A. Cahid Civelek

Circumferential wall thickness measurements of the human left ventricle: Reference data for thallium-201 single-photon emission computed tomography

New heart imaging methods, including echocardiography, single-photon emission computed tomography (SPECT) and nuclear magnetic resonance, involve measurements of left ventricular (LV) wall thickness in cross sections perpendicular to the LV long axis. To provide a reference base, LV myocardial wall thicknesses were measured in human autopsy specimens. Short-axis views were chosen at the base of the heart, at the level of the papillary muscles and at a level close to the apex. At the 3 levels, LV wall thicknesses were measured for each of 36 circumferential sectors. The measurements revealed a nonuniformity of LV myocardial wall thickness, related to the papillary muscles, the anterior and posterior junctions with the right ventricle and the thinness of the ventricular septum. These findings help to explain the structured appearance of SPECT 201-thallium short-axis views.

Detection of left anterior descending coronary artery disease in patients with left bundle branch block

The detection of coronary artery disease is difficult if a patient has electrocardiographic evidence of left bundle branch block (BBB). Septal blood flow may be reduced in patients with left BBB, despite no angiographic evidence of left anterior descending (LAD) coronary artery disease. We have developed a new method of quantification of Thallium-201 single-photon emission computed tomographic (SPECT) images with the aim of better separating patients with left BBB and LAD disease from those with left BBB alone. The study cohort comprised 8 normal subjects (group I) and 20 patients with left BBB and chest pain who underwent thallium-201 SPECT imaging and coronary angiography. Eight patients (group II) had < or = 50% LAD stenosis, and 12 (group III) had > or = 70% LAD stenosis. Septal abnormality scores on the second short-axis slice from the base were computed, based on comparison of each subjects short-axis circumferential profile with a normal reference curve. This followed a procedure in which each profile was scaled to minimize differences in its absolute level in relation to the reference curve. Septal abnormality scores on stress images were 0.8 +/- 22 for group I, 27 +/- 43 for group II, and 165 +/- 67 for group III (p = 0.15 for group I vs II, and p < 0.0001 between groups I and III, and II and III).(ABSTRACT TRUNCATED AT 250 WORDS)

Reduced left ventricular cavitary activity (“black hole sign”) in thallium-201 SPECT perfusion images of anteroapical transmural myocardial infarction

Apparently reduced left ventricular (LV) cavitary thallium activity in both planar and tomographic perfusion images has been previously observed by these and other investigators. With single-photon emission computerized tomography, we have clinically noted that this black hole sign was associated with an aneurysm in the setting of a transmural anterior or anteroapical perfusion defect. We have now prospectively studied the etiology and predictive value of this sign in 84 consecutive patients with an anterior, anteroapical transmural perfusion defect. Of the 84 patients, 49 had both LV aneurysm (confirmed by contrast ventriculography, echocardiography or gated blood pool studies) and a black hole sign. Only 1 patient with an aneurysm did not have the black hole sign, and 2 without aneurysm did. Thus, it is concluded that this sign is highly accurate in diagnosing LV aneurysm. Because thallium-201 single-photon emission computerized tomography imaging is often performed as one of the first diagnostic tests soon after myocardial infarction, this has important clinical management implications.

Rest thallium-201 myocardial perfusion imaging in a patient with leukaemic infiltration of the heart

Despite the high incidence of leukaemic infiltration of the heart, only 8 cases of atrioventricular block due to leukaemia have been reported in the literature. Improvement in the heart block associated with disappearance of the leukaemic infiltrate has not been reported. A rest thallium-201 study was used in a 65-year-old man to demonstrate leukaemic infiltration of the heart which was associated with complete heart block. After chemotherapy, when the tumour burden was reduced and the leukaemia in remission, his heart block resolved, and a follow-up thallium scan was normal.

Lung scan in the diagnosis and management of patent foramen ovale pulmonary embolism, paradoxical embolism.

This case illustrates the reopening of foramen ovale in a young patient with chronic pulmonary hypertension caused by bronchiectasis and chronic pulmonary fibrosis, which resulted in a prominent right-to-left shunt and severe hypoxia. Her clinically unsuspected right-to-left shunt was discovered during ventilation-perfusion scan, which was performed for the evaluation of pulmonary embolism. She had common variable immune deficiency, a primary immunodeficiency disease in which B-lymphocytes produce few or no antibodies. Most patients with this syndrome have an intrinsic defect in their B-lymphocytes that results in reduced immunoglobulin production. In these patients, recurrent respiratory tract infections are common and may result in chronic lung disease, fibrosis, particularly bronchiectasis (20-30%) and even cor pulmonale as happened in our patient [J. Clin. Immunol. 9 (1989) 22-33.].

Thigh splints in a young female soccer player.

The term thigh splints has been used to describe an avulsion injury at the adductor insertion sites of the femur. The condition is analogous to the much more common shin splints. The authors describe this condition in a 17-year-old female high school soccer player. Her clinical history and initial radiographic study suggested osteoid osteoma. However, the delayed-phase radionuclide bone scan showed similar increased uptake at symmetric skeletal locations in the proximal femurs at the site of the junction of adductor brevis and adductor longus insertions, confirming a diagnosis of avulsion injury. No hyperemia was evident on blood-flow images.

Asymptomatic large main pulmonary artery thromboembolism with a low-probability ventilation-perfusion lung scan.

&NA; The incidence of the interpretation of low-probability lung scans in asymptomatic patients with large central pulmonary embolisms and the prognostic implication of the ventilation–perfusion scan appearance in this clinical setting is not documented.

Testicular involvement of sarcoidosis diagnosed by gallium-67 scintigraphy

Gallium-67 scintigraphy helped to determine the extent of systemic sarcoidosis and demonstrated testicular involvement in a 32-year-old black man who presented with ataxia, weight loss, and a left testicular mass. To our knowledge, this is the first case of testicular sarcoidosis demonstrated by gallium-67 scintigraphy in a patient with systemic sarcoidosis.

68Ga-PSMA-11 PET: Better at Detecting Prostate Cancer than Multiparametric MRI?

P cancer is the third most commonly diagnosed cancer in the United States, with metastatic disease present in approximately 17% of patients at initial staging (1). Although screening for prostate cancer by using serum prostate-specific antigen remains controversial, the work-up for diagnosis is traditionally prompted by elevated prostate-specific antigen and followed by a physical examination and systematic transrectal US-guided biopsy to validate the presence of cancer. Later, additional noninvasive imaging tests may be incorporated for further staging, restaging, or diagnosing recurrence, as well as for therapeutic monitoring (1). Multiparametric MRI has been shown to address some of the limitations of conventional noninvasive imaging tests and is now recommended for assessing men suspected of having prostate cancer but with negative results at transrectal US-guided biopsy (1–5). Limitations of these conventional noninvasive imaging tests cannot adequately address a variety of relevant clinical issues, including risk stratification of the patients before initiation of the therapy, reliable staging of therapy-naive patients who are at risk for pelvic lymph node metastases or systemic disease, and detection of biochemical recurrence at low prostate-specific antigen levels in patients previously treated for prostate cancer with curative intent (6). To alleviate these limitations, several molecular imaging agents have been developed for the management of prostate cancer, which could be grouped as agents that target cell metabolism, hormone receptors, and membrane proteins. These agents could be labeled with several PET radiotracers including carbon 11 choline, gallium 68 (68Ga), or fluorine 18 fluorocholine (18F), all suitable for PET, or hybrid devices such as PET with CT or PET with MRI (1,6). For example, the 68Gaor 18F-labeled prostate-specific membrane antigen (PSMA) agents are transmembrane glycoproteins associated with tumor progression and disease recurrence, which are overexpressed in prostate cancer cells (1,6,7). These PSMA agents have shown improved diagnostic accuracy for detection of recurrent disease compared with cross-sectional imaging alone because molecular imaging of prostate cancer can provide a whole-body evaluation of tumor biology. To provide anatomic localization of PSMA-avid foci and to compensate for the depth of the centrally located tissue activities, PET images are typically coregistered with CT, which improves the diagnostic accuracy of the PET images (1). There is an increasing number of studies using PSMA agents labeled with PET radiotracers that have demonstrated improved detection rates of PET/CT studies for intraprostatic tumor, with sensitivities ranging from 67% to 97% (1). In this issue of Radiology, the study by Hicks et al, and previously Eiber et al, elegantly demonstrates that using a 68Ga-PSMA PET portion of the PET/MRI studies improved cancer localization of intraprostatic local disease or disease elsewhere when compared with multiparametric MRI sequences interpreted alone (1,8). These reports intuitively suggest that 68Ga(or 18F-) labeled PSMA PET/ MRI studies would be more accurate in localizing intraprostatic local disease or disease elsewhere when compared with PET and multiparametric MRI studies alone. Such additional improvements in sensitivity and perhaps accuracy are most likely due to the synergistic effect of each of the components (modalities) of the hybrid PET/MRI device. Combining the functional information from 68GaPSMA PET with the well-established powerful technique of multiparametric MRI results in more accurate diagnostic power. The limitation of the study by Hicks et al was that although the findings of their cohort were obtained by using hybrid PET/MRI equipment, they separated the results obtained from each modality, that is, 68Ga-PSMA PET portion of the PET/MRI and the multiparametric MRI for comparison purposes, as they were obtained separately. Yet their findings indicated that 68Ga-PSMA-PET improves sensitivity for detection of prostate cancer compared with multiparametric MRI. Tangible advantage of the use of hybrid PET/MRI in the clinic is that both modality images become available for review instantaneously, and this technique provides most precise registration of the image data sets for lesion localization and identification when compared with the images obtained at different time points. The excellent specificity and sensitivity provided by existing PSMA PET radiotracers and the discovery of newer radiotracers, as well as the advances occurring in hardware technologies of both modalities, will further enhance the ability of independent 68Ga-PSMA PET interpretation. Based on available preliminary data, one might conclude that at least similar improvements in diagnostic accuracy of 68Ga-PSMA-11 PET: Better at Detecting Prostate Cancer than Multiparametric MRI?