Diagnosis of malignant breast disease by axillary lymphoscintigraphy: a preliminary report

Preoperative lymphoscintigraphy during lymphatic mapping for breast cancer: improved sentinel node imaging using subareolar injection of technetium 99m sulfur colloid

BACKGROUND

Preoperative lymphoscintigraphy has been recommended to confirm the successful uptake and direction of migration of radiotracer into sentinel nodes during lymphatic mapping for breast cancer. In addition, preoperative lymphatic mapping may provide a visually useful aid to the relative location of sentinel nodes within a nodal basin. One common method of breast lymphoscintigraphy involves injections of unfiltered technetium 99m sulfur colloid (Tc-99m-SC) directly into parenchymal tissues surrounding a tumor or biopsy cavity (IP injection). Because of the many imaging failures and prolonged imaging times of IP lymphoscintigraphy, the procedure has fallen into disfavor by oncologic surgeons. The purpose of this study is to document the increased success rate of preoperative breast lymphoscintigraphy using a new anatomic site of injection, the subareolar lymphatic plexus (SA injection).

STUDY DESIGN

In the 12 months between December 1, 1998, and December 29, 1999, 42 women with stage I and II breast cancer underwent preoperative lymphoscintigraphy by either the IP (n = 12, December 1998 to May 1999) or SA (n = 30, May 1999 to December 1999) route of injection. Both groups were injected with 1 mCi (37 MBq) of unfiltered Tc-99m-SC followed immediately by external gamma-camera imaging. The success rate for preoperative sentinel node imaging and the total imaging time were recorded in both groups.

RESULTS

The success rate of identifying a sentinel node by SA lymphoscintigraphy was 90% (n = 27 of 30 patients), compared with 50% (n = 6 of 12 patients) for IP lymphoscintigraphy (p = 0.009). The imaging time in the SA injection group was 34 +/- 16 minutes, which was 59% shorter than the imaging time in the IP injection group of 82 +/- 48 minutes (p < 0.001). No uptake into internal mammary nodes was seen in either group.

CONCLUSIONS

Moving the site of injection ofunfiltered Tc-99m-SC to the subareolar lymphatic plexus (SA injection) increased the success rate of preoperative lymphoscintigraphy to 90%, compared with 50% using IP injections. Preoperative SA lymphoscintigraphy resulted in the rapid visualization of axillary sentinel nodes within 30 minutes of SA injection, enabling a visual determination of the approximate number of sentinel nodes and their relative locations within the axilla. We conclude SA injection of unfiltered Tc-99m-SC is superior to IP injections when performing preoperative breast lymphoscintigraphy and is a visually useful aid to lymphatic mapping for breast cancer.

The Feasibility and Accuracy of the Sentinel Lymph Node Biopsy for Breast Carcinoma

As the procedure of sentinel lymph node biopsy for breast cancer becomes more widely available, the practicality of it in the hands of general surgeons should be assessed. This is a study of the accuracy and use of this procedure. A prospective study was conducted at two university-affiliated teaching hospitals. Ninety-one patients with invasive breast cancer were enrolled in the study. Twelve patients were excluded from analysis. The remaining 79 patients were injected peritumorally with technetium-99m-labeled sulfur colloid and isosulfan vital blue dye. The sentinel lymph node was located and excised using a gamma probe, and the definitive breast cancer operation was completed, including an axillary dissection. Histology of the sentinel lymph node specimen was compared with that of the axilla. Sentinel lymph nodes were located in 64 (81.0%) of the 79 patients. Sentinel lymph nodes and axillary nodes were benign in 44 (68.8%) of the 64 patients; these patients could potentially have been spared the axillary dissection. Fourteen (21.9%) patients had metastatic cancer to the sentinel nodes only, and five (7.8%) patients had axillary metastasis beyond the sentinel lymph node. Among the 64 patients, there was one false negative. Sensitivity and specificity when a sentinel lymph node was found were 95.0 per cent and 100 per cent, respectively. The sentinel lymph node accurately predicted the axillary contents 98.4 per cent of the time. This study demonstrates that the sentinel lymph node can be identified and is reliable in predicting axillary node status. This study also shows that the procedure has a notable learning curve, but can be used by general surgeons with a commitment to the care of breast cancer patients.

Lymphoscintigraphy in vulvar cancer: a pilot study

This pilot study was undertaken to correlate the patterns of lymphatic drainage demonstrated by vulvar lymphoscintigraphy with the clinical and pathologic findings of the inguino-femoral lymph nodes in patients with vulvar cancer. Ten patients were studied with the radionuclide Technetium-antimony trisulfide colloid (Tc 99m ASC) using a perilesional technique. Images were obtained at 2-4 hr postinjection. Four of the six patients with central lesions or lesions that crossed the midline had bilateral groin uptake, and two had unilateral uptake to the side on which the lesion was predominantly located. Three of these patients, each with suspicious groin nodes bilaterally, had metastatic nodal disease, two unilateral and one bilateral, in whom the uptake was bilateral and unilateral, respectively. Three of the four patients with unilateral lesions had ipsilateral groin drainage only and one had no drainage. Three underwent a bilateral lymphadenectomy and none had metastasis. The pattern of Tc 99m ASC uptake was not predictive of metastatic nodal disease. In two of the three patients with unilateral groin recurrence the side of recurrence was the same as that demonstrated on lymphoscintigraphy, and in the third case there was bilateral drainage. Further data are needed to determine the role of lymphoscintigraphy in the management of vulvar cancer.

Lack of efficacy of lymphoscintigraphy in detecting axillary lymph node metastases from breast cancer

Preoperative detection of metastases in regional lymph nodes should constitute a fundamental step towards a better management of breast cancer. The National Cancer Institute of Milan has traditionally been engaged in this particular problem, that is, the search for a new imaging technique for detecting lymph nodal metastases from breast cancer. In 1984 axillary lymphoscintigraphy was performed on 26 patients with operable breast cancer by periareolar injection of 100 mu Ci of 99mTc sulphur microcolloid. The regional lymph nodes were identified as spot areas and a comparison was made between the number of primary draining axillary lymph nodes and their pathological examination. In only 2 of the 26 patients have more than 3 spot areas been revealed by axillary scintiscan, but this finding did not correspond to metastatic invasion. The lymphoscintigraphy pattern of the other 24 patients did not suggest any pathological condition. From our experience the method does not appear to help either a precise diagnosis of breast disease or the definition of the extent of mammary cancer.

Lymphatic metastasis and its treatment

The treatment of lymphatic metastasis depends on an understanding of its basic biology. We are still uncertain as to how human cancer cells enter lymphatic vessels and as to what reactions if any in the draining lymph node inhibit metastasis. We are uncertain as to whether lymphatic metastasis is an indicator or a governor of rapid dissemination, and poor prognosis. We are uncertain as to whether it is worth attempting to treat lymphatic metastases by means supplementary to those used in treating systemic tumour dissemination. It may be possible to obtain local cure of a local lesion by local lymphatic therapy and to concentrate therapy locally by intralymphatic infusion of a chemotherapeutic agent or encapsulation in liposomes. This is at best accessory to obtaining systemic cure of systemically disseminated neoplasm. Optimal results could be expected from appropriate combinations of local and systemic immunotherapy, chemotherapy and radiotherapy, after appropriate surgical reduction in tumour bulk.

Abdominal lymphoscintigraphy: an effective substitute for lymphography?

Abdominal lymphoscintigraphy is a quick, easy, cheap and relatively non-invasive technique. In our study it appeared to be as accurate as lymphography, giving a positive correlation in 25 out of 32 patients (78%). In 11% of cases the lymphoscintigram detected an abnormality of lymph node function before macroscopic morphological change was seen in the lymphogram, indicating that in some instances lymphoscintigraphy is more sensitive than lymphography. The reason for this is unknown, although possible mechanisms are discussed and these are the subject of current further study. We believe this to be the first report of lymphoscintigraphy being more sensitive than lymphography for detecting lymph node disease.

Radionuclide lymphoscintigraphy with technetium 99m antimony sulfide colloid to identify lymphatic drainage of cutaneous melanoma at ambiguous sites in the head and neck and trunk

Frequently the primary lesion of high-risk cutaneous melanoma (level III, greater than or equal to 1.5mm; greater than or equal to 1.0 mm with ulceration) is in an ambiguous lymphatic drainage site on the trunk, pelvic and shoulder girdles, and head and neck area. Lymphoscintigrams were performed by a circumferential intradermal injection of the biopsy site using technetium 99m (99mTc) antimony sulfide colloid in a total dose of 0.2 to 0.6 mCi in a volume of 0.1 to 0.5 ml. Imaging was done with a large-field gamma camera with high-resolution parallel hole collimator. Technetium 99m antimony sulfide colloid is an ideal agent for lymphoscintigrams because of small particle size (3-30 micron), which permits early migration into the interstitial space and lymphatics and rapid pickup by lymph nodes. Although it is a gamma emmitter with high activity, it has a short half-life and does not induce tissue necrosis. It does not localize the site of lymph node metastases, but indicates only the drainage pattern. Images were obtained at 1, 5, 10, 15, 30, and 60 minutes, respectively, and then three times every hour. Surgery was usually performed 24 hours later. The majority of patients had lesions with ambiguous drainage sites: head and neck (4 of 5 patients) and trunk (9 of 13 patients). The drainage by scan was to unpredictive sites in 72%, and resulted in a change of treatment planning by location and extent of ablation with node dissection in 9 of 18 patients. Ambiguous dissection sites included: (1) question of preauricular dissection with parotidectomy versus posterior auricular and cervical dissection for selected scalp lesions; (2) low-neck with or without axillary dissection for upper chest and shoulder lesions; and (3) axillary versus groin dissections for midflank lesions at zone of ambiguity between axilla and groin. It was concluded that preoperative 99mTc antimony sulfide lymphoscintigraphy is a highly useful planning technique in determining the appropriate lymphatic drainage basin for dissection in selected melanoma patients.

Diagnosis and treatment of neoplasms with radionuclide-labeled antibodies

The in vivo use of radionuclide-labeled antibodies to several types of tumor-associated antigens or products has proven to be a reliable method for defining primary, recurrent, metastatic, and occult carcinoma. Specificity for the radioimmunodetection procedure is high; however, the sensitivity varies depending on the size and site of the lesions. The relative roles of polyclonal- and monoclonal-type antibodies are still to be defined, since at this stage of development little difference can be demonstrated in the detection of tumor with either one. The introduction of emission computed tomography should simplify the imaging techniques appreciably and improve the resolution between nontarget and target radioactivity. Satisfactory radionuclide labels with photon energies more compatible with current imaging equipment will enhance resolution and sensitivity.

An evaluation of pelvic lymphoscintigraphy in the staging of colorectal carcinoma

Lymphoscintigraphy was used to delineate the lymphatic drainage of the rectum and distal colon in 18 patients with carcinoma of the rectum or sigmoid colon, in four with inflammatory disease of the large bowel and in 20 controls without colorectal pathology. Abdominal imaging was performed after submucosal injection of either 4 mCi 99mTc-antimony sulphide colloid or 0.5 mCi 99mTc-dextran into the rectum through a proctoscope. In nine patients with colorectal carcinoma, abdominal imaging was performed immediately pre-operatively and the excised specimen of large bowel was also imaged in vitro immediately postoperatively. The presence or absence of nodal uptake of radionuclide on abdominal scanning did not discriminate between normal and diseased large bowel, and the extent of nodal uptake demonstrated either by abdominal scans or by in vitro scans of excised specimens bore no relationship to the presence or absence of nodal metastases demonstrated histologically in the cancer patients. Pelvic lymphoscintigraphy as performed in this study has no demonstrable value in the diagnosis or staging of colorectal cancer.

The effect of breast biopsy on reactive changes in the axillary lymph nodes

The reactive changes in the axillary lymph nodes of 50 breast cancer patients treated by mastectomy immediately following frozen section diagnosis have been compared with the changes in the nodes of 50 patients whose biopsy preceded mastectomy by between 2 and 5 days. The frequency of sinus histiocytosis was significantly greater in those patients who had been subjected to previous biopsy. This finding suggests that prior breast biopsy may negate the prognostic significance of sinus histiocytosis in breast cancer.

The preoperative detection of axillary lymph node metastases in breast cancer by isotope imaging

Axillary lymphoscintigraphy using 99Tcm-labelled liposomes was carried out in 40 patients with breast cancer as a part of pretreatment staging in an attempt to improve the accuracy of axillary evaluation. Patients were injected interstitially in the periareolar region of each breast with 250–300 μCi of 99Tcm-labelled liposomes. Subsequently the patients were imaged with a gamma-camera using computerized data processing. Interpretation of images was based on prior experimental data; a diminished uptake of isotope by the primary regional lymph node (PRLN) and the group of axillary regional lymph nodes (RLN) draining the tumour, when compared to the control side, was considered to be abnormal and to suggest node metastases. An equal or enhanced uptake by the PRLN or RLN draining the tumour, when compared to the control side, was considered normal, indicating an absence of lymph node metastases. Eighteen patients (45 per cent) had abnormal scans and 14 patients (35 per cent) had normal scans. Eight patients (20 per cent) had technically unsatisfactory images where axillary nodes could not be identified. Twenty-two patients of the 32 with evaluable scans had correlation of preoperative images with postsurgical axillary lymph node histopathology. One patient out of 12 with an abnormal scan had normal lymph nodes on serial sectioning, and 2 patients out of 10 with normal scans had lymph node metastases. Eight of the 32 patients (25 per cent) with evaluable images had enhanced uptake of isotope by the PRLN and RLN draining the tumour. In 3 of these cases a marked reactive hyperplasia only was shown on histopathological examination, in 2 cases the reactive hyperplasia was associated with lymph node metastases, accounting for the 2 false negative interpretations. This preliminary study suggests that axillary lymphoscintigraphy may be of value in preoperative staging in breast cancer. Long term studies are needed to evaluate the prognostic potential of such a test as a measure of macrophage function. Further studies, by blind replication, are required to evaluate the accuracy of axillary lymph node imaging.

Lymphoscintigraphy--techniques and applications in the management of breast carcinoma

Radiocolloid lymphoscintigraphy is a versatile, simple technique which has been utilized extensively in the assessment of lymphatic function and structure in anatomic regions accessible to neither clinical examination nor radiocontrast lymphography, as well as in circumstances where radiocontrast lymphography is not feasible. The most important requirement for an effective study are: (a) Determination of the appropriate injection site for reproducibly visualizing the majority of the lymphatics under study and, (b) use of an agent with the optimum properties of a preformed small, uniform, well-dispersed particle colloid. Multiple applications of lymphoscintigraphy in the patient with breast carcinoma have demonstrated its value in distinguishing abnormalities of the internal mammary lymphatics shown to have significant prognostic implications, in providing accurate localization of the parasternal lymphatics for radiation therapy and its potential for determining the status of axillary lymphatics in lieu of surgical intervention. The following review is based on an experience of over 6500 studies in 5550 patients with breast carcinoma.

Lymphatic metastasis

Lymphatic metastasis is an important mechanism in the spread of human cancer. During its course, tumor cells first penetrate the basement of membrane of the epithelium, in which they arise, and then the underlying connective tissue, carried partly by hydrostatic pressure. They enter the lymphatic partly by active movement, pass up the lymphatic trunk; they then settle and proliferate in the subcapsular sinus, penetrate its endothelium and proliferate and destroy the node. There are varied forms of immune response in the node and in human nodes often a complex fibrous and vascular response. The degree of lymphocytic response may be important for prognosis. The nodal reaction may be stimulated by release of antigens from the tumor. One of the most studied animal models of lymphatic metastasis is that which occurs in the politeal node after injection of tumor into the footpad. This model has been used to show that tumor cells enter lymphatics through gaps in endothelium, probably between endothelial cells, and that lymph nodes can destroy small numbers of tumor cells. Local immunotherapy and chemotherapy can sterilize a lymph node of tumor cells; the modes of treatment used have included intralymphatic injection and encapsulation of chemotherapeutic agents in liposomes. Prior radiotherapy may accelerate metastasis possibly by making tumor cells shed into lymphatic vessels. Lymph nodes are rather poor barriers to tumor cells. The prognostic significance of lymph node metastasis varies within tumor type; if hematogenous metastasis is early, then the presence of lymph node metastasis is of lesser prognostic significance. Lymph nodes can probably destroy only small numbers of tumor cells. Tumor cell heterogeneity is of importance in many aspects of metastasis; while clonal variation may be of importance in determining lymph node metastasis, it is not yet clear how important this is, nor whether specific clones metastasize specifically to lymph nodes. Lymphography is well established in diagnosis of lymphatic metastasis. A recent interesting development has been to inject antibodies labeled with a radioactive label, and image the label in lymph nodes with a gamma-camera. If anti-tumor antibodies are used in this way it may be possible to detect lymph node metastasis. Within the expanding field of tumor metastasis, lymphatic metastasis needs much more attention, particularly in relation to the diagnosis and treatment of the lymphatic spread of human cancer.

Iliopelvic lymphoscintigraphy

In patients with genitourinary cancers, it is critically important that lymph node metastases be detected prior to surgery. Information regarding the status of these nodes will influence the type and extent of therapy. Radiologic tests currently available for lymph node imaging--contrast lymphangiography, ultrasound, and computed tomography--are sometimes associated with a high false-negative rate. Iliopelvic lymphoscintigraphy, when performed following bilateral perianal injections of 99mTc-antimony trisulfide colloid, offers a physiologic method for visualizing these nodes and allows demonstration of the internal iliac chain, often not visualized on contrast lymphangiographic studies. Additionally, data from initial patient trials suggest that this technique offers a clinically acceptable level of sensitivity and specificity. This article details the methodology of the technique, and addresses reproducibility, sensitivity, specificity, and image interpretation.

Postoperative axillary lymphoscintigraphy in the management of breast cancer

Postoperative axillary lymphoscintigrams have been performed according to a technique of two-staged injection in 313 patients who had undergone a radical mastectomy with axillary dissection for breast cancer. Total absence of visualization of residual nodes suggests that dissection could be said to be complete in only 35.8% of the investigated patients, or because of metastatic disease causing blockage. The visualized residual nodes in patients represent a risk of developing nodal relapse, especially with positive pathological demonstration of axillary node invasion and without nodal irradiation. On the other hand, when the investigation showed the interruption of the lymphatic pathways of the arm, patients developed upper limb edemas more frequently. It is concluded that this simple and non traumatic technique is of value in order to assess the immediate postoperative axillary nodal status, and that it may influence the treatment of the patients.

Internal mammary lymphoscintigraphy: current status in the treatment of breast cancer

In the management of breast carcinomas, the internal mammary lymphoscintigraphy represents a simple, nontraumatic and reproducible technique to visualize and investigate the internal mammary nodes. As suggested by the total absence of visualization of nodes on the operated side in all or in the two upper intercostal spaces, internal mammary chain invasion concerns 30% of the population. This frequency increases with the clinical staging of the tumor, its size, and the extent of the disease in the axilla. It is higher for tumors of inner rather than of outer quadrants. When internal mammary lymphoscintigrams are compared in frontal view to the limits of the usual irradiation fields, parasternal nodes outside these limits or in borderline position are observed in 15 to 34% of the population according to the X-ray technique used. Furthermore, 40% of the tangential irradiation fields does not give an adequate irradiation dose to the internal mammary nodes. In one case out of four, IMLSc allows the reduction of useless heart- and lung-irradiated volumes. Internal mammary node invasion as demonstrated by lymphoscintigraphy has been demonstrated to have a prognostic value as the anatomopathological axillary node status, concerning both survival and disease evolution rates. IMLSc, when compared to the other possible investigation techniques of these nodes (X-ray computed tomography, echography or surgery, etc.), represents at the present time the investigation method of choice with the widest implications (diagnostic, therapeutic, and prognostic).

Axillary lymphoscintigraphy: current status in the treatment of breast cancer

Postoperative axillary lymphoscintigraphy has been performed after time-differentiated intercostal and interdigital injections of a 99Tc-labeled sulfur microcolloid in 313 patients suffering from breast cancer who underwent radical surgery with axillary dissection. As demonstrated by the absence of visualized lymph nodes after both injections, the axillary dissection could be considered as complete in only 34.6% of the investigated patients. The greatest part of lymph nodes, remaining after surgery, corresponds to the inferior and central groups (after interdigital injection). In 15% of the cases the intercostal injection leads to the demonstration of external mammary lymph nodes. According to the analysis of 202 cases with at least 1 year follow-up, the existence of visualized residual lymph nodes represents a factor of risk to develop nodal relapse especially in patients with positive peroperative axillary lymph node status who did not receive postoperative X-ray treatment. Upper limb edema occurs in 22.5% of the cases; mainly in patients with negative lymphoscintigraphic findings (demonstrating the interruption of the axillary lymphatic flux) and without nodal irradiation. Postoperative axillary lymphoscintigraphic findings should be evaluated in connection with the peroperative axillary lymph node status as established according to the histological analysis, and should take into account the number of removed lymph nodes. Preoperative axillary lymphoscintigraphy seems to be a less contributive examination technique.

High colloidal uptake in axillary nodes with metastatic disease

Axillary lymphoscintigraphy using 99Tcm antimony sulphide colloid has been carried out in 29 patients with suspected breast cancer and was correlated with histology. Of the 23 with proved tumour, axillary node metastases were found in 19 and, although 10 did have diminished uptake on the side of the lesion, 5 had an equal uptake in both sides and 4 had an increased uptake on the side of the lesion. Further, some of the nodes in which the high uptake had occurred were those heavily infiltrated by tumour. It is concluded that: a, lymphoscintigraphy with antimony sulphide colloid is not a reliable technique for the detection of metastatic disease in the regional nodes; b, any lymphoscintigraphy with this or any other agent requires more meticulous histological correlation than hitherto before it can be assumed to have any proved clinical value.

Scintiscanning of the breast with 99Tcm-diethylene triamine penta-acetic acid--a prospective blind evaluation

In this blind prospective study of breast scintiscanning with 99Tcm-diethylene triamine penta-acetic acid (DTPA) in 67 female patients presenting at a primary breast referral clinic, we have observed that this investigation has a high diagnostic accuracy in distinguishing benign from malignant lesions of the breast. The predictive value of the test when positive in establishing the presence of cancer is 94 per cent with a false negative rate of 6 per cent. The predictive value of the test when negative in excluding cancer in 97 per cent with a false positive rate of 3 per cent. Initial studies also indicate the potential value of DTPA breast scintiscanning in delineating the activity of painful benign lesions of the breast.

Lymphoscintigraphy cannot diagnose breast cancer

Axillary lymphoscintigraphy was performed by the technique of Agwunobi and Boak (1) in 68 patients with operable cancer of the breast and 11 patients with benign disease. Contrary to their previous report, scans were found to be indistinguishable from normal in the majority of breast cancer patients with interpretable scans, and no pattern of uptake was found which was typical of carcinoma in the corresponding breast.

Reliability of axillary lymph node scintiphotography in suspected carcinoma of the breast

The ability of axillary lymph nodes to take up 99Tcm-labelled antimony sulphide colloid in suspected carcinoma of the breast was investigated in 111 consecutive patients. Eight out of 17 patients with histologically confirmed carcinoma of the breast had a low colloid uptake on the affected side, i.e. a positive scintiphoto. Eighty-two out of 94 patients with benign breast disease had an equal colloid uptake on the two sides or increased uptake on the symptomatic side, i.e. a negative scintiphoto. The reliability of the test is low and the test can neither be recommended for screening to select patients for further investigations nor as a routine examination.

Prediction of axillary metastases in breast cancer by lymphoscintigraphy

A new technique of axillary lymphoscintigraphy has been investigated in thirty patients with breast carcinoma. Intradermal injection of 100 muCi technetium-99m antimony sulphide colloid in 0.1 ml buffer produced satisfactory scans of axillary lymph-nodes in twenty-seven patients (90%). Ten patients with node metastases from breast cancer (9 confirmed histologically) had a defect in the lower axillary uptake on the side of the lesion. Three of the remaining seventeen patients with breast cancer and normal scans had nodal metastases seen histologically, but in two these were micro-metastases only. Axillary lymphoscintigraphy improved considerably the clinical assessment of node status, and corrected the clinical classification in five of six patients who had been misclassified by clinical examination.

Prostatic lymphoscintigraphy

Techniques of prostatic lymphoscintigraphy using 99mTc phytate (TP) and 99mTc antimony sulphide colloid (ASC) have been evaluated in 30 patients. The most successful technique was a superficial perianal injection of ASC. In general, definition of the regional lymph nodes lacked the precision and clarity that would be required for the technique to be used in staging of prostatic or other pelvic tumours; further development of the technique is recommended.

99Tcm-polyphosphate uptake by breast tumours

Technetium polyphosphate uptake by breast tumours has been investigated in 69 patients. Although 70 per cent (38 out of 54) of malignant tumours took up the isotope in comparison with 45 per cent (5 out of 11) of benign lesions, this technique would be unreliable for diagnostic purposes.