Athar Haroon

Quantification of Myocardial Perfusion Reserve Using Dynamic SPECT Imaging in Humans: A Feasibility Study

Myocardial perfusion imaging (MPI) is well established in the diagnosis and workup of patients with known or suspected coronary artery disease (CAD); however, it can underestimate the extent of obstructive CAD. Quantification of myocardial perfusion reserve with PET can assist in the diagnosis of multivessel CAD. We evaluated the feasibility of dynamic tomographic SPECT imaging and quantification of a retention index to describe global and regional myocardial perfusion reserve using a dedicated solid-state cardiac camera. Methods: Ninety-five consecutive patients (64 men and 31 women; median age, 67 y) underwent dynamic SPECT imaging with 99mTc-sestamibi at rest and at peak vasodilator stress, followed by standard gated MPI. The dynamic images were reconstructed into 60–70 frames, 3–6 s/frame, using ordered-subsets expectation maximization with 4 iterations and 32 subsets. Factor analysis was used to estimate blood-pool time–activity curves, used as input functions in a 2-compartment kinetic model. K1 values (99mTc-sestamibi uptake) were calculated for the stress and rest images, and K2 values (99mTc-sestamibi washout) were set to zero. Myocardial perfusion reserve (MPR) index was calculated as the ratio of the stress and rest K1 values. Standard MPI was evaluated semiquantitatively, and total perfusion deficit (TPD) of at least 5% was defined as abnormal. Results: Global MPR index was higher in patients with normal MPI (n = 51) than in patients with abnormal MPI (1.61 [interquartile range (IQR), 1.33–2.03] vs. 1.27 [IQR, 1.12–1.61], P = 0.0002). By multivariable regression analysis, global MPR index was associated with global stress TPD, age, and smoking. Regional MPR index was associated with the same variables and with regional stress TPD. Sixteen patients undergoing invasive coronary angiography had 20 vessels with stenosis of at least 50%. The MPR index was 1.11 (IQR, 1.01–1.21) versus 1.30 (IQR, 1.12–1.67) in territories supplied by obstructed and nonobstructed arteries, respectively (P = 0.02). MPR index showed a stepwise reduction with increasing extent of obstructive CAD (P = 0.02). Conclusion: Dynamic tomographic imaging and quantification of a retention index describing global and regional perfusion reserve are feasible using a solid-state camera. Preliminary results show that the MPR index is lower in patients with perfusion defects and in regions supplied by obstructed coronary arteries. Further studies are needed to establish the clinical role of this technique as an aid to semiquantitative analysis of MPI.

Multicenter study evaluating extraprostatic uptake of 11C-choline, 18F-methylcholine, and 18F-ethylcholine in male patients: physiological distribution, statistical differences, imaging pearls, and normal variants.

AimThe aim of the study was to evaluate the visceral localization of the three most commonly used choline-based radiotracers (11C-choline, 18F-methylcholine, and 18F-ethylcholine) with the aim of analyzing uptake in metabolically and anatomically disease-free patients. Materials and methodsA total of 1250 standardized uptake values (SUVmax, SUVmean) were analyzed in 45 anatomical regions in 45 patients (15 patients with 11C-choline, 15 with 18F-methylcholine, and 15 with 18F-ethylcholine). These patients were selected from a cohort of 3721 choline PET/computed tomography studies performed at three teaching hospitals over a period of 10 years. They had no evidence of metabolically active primary disease, metastatic disease, or altered morphology on the computed tomography component of the study or any evidence of disease elsewhere on other imaging modalities. The sites of primary disease (prostate and seminal vesicles) were excluded from evaluation. ResultsNo adverse effect was documented when using the three tracers. Visceral localization was the same for all three tracers. Viscera with a statistical difference in intensity of uptake included the choroid plexus (P=0.0001), occipital lobe (P=0.014), parietal lobe (P=0.008), cerebellum (P=0.003), parotid gland (P=0.005), submandibular gland (P=0.001), tonsils (P=0.001), thyroid (P=0.0001), lungs (P=0.001), aorta (P=0.001), pulmonary artery (P=0.0001), liver segments I (P=0.005), III (P=0.005), IVB (P=0.03), and V (P=0.01), spleen [hilum (P=0.0009), body (P=0.0001)], pancreas [head (P=0.0001), body (P=0.01), tail (P=0.002)], esophagus (P=0.001), stomach (P=0.0001), duodenum (P=0.0002), large intestine (P=0.008), and rectum (P=0.0001). Elsewhere, no statistical difference was observed. Excreted activity was noted in the kidneys and bladder. ConclusionThis study demonstrates that the visceral localization of 11C-choline, 18F-methylcholine, and 18F-ethylcholine in disease-free patients is similar. Depending on the tracer uptake pattern, the viscera can be divided into two distinct categories: those with a statistically significant difference in uptake and those with no difference in uptake. The study outlines the range of SUVs for various organs for the three tracers and identifies some of the potential pitfalls in the evaluation of ‘nonavid’ but clinically significant presentation of different disease entities.

Localization of parathyroid disease with 'sequential multiphase and dual-tracer' technique and comparison with neck ultrasound.

ObjectiveThe aim of the study was to evaluate the accuracy of the sequential multiphase and dual-tracer (SMADT) technique utilizing technetium-99m pertechnetate (99mTcO4) and dynamic technetium-99m-2-methoxyisobutylisonitrile (99mTc-MIBI) with single-photon emission computed tomography/computed tomography (SPECT/CT) for localization of hyperfunctioning parathyroid tissue and compare the results with ultrasound (US). Materials and methodsSixty-four patients with hyperparathyroidism were scanned over 4 years. For the SMADT technique, 80 MBq 99mTcO4 was injected with dynamic thyroid image acquisition started at 20 min, followed by 900 MBq 99mTc-MIBI injection at 30 min; the dynamic imaging continued for 50 min. SPECT was acquired at 60 min, with SPECT/CT of the neck at 3 h. Subsequent subtraction and statistical difference analyses were performed. Neck US was carried out within 3 months. Findings for each parathyroid gland and thyroid were classified as positive or negative. The patients underwent surgical resection of parathyroid tissue on the basis of imaging results. SMADT and US findings were correlated with histology as the gold standard. ResultsEighty-six histological samples were resected. The sensitivity of SMADT for localization to individual glands was 70.6% [95% confidence interval (CI)=58.1–80.7%] and that for neck US was 60.3% (95% CI=47.7–71.8%, P=0.26). Specificity was 94.4% (95% CI=70.6–99.7%) for SMADT and 72.2% (95% CI=46.4–89.2%) for neck US (P=0.13). Sensitivities in multigland disease were 63.6% (95% CI=31.6–87.6%) for SMADT and 36.4% (95% CI=12.4–68.4%) for US (P=0.37) and in nodular thyroid disease were 83.8% (95% CI=67.3–93.2%) and 66.7% (95% CI=48.9–80.9%), respectively (P=0.07). ConclusionSMADT results in better localization of varying parathyroid pathologies and complements the role of US in patients with multigland disease and nodular thyroid.

Spectrum of metastatic and nonmetastatic skeletal findings with dual-phase 18F-FECH PET/CT in patients with biochemical relapse of prostate cancer

Introduction The aim of this study was to evaluate the spectrum of skeletal findings on dual-phase fluorine-18-fluoroethylcholine (18F-FECH) PET/CT performed during the work-up of patients referred for suspected prostate cancer relapse. Materials and methods Three hundred 18F-FECH PET/CT scans were evaluated prospectively. The low-dose CT features of all cases were categorized as isodense, sclerotic, lytic or mixed lytic/sclerotic and maximum standardized uptake value (SUVmax) values were calculated. Findings on 18F-FECH PET/CT were correlated with Technetium-99m-methylene diphosphonate planar bone scans and serum prostate-specific antigen. Results Patient age range was 50–90 years (median 71 years) and prostate-specific antigen values were in the range 0.04–372 ng/ml (Roche Modular method). Seventy-two lesions were detected on 18F-FECH PET/CT in 45 patients, including 31 (43%) in the pelvis, 17 (23%) in the spine (cervical 3, thoracic 8 and lumbar spine 6) and 10 (13%) in the ribs. Evaluation of low-dose CT in combination with PET helped to characterize benign findings in 21 (29%) lesions. The SUVmax for all except one benign lesion ranged from 0.49 to 2.15. In 51 (71%) lesions because of metastatic disease, SUVmax was 0.6–11.6 for those classified as sclerotic on low-dose CT, 0.7–8.58 for lytic lesions, 1.1–7.65 for isodense lesions and 1.27–3.53 for mixed lytic/sclerotic lesions. Of the 56 18F-FECH-avid lesions, 21 lesions showed avidity on bone scan [3 (23%) of the 13 isodense lesions, 14 (40%) of the 35 sclerotic lesions, 2 (50%) of the lytic lesions and 2 (50%) of the mixed sclerotic/lytic lesions]. Conclusion 18F-FECH PET/CT identified bone lesions in 15% of patients with suspected prostate cancer relapse. SUVmax in isolation cannot be used to characterize these lesions as benign or malignant. Minimal overlap of benign and malignant lesions was observed above SUVmax of 2.5. Low-dose CT of PET/CT is a useful tool to aid characterization.

(18)F-FECH PET/CT to Assess Clinically Significant Disease in Prostate Cancer: Correlation With Maximum and Total Cancer Core Length Obtained via MRI-Guided Template Mapping Biopsies.

OBJECTIVE The objective of this study was to detect clinically significant and insignificant prostate cancer on 18F-fluoroethylcholine (FECH) PET/CT and to correlate findings with transperineal template-guided prostate mapping (TPM) biopsy. SUBJECTS AND METHODS Fifty-six lobes of the prostate were analyzed in 28 men who underwent FECH PET/CT and TPM. Whole-body images and pelvic images were acquired at 60 and 90 minutes after tracer administration. FECH PET/CT findings were correlated with TPM. Sensitivity, specificity, positive predictive values, negative predictive values, and AUC of dual phase FECH PET/CT were calculated. RESULTS Mean age of the patients was 68.8 years (range, 53-79 years), and mean prostate-specific antigen level was 12.1 ng/mL (range, 0.6-45 ng/mL). Mean maximum cancer core length was 4.4 mm (median, 4 mm; range, 1-14 mm) and mean total cancer core length, 14.6 mm (median, 14.6 mm; range, 1-82 mm). Prostate cancer was identified in 38 lobes with a Gleason score of 6 in five lobes (13%), 7 in 27 lobes (71%), 8 in four lobes (11%), and 9 in two lobes (5%). FECH PET/CT showed findings of prostate cancer in 46/56 lobes (82%). The ranges for maximum standardized uptake value for 60- and 90-minute FECH PET/CT were 1.3-11.4 and 1.2-10.9, respectively. Clinically significant cancer was seen in 30 of 38 positive lobes; eight had clinically insignificant disease. For 60-minute imaging, the sensitivity, specificity, and ROC AUC were 75%, 75%, and 0.746 (95% CI, 0.612-0.853). For 90-minute imaging, the sensitivity, specificity, and ROC AUC were 73.7%, 58.3%, and 0.646 (95% CI, 0.498-0.776). Overall sensitivity, specificity, positive predictive value, and negative predictive value were 95%, 50%, 82.6%, and 80%, respectively. CONCLUSION FECH PET/CT can detect prostate cancer and localizes TPM biopsy-proven clinically significant prostate cancer with sensitivity of greater than 89.7%. Of the two imaging durations, 60-minute imaging is more sensitive and specific than 90-minute imaging.

Diffuse large B cell lymphoma: cutaneous manifestation

A 47-year-old gentleman was diagnosed with diffuse B cell lymphoma. His initial presentation was skin lesions. He was then referred for patch test with a diagnosis of periorbital eczema. Later, patient developed varicose veins and skin lesions in the right leg which was operated upon with poor healing and subsequent skin biopsy of the lesions demonstrated diffuse large B cell lymphoma (DLBCL). The bone marrow biopsy proved marrow involvement. He had no B symptoms. His past medical history includes brain abscess aged 9 …