Gilbert A. Hurwitz

Investigation of measures to reduce interfering abdominal activity on rest myocardial images with Tc-99m sestamibi.

With the new myocardial agent Tc-99m sestamibi, relatively high abdominal uptake represents a major limiting factor. The effect of a standard feeding (commercial milkshake taken immediately after injection), and posture (standing versus sitting for 10 minutes postinjection) on the resting biodistribution of sestamibi was investigated in patients receiving 3 to 5 MBq/kg injections as part of rest-stress tomography. Ancillary anterior 1-minute images of heart and abdomen were obtained at 15 minutes postinjection and 90 to 140 minutes postinjection in 32 patients, randomized to feeding and postural treatments. Feeding decreased the activity in the gallbladder at both 15 and 110 minutes, but had no effect on liver parenchyma; activity in a background rectangle immediately beneath the heart was decreased by feeding only on the 15-minute images. An effect of posture was not apparent. Further study of the acute effects of a milkshake in eight patients showed a prompt reduction of 26% in a subdiaphragmatic background rectangle, but a more gradual decline in gallbladder counts. Thus, feeding of lipid after injection is not an essential component of sestamibi imaging protocols; oral administration of fluid immediately before imaging may help reduce interfering gastric activity.

Three-phase bone scintigraphy. Asymmetric patterns in the upper extremities of asymptomatic normals and reflex sympathetic dystrophy patients.

Three-phase Tc-99m MDP scans of 61 patients with asymptomatic upper extremities randomly mixed with 17 studies of patients previously diagnosed with reflex sympathetic dystrophy were blindly interpreted by three observers. Asymmetry in any of the phases was recorded and a final diagnostic impression made. Thirteen of 17 reflux sympathetic dystrophy studies were rated abnormal by at least two observers. Mild to striking asymmetry was occasionally seen in all three phases in asymptomatic upper extremities. Twenty of 61 asymptomatic patients (33%) were rated abnormal by at least one observer, and 5 of 61 studies (8%) were rated abnormal by all observers. Asymmetries in normal patients occurred more commonly in the earlier phases, while asymmetry in the delayed images was mild in all but one. Tightening the criteria to exclude mild asymmetry in delayed images resulted in unacceptably low sensitivity for reflex sympathetic dystrophy (29%). Interob-server variability was most prominent in the flow and immediate images. In the diagnosis of reflex sympathetic dystrophy a greater reliance should be placed on the delayed images, which in themselves have an overall sensitivity of 94%. It is important, however, to recognize that occasional mild and rare moderate asymmetries in even the delayed images of normal individuals result in an overall lower specificity of 77%.

An atlas of renography with Tc-99m sestamibi comparison with Tc-99m DTPA

Tc-99m sestamibil demonstrates considerable renal uptake followed by net urinary clearance similar to that of creatinine. The authors have previously shown that renograms could be obtained in cardiac patients by imaging during the rest injection of the perfusion agent. The present study shows correlating Tc-99m sestamibi and Tc-99m DTPA studies in hypertensive patients with a spectrum of findings, including aortic aneurysms, asymmetry due to renovascular disease, cysts, bilateral renal dysfunction, and horseshoe kidney. Tc-99m sestamibi images have persisting background activity in the liver and spleen, but show renal structure and function in adequate detail. Quantitative analysis confirms that Tc-99m sestamibi has higher renal uptake, but less excretion than Tc-99m DTPA. Review of these correlating studies suggests straightforward transfer of diagnostic expertise with standard renography to this new application.

Automated three-dimensional spatial standardization and quantification of myocardial perfusion tomography: alternative to polar maps

We developed a novel clinical tool (PERFIT) for automated 3-D voxel-based quantification of myocardial perfusion, validated it with a wide spectrum of angiographically correlated cases, compared it to previous approaches, and tested its agreement with visual expert reading. A multistage, 3-D iterative inter- subject registration of patient images to normal stress and rest cardiac templates was applied, including automated masking of external activity before final fit. The reference templates were adjusted to the individual left ventricles by template erosion, for further shape correction. 125 angiographically correlated cases including multi-vessel disease, infarction, and dilated ventricles were tested. In addition, standard polar maps were generated automatically from the registered data. Results of consensus visual reading (V) and PERFIT (P) were compared. The iterative fitting was successful in 245/250 (99%) stress and rest images. PERFIT found defects on stress in 2/29 normal patients and 95/96 abnormal patients. Overall correlation between V and P findings was r equals 0.864. In all abnormal groups (n equals 96), PERFIT average defect sizes expressed as the percentage the myocardial volume were 9.6% for rest and 22.3% for stress, versus 11.4% (rest) and 23% (stress) for visual reading. Automatic quantification by PERFIT is consistent with visual analysis; it can be applied to the analysis whole spectrum of clinical images, and can aid physicians in interpretation of myocardial perfusion.

Massive Uptake of Tc-99m MDP in Mucinous Adenocarcinoma of the Colon Metastatic to Liver: Appearance on SPECT

Tc-99m MDP uptake has been described in mucinous adenocarcinoma metastatic to the liver. Uptake is demonstrated in a very large metastatic focus on SPECT imaging in a patient who has survived for 3 years after primary resection and 1 year after diagnosis of liver metastasis.

Comparison of Tl-201 renal uptake with Tc-99m DTPA angiorenography in patients with hypertension. Measures of renal asymmetry.

Renal uptake of TI-201 reflects renal perfusion and may have a role in defining renal asymmetry in patients with hypertension who are referred for myocardial scintigraphy. The authors compared two methods of quantitating differential renal uptake of TI-201, with similar data obtained from the angiographic and renal uptake (RU) phases of Tc-99m DTPA scintigraphy in 35 patients with hypertension. For TI-201, asymmetry in renal counts was quantitated based on a simple outline technique or on interpolative background subtraction of 5-minute posterior images. Inter-observer and intra-observer variability among duplicate measurements were lower for TI-201, particularly with interpolative background subtraction, than for Tc-99m DTPA. Renal/background ratios were similar for TI-201 and RU-phase Tc-99m DTPA images when considering liver, spleen, or inter-renal regions as background; however, paraspinal uptake was relatively higher with TI-201 (P < 0.01). Qualitatively, renal asymmetry scores with the two radiotracers agreed (r = 0.89, blinded readings by four observers), although asymmetry was more marked with TI-201 (P = 0.06). Measurements with TI-201 agreed with both phases of Tc-99m DTPA (r = 0.96 to 0.98), but interpolative background subtraction systematically yielded greater inter-renal asymmetry than RU (P < 0.01), reflecting the qualitative impression. Thus, ancillary TI-201 imaging reflects differences between the kidneys in a fashion similar but not identical to Tc-99m DTPA scintigraphy.

Renal uptake of Tl-201 in hypertensive patients undergoing myocardial perfusion imaging

The detection of renovascular disease (RVD) has particular relevance in hypertensive patients (HP) who have symptoms of target organ damage. To evaluate the possibility of RVD in HP undergoing myocardial perfusion scintigraphy for chest pain symptoms, posterior renal images were obtained at 1-3 hours after Tl-201 injection. Analog and computer images were obtained for 5 minutes in 45 HP; 12 patients with no history of hypertension or renal disease served as normal controls. For qualitative analysis, images were coded and read by three observers as to symmetry of renal uptake. Differential renal uptake of Tl-201 (DRU) was quantitated on computer images. In normal controls, uptake was agreed on as symmetric. In HP, 6 patients had marked asymmetry of DRU and 4 had possibly significant asymmetry; 2 had decreased uptake in both kidneys suggesting bilateral RVD or nephrosclerosis. Objective correlation with DRU was obtained in 10 HP who had contrast angiography, confirming 4 cases of unilateral RVD and 2 of bilateral RVD. Thirteen patients also had renography with Tc-99m DTPA; differential renal function by this modality correlated well with DRU of Tl-201 (r = 0.98). Thus, DRU of Tl-201 can be used as a supplement to myocardial scintigraphy to identify HP who require further evaluation and treatment of RVD.