary lymph nodes.

PURPOSE Clinically palpable lymph nodes (CPLN) are usually considered a contraindication to sentinel lymph node biopsy (SLNB) but one third of these patients are node negative. The aim of the present study is to evaluate the clinical usefulness of combining SLNB and preoperative axillary ultrasonography (AUS) with FNAC in patients with clinically palpable but indeterminate axillary lymph nodes. MATERIALS AND METHODS Fifty three patients with primary breast cancer and CPLN (mean age, 51.6 years; median age 51 years; age range, 28-73 years) were included in the study. All patients underwent AUS and fine needle aspiration (FNAC) followed by SLNB in FNAC negative patients (Group A). Patients with proven metastasis subsequently had axillary lymph node dissection (ALND) (Group B). Standard SLN scintigraphy was performed 2-4h before surgery by injecting Tc-99m labeled nano-colloid intra-dermally in the periareolar region. RESULTS Nodal metastases were documented at FNAC in 26 (49%) of the 53 patients with subsequent ALND (Group B). All 27 patients (51%) with negative FNAC results (Group A) underwent SLNB, which revealed metastasis in 6 (11%) patients. The remaining 21 (40%) patients were tumor negative and all these patients remain disease free during the follow-up period of 12-36 months with NPV of 100%. SLN was identified in all patients (100% success rate). Preoperative AUS sensitivity was 78%, specificity 76%, PPV 83%, NPV 69% and accuracy 77% (p=0.001). In comparison, ultrasound guided FNAC sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 81%, 100%, 100%, 78%, 89% respectively (p=0.001). CONCLUSIONS The inaccuracy of clinical assessment allows widening of indication of SLNB. Preoperative ultrasonography and guided FNAC can help in selecting the patients suitable for ALND or SLNB. Patients who are FNAC positive can proceed to ALND whilst FNAC negative samples can undergo SLNB. This combination strategy may be helpful in avoiding unnecessary ALND.

Hybrid SPECT/CT Imaging in the Management of Differentiated Thyroid Carcinoma

Differentiated thyroid cancer (DTC) has a good prognosis overall; however, lifelong follow-up is required for many cases. Radioiodine planar imaging with iodine-123 (I-123) or radioiodine-131 (I-131) remains the standard in the follow-up after initial surgery and ablation of residual thyroid tissue using I-131 therapy. Radioiodine imaging is also used in risk-stratifying and for staging of thyroid cancer, and in long-term follow-up. Unfortunately, the lack of anatomical detail on planar gamma camera imaging and superimposition of areas presenting with increased radioiodine uptake can make accurate diagnosis and localization of radioiodine-avid metastatic disease challenging, leading to false positive results and potentially to over-treatment of patients. Hybrid SPECT/CT allows precise anatomical localization and superior characterization of foci of increased tracer uptake when compared to planar imaging. This, in turn, allows the differentiation of pathological and physiological uptake, increasing the accuracy of image interpretation and ultimately improving the accuracy of DTC staging and subsequent patient management. In this review, we look at the unique and emerging role that SPECT/CT plays in the management of DTC, illustrated by examples from our own clinical practice.

Scintimammography in conjunction with ultrasonography for local breast cancer recurrence in post-mastectomy breast

The aim of this study was to compare the usefulness of (99)Tc(m)-methoxy-isobutyl-isonitrile (MIBI) scintimammography and ultrasonography, alone and in combination, for the detection of chest wall recurrence in the post-mastectomy breast. A total of 41 consecutive post-mastectomy patients (mean age 46.6 years; median age 45 years) with clinical suspicion of breast cancer recurrence were evaluated. For scintimammography all patients received a 740-900 MBq iv injection of (99)Tc(m)-MIBI; planar images were taken 5-10 min post-injection followed by supine single photon emission CT. Breast ultrasonography was performed in each patient using a 7.5 MHz transducer. Both MIBI uptake and ultrasound findings were documented using standard protocols. All patients had fine needle aspiration cytology biopsy (FNAC), core biopsy or excision biopsy for final tissue diagnosis. Of the 41 patients, 24 had true positive signs of local breast cancer recurrence upon ultrasonography, 10 were diagnosed as true negatives, a sensitivity of 86%, specificity 77%, positive predictive value (PPV) 89%, negative predictive value (NPV) 71% and accuracy 83% (p = 0.001). By comparison, scintimammography findings were found to be true positive in 25 patients and true negative in 12 patients - sensitivity 89%, specificity 92%, PPV 96%, NPV 80% and accuracy 90% (p = 0.001). Using a combination of these two modalities, the combined sensitivity was 100%, specificity 77%, PPV 90%, NPV 100% and accuracy 93%. The high NPV of the two studies in combination implies a potential use of this approach to exclude recurrent disease in patients with a low initial index of suspicion and/or when histology is indeterminate.

A proof-of-concept study analyzing the clinical utility of fluorine-18-sodium fluoride PET-CT in skeletal staging of oncology patients with end-stage renal disease on dialysis

Purpose The quality of conventional bone scintigraphy can be poor in patients with end-stage renal disease (ESRD). Fluorine-18-sodium fluoride (18F-NaF) PET-computed tomography (CT) has rapid single-pass extraction, fast clearance from the soft tissues and a better target to background ratio. The aim of the present study is to preliminarily assess the superior tracer kinetics of 18F-NaF in ESRD patients. Materials and methods A cohort comprising of 13 patients with ESRD (mean age 65.5 years; median age 68.5 years; six men and seven women) and a control group of 20 patients with normal renal function (mean age 64±7.7 years, nine men and 11 women) were analyzed qualitatively and quantitatively. Both sets of patients were referred for osseous staging of malignancy. All patients underwent a PET-CT scan after an injection of 0.06 mCi/kg of 18F-NaF. Results Qualitative analysis of the ESRD and the control group did not show a significant difference. The signal to noise ratio in the ESRD group (26.24±10.5) and the control group was similar (22.06±10.9), P=0.35. The extraction of radiotracer in bone was higher in ESRD with a bone to soft tissue index of 4.03±2.2 versus 2.48±1.0 in control patients (P=0.01). 18F-NaF PET-CT was positive for bone metastases in three patients and negative in 10 patients. Of the 48 total lesions, 34 (71%) were classified as benign on 18F-NaF PET-CT, whereas 10 (21%) were classified as malignant and four (8%) were classified as equivocal. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 18F-NaF PET-CT were 91, 89.5, 90, 71.4, and 89.7%, respectively (P<0.001). Conclusion The image quality of 18F-NaF PET-CT in patients with ESRD was comparable to imaging in patients with normal renal function. This can potentially translate into better diagnostic performance in patients with ESRD.

18F-NaF PET-CT in Symptomatic Fabella Syndrome

Fabella is a sesamoid bone, located within the tendon of the lateral head of the gastrocnemius muscle. It may be associated with posterolateral knee pain because of repetitive friction over the posterolateral femoral condyle. We report a case of a 64-year-old woman presenting with right posterolateral knee pain. F-NaF PET-CT demonstrated increased uptake posterior to the right knee joint localizing to a fabella. Standard examination and radiographic imaging excluded other causes for posterolateral knee pain, and the increased activity was considered to be secondary to fabella syndrome. NaF PET-CT can provide useful information in the evaluation of posterolateral knee pain.

Incremental Diagnostic Value and Impact on Patient Management of Somatostatin Receptor Scintigraphy with Indium-111-Pentetreotide in Gastroenteropancreatic Neuroendocrine Tumors

Objective: To evaluate the efficacy of somatostatin analog scintigraphy with indium-111-pentetreotide and its overall impact on management in patients with gastroenteropancreatic neuroendocrine tumors (GEP-NET). Subjects and Methods: Twenty-two consecutive patients with a proven or clinically suspected GEP-NET with or without proven metastases were imaged at 24 and 48 h after injection of 111In-pentetreotide. The scintigraphic findings were compared with results from conventional imaging methods. The final diagnosis was based on histopathological and surgical findings and complementary radiology. Results: Somatostatin receptor-positive lesions were found in 20 of the patients, whereas conventional methods were positive in 18 patients. Additionally, 13 new tumor sites were discovered by somatostatin receptor scintigraphy in 5 patients (liver: 6; chest: 2; bone: 1; abdomen: 4). The surgical therapeutic strategy was changed in 7 patients (32%). Conclusions: Our data reinforced that scintigraphy with 111In-pentetreotide represents the imaging modality of choice in the initial evaluation of GEP-NET. It is highly accurate and can identify clinically unsuspected lesions and optimize the overall staging. It also guides optimal therapy choice and most importantly identifies patients with inoperable or metastatic disease who might be candidates for high-dose targeted therapy.

The clinical significance of incidental soft tissue uptake on whole body 18F-sodium fluoride bone PET-CT

18F-sodium fluoride (NaF) is a PET bone imaging agent and is commonly used in imaging patients with cancer; however, similar to technetium-99m medronic acid (99mTc-MDP), it can be useful in the evaluation of benign bone and joint conditions. NaF is an excellent bone-seeking agent with high bone uptake due to rapid single-pass extraction. It has negligible plasma protein binding, rapid blood, renal clearance, high bone uptake and almost all NaF delivered is retained by bone after a single pass of blood; however, uptake of NaF can be observed in non-osseous structures such as the arterial vasculature, gastrointestinal tract, genitourinary tract, and viscera. In this article, we present a spectrum of clinical cases with non-osseous NaF uptake in patients referred for cancer staging.

Inguinal Herniation of Urinary Bladder on F-18 Sodium Fluoride (NaF) PET-CT

Inguinal herniation of urinary bladder is uncommon and usually an incidental finding in asymptomatic patients. In some of these patients, residual urine volume and consequently, urinary tracer activity can be higher in the herniated bladder than the native bladder, in which case interpretation can be challenging on conventional planar imaging. We describe an interesting case of physiological activity in a herniated bladder simulating a “tear-drop”. This case serves an important reminder that whilst F-18 NaF PET-CT has a similar spectrum of urinary activity to conventional bone scintigraphy; morphological correlation on hybrid imaging is invaluable in ensuring the physiological nature of uptake.

Diagnostic Challenge of Staging Metastatic Bone Disease in the Morbidly Obese Patients: A Primary Study Evaluating the Usefulness of 18F-Sodium Fluoride (NaF) PET-CT

Purpose Optimizing diagnostic imaging may be challenging in obese patients. The quality of conventional bone scintigraphy can be poor in the morbidly obese due to a combination of factors including high background soft tissue activity. In comparison, sodium fluoride (18F-NaF PET-CT) has a better target-to-background ratio attributed to rapid single-pass extraction and fast clearance from the soft tissues. The aim of the present study is to assess the diagnostic efficacy of 18F-NaF PET-CT in the evaluation of bone metastases in obese cancer patients. Patients and Methods Two hundred twelve morbidly obese patients (body mass index, 45 ± 5.1 kg/m2; mean age, 57 years; range, 32–81 years) with body mass index greater than 40 kg/m2 referred for NaF PET-CT for osseous staging of malignancy were retrospectively analyzed. All patients underwent PET-CT scan by injecting 2.2 MBq/kg (0.06 mCi/kg) of 18F-NaF. Results 18F-NaF PET-CT was definitely benign in 145, possibly benign in 3, equivocal in 4, possibly malignant in 13, and definitely malignant in 47 patients. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 18F-NaF PET-CT were 93.1%, 96.1%, 90%, 97.3%, and 95.2%, respectively (95% confidence interval). Conclusions The results of the present study indicate that 18F-NaF PET-CT retains its high diagnostic accuracy in morbidly obese patients and, by inference, can be a preferred functional modality in these patients.